Computed Tomography, Radiation Dosage
Conditions
Keywords
Computed tomography, Radiation dose, Dose reduction, Breast displacement, Chrysalis device, Image quality
Brief summary
The primary hypothesis of this study is that breast displacement out of the direct plane of imaging during computed tomography (CT) of the abdomen will reduce effective radiation dose to the female breast. Secondary hypotheses are that image noise and artifacts will also be decreased.
Detailed description
Computed tomography (CT) is a significant source of medical-related radiation, and radiation-related cancer risk is increasingly recognized in the medical and lay community. One of the groups at greatest risk for radiation-induced malignancies is young females due to the radiosensitivity of female breast tissue. Breast tissue frequently lies within the imaging plane for CT of the abdomen with limited gain in diagnostic information. We propose displacing this breast tissue out of the direct imaging plane will decrease unnecessary radiation exposure and may also indirectly improve image quality. A device called Chrysalis has been designed and received FDA approval for the purposes of displacing female breast tissue during CT.
Interventions
DEVICEChrysalis breast displacement device
Chrysalis is a cloth device secured with velcro and buckles around the upper abdomen and chest following manual cephalad breast displacement.
Sponsors
University of Washington
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
SUPPORTIVE_CARE
Masking
NONE
Eligibility
Sex/Gender
FEMALE
Age
18 Years to 60 Years
Healthy volunteers
No
Inclusion criteria
* scheduled for CT of the abdomen and pelvis at Harborview Medical Center * able to provide written informed consent
Exclusion criteria
* Inability to provide written consent for self (minor, intubated, sedated, mentally incapacitated, in excessive physical distress) * Chest or breast surgery within the previous 8 weeks * Breast implants * Open wounds to the chest wall * Fractures of the ribs or spine within the previous 3 months * Patients requiring oxygen therapy * Mastectomy * Breast radiation therapy * Scarring to the breasts which would prevent displacement * Claustrophobia is not an absolute exclusion criterion, but patient comfort will be a primary concern.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Skin Entrance Radiation Dose During Computed Tomography (CT) | from time potential subject approached about possible enrollment to time device and TLDs were removed, on average 1 hour | Skin entrance radiation doses will be measured with Thermoluminescent dosimeters (TLDs) affixed to the subject's chest and breast during CT of the abdomen. TLD #1 is at the inframammary fold, serving as internal control for each subject. Three additional TLDs (#2-4) are affixed to the subject's breast at 3 pre-ascribed locations. The same is done for the right and left breasts (8 TLDs total). TLDs will then be submitted to Landaeur for measurement. |
| Relative Skin Entrance Radiation Dose in % During Computed Tomography (CT) | from time potential subject approached about possible enrollment to time device and TLDs were removed, on average 1 hour | Relative skin entrance dose at the breast (group mean of patient's average skin entrance dose at TLDs 2-4) divided by skin entrance dose at the inframammary TLD (TLD 1) in %. For each patient, doses at TLDs 2-4 were averaged, and then the group mean of this was divided by the group mean at the inframammary TLD, then multiplied by 100 to get % dose. A relative dose of 20% means that the skin entrance dose at the breast was 20% of the skin entrance dose at the inframammary fold. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| CT Image Noise | two months | To evaluate image noise, mean of the Standard deviation (SD) of the pixel values, measured in Hounsfield units (HU), will be measured in Picture Archiving and Communication System (PACS) using a region of interest (ROI) measuring 90-110 mm\^2 in size drawn over each of these body regions: hepatic dome, spleen, renal cortex, retroperitoneal fat, subcutaneous fat, paraspinal muscles, and if present, breast tissue, avoiding vascular structures in each case. SD for ROI measuring 90-110 mm\^2 in size will also be drawn over the aorta and inferior vena cava (IVC), remote from contrast mixing artifact, and over medullary bone of the spine. HU is the linear scale by which digital image data are displayed in PACS and reflect relative attenuation compared to distilled water at a standard temperature and pressure (STP) (defined as 0 HU) and of pure air at STP (defined as -1000HU). Within a drawn ROI, the PACS will give the mean attenuation (in HU) and the standard deviation of HU (reflecting |
| Number of Participants With Presence of Artifacts Based on CT Image Quality | two months | CT images acquired will be reviewed for the presence of artifacts that might be attributed to the displacement device or to the presence of the breast tissue. To evaluate for artifacts, the exam will be qualitatively reviewed by a board certified radiologist for imaging artifacts, such as streak artifact. It will be noted on a per participant basis whether any imaging artifacts are identified. |
Countries
United States
Participant flow
Recruitment details
Recruitment: December 2010 to February 2012, at Harborview Medical Center (inpatient wards, outpatient clinics, and emergency departments)
Pre-assignment details
All women who were approached for the study were screened for exclusion criteria prior to enrollment. 110 eligible patients were approached, and 37 declined participation or met exclusion criteria. 1 subject was scanned but TLD readings were clearly erroneous and were therefore excluded. 72 subjects were ultimately included in analyses.
