TY - JOUR T1 - Influence of the scan time point on qualitative and semi-quantitative assessment of whole-body bone scintigraphy using <sup>99m</sup>Tc-HMDP: comparison between 2 h vs. 3 h. JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1560 LP - 1560 VL - 62 IS - supplement 1 AU - Sho Furuya AU - Satoshi Shimomura AU - Kenji Hirata AU - Toshikazu Nambu Y1 - 2021/05/01 UR - http://jnm.snmjournals.org/content/62/supplement_1/1560.abstract N2 - 1560Objectives: Bone scan plays an important role in the management of bone metastasis. Under the current protocol, the image acquisition is performed 3 to 4 hours (h) after intravenous injection of 99mTc-hydroxymethylene diphosphonate (HMDP). As the result, bone scan requires &gt;4 h and may cause patient stress. Generally, early acquisition produces images with low lesion-to-background contrast. However, high-resolution medical images may improve the performance of detecting hot spot. Recently, there are few reports about the quality of bone scan images in relation to uptake time. We hypothesized that the uptake time could be shortened using a high-resolution gamma camera for qualitative assessment. Bone Scan Index (BSI) has been recently used as semi-automated index reflecting the expansion of bone metastasis. BSI could be influenced by uptake time. Thus, the aims of this study were to assess 1) the concordance of diagnosis between two nuclear medicine physicians, 2) the qualitative assessment of the images, and 3) BSI acquired at 2 h and 3 h after injection. Methods: The study was approved by institutional review board. Twenty-eight patients who underwent bone scans using 99mTc-HMDP at Hokkaido Cancer Center, Sapporo, Japan, from June to September 2020 were enrolled. All patients were scanned twice; 2 h and 3 h after injection. Twenty-four patients were suspected or diagnosed as having bone metastasis while 4 patients presented with osteonecrosis of the jaw. Pairwise comparison was made for all the images acquired at 2 h and 3 h after injection. Two experienced nuclear medicine physicians (6 years and 35 years experiences) assessed the whole-body images visually without any clinical information. For intra-observer reproducibility, both physicians assessed the images twice on different days. Each physician counted the number of abnormal hot spots (bone metastasis or osteonecrosis of the jaw) and extent of disease (EOD) grading was applied (Table 1). The concordance rate of EOD score was assessed using Cohen’s kappa coefficient. Kappa scores of 0.41-0.60, 0.61-0.80, and greater than 0.80 were regarded to be indicative of moderate, good, and excellent agreement, respectively. In addition, quality of all images was classified as 1) good, 2) normal or 3) poor. In comparison of images, images acquired at 2 h was classified as A) superior (2h &gt; 3h), B) equivalent (2h = 3h) and C) inferior (2h &lt; 3h) to 3 h. BSI was calculated using the commercially available software VSBONE (Nihon Medi-Physics, Tokyo, Japan). A paired t test was carried out for the comparison of BSI between 2 and 3 h. p &lt; 0.05 was considered as statistically significant. In addition, Pearson’s correlation coefficient (R2) between 2 and 3 h was evaluated. Results: Twenty-eight patients (14 males) were included. The mean age was 70 years. The numbers of the images classified as EOD score 0, 1, 2, 3, 4 were as follows: for 2h images, 12, 10, 4, 2, 0 by Reviewer-1 and 14, 8, 4, 2, 0 by Reviewer-2; for 3h images, 15, 7, 4, 2, 0 by Reviewer-1 and 13, 9, 3, 3, 0 by Reviewer-2. The kappa scores for EOD agreement were 0.73 at 2h and 0.68 at 3h, and therefore considered good agreement. All images were classified as good or normal by any reviewers (i.e., no case classified as poor), although image comparison resulted in up to 80% images classified as 3h &gt; 2h. These results indicated that the quality of 2 h images has been ensured. In the semi-quantitative analysis, BSI was 2.23 ± 0.92 (2h) and 2.22 ± 0.92 (3h). Paired t test resulted in P = 0.99 (no significant difference), and the correlation coefficient was 0.98 (Fig 1). These results indicated a strong positive correlation between BSI acquired at 2 h vs. 3 h without any bias. Fig 2, 3 show representative images acquired at 2h and 3h. Conclusions: Our study indicated that the bone scan acquisition at 2 h after injection provides satisfactory images for both qualitative and quantitative assessments. ER -