Radiation Dose Reduction Strategy for SPECT/CT Bone Scan

Abstract

Purpose: The aim of this study is to introduce the optimization method of CT parameters to reduce patient radiation exposure in bone SPECT/CT while maintaining image quality. The results of the new protocol were then compared to the results of the standard protocol saved in the nuclear medicine department`s data at King Abdullah Medical City.Methodology: First part: Using Deluxe Jaszczak Phantom. The cylindrical phantom consisted of six bottles in a pie arrangement. These bottles were placed in the source tank. SPECT/CT scans were carried out with different x-ray tube current values (10, 20, 30, 40, 50, and 60 mA) at three different slices of thicknesses (2.5, 3.75, and 5mm). The contrast ratio (CR) and coefficients of variation (COV) in the SPECT images as well as the signal-to-noise ratio (SNR) and were all measured. An optimal acquisition protocol of SPECT/CT images with no artifacts on both CT and SPECT images, and acceptable CR, COV, and SNR values were obtained. Second part: The study was done on patients who required a SPECT/CT bone scan of the spine area (thoracic spine (T1-T12) and lumbar spine (L1-L5)). Some patients were excluded from this study because of the image quality that was affected by several factors. Different parameters obtained from the new reduced protocol were compared to old historical data saved in the system for patients who did the same image using the old standard protocol. The difference between the two systems was only in the current of the X-ray tube (the old 60 mA versus the new 40 mA).Result: The optimal set of parameters for bone SPECT/CT was determined based on a phantom part that has been implemented in clinical practice. Two groups of patients were examined according to the baseline and optimized protocols, respectively. The new SPECT/CT protocol substantially reduced patients’ radiation exposure as compared to the old protocol, while also maintaining the required diagnostic quality of SPECT and CT images.Conclusions: The newly established bone scan SPECT/CT protocol was implemented into clinical practice. It has significantly reduced patients’ exposure dose as compared to the old protocol while maintaining the required diagnostic quality of SPECT and CT images.