Clinical practicality of quantitative 99m-MDP SPECT/CT in patients with breast and prostate osseous metastatic disease

2135 Objectives: itle: Clinical practicality of quantitative 99m-MDP SPECT/CT in patients with breast and prostate osseous metastatic disease Objectives: Bone scans are the standard of care in both breast and prostate cancer patients to evaluate for osseous metastatic disease. However, traditional bone scintigraphy (whole body imaging and SPECT or SPECT/CT) is unable to quantitate disease progression, therefore oncologists use NaF PET/CT for this Introduction: Purpose: Quantitative reconstruction has recently become available for SPECT/CT but adds complexity (additional quality control and patient setup) and radiation dose from the CT. The purpose of this work is to 1) evaluate the practicality of quantitative SPECT/CT in patients with osseous metastatic disease for initial diagnoses and subsequent tracking, 2) establish an imaging protocol for future quantitative Tc-99m MDP SPECT/CT imaging studies, and 3) evaluate the feasibility of performing quantitative Tc-99m MDP SPECT/CT as a standard of care in patients with known osseous metastatic disease. Methods: Quantitative SPECT/CT (Siemens xSPECT Quant) was implemented on a clinical SPECT/CT system (Siemens Intevo T16). Quality control for quantitation includes routine calibration with a known source, preferably a NIST calibration source, and checked with a NEMA IEC Body Phantom (Data Spectrum Corporation) which consists of a body phantom, lung insert, and spheres ranging from 10 mm to 37 mm. The phantom sphere/background activity ratio was 4/1 and imaged with the clinical protocol. Patient set-up procedures include recording and input of patient demographics, assayed radiopharmaceutical dose/residual dose, and assay/injection times. Patients are injected intravenously with 25mCi (925 mBq) +/- 10% of Tc99m-MDP with imaging 2.5-3 hours following injection for their whole body scan and lateral images of the skull. If the clinician desires, this is followed by SPECT/CT using the quantitative protocol. A clinical protocol designed for tracking includes the whole torso, a 2-bed position SPECT/CT from the clavicles thru the pelvis. Both phantom and patient SPECT reconstruction used xSPECT Quant (based on the OSCG algorithm) which includes attenuation correction, scatter compensation and collimator resolution modeling. SPECT images from this algorithm are calibrated for SUV analysis and analyzed on MIM software workstations. Results: Phantom images gave background SUV average of 1 as expected. Maximum SUVs from the spheres varied with size due to partial volume effects. Sphere SUV max was 5.5, 5.4, 4.0, 2.7 for the 37 mm, 28 mm, 22 mm, and 17 mm spheres (activity ratio of 4.1). Patient images provided a different texture with quantitative reconstruction verses OSEM reconstruction. Lesions with both reconstructions were identified and SUVs recorded. At this time, quantitative measurements were not included in the clinical report. Implementation of quantitative disease tracking would require SPECT/CT at each patient visit. Conclusions: Phantom measurements showed that the quantitative reconstruction was accurate. Patient imaging demonstrated that the technique is feasible for the clinical setting. While there is some increased cost, time and effort in quantitative SPECT/CT, the ability to assess tumor response and regression using bone scans with SPECT/CT may eventually allow for the standard of care with its lower cost and availability than NaF PET/CT.