bone.wiki - User contributions [en]

Opportunistic CT

2025-05-01T21:53:14Z

Bryn.Matheson: /* Asynchronous calibration */

=Radiation Dose=

X-rays are a form of energy – like light and radio waves. X-rays are also called radiation. Unlike light waves, x-rays have enough energy to pass through your body. As the radiation moves through your body, it passes through bones, tissues, and organs differently. This allows a radiologist to create images of them. The radiologist is a specially trained doctor who can examine these images on a computer display. X-rays allow the radiologist to see the structures in your body in very fine detail.

==Dose Length Product==

Dose length product (DLP) is a measure of CT tube radiation output/exposure (measured in mGy.cm). It is related to volume CT dose index (CTDIvol), but CTDIvol represents the dose through a slice of an appropriate phantom. The dose length product accounts for the length of radiation output along the z-axis (the long axis of the patient). It may be described by the following equation:

DLP = (CTDIvol in mGy) . (length of scan in cm)

The dose length product does not take the size of the patient into account and is not a measure of absorbed dose. If the AP and lateral dimensions of the patient are available, then the size specific dose estimate (SSDE) can be used to estimate the absorbed dose.

==Effective Dose==

Some estimates of effective dose are summarized in the table below, taken from the cited sources.

{| class="wikitable"
|+ Estimates of Effective Dose1,2,3
|-
! Scan !! Effective Dose (mSv)
|-
| Head || 2.2
|-
| Full Spine || 20.6
|-
| Cervical || 3.6
|-
| Thoracic || 12.0
|-
| Lumbar || 5.0
|-
| Chest || 6.0
|-
| Chest/Abdo/Pelvis || 19.0
|-
| Abdo/Pelvis || 15.6
|-
| Knees || 0.16
|-
| Ankles || 0.14
|}

1Conference of Radiation Control Program Directors (CRCPD) Nationwide Evaluation of X-ray Trends (NEXT) 2005-2006 [https://crcpd.org/document/nationwide-evaluation-of-x-ray-trends-next-tabulation-and-graphical-summary-of-the-2005-2006-survey-of-computed-tomography/ report].

2CRCPD, Publication E-07-2, Tabulation and Graphical Summary of 2000 Survey of Computed Tomograph, (NEXT), August, 2007

3Biswas et al. Radiation Exposure from Musculoskeletal Computerized Tomographic Scans. The Journal of Bone and Joint Surgery, 2009.

Notes:

*Full Spine: From the base of the skull (C1) to the sacrum (through L5), effective dose of 20.6 mSv (adding up dose of all spine scans)

*Extended Chest/Abdo/Pelvis (or Full Spine + Abdo/Pelvis): From the base of the skull (C1) through the proximal femur. Effective dose of 25.2 mSv (cervical spine + chest + abdo/pelvis). Likely this is an overestimation.

Dose Length Product (DLP) of ARTININ scans is usually between 270 – 400 mGy-cm.

Converting between mGy-cm to effective dose (as described by the American Association of Physicists in Medicine (AAPM) Report No. 96):
E (mSv) = k × DLP
where <code>k</code> is the normalized effective dose per dose-length product for adults.

Estimated effective dose for ARTININ (as according to DLP):
E (mSv) = 0.015 × 400
E (mSv) = 6 mSv

Note that in the ARTININ consent we list 10 mSv, which is on the high end (which would be for a larger person).

Full spine (estimates of DLP taken from a few participants in the spinal cord injury group): 705 - 958. 55m mGy-cm

Note that DLP is over twice what is observed in ARTININ
E (mSv) = 0.015 × 958.55
E (mSv) = 14.5 mSv

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

==Calibration==
To ensure accurate material properties and comparability across clinical sites and scanners during quantitative analysis derived from clinical CT scans, the native in-scan Hounsfield Units (HUs) must be converted to their corresponding bone equivalent densities.

There are three main types of calibration for CT scans. All of these methods are available in our GitHub repository called [https://github.com/Bonelab/Ogo Ogo].

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Phantom calibration===

Phantom calibration is the current imaging gold standard for converting HUs to bone densities. Phantom calibration involves placing a calibration phantom with known density values of either solid CHA or liquid K2HPO4 under the patient in the scan field of view, as seen here:

[[Image:phantom_rods_noseg.png|600px]]

The solid CHA or liquid K2HPO4 found in the phantom acts as the bone equivalent reference standard. Phantom calibration requires sampling the in-scan HUs of the bone equivalent reference rods (from the calibration phantom) and comparing those values to the known reference values. A simple linear regression between the known values within the calibration phantom rods and the in-scan HUs can be created to convert the HUs to bone equivalent density (BMD).

The calibration curve takes the form of
BMD = (HU⋅a) + b

where a is the slope of the resulting calibration curve and b is the intercept. This calibration curve is applied to specific bone compartments in the image or to the entire image, creating a bone-equivalent density image. The values of a and b depend on many factors, such as the composition of the X-ray spectrum emitted by the X-ray tube, tube current, reconstruction kernel or table height, and as a result are scanner and image protocol dependent.

To run phantom calibration in Ogo, you will need two things:
<ol>
<li>The raw CT scan (.nii or .nii.gz)</li>
<li>A segmentation mask of the phantom rods</li>
</ol>

Typically, this is done using ITKSnap or some other automated method [TBD], and you segment the inside of the rods, making sure to stop before reaching the edge of the rod to avoid partial volume effects.

An example of the phantom rods segmented:

[[Image:phantom_rods_seg.png|600px]]

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Asynchronous calibration===

This also uses a phantom, but not at the same time as the scan of the patient. Sometimes it can be months or even years away. (This is an ongoing edited section...)

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Internal calibration===

This doesn't use a phantom, but instead uses the internal tissues as referents.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

Opportunistic CT

2025-03-07T22:45:17Z

Bryn.Matheson: /* Calibration */

=Radiation Dose=

X-rays are a form of energy – like light and radio waves. X-rays are also called radiation. Unlike light waves, x-rays have enough energy to pass through your body. As the radiation moves through your body, it passes through bones, tissues, and organs differently. This allows a radiologist to create images of them. The radiologist is a specially trained doctor who can examine these images on a computer display. X-rays allow the radiologist to see the structures in your body in very fine detail.

==Dose Length Product==

Dose length product (DLP) is a measure of CT tube radiation output/exposure (measured in mGy.cm). It is related to volume CT dose index (CTDIvol), but CTDIvol represents the dose through a slice of an appropriate phantom. The dose length product accounts for the length of radiation output along the z-axis (the long axis of the patient). It may be described by the following equation:

DLP = (CTDIvol in mGy) . (length of scan in cm)

The dose length product does not take the size of the patient into account and is not a measure of absorbed dose. If the AP and lateral dimensions of the patient are available, then the size specific dose estimate (SSDE) can be used to estimate the absorbed dose.

