Incremental value of 99mTc-MDP hybrid SPECT/CT over planar scintigraphy and SPECT in avascular necrosis of the femoral head.

Objective: The aim of the study was to evaluate the incremental value of technetium-99m-methylene diphosphonate (99mTc-MDP) single-photon emission tomography/computed tomography (SPECT/CT) over planar bone scintigraphy (BS) and SPECT in the diagnosis of avascular necrosis (AVN) of the femoral head.

Materials And Methods: The data of 44 patients (mean age 36 ± 16 years, 34 male and 10 female) who underwent 99mTc-MDP BS along with regional SPECT/CT for suspected femoral head AVN were retrospectively evaluated. Planar BS, SPECT and SPECT/CT images were evaluated by two nuclear medicine physicians in consensus. On the basis of diagnostic confidence, a score of 1-5 was given, with 1 being definitely AVN, 2 being probably AVN, 3 being equivocal, 4 being probably normal and 5 being definitely normal. Receiver operating characteristic analysis was performed and the area under the curve was calculated. For calculation of sensitivity, specificity and predictive values for planar, an interpretive score of less than or equal to 2 was taken as AVN and a score of 3 or more was taken as no AVN. Clinical and imaging follow-up and histopathological results were taken as the reference standard.

Results: Among 44 patients with 64 affected femoral heads, there were 48 true-positive, 13 true-negative, two false-positive and one false-negative lesion on SPECT/CT. The diagnostic accuracy of planar BS, SPECT and SPECT/CT was 67, 78 and 95%, respectively. Planar BS was found to have the lowest sensitivity (75%) and specificity (40%), whereas SPECT/CT had the highest sensitivity (98%) and specificity (87%). The area under the curve was highest for SPECT/CT (0.919), followed by SPECT (0.76) and planar BS (0.567). SPECT/CT was superior to both SPECT (P = 0.02) and planar BS (P < 0.001), whereas SPECT was superior to planar BS (P = 0.03).

Conclusion: SPECT/CT is superior to planar BS and SPECT alone for the diagnosis of AVN of the femoral head.