Benefits of hybrid SPECT/CT for 111In-oxine- and 99mTc-HMPAO-labeled leukocyte imaging

Objectives This retrospective study assessed the impact of the addition of SPECT/CT imaging on the diag-nostic accuracy of labeled leukocyte scintigraphy.

Methods Leukocyte scans performed between 12/2005-08/2009 were reviewed from 134 patients. All patients underwent planar whole body and SPECT/CT imaging within 24 hours of IV injection of either 111In-oxine or 99mTc-HMPAO labeled leukocytes. Leukocyte imaging identified a total of 221 lesions. Based on additional diagnostic tests (such as CT or MRI; fluid, or tissue sampling with microbiology) as well as clinical follow-up for at least 3 months, a final diagnosis could be established in 138 cases (from 109 patients). Group differences were assessed using stepwise regression analysis taking into account the type of radiolabel (111In-oxine or 99mTc-HMPAO) and the use of antibiotics per patient.

Results One hundred and thirteen focal lesions with established final diagnosis were detected on imaging in bone (n = 43), soft tissues (n = 34), surgical implants (n = 17) and vascular grafts (n = 19), while in 25 patients, no abnormality was seen (Table 1). Overall, leukocyte scanning including SPECT/CT yielded a sensitivity, specificity, positive and negative predictive value of 87.3, 82.7, 80.9, and 89.0 %, respectively. Compared to planar imaging and SPECT, hybrid SPECT/CT imaging significantly increased the number of correctly identified focal lesion locations by 27 % (30 of 113 cases). SPECT/CT imaging also improved overall reader confidence compared to planar and SPECT imaging in 77 (68 %) and 71 (63 %) of the 113 focal lesions, respectively. No significant differences in scan accuracy were seen between 111In-oxine or 99mTc-HMPAO labeled leukocyte studies, nor between scans obtained with or without antibiotic treatment.

Conclusions Hybrid SPECT/CT fusion leukocyte imaging has incremental value over planar imaging with SPECT by improving diagnostic accuracy of lesion identification and reader confidence