==Effective Dose==

Some estimates of effective dose are summarized in the table below, taken from the cited sources.

{| class="wikitable"
|+ Estimates of Effective Dose1,2,3
|-
! Scan !! Effective Dose (mSv)
|-
| Head || 2.2
|-
| Full Spine || 20.6
|-
| Cervical || 3.6
|-
| Thoracic || 12.0
|-
| Lumbar || 5.0
|-
| Chest || 6.0
|-
| Chest/Abdo/Pelvis || 19.0
|-
| Abdo/Pelvis || 15.6
|-
| Knees || 0.16
|-
| Ankles || 0.14
|}

1Conference of Radiation Control Program Directors (CRCPD) Nationwide Evaluation of X-ray Trends (NEXT) 2005-2006 [https://crcpd.org/document/nationwide-evaluation-of-x-ray-trends-next-tabulation-and-graphical-summary-of-the-2005-2006-survey-of-computed-tomography/ report].

2CRCPD, Publication E-07-2, Tabulation and Graphical Summary of 2000 Survey of Computed Tomograph, (NEXT), August, 2007

3Biswas et al. Radiation Exposure from Musculoskeletal Computerized Tomographic Scans. The Journal of Bone and Joint Surgery, 2009.

Notes:

*Full Spine: From the base of the skull (C1) to the sacrum (through L5), effective dose of 20.6 mSv (adding up dose of all spine scans)

*Extended Chest/Abdo/Pelvis (or Full Spine + Abdo/Pelvis): From the base of the skull (C1) through the proximal femur. Effective dose of 25.2 mSv (cervical spine + chest + abdo/pelvis). Likely this is an overestimation.

Dose Length Product (DLP) of ARTININ scans is usually between 270 – 400 mGy-cm.

Converting between mGy-cm to effective dose (as described by the American Association of Physicists in Medicine (AAPM) Report No. 96):
E (mSv) = k × DLP
where <code>k</code> is the normalized effective dose per dose-length product for adults.

Estimated effective dose for ARTININ (as according to DLP):
E (mSv) = 0.015 × 400
E (mSv) = 6 mSv

Note that in the ARTININ consent we list 10 mSv, which is on the high end (which would be for a larger person).

Full spine (estimates of DLP taken from a few participants in the spinal cord injury group): 705 - 958. 55m mGy-cm

Note that DLP is over twice what is observed in ARTININ
E (mSv) = 0.015 × 958.55
E (mSv) = 14.5 mSv

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

==Calibration==
To ensure accurate material properties and comparability across clinical sites and scanners during quantitative analysis derived from clinical CT scans, the native in-scan Hounsfield Units (HUs) must be converted to their corresponding bone equivalent densities.

There are three main types of calibration for CT scans. All of these methods are available in our GitHub repository called [https://github.com/Bonelab/Ogo Ogo].

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Phantom calibration===

Phantom calibration is the current imaging gold standard for converting HUs to bone densities. Phantom calibration involves placing a calibration phantom with known density values of either solid CHA or liquid K2HPO4 under the patient in the scan field of view, as seen here:

[[Image:phantom_rods_noseg.png|600px]]

The solid CHA or liquid K2HPO4 found in the phantom acts as the bone equivalent reference standard. Phantom calibration requires sampling the in-scan HUs of the bone equivalent reference rods (from the calibration phantom) and comparing those values to the known reference values. A simple linear regression between the known values within the calibration phantom rods and the in-scan HUs can be created to convert the HUs to bone equivalent density (BMD).

The calibration curve takes the form of
BMD = (HU⋅a) + b

where a is the slope of the resulting calibration curve and b is the intercept. This calibration curve is applied to specific bone compartments in the image or to the entire image, creating a bone-equivalent density image. The values of a and b depend on many factors, such as the composition of the X-ray spectrum emitted by the X-ray tube, tube current, reconstruction kernel or table height, and as a result are scanner and image protocol dependent.

To run phantom calibration in Ogo, you will need two things:
<ol>
<li>The raw CT scan (.nii or .nii.gz)</li>
<li>A segmentation mask of the phantom rods</li>
</ol>

Typically, this is done using ITKSnap or some other automated method [TBD], and you segment the inside of the rods, making sure to stop before reaching the edge of the rod to avoid partial volume effects.

An example of the phantom rods segmented:

[[Image:phantom_rods_seg.png|600px]]

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Asynchronous calibration===

This also uses a phantom, but not at the same time as the scan of the patient. Sometimes it can be months or even years away.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Internal calibration===

This doesn't use a phantom, but instead uses the internal tissues as referents.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

Opportunistic CT

2025-03-07T22:35:15Z

Bryn.Matheson: /* Phantom calibration */

=Radiation Dose=

X-rays are a form of energy – like light and radio waves. X-rays are also called radiation. Unlike light waves, x-rays have enough energy to pass through your body. As the radiation moves through your body, it passes through bones, tissues, and organs differently. This allows a radiologist to create images of them. The radiologist is a specially trained doctor who can examine these images on a computer display. X-rays allow the radiologist to see the structures in your body in very fine detail.

==Dose Length Product==

Dose length product (DLP) is a measure of CT tube radiation output/exposure (measured in mGy.cm). It is related to volume CT dose index (CTDIvol), but CTDIvol represents the dose through a slice of an appropriate phantom. The dose length product accounts for the length of radiation output along the z-axis (the long axis of the patient). It may be described by the following equation:

DLP = (CTDIvol in mGy) . (length of scan in cm)

The dose length product does not take the size of the patient into account and is not a measure of absorbed dose. If the AP and lateral dimensions of the patient are available, then the size specific dose estimate (SSDE) can be used to estimate the absorbed dose.

==Effective Dose==

Some estimates of effective dose are summarized in the table below, taken from the cited sources.

{| class="wikitable"
|+ Estimates of Effective Dose1,2,3
|-
! Scan !! Effective Dose (mSv)
|-
| Head || 2.2
|-
| Full Spine || 20.6
|-
| Cervical || 3.6
|-
| Thoracic || 12.0
|-
| Lumbar || 5.0
|-
| Chest || 6.0
|-
| Chest/Abdo/Pelvis || 19.0
|-
| Abdo/Pelvis || 15.6
|-
| Knees || 0.16
|-
| Ankles || 0.14
|}

1Conference of Radiation Control Program Directors (CRCPD) Nationwide Evaluation of X-ray Trends (NEXT) 2005-2006 [https://crcpd.org/document/nationwide-evaluation-of-x-ray-trends-next-tabulation-and-graphical-summary-of-the-2005-2006-survey-of-computed-tomography/ report].

2CRCPD, Publication E-07-2, Tabulation and Graphical Summary of 2000 Survey of Computed Tomograph, (NEXT), August, 2007

3Biswas et al. Radiation Exposure from Musculoskeletal Computerized Tomographic Scans. The Journal of Bone and Joint Surgery, 2009.

