⁸⁹Sr bremsstrahlung single photon emission computed tomography using a gamma camera for bone metastases

Objective: Strontium-89 chloride (⁸⁹Sr) bremsstrahlung single photon emission computed tomography (SPECT) imaging was evaluated for detecting more detailed whole body ⁸⁹Sr distribution. Methods: ⁸⁹Sr bremsstrahlung whole body planar and merged SPECT images were acquired using two-detector SPECT system. Energy window A (100 keV ± 50 %) for planar imaging and energy window A plus adjacent energy window B (300 keV ± 50 %) for SPECT imaging were set on the continuous spectrum. Thirteen patients with multiple bone metastases were evaluated. Bone metastases can be detected with ^99mTc-HMDP whole body planar and merged SPECT images and compared with ⁸⁹Sr bremsstrahlung whole body planar and merged SPECT images. Based on the location of metastatic lesions seen as hot spots on ^99mTc-HMDP images as a reference, the hot spots on ⁸⁹Sr bremsstrahlung images were divided into the same bone parts as ^99mTc-HMDP images (a total of 35 parts in the whole body), and the number of hot spots were counted. We also evaluated the incidence of extra-osseous uptakes in the intestine on ⁸⁹Sr bremsstrahlung whole body planar images. Results: A total of 195 bone metastatic lesions were detected in both ^99mTc-HMDP whole body planar and merged SPECT images. Detection of hot spot lesions in ⁸⁹Sr merged SPECT images (127 of 195; 66 %) was more frequent than in ⁸⁹Sr whole body planar images (108 of 195; 56 %), based on metastatic bone lesions in ^99mTc-HMDP whole body planar and merged SPECT images. A large intestinal ⁸⁹Sr accumulation was detected in 5 of the 13 patients (38 %). Conclusions: ⁸⁹Sr bremsstrahlung-merged SPECT imaging could be more useful for detailed detection of whole body ⁸⁹Sr distribution than planar imaging. Intestinal ⁸⁹Sr accumulation due to ⁸⁹Sr physiologic excretion was detected in feces for 4 days after tracer injection.