Computed Tomography Arteriograms (CTA) Volume Dose Reduction Study

Does Reduction in Contrast Administration Dose in Computed Tomography Arteriograms Degrade Image Quality? A Single Institutional Review of an Ultra-low Contrast Dose Protocol

The purpose of the study is to determine if the dose of contrast (Omnipaque) administered for Computed Tomography Arteriograms (CTA) can be reduced without degradation of image quality. The hypothesis is that there is no difference in image quality using ultra-low dose contrast in CTA exams compared to routine, standard of care dose exams.

Any adult patient age 18 and above, scheduled for routine CTA (Computed Tomography Arteriograms) of the chest or chest, abdomen and pelvis meeting inclusion criteria and not meeting any exclusion criteria will be included in the study. The patient will be administered a low dose of intravenous contrast based on the study examination as described below. CTA of the chest: 40 mL of intravenous contrast (Omnipaque) at a rate of 5mL/sec. A region of interest (ROI) to trigger the scan will be placed in the aortic arch. If scan is performed using high pitch helical mode, the scan delay will be increased by 2 seconds. CTA of the chest and abdomen or CTA of the chest, abdomen and pelvis: 50 mL of intravenous contrast (Omnipaque) at a rate 5mL/sec. A region of interest (ROI) to trigger the scan will be placed in the aortic arch. If scan is performed using high pitch helical mode, the scan delay will be increased by 2 seconds. Following the examination, the primary investigator (PI) or team members will evaluate the images obtained with low contrast dose and each patient's prior CTA examination performed with routine contrast dose, 100mL at a rate of 4mL/sec. This will be done by quantitative and qualitative measures. For the quantitative portion, the PI or team members will place regions of interest on predetermined arterial locations to obtain measure the degree of opacification. For qualitative measurement, the images will be presented in a blind fashion to two thoracic trained board certified radiologists and a board certified interventional radiologist to determine the quality of the images based on a Likert numerical scale. Qualitative and quantitative data for the images obtained with low contrast dose and those for the prior CTA examinations performed with routine contrast dose will be compared. This data along with details of the scan protocol (dose, dose rate, scanning parameters etc.) and demographic data (such as sex, age and BMI at the time of examination) will be recorded.

CTA of the chest: 40 mL of intravenous contrast at a rate of 5mL/sec. A region of interest (ROI) to trigger the scan will be placed in the aortic arch. If scan is performed using high pitch helical mode, the scan delay will be increased by 2 seconds. The Low Dose scan will then be compared to the standard of care high dose scan of the same area taken at a previous date.

CTA of the abdomen OR or CTA of the chest and abdomen or CTA of the abdomen and pelvis or CTA of the chest, abdomen and pelvis: 50 mL of intravenous contrast at a rate 5mL/sec. A region of interest (ROI) to trigger the scan will be placed in the aortic arch. If scan is performed using high pitch helical mode, the scan delay will be increased by 2 seconds. The Low Dose scan will then be compared to the standard of care high dose scan of the same area taken at a previous date.

The patient will be administered a low dose, 40mL of intravenous contrast (Omnipaque) at a rate of 5mL/sec based on the area of the body being scanned (chest versus chest and abdomen versus chest, abdomen and pelvis). This will be compared to the patient's prior examination performed with 100mL of intravenous contrast at a rate of 4mL/sec.

The patient will be administered a low dose, 50mL of intravenous contrast (Omnipaque) at a rate of 5mL/sec based on the area of the body being scanned (chest versus chest and abdomen versus chest, abdomen and pelvis). This will be compared to the patient's prior examination performed with 100mL of intravenous contrast at a rate of 4mL/sec.

Following image acquisition, quantitative analysis was performed by measurement of the attenuation of the contrast bolus by use of Hounsfield Units. Measurement was taken at the ascending aorta near the sinotubular junction.

Following image acquisition, quantitative analysis was performed by measurement of the attenuation of the contrast bolus by use of Hounsfield Units. A measurement was taken from the distal abdominal aorta prior to the bifurcation.

Following image acquisition, quantitative analysis was performed by measurement of the attenuation of the contrast bolus by use of Hounsfield Units. A measurement was taken from the proximal abdominal aorta at the level of the celiac axis.

Following image acquisition, quantitative analysis was performed by measurement of the attenuation of the contrast bolus by use of Hounsfield Units. A measurement was taken from the distal abdominal aorta prior to the bifurcation.

Following image acquisition, quantitative analysis was performed by measurement of the attenuation of the contrast bolus by use of Hounsfield Units. A measurement was taken from the right common femoral artery.

Following image acquisition, quantitative analysis was performed by measurement of the attenuation of the contrast bolus by use of Hounsfield Units. A measurement was taken from the right common femoral artery.

5 Point Grading Scale was used to determine CTA Vessel Opacification by a Board Certified Radiologist. Poor opacification with no difference in attenuation of the lumen compared to the wall of the vessel. Non diagnostic. Decreased opacification. Little to no difference in attenuation between the lumen and the wall. Non diagnostic. Moderate opacification of the lumen of the vessel. Diagnostic study. Good opacification of the lumen of the vessel. Excellent opacification of the lumen of the vessel with distinct difference in attenuation of the wall and lumen of the vessel.

5 Point Grading Scale was used to determine CTA Vessel Opacification by a second Board Certified Radiologist. Poor opacification with no difference in attenuation of the lumen compared to the wall of the vessel. Non diagnostic. Decreased opacification. Little to no difference in attenuation between the lumen and the wall. Non diagnostic. Moderate opacification of the lumen of the vessel. Diagnostic Good opacification of the lumen of the vessel. Excellent opacification of the lumen of the vessel with distinct difference in attenuation of the wall and lumen of the vessel.

Inclusion Criteria: Any adult patient scheduled for a computed tomographic arteriogram (CTA) of the chest or chest, abdomen and pelvis who had undergone a prior CTA performed with the standard contrast dose (100 mL) at this institution will be included in the study The follow-up scan will be routine standard of care, no emergency imaging patient will be approached for this research Exclusion Criteria: Patients with no prior CTA imaging for comparison Any pediatric patient (age <18) BMI >40 Inability to follow instructions Allergy to intravenous contrast GFR less than 30 mL/min/1.73 m2

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