Notes:

*Full Spine: From the base of the skull (C1) to the sacrum (through L5), effective dose of 20.6 mSv (adding up dose of all spine scans)

*Extended Chest/Abdo/Pelvis (or Full Spine + Abdo/Pelvis): From the base of the skull (C1) through the proximal femur. Effective dose of 25.2 mSv (cervical spine + chest + abdo/pelvis). Likely this is an overestimation.

Dose Length Product (DLP) of ARTININ scans is usually between 270 – 400 mGy-cm.

Converting between mGy-cm to effective dose (as described by the American Association of Physicists in Medicine (AAPM) Report No. 96):
E (mSv) = k × DLP
where <code>k</code> is the normalized effective dose per dose-length product for adults.

Estimated effective dose for ARTININ (as according to DLP):
E (mSv) = 0.015 × 400
E (mSv) = 6 mSv

Note that in the ARTININ consent we list 10 mSv, which is on the high end (which would be for a larger person).

Full spine (estimates of DLP taken from a few participants in the spinal cord injury group): 705 - 958. 55m mGy-cm

Note that DLP is over twice what is observed in ARTININ
E (mSv) = 0.015 × 958.55
E (mSv) = 14.5 mSv

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

==Calibration==
To ensure accurate material properties and comparability across clinical sites and scanners for quantitative analysis of bone derived from clinical CT scans, the native in-scan Hounsfield Units (HUs) must be converted to their corresponding bone equivalent densities.

There are three main types of calibration for CT scans. All of these methods are available in our GitHub repository called [https://github.com/Bonelab/Ogo Ogo].

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Phantom calibration===

Phantom calibration is the current imaging gold standard for converting HUs to bone densities. Phantom calibration involves placing a calibration phantom with known density values of either solid CHA or liquid K2HPO4 under the patient in the scan field of view, as seen here:

[[Image:phantom_rods_noseg.png|600px]]

The solid CHA or liquid K2HPO4 found in the phantom acts as the bone equivalent reference standard. Phantom calibration requires sampling the in-scan HUs of the bone equivalent reference rods (from the calibration phantom) and comparing those values to the known reference values. A simple linear regression between the known values within the calibration phantom rods and the in-scan HUs can be created to convert the HUs to bone equivalent density (BMD).

The calibration curve takes the form of
BMD = (HU⋅a) + b

where a is the slope of the resulting calibration curve and b is the intercept. This calibration curve is applied to specific bone compartments in the image or to the entire image, creating a bone-equivalent density image. The values of a and b depend on many factors, such as the composition of the X-ray spectrum emitted by the X-ray tube, tube current, reconstruction kernel or table height, and as a result are scanner and image protocol dependent.

To run phantom calibration in Ogo, you will need two things:
<ol>
<li>The raw CT scan (.nii or .nii.gz)</li>
<li>A segmentation mask of the phantom rods</li>
</ol>

Typically, this is done using ITKSnap or some other automated method [TBD], and you segment the inside of the rods, making sure to stop before reaching the edge of the rod to avoid partial volume effects.

An example of the phantom rods segmented:

[[Image:phantom_rods_seg.png|600px]]

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Asynchronous calibration===

This also uses a phantom, but not at the same time as the scan of the patient. Sometimes it can be months or even years away.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Internal calibration===

This doesn't use a phantom, but instead uses the internal tissues as referents.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

Opportunistic CT

2025-03-07T22:32:44Z

Bryn.Matheson: /* Calibration */

=Radiation Dose=

X-rays are a form of energy – like light and radio waves. X-rays are also called radiation. Unlike light waves, x-rays have enough energy to pass through your body. As the radiation moves through your body, it passes through bones, tissues, and organs differently. This allows a radiologist to create images of them. The radiologist is a specially trained doctor who can examine these images on a computer display. X-rays allow the radiologist to see the structures in your body in very fine detail.

==Dose Length Product==

Dose length product (DLP) is a measure of CT tube radiation output/exposure (measured in mGy.cm). It is related to volume CT dose index (CTDIvol), but CTDIvol represents the dose through a slice of an appropriate phantom. The dose length product accounts for the length of radiation output along the z-axis (the long axis of the patient). It may be described by the following equation:

DLP = (CTDIvol in mGy) . (length of scan in cm)

The dose length product does not take the size of the patient into account and is not a measure of absorbed dose. If the AP and lateral dimensions of the patient are available, then the size specific dose estimate (SSDE) can be used to estimate the absorbed dose.

==Effective Dose==

Some estimates of effective dose are summarized in the table below, taken from the cited sources.

{| class="wikitable"
|+ Estimates of Effective Dose1,2,3
|-
! Scan !! Effective Dose (mSv)
|-
| Head || 2.2
|-
| Full Spine || 20.6
|-
| Cervical || 3.6
|-
| Thoracic || 12.0
|-
| Lumbar || 5.0
|-
| Chest || 6.0
|-
| Chest/Abdo/Pelvis || 19.0
|-
| Abdo/Pelvis || 15.6
|-
| Knees || 0.16
|-
| Ankles || 0.14
|}

1Conference of Radiation Control Program Directors (CRCPD) Nationwide Evaluation of X-ray Trends (NEXT) 2005-2006 [https://crcpd.org/document/nationwide-evaluation-of-x-ray-trends-next-tabulation-and-graphical-summary-of-the-2005-2006-survey-of-computed-tomography/ report].

2CRCPD, Publication E-07-2, Tabulation and Graphical Summary of 2000 Survey of Computed Tomograph, (NEXT), August, 2007

3Biswas et al. Radiation Exposure from Musculoskeletal Computerized Tomographic Scans. The Journal of Bone and Joint Surgery, 2009.

Notes:

*Full Spine: From the base of the skull (C1) to the sacrum (through L5), effective dose of 20.6 mSv (adding up dose of all spine scans)

*Extended Chest/Abdo/Pelvis (or Full Spine + Abdo/Pelvis): From the base of the skull (C1) through the proximal femur. Effective dose of 25.2 mSv (cervical spine + chest + abdo/pelvis). Likely this is an overestimation.

Dose Length Product (DLP) of ARTININ scans is usually between 270 – 400 mGy-cm.

Converting between mGy-cm to effective dose (as described by the American Association of Physicists in Medicine (AAPM) Report No. 96):
E (mSv) = k × DLP
where <code>k</code> is the normalized effective dose per dose-length product for adults.

Estimated effective dose for ARTININ (as according to DLP):
E (mSv) = 0.015 × 400
E (mSv) = 6 mSv

Note that in the ARTININ consent we list 10 mSv, which is on the high end (which would be for a larger person).

