To evaluate the role of bone SPECT in diagnosing metastasis to the skull base in cancer patients.
Skull base metastasis often causes characteristic clinical syndromes. Antitumor treatment ameliorates or stabilizes symptoms in most patients. Diagnosis may be difficult when neuroimaging studies are negative (as occurs in about one-quarter of patients). Case reports have suggested a role for bone SPECT in these patients.
We reviewed the charts of all patients (1993-1996) at our institution who had skull base SPECT and at least one neuroimaging study (CT or MRI) for clinically suspected metastasis to the base of the skull. Bone SPECT, CT, and MRI were blindly re-evaluated.
We studied 56 patients, of whom 36 had skull base metastasis. Twenty patients had other causes of the clinical syndrome, including leptomeningeal and posterior fossa metastasis, or benign causes. In 29 of 36 patients (81%) with skull base metastasis, CT or MRI clearly demonstrated the lesion. Bone SPECT identified a hot spot in the appropriate region of the skull base in 28 of 36 patients (78%). All seven patients with negative CT or MRI had positive SPECT and four of these had a response to anti-tumor treatment.
SPECT of the skull base can demonstrate lesions not identifiable by CT or MRI. In cancer patients suspected of having skull base metastasis, we recommend SPECT of the skull base when CT or MRI studies are negative.
[Show abstract][Hide abstract] ABSTRACT: Background: The authors evaluated the performance of 99m Tc-MDP planar skull bone scan in detecting basal skull lesions in patients with nasopharyngeal carcino- ma, proposed a strategy for effective use of planar and SPECT skull bone scan in the imaging of NPC patients, and evaluated the influence of increased mastoid bone uptake on the interpretation of planar skull bone scans. Methods: One hundred and seventeen patients with nasopharyngeal carcinoma underwent whole body, bilateral planar skull, and skull SPECT bone scans. The findings for the skull base and mastoid bone on planar and SPECT images as interpreted by three nuclear medicine physicians from different hospitals were com- pared to reach a consensus. The SPECT consensus was then used as the final result for performance evalu- ation of the planar images. Results: The planar skull bone scan had a sensitivity of 78%, a specificity of 77%, an accuracy of 78%, a posi- tive predictive value of 94%, and a negative predictive value of 45%. The consensus results and performance between the patients with and without mastoid lesions showed no significant statistical differences. Conclusion: We recommend NPC patients with nega- tive or equivocal findings on planar skull bone scan undergo skull SPECT for further evaluation while those with positive findings may save the SPECT unless oth- erwise indicated. Increased uptake in mastoid bone does not adversely affect the reading of planar skull bone scan.
[Show abstract][Hide abstract] ABSTRACT: Single photon emission computed tomography (SPECT) of the bone is the second most frequently performed SPECT examination in routine nuclear medicine practice, with cardiac SPECT being the most frequent. Compared with planar scintigraphy, SPECT increases image contrast and improves lesion detection and localization. Studies have documented the unique diagnostic information provided by SPECT, particularly for avascular necrosis of the femoral head, in patients with back pain, for the differential diagnosis between malignant and benign spinal lesions, in the detection of metastatic cancer in the spine, for the diagnosis of temporomandibular joint internal derangement, and for the evaluation of acute and chronic knee pain. Although less rigorously documented, SPECT is being increasingly used in all types of situations that demand more precise anatomic localization of abnormal tracer uptake. The effectiveness of bone SPECT increases with the selection of the proper collimator, which allows one to acquire adequate counts and minimize the patient-to-detector distance. Low-energy, ultrahigh-resolution or high-resolution collimation is preferred over all-purpose collimators. Multihead gamma cameras can increase the counts obtained or shorten acquisition time, making SPECT acquisitions more practical in busy departments and also increasing image quality compared with single-head cameras. Iterative reconstruction, with the use of ordered subsets estimation maximization, provides better quality images than classical filtered back projection algorithms. Three-dimensional image analysis often aids lesion localization.
Seminars in Nuclear Medicine 02/2001; 31(1):3-16. DOI:10.1053/snuc.2001.18736 · 3.34 Impact Factor
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