Comparison of bone scintigraphy and MRI imaging in detecting vertebral metastatic tumors

Objective: To compare the diagnostic value of bone scintigraphy and MRI in detecting vertebral metastastic tumors. Method:A retrospective comparison was made between 99mTc-MDP bone scintigraphy and corresponding spine MRI in 76 patients who had complementary studies within 1 month. There were 42 male and 34 female patients diagnosed with cancer prior to these studies. Cancer diagnoses included 29 lung, 15 breast, 5 liver, 5 esophagus, 4 rectum, 2 bladder, 2 thymus, 1 nasopharynx, 1 endometrium, 3 cervix uterus, 1 mucinous cystadenocarcinoma, 2 stomach,1syringocarcinoma. Ninteen patients complained backpain. Forty-two patients had bone scintigraphies done before MRI, 30 patients had MRI done after bone scintigraphy, only 4 patients had both studies on the same day. The spinal and pelvic bones which were in the scan field of MRI were observed to compare the demonstration of the lesions using bone scintigraphy and MRI. Bone scintigraphy were obtained using GE STARCAM 4000 SPECT, equipped with a parallel-hole, low-energy, high resolution collimator, 2 to 3 hrs after intravenous injection of 25 mCi (925MBq) of 99mTc-MDP, in anterior and post position after urinating.. MR studies were performed with a GE 1.5 tesla signal scanner. All patients were studied with T1-weihgted and T2-weighted spin echo sequences obtained in the sagittal plane, T1-weighted in trasversal plane ordinarily, and contrast enhancement or in coronal plane if necessary. The spinal and pelvic bones which were in the scan field of MRI were observed to compare the demonstration of the lesions using bone scintigraphy and MRI. Bone scintigraphy regions were read positive when its uptake of tracer was increased or decreased obviously compared to adjacent or contralateral structures. The criteria for the MRI diagnosis of metastases were the presence fof a well defined focus of low signals on the T1-weighted images , high and low mixed or high signal intensity on T2-weighted spin echo sequences.The comparison of the paired data were determined with a chi-square test and #P­# 0.05 was considered significant Results: Among the 76 patients, bone scintigraphy and MRI almost detected the same vertebral metastatic cases and metastatic foci .The rate of positive cases was 83.95% (68/81) and 75.30% (61/81). The rate of positive metastatic foci was 31.15% (167/536) and 29.10% (156/536). Two methods revealed that the lesions most commonly located in thoracic vertebrae, MRI detected more metastatic foci than bone scintigraphy in the site 83%(83/237) and 64% (64/237). There was no difference between bone scintigraphy and MRI in detecting metastatic foci in lumbar vertebrae. Bone scintigraphy was better than MRI in detecting cervical spine and sacrum (15/63 and 6/63 , 23/78 and 10/78 , respectively ) . MRI was better than bone scintigraphy in detecting multiple metastatic foci (143/237 and 116/237, respectively ). There were fasle positive of single focus both in bone scintigraphy (3/16) and MRI (2/11), and fasle negative foci in rapidly progressive condition in bone scintigraphy. Bone scintigraphy revealed 111 foci outside spine in 42 patients. Conclusion: The sensitivity of bone scintigraphy and MRI in detecting vertebral metastatic lesions were similar. MRI is more efficient in detecting thoracic and multiple vertebral metastases. However bone scintigraphy is more efficient in detecting vertebral metastases in cervical spine and sacrum than MRI. Considering its cost and the convenience of performing a whole-body survey for metastasis, bone scintigraphy remains the study of choice for initial evaluation of patients with cancer. MRI is a further complementary technique when bone scintigraphy findings are inadequate for answering clinical questions