Full spine (estimates of DLP taken from a few participants in the spinal cord injury group): 705 - 958. 55m mGy-cm

Note that DLP is over twice what is observed in ARTININ
E (mSv) = 0.015 × 958.55
E (mSv) = 14.5 mSv

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

==Calibration==
To ensure accurate material properties and comparability across clinical sites and scanners for quantitative analysis of bone derived from clinical CT scans, the native in-scan Hounsfield Units (HUs) must be converted to their corresponding bone equivalent densities.

There are three main types of calibration for CT scans. All of these methods are available in our GitHub repository called [https://github.com/Bonelab/Ogo Ogo].

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Phantom calibration===

Phantom calibration is the current imaging gold standard for converting HUs to bone densities. Phantom calibration involves placing a calibration phantom with known density values of either solid CHA or liquid K2HPO4 under the patient in the scan field of view, as seen here:

[[Image:phantom_rods_noseg.png|600px]]

The solid CHA or liquid K2HPO4 found in the phantom acts as the bone equivalent reference standard. Phantom calibration requires sampling the in-scan HUs of the bone equivalent reference rods (from the calibration phantom) and comparing those values to the known reference values. A simple linear regression between the known values within the calibration phantom rods and the in-scan HUs can be created to convert the HUs to bone equivalent density (BMD).

The calibration curve takes the form of
BMD = (HU⋅a) + b

where a is the slope of the resulting calibration curve and b is the intercept. This calibration curve is applied to specific bone compartments in the image or to the entire image, creating a bone-equivalent density image. The values of a and b depend on many factors, such as the composition of the X-ray spectrum emitted by the X-ray tube, tube current, reconstruction kernel or table height, and as a result are scanner and image protocol dependent.

To run phantom calibration in Ogo, you will need two things:
1. The raw CT scan (.nii or .nii.gz)
2. A segmentation mask of the phantom rods. Typically, this is done using ITKSnap or some other automated method [TBD], and you segment the inside of
the rods, making sure to stop before reaching the edge of the rod to avoid partial volume effects.

An example of the phantom rods segmented:

[[Image:phantom_rods_seg.png|600px]]

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Asynchronous calibration===

This also uses a phantom, but not at the same time as the scan of the patient. Sometimes it can be months or even years away.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Internal calibration===

This doesn't use a phantom, but instead uses the internal tissues as referents.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

Opportunistic CT

2025-03-07T22:31:01Z

Bryn.Matheson: /* Phantom calibration */

=Radiation Dose=

X-rays are a form of energy – like light and radio waves. X-rays are also called radiation. Unlike light waves, x-rays have enough energy to pass through your body. As the radiation moves through your body, it passes through bones, tissues, and organs differently. This allows a radiologist to create images of them. The radiologist is a specially trained doctor who can examine these images on a computer display. X-rays allow the radiologist to see the structures in your body in very fine detail.

==Dose Length Product==

Dose length product (DLP) is a measure of CT tube radiation output/exposure (measured in mGy.cm). It is related to volume CT dose index (CTDIvol), but CTDIvol represents the dose through a slice of an appropriate phantom. The dose length product accounts for the length of radiation output along the z-axis (the long axis of the patient). It may be described by the following equation:

DLP = (CTDIvol in mGy) . (length of scan in cm)

The dose length product does not take the size of the patient into account and is not a measure of absorbed dose. If the AP and lateral dimensions of the patient are available, then the size specific dose estimate (SSDE) can be used to estimate the absorbed dose.

==Effective Dose==

Some estimates of effective dose are summarized in the table below, taken from the cited sources.

{| class="wikitable"
|+ Estimates of Effective Dose1,2,3
|-
! Scan !! Effective Dose (mSv)
|-
| Head || 2.2
|-
| Full Spine || 20.6
|-
| Cervical || 3.6
|-
| Thoracic || 12.0
|-
| Lumbar || 5.0
|-
| Chest || 6.0
|-
| Chest/Abdo/Pelvis || 19.0
|-
| Abdo/Pelvis || 15.6
|-
| Knees || 0.16
|-
| Ankles || 0.14
|}

1Conference of Radiation Control Program Directors (CRCPD) Nationwide Evaluation of X-ray Trends (NEXT) 2005-2006 [https://crcpd.org/document/nationwide-evaluation-of-x-ray-trends-next-tabulation-and-graphical-summary-of-the-2005-2006-survey-of-computed-tomography/ report].

2CRCPD, Publication E-07-2, Tabulation and Graphical Summary of 2000 Survey of Computed Tomograph, (NEXT), August, 2007

3Biswas et al. Radiation Exposure from Musculoskeletal Computerized Tomographic Scans. The Journal of Bone and Joint Surgery, 2009.

Notes:

*Full Spine: From the base of the skull (C1) to the sacrum (through L5), effective dose of 20.6 mSv (adding up dose of all spine scans)

*Extended Chest/Abdo/Pelvis (or Full Spine + Abdo/Pelvis): From the base of the skull (C1) through the proximal femur. Effective dose of 25.2 mSv (cervical spine + chest + abdo/pelvis). Likely this is an overestimation.

Dose Length Product (DLP) of ARTININ scans is usually between 270 – 400 mGy-cm.

Converting between mGy-cm to effective dose (as described by the American Association of Physicists in Medicine (AAPM) Report No. 96):
E (mSv) = k × DLP
where <code>k</code> is the normalized effective dose per dose-length product for adults.

Estimated effective dose for ARTININ (as according to DLP):
E (mSv) = 0.015 × 400
E (mSv) = 6 mSv

Note that in the ARTININ consent we list 10 mSv, which is on the high end (which would be for a larger person).

Full spine (estimates of DLP taken from a few participants in the spinal cord injury group): 705 - 958. 55m mGy-cm

Note that DLP is over twice what is observed in ARTININ
E (mSv) = 0.015 × 958.55
E (mSv) = 14.5 mSv

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

==Calibration==
To ensure accurate material properties and comparability across clinical sites and scanners for quantitative analysis of bone derived from clinical CT scans, the native in-scan Hounsfield Units (HUs) must be converted to their corresponding bone equivalent densities.

There are three main types of calibration for CT scans. All of these methods are available in our GitHub repository called [https://github.com/Bonelab/Ogo Ogo].

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Phantom calibration===

Phantom calibration is the current imaging gold standard for converting HUs to bone densities. Phantom calibration involves placing a calibration phantom with known density values of either solid CHA or liquid K2HPO4 under the patient in the scan field of view, as seen here:

[[Image:phantom_rods_noseg.png|600px]]

The solid CHA or liquid K2HPO4 found in the phantom acts as the bone equivalent reference standard. Phantom calibration requires sampling the in-scan HUs of the bone equivalent reference rods (from the calibration phantom) and comparing those values to the known reference values. A simple linear regression between the known values within the calibration phantom rods and the in-scan HUs can be created to convert the HUs to bone equivalent density (BMD).

