Detecting lumbar lesions in Tc-MDP SPECT by deep learning: comparison with physicians.

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Abstract

99m Tc-MDP SPECT is an established tool for diagnosing lumbar stress, a common cause of low back pain (LBP) in pediatric patients. However, detection of small stress lesions is complicated by the low quality of SPECT, leading to significant inter-reader variability. The study objectives were to develop an approach based on a deep convolutional neural network (CNN) for detecting lumbar lesions in 99m Tc-MDP scans and to compare its performance to that of physicians in a localization receiver operating characteristic (LROC) study.
Sixty-five lesion-absent (LA) 99m Tc-MDP studies performed in pediatric patients for evaluating LBP were retrospectively identified. Projections for an artificial focal lesion were acquired separately by imaging a 99m Tc capillary tube at multiple distances from the collimator. An approach was developed to automatically insert lesions into LA scans to obtain realistic lesion-present (LP) 99m Tc-MDP images while ensuring knowledge of the ground truth. A deep CNN was trained using 2.5D views extracted in LP and LA 99m Tc-MDP image sets. During testing, the CNN was applied in a sliding-window fashion to compute a 3D “heatmap” reporting the probability of a lesion being present at each lumbar location. The algorithm was evaluated using cross-validation on a 99m Tc-MDP test dataset which was also studied by five physicians in a LROC study. LP images in the test set were obtained by incorporating lesions at sites selected by a physician based on clinical likelihood of injury in this population.
The deep learning (DL) system slightly outperformed human observers, achieving an area under the LROC curve (AUCLROC ) of 0.830 (95% confidence interval (CI): [0.758,0.924]) compared to 0.785 (95% CI: [0.738,0.830]) for physicians. The AUCLROC for the DL system was higher than that of two readers (difference in AUCLROC (ΔAUCLROC ) = 0.049 and 0.053) who participated to the study, and slightly lower than that of two other readers (ΔAUCLROC = -0.006 and -0.012). Another reader outperformed DL by a more substantial margin (ΔAUCLROC = -0.053).
The DL system provides comparable or superior performance than physicians in localizing small 99m Tc-MDP positive lumbar lesions.
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