SPECT/CT imaging characteristics and clinical analysis of 81 cases of super scan

Objectives: The aim of this study was to explore the SPECT/CT imaging features of super scan, as well as the differences of clinical manifestations, age, serum calcium level, phosphorus level, alkaline phosphatase (ALP) level and lactate dehydrogenase (LDH) level among groups with different causes.

Methods: A total of 10000 patients with 99mTc-MDP SPECT/CT in our hospital from January 2010 to December 2019 were collected, including 81 cases of super scan. The SPECT/CT imaging characteristics and clinical data of 81 cases of super scan were analyzed retrospectively. Based on the different causes of benign diseases and malignant tumors, they were divided into bone metastases group and metabolic osteopathy group. Then, the bone metastases group were divided into the following subgroups: prostate cancer, breast cancer, lung cancer and digestive system malignant tumors according to the primary disease of bone metastases. The SPECT/CT imaging features including the SPECT pattern (type I and II), location and bone destructive pattern in CT scan. The history and location of bone pain, results of laboratory tests were recorded and compared between groups and among subgroups. Statistical analysis was performed using SPSS 26.0.

Results: Of the 10000 patients undergoing 99mTc-MDP SPECT/CT, the positive rate of super scan was 0.81% (81/10000), of which bone metastases were the most common cause, followed by metabolic bone disease. Among the 81 cases, there were 71 cases of bone metastases and 10 cases of metabolic osteopathy. When compared the SPECT pattern, there were mainly focal scattered (type II) images in the bone metastases group (85.9%) and homogeneous symmetrical (type I) images in the metabolic osteopathy group (60%). On sectional CT, we found that most of lesions with bone metastases were osteogenic bone destruction (73.9%), while those in metabolic osteopathy were osteolytic bone destruction (57.1%), and the difference was statistically significant (p < 0.05). Local bone pain was the main clinical manifestation in all the patients(58.0% ), and low back pain was the most common location in patients with bone metastases (60%), and rib pain was the main location in patients with metabolic osteopathy (42.9%). The age and serum LDH level of patients with bone metastases was statistically higher than that of metabolic osteopathy group, and serum calcium level was statistically lower than that of metabolic osteopathy group (p < 0.05). The comparison among different primary tumors in the bone metastasis group showed that the serum calcium level of breast cancer patients was highest among that of prostate cancer and digestive system malignant tumors, and the LDH level of lung cancer patients was highest among that of prostate cancer and digestive system malignant tumors, the difference was statistically significant (p < 0.05).

Conclusions: There are many causes of super scan, of which bone metastases are the most common cause, followed by metabolic bone diseases. SPECT/CT images and clinical features of patients are different with different causes. As for SPECT imaging pattern, bone metastases group mainly showed focal scattered type (type II), the lesions showed osteogenic bone destruction on sectional CT, while in metabolic osteopathy group, they were mainly homogeneous symmetrical type (type I), showed osteolytic bone destruction on CT scan. Local bone pain was the main clinical manifestation in all the patients, and low back pain was the most common location in patients with bone metastases, and rib pain was the main locationin patients with metabolic osteopathy. The age and serum LDH level of patients with bone metastases was higher than that of metabolic osteopathy group, and serum calcium level was lower than that of metabolic osteopathy group.