The calibration curve takes the form of
BMD = (HU⋅a) + b

where a is the slope of the resulting calibration curve and b is the intercept. This calibration curve is applied to specific bone compartments in the image or to the entire image, creating a bone-equivalent density image. The values of a and b depend on many factors, such as the composition of the X-ray spectrum emitted by the X-ray tube, tube current, reconstruction kernel or table height, and as a result are scanner and image protocol dependent.

To run phantom calibration in Ogo, you will need two things:
1. The raw CT scan (.nii or .nii.gz)
2. A segmentation mask of the phantom rods. Typically, this is done using ITKSnap or some other automated method [TBD], and you segment the inside of the rods, making sure to stop before reaching the edge of the rod to avoid partial volume effects.

An example of the phantom rods segmented:

[[Image:phantom_rods_seg.png|600px]]

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Asynchronous calibration===

This also uses a phantom, but not at the same time as the scan of the patient. Sometimes it can be months or even years away.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Internal calibration===

This doesn't use a phantom, but instead uses the internal tissues as referents.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

Opportunistic CT

2025-03-07T22:27:43Z

Bryn.Matheson: /* Phantom calibration */

=Radiation Dose=

X-rays are a form of energy – like light and radio waves. X-rays are also called radiation. Unlike light waves, x-rays have enough energy to pass through your body. As the radiation moves through your body, it passes through bones, tissues, and organs differently. This allows a radiologist to create images of them. The radiologist is a specially trained doctor who can examine these images on a computer display. X-rays allow the radiologist to see the structures in your body in very fine detail.

==Dose Length Product==

Dose length product (DLP) is a measure of CT tube radiation output/exposure (measured in mGy.cm). It is related to volume CT dose index (CTDIvol), but CTDIvol represents the dose through a slice of an appropriate phantom. The dose length product accounts for the length of radiation output along the z-axis (the long axis of the patient). It may be described by the following equation:

DLP = (CTDIvol in mGy) . (length of scan in cm)

The dose length product does not take the size of the patient into account and is not a measure of absorbed dose. If the AP and lateral dimensions of the patient are available, then the size specific dose estimate (SSDE) can be used to estimate the absorbed dose.

==Effective Dose==

Some estimates of effective dose are summarized in the table below, taken from the cited sources.

{| class="wikitable"
|+ Estimates of Effective Dose1,2,3
|-
! Scan !! Effective Dose (mSv)
|-
| Head || 2.2
|-
| Full Spine || 20.6
|-
| Cervical || 3.6
|-
| Thoracic || 12.0
|-
| Lumbar || 5.0
|-
| Chest || 6.0
|-
| Chest/Abdo/Pelvis || 19.0
|-
| Abdo/Pelvis || 15.6
|-
| Knees || 0.16
|-
| Ankles || 0.14
|}

1Conference of Radiation Control Program Directors (CRCPD) Nationwide Evaluation of X-ray Trends (NEXT) 2005-2006 [https://crcpd.org/document/nationwide-evaluation-of-x-ray-trends-next-tabulation-and-graphical-summary-of-the-2005-2006-survey-of-computed-tomography/ report].

2CRCPD, Publication E-07-2, Tabulation and Graphical Summary of 2000 Survey of Computed Tomograph, (NEXT), August, 2007

3Biswas et al. Radiation Exposure from Musculoskeletal Computerized Tomographic Scans. The Journal of Bone and Joint Surgery, 2009.

Notes:

*Full Spine: From the base of the skull (C1) to the sacrum (through L5), effective dose of 20.6 mSv (adding up dose of all spine scans)

*Extended Chest/Abdo/Pelvis (or Full Spine + Abdo/Pelvis): From the base of the skull (C1) through the proximal femur. Effective dose of 25.2 mSv (cervical spine + chest + abdo/pelvis). Likely this is an overestimation.

Dose Length Product (DLP) of ARTININ scans is usually between 270 – 400 mGy-cm.

Converting between mGy-cm to effective dose (as described by the American Association of Physicists in Medicine (AAPM) Report No. 96):
E (mSv) = k × DLP
where <code>k</code> is the normalized effective dose per dose-length product for adults.

Estimated effective dose for ARTININ (as according to DLP):
E (mSv) = 0.015 × 400
E (mSv) = 6 mSv

Note that in the ARTININ consent we list 10 mSv, which is on the high end (which would be for a larger person).

Full spine (estimates of DLP taken from a few participants in the spinal cord injury group): 705 - 958. 55m mGy-cm

Note that DLP is over twice what is observed in ARTININ
E (mSv) = 0.015 × 958.55
E (mSv) = 14.5 mSv

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

==Calibration==
To ensure accurate material properties and comparability across clinical sites and scanners for quantitative analysis of bone derived from clinical CT scans, the native in-scan Hounsfield Units (HUs) must be converted to their corresponding bone equivalent densities.

There are three main types of calibration for CT scans. All of these methods are available in our GitHub repository called [https://github.com/Bonelab/Ogo Ogo].

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Phantom calibration===

Phantom calibration is the current imaging gold standard for converting HUs to bone densities. Phantom calibration involves placing a calibration phantom with known density values of either solid CHA or liquid K2HPO4 under the patient in the scan field of view, as seen below.

[[Image:phantom_rods_noseg.png|600px]]

The solid CHA or liquid K2HPO4 found in the phantom acts as the bone equivalent reference standard. Phantom calibration requires sampling the in-scan HUs of the bone equivalent reference rods (from the calibration phantom) and comparing those values to the known reference values. A simple linear regression between the known values within the calibration phantom rods and the in-scan HUs can be created to convert the HUs to bone equivalent density (BMD).

The calibration curve takes the form of
BMD = (HU⋅a) + b

where a is the slope of the resulting calibration curve and b is the intercept. This calibration curve is applied to specific bone compartments in the image or to the entire image, creating a bone-equivalent density image. The values of a and b depend on many factors, such as the composition of the X-ray spectrum emitted by the X-ray tube, tube current, reconstruction kernel or table height, and as a result are scanner and image protocol dependent.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Asynchronous calibration===

This also uses a phantom, but not at the same time as the scan of the patient. Sometimes it can be months or even years away.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Internal calibration===

This doesn't use a phantom, but instead uses the internal tissues as referents.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

File:Phantom rods seg.png

2025-03-07T22:24:58Z

Bryn.Matheson: Example of phantom calibration with segmentation overlayed

Example of phantom calibration with segmentation overlayed

File:Phantom rods noseg.png

2025-03-07T22:24:25Z

Bryn.Matheson: Example of phantom calibration

Example of phantom calibration

Opportunistic CT

2025-03-07T22:07:58Z

Bryn.Matheson: /* Calibration */

=Radiation Dose=

X-rays are a form of energy – like light and radio waves. X-rays are also called radiation. Unlike light waves, x-rays have enough energy to pass through your body. As the radiation moves through your body, it passes through bones, tissues, and organs differently. This allows a radiologist to create images of them. The radiologist is a specially trained doctor who can examine these images on a computer display. X-rays allow the radiologist to see the structures in your body in very fine detail.

