Ernest Mark Scalzetti MD, Presenter: Nothing to Disclose

Maya Gabbour, Abstract Co-Author: Nothing to Disclose

Monica Neuffer DO, Abstract Co-Author: Nothing to Disclose

Kent M. Ogden MD, Abstract Co-Author: Nothing to Disclose

Many patients have a CT pulmonary angiogram (CTPA) to evaluate for acute pulmonary embolism (PE). We performed a longitudinal followup study of a cohort of such patients who had a CTPA, to determine how often they receive additional CTPAs in successive years and their cumulative radiation dose.

We received an IRB waiver for review of patient records. We identified all patients referred for CTPA, for evaluation of acute PE, in 2005. All were followed through 2009 for additional CTPAs at our institution. We recorded technical details of each CTPA to permit estimation of an effective radiation dose. The scans were reviewed by an experienced thoracic radiologist, cumulative effective doses were calculated, and additional clinical information was retrieved for all patients who had >2 CTPAs.

650 patients received at least one CTPA in 2005. Through 2009, 126 of them had >1 CTPA (19.4%), 38 had >2 (5.9%) and 17 had >3 (2.6%). Median effective dose per scan was 4.3 mSv (range 2.6-8.0 mSv). The largest number of CTPAs was 17, in a 33 year old female who had no predisposing condition for PE, for a cumulative effective dose of 60 mSv. The largest cumulative dose was estimated at 112 mSv in a 44 year old female patient who underwent 14 CTPAs; she also had no predisposing condition for PE. Of the 38 patients who had >2 CTPAs, 23 were female (61%, p=NS), the median age was 51 years (range 28-87), median cumulative effective dose was 13 mSv (range 8-112 mSv), and 11 (6%) of the 173 total CTPAs showed an acute PE. Of the 5 patients who had >6 CTPAs, all were female, the median age was 40 years (range 33-48 years), the median cumulative effective dose was 60 mSv (range 29-112 mSv), and none of the 58 total CTPAs was positive for acute PE.

Fewer than 20% of patients received a repeat CTPA during a followup period of at least 4 years. Patients who were referrred repeatedly and incurred the largest cumulative doses tended to be females of younger age; very few of these scans led to a diagnosis of acute PE. Cumulative effective doses exceeded 50 mSv in 4 patients; this level of radiation dose is expected to have a measurable impact on lifetime risk of fatal cancer.

Multiple CTPAs can lead to clinically meaningful radiation doses with little or no clinical benefit. Our study promotes awareness of this issue. Improved case selection is needed to avoid this outcome

Scalzetti, E, Gabbour, M, Neuffer, M, Ogden, K, Repeated Referrals for CT Pulmonary Angiography and Cumulative Radiation Dose: Longitudinal Follow-up of a Single Institution Cohort.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11005719.html