3D printing of anatomically realistic phantoms with detection tasks to assess the diagnostic performance of CT images.

OBJECTIVES: Detectability experiments performed to assess the diagnostic performance of computed tomography (CT) images should represent the clinical situation realistically. The purpose was to develop anatomically realistic phantoms with low-contrast lesions for detectability experiments. METHODS: Low-contrast lesions were digitally inserted into a neck CT image of a patient. The original and the manipulated CT images were used to create five phantoms: four phantoms with lesions of 10, 20, 30, and 40 HU contrast and one phantom without any lesion. Radiopaque 3D printing with potassium-iodide-doped ink (600 mg/mL) was used. The phantoms were scanned with different CT settings. Lesion contrast was analyzed using HU measurement. A 2-alternative forced choice experiment was performed with seven radiologists to study the impact of lesion contrast on detection accuracy and reader confidence (1 = lowest, 5 = highest). RESULTS: The phantoms reproduced patient size, shape, and anatomy. Mean +/- SD contrast values of the low-contrast lesions were 9.7 +/- 1.2, 18.2 +/- 2, 30.2 +/- 2.7, and 37.7 +/- 3.1 HU for the 10, 20, 30, and 40 HU contrast lesions, respectively. Mean +/- SD detection accuracy and confidence values were not significantly different for 10 and 20 HU lesion contrast (82.1 +/- 6.3% vs. 83.9 +/- 9.4%, p = 0.863 and 1.7 +/- 0.4 vs. 1.8 +/- 0.5, p = 0.159). They increased to 95 +/- 5.7% and 2.6 +/- 0.7 for 30 HU lesion contrast and 99.5 +/- 0.9% and 3.8 +/- 0.7 for 40 HU lesion contrast (p < 0.005). CONCLUSIONS: A CT image was manipulated to produce anatomically realistic phantoms for low-contrast detectability experiments. The phantoms and our initial experiments provide a groundwork for the assessment of CT image quality in a clinical context. KEY POINTS: * Phantoms generated from manipulated CT images provide patient anatomy and can be used for detection tasks to evaluate the diagnostic performance of CT images. * Radiologists are unconfident and unreliable in detecting hypodense lesions of 20 HU contrast and less in an anatomical neck background. * Detectability experiments with anatomically realistic phantoms can assess CT image quality in a clinical context.