==Dose Length Product==

Dose length product (DLP) is a measure of CT tube radiation output/exposure (measured in mGy.cm). It is related to volume CT dose index (CTDIvol), but CTDIvol represents the dose through a slice of an appropriate phantom. The dose length product accounts for the length of radiation output along the z-axis (the long axis of the patient). It may be described by the following equation:

DLP = (CTDIvol in mGy) . (length of scan in cm)

The dose length product does not take the size of the patient into account and is not a measure of absorbed dose. If the AP and lateral dimensions of the patient are available, then the size specific dose estimate (SSDE) can be used to estimate the absorbed dose.

==Effective Dose==

Some estimates of effective dose are summarized in the table below, taken from the cited sources.

{| class="wikitable"
|+ Estimates of Effective Dose1,2,3
|-
! Scan !! Effective Dose (mSv)
|-
| Head || 2.2
|-
| Full Spine || 20.6
|-
| Cervical || 3.6
|-
| Thoracic || 12.0
|-
| Lumbar || 5.0
|-
| Chest || 6.0
|-
| Chest/Abdo/Pelvis || 19.0
|-
| Abdo/Pelvis || 15.6
|-
| Knees || 0.16
|-
| Ankles || 0.14
|}

1Conference of Radiation Control Program Directors (CRCPD) Nationwide Evaluation of X-ray Trends (NEXT) 2005-2006 [https://crcpd.org/document/nationwide-evaluation-of-x-ray-trends-next-tabulation-and-graphical-summary-of-the-2005-2006-survey-of-computed-tomography/ report].

2CRCPD, Publication E-07-2, Tabulation and Graphical Summary of 2000 Survey of Computed Tomograph, (NEXT), August, 2007

3Biswas et al. Radiation Exposure from Musculoskeletal Computerized Tomographic Scans. The Journal of Bone and Joint Surgery, 2009.

Notes:

*Full Spine: From the base of the skull (C1) to the sacrum (through L5), effective dose of 20.6 mSv (adding up dose of all spine scans)

*Extended Chest/Abdo/Pelvis (or Full Spine + Abdo/Pelvis): From the base of the skull (C1) through the proximal femur. Effective dose of 25.2 mSv (cervical spine + chest + abdo/pelvis). Likely this is an overestimation.

Dose Length Product (DLP) of ARTININ scans is usually between 270 – 400 mGy-cm.

Converting between mGy-cm to effective dose (as described by the American Association of Physicists in Medicine (AAPM) Report No. 96):
E (mSv) = k × DLP
where <code>k</code> is the normalized effective dose per dose-length product for adults.

Estimated effective dose for ARTININ (as according to DLP):
E (mSv) = 0.015 × 400
E (mSv) = 6 mSv

Note that in the ARTININ consent we list 10 mSv, which is on the high end (which would be for a larger person).

Full spine (estimates of DLP taken from a few participants in the spinal cord injury group): 705 - 958. 55m mGy-cm

Note that DLP is over twice what is observed in ARTININ
E (mSv) = 0.015 × 958.55
E (mSv) = 14.5 mSv

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

==Calibration==
To ensure accurate material properties and comparability across clinical sites and scanners for quantitative analysis of bone derived from clinical CT scans, the native in-scan Hounsfield Units (HUs) must be converted to their corresponding bone equivalent densities.

There are three main types of calibration for CT scans. All of these methods are available in our GitHub repository called [https://github.com/Bonelab/Ogo Ogo].

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Phantom calibration===

Phantom calibration is the current imaging gold standard for converting HUs to bone densities. Phantom calibration involves placing a calibration phantom with known density values of either solid CHA or liquid K2HPO4 under the patient in the scan field of view, as seen below.

The solid CHA or liquid K2HPO4 found in the phantom acts as the bone equivalent reference standard. Phantom calibration requires sampling the in-scan HUs of the bone equivalent reference rods (from the calibration phantom) and comparing those values to the known reference values. A simple linear regression between the known values within the calibration phantom rods and the in-scan HUs can be created to convert the HUs to bone equivalent density (BMD).

The calibration curve takes the form of
BMD = (HU⋅a) + b

where a is the slope of the resulting calibration curve and b is the intercept. This calibration curve is applied to specific bone compartments in the image or to the entire image, creating a bone-equivalent density image. The values of a and b depend on many factors, such as the composition of the X-ray spectrum emitted by the X-ray tube, tube current, reconstruction kernel or table height, and as a result are scanner and image protocol dependent.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Asynchronous calibration===

This also uses a phantom, but not at the same time as the scan of the patient. Sometimes it can be months or even years away.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Internal calibration===

This doesn't use a phantom, but instead uses the internal tissues as referents.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

Opportunistic CT

2025-03-07T22:07:46Z

Bryn.Matheson: /* Calibration */

=Radiation Dose=

X-rays are a form of energy – like light and radio waves. X-rays are also called radiation. Unlike light waves, x-rays have enough energy to pass through your body. As the radiation moves through your body, it passes through bones, tissues, and organs differently. This allows a radiologist to create images of them. The radiologist is a specially trained doctor who can examine these images on a computer display. X-rays allow the radiologist to see the structures in your body in very fine detail.

==Dose Length Product==

Dose length product (DLP) is a measure of CT tube radiation output/exposure (measured in mGy.cm). It is related to volume CT dose index (CTDIvol), but CTDIvol represents the dose through a slice of an appropriate phantom. The dose length product accounts for the length of radiation output along the z-axis (the long axis of the patient). It may be described by the following equation:

DLP = (CTDIvol in mGy) . (length of scan in cm)

The dose length product does not take the size of the patient into account and is not a measure of absorbed dose. If the AP and lateral dimensions of the patient are available, then the size specific dose estimate (SSDE) can be used to estimate the absorbed dose.

==Effective Dose==

Some estimates of effective dose are summarized in the table below, taken from the cited sources.

{| class="wikitable"
|+ Estimates of Effective Dose1,2,3
|-
! Scan !! Effective Dose (mSv)
|-
| Head || 2.2
|-
| Full Spine || 20.6
|-
| Cervical || 3.6
|-
| Thoracic || 12.0
|-
| Lumbar || 5.0
|-
| Chest || 6.0
|-
| Chest/Abdo/Pelvis || 19.0
|-
| Abdo/Pelvis || 15.6
|-
| Knees || 0.16
|-
| Ankles || 0.14
|}

1Conference of Radiation Control Program Directors (CRCPD) Nationwide Evaluation of X-ray Trends (NEXT) 2005-2006 [https://crcpd.org/document/nationwide-evaluation-of-x-ray-trends-next-tabulation-and-graphical-summary-of-the-2005-2006-survey-of-computed-tomography/ report].

