AR: Pediatric rads choose CT for PE, dose knowledge limited
CT pulmonary angiography (CTPA) has become the imaging modality of choice for pediatric radiologists evaluating suspected cases of pulmonary embolism (PE), despite nearly 90 percent of radiologists admitting they do not know the typical dose-length-product of their studies, according to research published in the December edition of Academic Radiology.

"Although ventilation-perfusion scanning and conventional pulmonary angiography have traditionally served as the mainstay of imaging for suspected PE in children, recent studies suggest an increasing role of CTPA for this indication," noted Edward Y. Lee, MD, MPH, and colleagues of Children's Hospital Boston and Harvard Medical School. "However, to our knowledge, there is no published information regarding how CTPA is performed in children across different institutions in both academic and private practice settings."

The authors sought to measure the techniques and policies utilized to evaluate children with clinical suspicion of PE among member institutions of the Society of Pediatric Radiology (SPR). The researchers sent surveys to 416 hospitals querying whether institutions performed CTPA on children with suspected PE. All participants were also asked demographic questions about their institution, with CTPA-performing practices additionally questioned about whether their institution had written policies for CTPA, the frequency of use of the procedure, technique and radiation dose protocols and questions comparing CTPA usage to other PE modalities.

Completed surveys were submitted by 118 of the 416 SPR-member institutions, with some additional repeated responses excluded due to the survey's focus on institutional CPTA utilization, rather than usage by individual radiologists. One hundred four of the participating institutions reported performing CTPA in children with suspected PE. Of these institutions, 93 hospitals said CTPA is their study of choice for suspected cases of PE.

With studies confirming that children represent the most vulnerable population to CT radiation, the authors observed that 58 percent of CTPA-performing institutions reported modifying their CT protocols to reduce radiation exposure to children. Academic institutions were significantly more likely to reduce radiation exposure than private hospitals, with 66 percent of academic hospitals reporting dose reductions, compared with 30 percent of private practices.

Eighty-eight percent of CTPA-performing institutions could not estimate the typical radiation dose-length-product (DLP) for a 20-kg child during CTPA evaluation for PE. The remaining 13 respondents listed a range of DLP values from 23 to 1000, with a median DLP of 100.

"[O]ur survey results suggest that CTPA is now commonly used for this indication," the authors observed. "Indeed, a majority of survey respondents reported that CTPA is the study of choice for suspected PE in children.

"A slight majority of respondents reported that they currently modify CTPA protocols for radiation dose reduction for the evaluation of PE in children. The most commonly reported methods of dose reduction included reduced mAs, use of automatic exposure control, and reduced kVp. However, because dose reduction methods were more commonly reported among those respondents in academic settings, our findings suggest the potential need for educational efforts targeted to those in private practice settings," the authors argued.

Lee and co-authors proposed a litany of recommendations based on their findings for CTPA protocols, including:

• Radiology departments should publish a written policy for imaging patients with suspicion of PE;
• Chest radiographs should be performed before CTPA as the former may obviate the need for CTPA; and
• All available radiation dose reduction methods recommended by SPR's "Image Gently" campaign should be carefully considered in performing patient exams for PE.

The authors also listed several limitations to their study, including potential nonresponse bias, wherein CTPA-performing institutions may have elicited a higher response rate than hospitals that do not perform CTPA in pediatric patients. Lee and colleagues also acknowledged that their findings may have limited generalizability due to the study's focus on institutional, not individual, radiologic examination protocols, and because 91 percent of respondents represented academic centers.

Overall, the authors found that "[m]ost survey respondents perform CTPA as the study of choice for evaluating PE in children, but there is considerable variability in their policies and practices. Respondents from academic medical centers are more likely to employ radiation dose-reduction techniques for CTPA than those in private practice settings."