Objective To explore the differences in the imaging features, clinical manifestations, age, and laboratory examination results of patients who underwent ⁹⁹Tc^m-methylenediphosphonate (MDP) SPECT/CT super bone scan.

Methods A total of 97 patients with super bone scan, including 54 males and 43 females, aged 25–85 (62.4±14.3) years, were recruited from 47 671 patients who underwent ⁹⁹Tc^m-MDP SPECT/CT imaging in the General Hospital of Ningxia Medical University from June 2012 to July 2021. The clinical manifestation, imaging, age, and laboratory examination data of the 97 patients were retrospectively analyzed. In accordance with different etiologies, the patients were divided into the bone metastases group (71 cases) and the metabolic bone disease group (26 cases, including parathyroid adenoma (9 cases), renal bone disease (6 cases), and osteoporosis (11 cases)). In accordance with the location of the primary tumor, 71 patients with bone metastases were divided into four subgroups (prostate cancer group (40 cases); breast cancer group (15 cases); lung cancer group (8 cases); malignant digestive system tumors (8 cases), including gastric cancer (4 cases), rectal cancer (2 cases), esophageal cancer (1 case) and primary liver cancer (1 case)). The differences in ⁹⁹Tc^m-MDP SPECT whole-body bone scan and SPECT/CT fusion imaging features, clinical manifestations, age, and laboratory examination (serum calcium, serum phosphorus, alkaline phosphatase (ALP), and lactate dehydrogenase (LDH)) results between the bone metastasis group and the metabolic bone disease group and among the four subgroups of the bone metastasis group were statistically analyzed. Independent samples t-test, one-way ANOVA, Wilcoxon rank sum test, and Kruskal-Wallis H test were used to compare measurement data, and χ² test was applied to compare classified variable data.

Results Bone metastases (73.2%, 71/97) were the most common cause of super bone scan (among the primary tumors, prostate cancer was more common (56.3%, 40/71), followed by metabolic bone disease (26.8%, 26/97)). The bone metastasis group mainly exhibited focal scattered distribution type (type Ⅱ, 85.9%, 61/71), and the metabolic bone disease group presented mainly homogeneous and symmetrical type (type Ⅰ, 61.5%, 16/26), and the difference between the two groups was statistically significant (χ²=21.84, P<0.001). Osteogenic (74.6%, 53/71) and mixed types (19.7%, 14/71) were the main types of bone destruction in the bone metastases group, while osteolytic type (73.1%, 19/26) was the main type of bone destruction in the metabolic bone disease group, and the differences were statistically significant (χ²=39.76, 15.95; both P<0.001). In all patients, bone pain was the first symptom, and regional bone pain was the main clinical manifestation (56.7%, 55/97). Low back pain was the most common symptom in the bone metastasis group (60.0%, 24/40) and rib pain was the most common symptom in the metabolic bone disease group (40.0%, 6/15) with a significant difference between the two groups (χ²=11.11, P<0.05). Patients with bone metastasis had higher age, serum ALP and LDH levels and lower serum calcium levels than patients with metabolic osteopathy with statistically significant differences (t=4.89; Z=−2.28, −3.65; t=−5.96; all P<0.05). However, there was no significant difference in serum phosphorus levels between the two groups (t=0.01, P>0.05). No significant differences in the types of bone destruction, clinical manifestations, and local bone pain sites in SPECT whole-body bone scan and SPECT/CT fusion imaging were found among the four subgroups of the bone metastasis group (χ²=2.71–13.07; all P>0.05). Among the four subgroups of the bone metastasis group, the patients with breast cancer had the lowest age and the highest serum calcium levels, the patients with prostate cancer had the highest age, and the patients with lung cancer had the highest LDH levels, the differences were statistically significant (F=14.43, 5.13; H=13.47; all P<0.05). There were no significant differences in serum phosphorus and ALP levels (F=2.41; H=6.28; both P>0.05).

Conclusions Bone metastases, followed by metabolic bone disease, are the most common causes for super bone scan. There were differences in ⁹⁹Tc^m-MDP SPECT whole body bone scan, focal ⁹⁹Tc^m-MDP SPECT/CT fusion imaging, clinical manifestation, age, and laboratory examination results in patiens with the two etiologies of super bone scan. ⁹⁹Tc^m-MDP SPECT/CT has a certain value in the identification of the two etiologies by super bone scan.