2CRCPD, Publication E-07-2, Tabulation and Graphical Summary of 2000 Survey of Computed Tomograph, (NEXT), August, 2007

3Biswas et al. Radiation Exposure from Musculoskeletal Computerized Tomographic Scans. The Journal of Bone and Joint Surgery, 2009.

Notes:

*Full Spine: From the base of the skull (C1) to the sacrum (through L5), effective dose of 20.6 mSv (adding up dose of all spine scans)

*Extended Chest/Abdo/Pelvis (or Full Spine + Abdo/Pelvis): From the base of the skull (C1) through the proximal femur. Effective dose of 25.2 mSv (cervical spine + chest + abdo/pelvis). Likely this is an overestimation.

Dose Length Product (DLP) of ARTININ scans is usually between 270 – 400 mGy-cm.

Converting between mGy-cm to effective dose (as described by the American Association of Physicists in Medicine (AAPM) Report No. 96):
E (mSv) = k × DLP
where <code>k</code> is the normalized effective dose per dose-length product for adults.

Estimated effective dose for ARTININ (as according to DLP):
E (mSv) = 0.015 × 400
E (mSv) = 6 mSv

Note that in the ARTININ consent we list 10 mSv, which is on the high end (which would be for a larger person).

Full spine (estimates of DLP taken from a few participants in the spinal cord injury group): 705 - 958. 55m mGy-cm

Note that DLP is over twice what is observed in ARTININ
E (mSv) = 0.015 × 958.55
E (mSv) = 14.5 mSv

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

==Calibration==
To ensure accurate material properties and comparability across clinical sites and scanners for quantitative analysis of bone derived from clinical CT scans, the native in-scan Hounsfield Units (HUs) must be converted to their corresponding bone equivalent densities.

There are three main types of calibration for CT scans. All of these methods are available in our GitHub repository called [https://github.com/Bonelab/Ogo Ogo].

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Phantom calibration===

Phantom calibration is the current imaging gold standard for converting HUs to bone densities. Phantom calibration involves placing a calibration phantom with known density values of either solid CHA or liquid K2HPO4 under the patient in the scan field of view, as seen below.

The solid CHA or liquid K2HPO4 found in the phantom acts as the bone equivalent reference standard. Phantom calibration requires sampling the in-scan HUs of the bone equivalent reference rods (from the calibration phantom) and comparing those values to the known reference values. A simple linear regression between the known values within the calibration phantom rods and the in-scan HUs can be created to convert the HUs to bone equivalent density (BMD).

The calibration curve takes the form of
BMD = (HU⋅a) + b

where a is the slope of the resulting calibration curve and b is the intercept. This calibration curve is applied to specific bone compartments in the image or to the entire image, creating a bone-equivalent density image. The values of a and b depend on many factors, such as the composition of the X-ray spectrum emitted by the X-ray tube, tube current, reconstruction kernel or table height, and as a result are scanner and image protocol dependent.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Asynchronous calibration===

This also uses a phantom, but not at the same time as the scan of the patient. Sometimes it can be months or even years away.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Internal calibration===

This doesn't use a phantom, but instead uses the internal tissues as referents.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

Opportunistic CT

2025-03-07T22:06:08Z

Bryn.Matheson: /* Phantom calibration */

=Radiation Dose=

X-rays are a form of energy – like light and radio waves. X-rays are also called radiation. Unlike light waves, x-rays have enough energy to pass through your body. As the radiation moves through your body, it passes through bones, tissues, and organs differently. This allows a radiologist to create images of them. The radiologist is a specially trained doctor who can examine these images on a computer display. X-rays allow the radiologist to see the structures in your body in very fine detail.

==Dose Length Product==

Dose length product (DLP) is a measure of CT tube radiation output/exposure (measured in mGy.cm). It is related to volume CT dose index (CTDIvol), but CTDIvol represents the dose through a slice of an appropriate phantom. The dose length product accounts for the length of radiation output along the z-axis (the long axis of the patient). It may be described by the following equation:

DLP = (CTDIvol in mGy) . (length of scan in cm)

The dose length product does not take the size of the patient into account and is not a measure of absorbed dose. If the AP and lateral dimensions of the patient are available, then the size specific dose estimate (SSDE) can be used to estimate the absorbed dose.

==Effective Dose==

Some estimates of effective dose are summarized in the table below, taken from the cited sources.

{| class="wikitable"
|+ Estimates of Effective Dose1,2,3
|-
! Scan !! Effective Dose (mSv)
|-
| Head || 2.2
|-
| Full Spine || 20.6
|-
| Cervical || 3.6
|-
| Thoracic || 12.0
|-
| Lumbar || 5.0
|-
| Chest || 6.0
|-
| Chest/Abdo/Pelvis || 19.0
|-
| Abdo/Pelvis || 15.6
|-
| Knees || 0.16
|-
| Ankles || 0.14
|}

1Conference of Radiation Control Program Directors (CRCPD) Nationwide Evaluation of X-ray Trends (NEXT) 2005-2006 [https://crcpd.org/document/nationwide-evaluation-of-x-ray-trends-next-tabulation-and-graphical-summary-of-the-2005-2006-survey-of-computed-tomography/ report].

2CRCPD, Publication E-07-2, Tabulation and Graphical Summary of 2000 Survey of Computed Tomograph, (NEXT), August, 2007

3Biswas et al. Radiation Exposure from Musculoskeletal Computerized Tomographic Scans. The Journal of Bone and Joint Surgery, 2009.

Notes:

*Full Spine: From the base of the skull (C1) to the sacrum (through L5), effective dose of 20.6 mSv (adding up dose of all spine scans)

*Extended Chest/Abdo/Pelvis (or Full Spine + Abdo/Pelvis): From the base of the skull (C1) through the proximal femur. Effective dose of 25.2 mSv (cervical spine + chest + abdo/pelvis). Likely this is an overestimation.

Dose Length Product (DLP) of ARTININ scans is usually between 270 – 400 mGy-cm.

Converting between mGy-cm to effective dose (as described by the American Association of Physicists in Medicine (AAPM) Report No. 96):
E (mSv) = k × DLP
where <code>k</code> is the normalized effective dose per dose-length product for adults.

Estimated effective dose for ARTININ (as according to DLP):
E (mSv) = 0.015 × 400
E (mSv) = 6 mSv

Note that in the ARTININ consent we list 10 mSv, which is on the high end (which would be for a larger person).

Full spine (estimates of DLP taken from a few participants in the spinal cord injury group): 705 - 958. 55m mGy-cm

Note that DLP is over twice what is observed in ARTININ
E (mSv) = 0.015 × 958.55
E (mSv) = 14.5 mSv

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

==Calibration==

There are three main types of calibration for CT scans. All of these methods are available in our GitHub repository called [https://github.com/Bonelab/Ogo Ogo].

