Patient arm position during quantitative bone single-photon emission computed tomography/computed tomography acquisition can affect image quality and quantitative accuracy: a phantom study

Purpose The present study used a phantom to determine the effects of various arm positions on bone SPECT/computed tomography (CT) images and the optimal arm position to acquire good-quality and quantitatively accurate images. Materials and methods We designed a phantom study of five simulated arm positions that are assumed during SPECT image acquisition. All SPECT data were acquired during a total of 120 projections of 10 and 100 s/view over 360° in a non-circular mode and reconstructed using Flash 3D (Siemens Healthineers). We evaluated contrast (Q H,17 mm ), image noise (N B,17 mm ), contrast-to-noise ratios (QNRs), and visual scores according to the guidelines for bone SPECT acquisition protocols published by the Japanese Society of Nuclear Medicine Technology. The SUV mean , SUV max , and SUV peak were calculated and quantitative errors were evaluated using the recovery coefficient (RC) and the root means square error (RMSE). Results The spatial resolution of SPECT images was better when the arms were down than raised with simulated shoulder disorders. Raised arms with shoulder disorders significantly increased the N B,17 mm and decreased the Q H,17 mm , and the QNR in each image differed over a range from 2.2 to 5.2. The visual score was >1.5 with the arms down, raised normally, and raised with moderate shoulder disorders. The SUV max and SUV peak were overestimated compared with 100-min data for all images, whereas SUV mean was underestimated. Raised arms with a shoulder disorder decreased RC max , and RC mean and RC peak suppressed differences among arm positions. In addition, RMSE with the arms down and raised normally were close to that for 100-min data. Conclusion Bone SPECT images with good quality and quantitative accuracy can be acquired with patients holding their arms down by their sides. This will help patients with shoulder pain who have difficulties raising their arms.