SPECT/CT imaging of bone in pediatric patients

Objectives To determine if low dose co-registered (co-reg) CT added to bone SPECT provides additional useful diagnostic information in pediatric patients (pt).

Methods Bone SPECT/CT studies in 49 pt (age 6 - 25 yr, median 14 yr) were reviewed . Indications were back pain in 37, hip/leg pain 5, tumor 5 and other 2. Pt received planar and SPECT imaging and a co-reg low dose CT scan. During the study period, 37% of all bone SPECT pt had co-reg CT; co-reg CT was performed in pt with planar bone scan, radiographic or MRI findings. CT was limited to the area of greatest concern, and acquired at approximately 30% of the exposure parameters used for a diagnostic CT. Effective dose (ED) was calculated for the CT parameters and z-axis limits in this study by the ImPACT program.

Results CT or SPECT bone imaging was abnormal in 46/49 with SPECT abnormal in 39/49 and CT abnormal in 36/49. SPECT/CT findings in back pain pt included sclerotic pars interarticularis (pars) in 7 pt (6 SPECT+), pars defect(s) in 13 (8 SPECT+), pars uptake with normal CT in 7, facet joint abnormality in 6, spinous process uptake in 2, unilateral sacralized vertebra in 3 (2 SPECT+), sacroiliac joint uptake in 4 (1 CT+) and other findings in 8 (9 pt had multiple findings). Co-reg CT added diagnostic information in 38/49. The CT z-axis field included 2 vertebral bodies in 12 and 3 vertebrae in 12 studies. For 2 vertebral bodies the calculated additional ED for CT was 25 mrem (0.25 mSv).

Conclusions Co-reg CT adds diagnostic information to bone SPECT in a high percentage of patients when selectively utilized, providing more complete evaluation of back pain at low added ED.