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Phantom calibration===

Phantom calibration is the current imaging gold standard for converting Hounsfield Units (HUs) to bone densities. Phantom calibration involves placing a calibration phantom with known density values of either solid CHA or liquid K2HPO4 under the patient in the scan field of view, as seen below.

The solid CHA or liquid K2HPO4 found in the phantom acts as the bone equivalent reference standard. Phantom calibration requires sampling the in-scan HUs of the bone equivalent reference rods (from the calibration phantom) and comparing those values to the known reference values. A simple linear regression between the known values within the calibration phantom rods and the in-scan HUs can be created to convert the HUs to bone equivalent density (BMD).

The calibration curve takes the form of
BMD = (HU⋅a) + b

where a is the slope of the resulting calibration curve and b is the intercept. This calibration curve is applied to specific bone compartments in the image or to the entire image, creating a bone-equivalent density image. The values of a and b depend on many factors, such as the composition of the X-ray spectrum emitted by the X-ray tube, tube current, reconstruction kernel or table height, and as a result are scanner and image protocol dependent.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Asynchronous calibration===

This also uses a phantom, but not at the same time as the scan of the patient. Sometimes it can be months or even years away.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

===Internal calibration===

This doesn't use a phantom, but instead uses the internal tissues as referents.

[[Image:Redirect.jpg|15px]] [[#top|''Return to Contents'']] or [[Main_Page|''Return to Main Page'']]

Opportunistic CT

2025-03-07T22:04:59Z

Bryn.Matheson: /* Phantom calibration */

=Radiation Dose=

X-rays are a form of energy – like light and radio waves. X-rays are also called radiation. Unlike light waves, x-rays have enough energy to pass through your body. As the radiation moves through your body, it passes through bones, tissues, and organs differently. This allows a radiologist to create images of them. The radiologist is a specially trained doctor who can examine these images on a computer display. X-rays allow the radiologist to see the structures in your body in very fine detail.

==Dose Length Product==

Dose length product (DLP) is a measure of CT tube radiation output/exposure (measured in mGy.cm). It is related to volume CT dose index (CTDIvol), but CTDIvol represents the dose through a slice of an appropriate phantom. The dose length product accounts for the length of radiation output along the z-axis (the long axis of the patient). It may be described by the following equation:

DLP = (CTDIvol in mGy) . (length of scan in cm)

The dose length product does not take the size of the patient into account and is not a measure of absorbed dose. If the AP and lateral dimensions of the patient are available, then the size specific dose estimate (SSDE) can be used to estimate the absorbed dose.

==Effective Dose==

Some estimates of effective dose are summarized in the table below, taken from the cited sources.

{| class="wikitable"
|+ Estimates of Effective Dose1,2,3
|-
! Scan !! Effective Dose (mSv)
|-
| Head || 2.2
|-
| Full Spine || 20.6
|-
| Cervical || 3.6
|-
| Thoracic || 12.0
|-
| Lumbar || 5.0
|-
| Chest || 6.0
|-
| Chest/Abdo/Pelvis || 19.0
|-
| Abdo/Pelvis || 15.6
|-
| Knees || 0.16
|-
| Ankles || 0.14
|}

1Conference of Radiation Control Program Directors (CRCPD) Nationwide Evaluation of X-ray Trends (NEXT) 2005-2006 [https://crcpd.org/document/nationwide-evaluation-of-x-ray-trends-next-tabulation-and-graphical-summary-of-the-2005-2006-survey-of-computed-tomography/ report].

2CRCPD, Publication E-07-2, Tabulation and Graphical Summary of 2000 Survey of Computed Tomograph, (NEXT), August, 2007

3Biswas et al. Radiation Exposure from Musculoskeletal Computerized Tomographic Scans. The Journal of Bone and Joint Surgery, 2009.

Notes:

*Full Spine: From the base of the skull (C1) to the sacrum (through L5), effective dose of 20.6 mSv (adding up dose of all spine scans)

*Extended Chest/Abdo/Pelvis (or Full Spine + Abdo/Pelvis): From the base of the skull (C1) through the proximal femur. Effective dose of 25.2 mSv (cervical spine + chest + abdo/pelvis). Likely this is an overestimation.

Dose Length Product (DLP) of ARTININ scans is usually between 270 – 400 mGy-cm.

Converting between mGy-cm to effective dose (as described by the American Association of Physicists in Medicine (AAPM) Report No. 96):
E (mSv) = k × DLP
where <code>k</code> is the normalized effective dose per dose-length product for adults.

Estimated effective dose for ARTININ (as according to DLP):
E (mSv) = 0.015 × 400
E (mSv) = 6 mSv

Note that in the ARTININ consent we list 10 mSv, which is on the high end (which would be for a larger person).

Full spine (estimates of DLP taken from a few participants in the spinal cord injury group): 705 - 958. 55m mGy-cm

Note that DLP is over twice what is observed in ARTININ
E (mSv) = 0.015 × 958.55
E (mSv) = 14.5 mSv

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==Calibration==

There are three main types of calibration for CT scans. All of these methods are available in our GitHub repository called [https://github.com/Bonelab/Ogo Ogo].

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===Phantom calibration===

Phantom calibration is the current imaging gold standard for converting Hounsfield Units (HUs) to bone densities. Phantom calibration involves placing a calibration phantom with known density values of either solid CHA or liquid K2HPO4under the patient in the scan field of view, as seen below.

The solid CHA or liquid K2HPO4 found in the phantom acts as the bone equivalent reference standard. Phantom calibration requires sampling the in-scan HUs of the bone equivalent reference rods (from the calibration phantom) and comparing those values to the known reference values. A simple linear regression between the known values within the calibration phantom rods and the in-scan HUs can be created to convert the HUs to bone equivalent density (BMD).

The calibration curve takes the form of
BMD = (HU⋅a) + b

where a is the slope of the resulting calibration curve and b is the intercept. This calibration curve is applied to specific bone compartments in the image or to the entire image, creating a bone-equivalent density image. The values of a and b depend on many factors, such as the composition of the X-ray spectrum emitted by the X-ray tube, tube current, reconstruction kernel or table height, and as a result are scanner and image protocol dependent.

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===Asynchronous calibration===

This also uses a phantom, but not at the same time as the scan of the patient. Sometimes it can be months or even years away.

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===Internal calibration===

This doesn't use a phantom, but instead uses the internal tissues as referents.

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Opportunistic CT

2025-03-03T17:12:57Z

Bryn.Matheson: /* Asynchronous calibration */

Opportunistic CT

2025-03-03T17:12:46Z

Bryn.Matheson: /* Asynchronous calibration */

Opportunistic CT

2025-03-03T17:12:02Z

Bryn.Matheson: /* Asynchronous calibration */

Opportunistic CT

2025-03-03T17:11:09Z

Bryn.Matheson: /* Asynchronous calibration */

Opportunistic CT

2025-03-03T17:10:39Z

Bryn.Matheson: /* Calibration */