Participants by arm
| Arm | Count |
|---|---|
| Standard CT Women assigned to undergo CT using the standard dose reduction methods (including bismuth shielding and tube current modulation) but without the Chrysalis device. | 36 |
| Chrysalis CT Women assigned to undergo CT using the standard dose reduction methods (including bismuth shielding and tube current modulation) plus application of the Chrysalis device for breast displacement. | 36 |
| Total | 72 |
Baseline characteristics
| Characteristic | Chrysalis CT | Standard CT | Total |
|---|---|---|---|
| Age, Categorical <=18 years | 0 Participants | 0 Participants | 0 Participants |
| Age, Categorical >=65 years | 0 Participants | 0 Participants | 0 Participants |
| Age, Categorical Between 18 and 65 years | 36 Participants | 36 Participants | 72 Participants |
| Age, Continuous | 40.3 years STANDARD_DEVIATION 12.8 | 40.2 years STANDARD_DEVIATION 12.9 | 40.3 years STANDARD_DEVIATION 12.8 |
| Region of Enrollment United States | 36 participants | 36 participants | 72 participants |
| Sex: Female, Male Female | 36 Participants | 36 Participants | 72 Participants |
| Sex: Female, Male Male | 0 Participants | 0 Participants | 0 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | — / — | — / — |
| other Total, other adverse events | 0 / 36 | 0 / 36 |
| serious Total, serious adverse events | 0 / 36 | 0 / 36 |
Outcome results
Primary
Relative Skin Entrance Radiation Dose in % During Computed Tomography (CT)
Relative skin entrance dose at the breast (group mean of patient's average skin entrance dose at TLDs 2-4) divided by skin entrance dose at the inframammary TLD (TLD 1) in %. For each patient, doses at TLDs 2-4 were averaged, and then the group mean of this was divided by the group mean at the inframammary TLD, then multiplied by 100 to get % dose. A relative dose of 20% means that the skin entrance dose at the breast was 20% of the skin entrance dose at the inframammary fold.
Time frame: from time potential subject approached about possible enrollment to time device and TLDs were removed, on average 1 hour
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Standard CT | Relative Skin Entrance Radiation Dose in % During Computed Tomography (CT) | 37 percentage of dose | Standard Deviation 30 |
| Chrysalis CT | Relative Skin Entrance Radiation Dose in % During Computed Tomography (CT) | 36 percentage of dose | Standard Deviation 11 |
Comparison: Powered to detect difference of 10% at 80% power if 66 or more subjects enrolled.p-value: 0.00395% CI: [4, 25]Regression, Linear
Primary
Skin Entrance Radiation Dose During Computed Tomography (CT)
Skin entrance radiation doses will be measured with Thermoluminescent dosimeters (TLDs) affixed to the subject's chest and breast during CT of the abdomen. TLD #1 is at the inframammary fold, serving as internal control for each subject. Three additional TLDs (#2-4) are affixed to the subject's breast at 3 pre-ascribed locations. The same is done for the right and left breasts (8 TLDs total). TLDs will then be submitted to Landaeur for measurement.
