Radiology: Primary 2D and 3D CTC review yield comparable accuracy

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Radiologists’ preferences and use of 2D, 3D or 2D/3D CT colonography (CTC) does not affect their performance in the detection of polyps 6 mm or larger, according to a large multi-institution study published in the May issue of Radiology.

“[T]here are often two camps of CT colonographic readers, those who prefer a primary two-dimensional (2D) approach and those who prefer a primary three-dimensional (3D) approach,” explained Amy K. Hara, MD, from the department of diagnostic radiology at the Mayo Clinic in Scottsdale, Ariz., and co-authors.

As radiologists’ usage of CTC grows, debate and lack of consensus in the literature over the modality’s effectiveness in the detection of smaller polyps has led to payors’ reticence and denials of CTC screening as a less invasive replacement to colonoscopy.

Meanwhile, studies have continued to examine the accuracy of CTC screening. The present study, supported by the National Cancer Institute and the American College of Radiology Imaging Network (ACRIN), sought to examine the effect of radiologists’ preferences and use of 2D vs. 3D CTC in the detection of polyps 6 mm and larger.

Fifteen radiologists, each from distinct institutions, were recruited for the study, with eight readers indicating at the study’s start their preference for 2D CTC, six radiologists for a complete 2D and 3D workup and one reader who preferred 3D CTC. Readers were then randomly assigned to a primary 2D or 3D CTC method, with radiologists’ performances compared with standard colonoscopy findings in all 2,531 exams.

Radiologists’ preference for 2D or 3D CTC did not significantly affect their performance in the detection of polyps 10 mm or larger. Among radiologists who preferred 2D CTC, sensitivity and specificity reached 0.84 and 0.86, respectively, compared with sensitivity of 0.84 and specificity of 0.83 among readers who preferred 2D and 3D CTC.

Reader sensitivity decreased to between 0.70 and 0.75 with the inclusion of polyps 6 mm or larger; however, no significant differences were observed in performance between groups. Specificity remained constant around 0.86, regardless of polyp size.

Moreover, neither radiologists’ specific preference for 2D or 3D CTC, nor whether or not they were permitted to use their preferred method, affected their sensitivity or specificity across any criteria.

“Our results showed that there was no significant difference in overall performance on the basis of readers’ preferences,” noted Hara and colleagues.

“In other words, readers who preferred a primary 2D approach had equivalent diagnostic performance compared with readers who preferred a primary 3D approach or those who preferred both 2D and 3D combined,” the authors continued.

Hara and colleagues interpreted their findings in the context of mixed preferences and training methods for CTC across various studies and institutions, concluding: “The results of this study demonstrate that, although a reader may have a personal preference for a specific CT colonographic interpretation technique, with proper training on the use of 2D and 3D methods, comparable performance can be achieved.”