Time frame: from time potential subject approached about possible enrollment to time device and TLDs were removed, on average 1 hour
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Standard CT | Skin Entrance Radiation Dose During Computed Tomography (CT) | Mean entrance skin dose at inframammary fold | 1775 mrad | Standard Deviation 1634 |
| Standard CT | Skin Entrance Radiation Dose During Computed Tomography (CT) | Mean breast entrance skin dose (average TLD2-4) | 625 mrad | Standard Deviation 677 |
| Chrysalis CT | Skin Entrance Radiation Dose During Computed Tomography (CT) | Mean entrance skin dose at inframammary fold | 1325 mrad | Standard Deviation 1158 |
| Chrysalis CT | Skin Entrance Radiation Dose During Computed Tomography (CT) | Mean breast entrance skin dose (average TLD2-4) | 259 mrad | Standard Deviation 334 |
Secondary
CT Image Noise
To evaluate image noise, mean of the Standard deviation (SD) of the pixel values, measured in Hounsfield units (HU), will be measured in Picture Archiving and Communication System (PACS) using a region of interest (ROI) measuring 90-110 mm\^2 in size drawn over each of these body regions: hepatic dome, spleen, renal cortex, retroperitoneal fat, subcutaneous fat, paraspinal muscles, and if present, breast tissue, avoiding vascular structures in each case. SD for ROI measuring 90-110 mm\^2 in size will also be drawn over the aorta and inferior vena cava (IVC), remote from contrast mixing artifact, and over medullary bone of the spine. HU is the linear scale by which digital image data are displayed in PACS and reflect relative attenuation compared to distilled water at a standard temperature and pressure (STP) (defined as 0 HU) and of pure air at STP (defined as -1000HU). Within a drawn ROI, the PACS will give the mean attenuation (in HU) and the standard deviation of HU (reflecting
Time frame: two months
Population: In some cases, a reliable measurement of noise could not be measured on the location. For example, if the breast was not included on the CT, breast noise could not be measured (12 controls and 21 Chrysalis). Too little retroperitoneal or subcutaneous fat was present to draw the relevant ROI in 1 control and 1 Chrysalis subject, respectively.
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Standard CT | CT Image Noise | Retroperitoneal fat | 24.4 Hounsfield units | Standard Deviation 7.9 |
| Standard CT | CT Image Noise | Liver dome | 17.1 Hounsfield units | Standard Deviation 5.9 |
| Standard CT | CT Image Noise | Spleen | 23.2 Hounsfield units | Standard Deviation 8.1 |
| Standard CT | CT Image Noise | Kidney | 26.8 Hounsfield units | Standard Deviation 8 |
| Standard CT | CT Image Noise | Aorta (without mixing artifact) | 19.7 Hounsfield units | Standard Deviation 5 |
| Standard CT | CT Image Noise | IVC (without mixing artifact) | 21.1 Hounsfield units | Standard Deviation 5.1 |
| Standard CT | CT Image Noise | Subcutaneous fat | 13.3 Hounsfield units | Standard Deviation 4 |
| Standard CT | CT Image Noise | Medullary Bone of Spine | 31.2 Hounsfield units | Standard Deviation 7.4 |
| Standard CT | CT Image Noise | Paraspinal muscle | 19.8 Hounsfield units | Standard Deviation 7.7 |
| Standard CT | CT Image Noise | Breast (if imaged) | 26.0 Hounsfield units | Standard Deviation 9.9 |
| Chrysalis CT | CT Image Noise | Medullary Bone of Spine | 34.8 Hounsfield units | Standard Deviation 18.2 |
| Chrysalis CT | CT Image Noise | Retroperitoneal fat | 23.4 Hounsfield units | Standard Deviation 7 |
| Chrysalis CT | CT Image Noise | IVC (without mixing artifact) | 22.9 Hounsfield units | Standard Deviation 5.7 |
| Chrysalis CT | CT Image Noise | Liver dome | 16.4 Hounsfield units | Standard Deviation 6.9 |
| Chrysalis CT | CT Image Noise | Breast (if imaged) | 26.1 Hounsfield units | Standard Deviation 11.1 |
| Chrysalis CT | CT Image Noise | Spleen | 21.1 Hounsfield units | Standard Deviation 7.3 |
| Chrysalis CT | CT Image Noise | Subcutaneous fat | 12.9 Hounsfield units | Standard Deviation 3.5 |
| Chrysalis CT | CT Image Noise | Kidney | 24.5 Hounsfield units | Standard Deviation 6.8 |
| Chrysalis CT | CT Image Noise | Paraspinal muscle | 17.9 Hounsfield units | Standard Deviation 5.6 |
| Chrysalis CT | CT Image Noise | Aorta (without mixing artifact) | 21.1 Hounsfield units | Standard Deviation 7.26 |
Secondary
Number of Participants With Presence of Artifacts Based on CT Image Quality
CT images acquired will be reviewed for the presence of artifacts that might be attributed to the displacement device or to the presence of the breast tissue. To evaluate for artifacts, the exam will be qualitatively reviewed by a board certified radiologist for imaging artifacts, such as streak artifact. It will be noted on a per participant basis whether any imaging artifacts are identified.
Time frame: two months
| Arm | Measure | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|
| Standard CT | Number of Participants With Presence of Artifacts Based on CT Image Quality | 0 Participants |
| Chrysalis CT | Number of Participants With Presence of Artifacts Based on CT Image Quality | 0 Participants |