Value of a Lower-Limb Immobilization Device for Optimization of SPECT/CT Image Fusion

Abstract

The foot and the ankle are small structures commonly affected by disorders, and their complex anatomy represents a significant diagnostic challenge. By providing information on anatomic and bone structure that cannot be obtained from functional imaging, SPECT/CT image fusion can be particularly useful in increasing diagnostic certainty about bone pathology. However, because of the lengthy duration of a SPECT acquisition, a patient's involuntary movements may lead to misalignment between SPECT and CT images. Patient motion can be reduced using a dedicated patient support. We designed an ankle-and foot-immobilizing device and measured its efficacy at improving image fusion. Methods: We enrolled 20 patients who underwent SPECT/CT of the ankle and foot with and without a foot support. The misalignment between SPECT and CT images was computed by manually measuring 14 fiducial markers chosen among anatomic landmarks also visible on bone scintigraphy. ANOVA was performed for statistical analysis. Results: The absolute average difference without and with support was 5.1 ± 5.2 mm (mean ± SD) and 3.1 ± 2.7 mm, respectively, which is significant (P , 0.001). Conclusion: The introduction of the foot support significantly decreased misalignment between SPECT and CT images, which may have a positive clinical influence in the precise localization of foot and ankle pathology.Key Words: SPECT/CT; misalignment; lower limb; patient motion Nucl Med Technol 2015; 43:98-102 DOI: 10.2967/jnmt.114.145771 SPECT/ CT is an imaging technique combining both functional and anatomic information (1-5) in the identification and characterization of different disorders (2), including endocrine and neuroendocrine diseases, infection and inflammation (2,4,(6)(7)(8), and benign and malignant bone diseases (2,4). SPECT/CT is currently a main, growing focus of interest in the assessment of musculoskeletal disorders (5). JThe high sensitivity provided by SPECT combined with the increased specificity provided by CT (7,9) can increase accuracy and confidence in areas of special diagnostic difficulty, such as the foot and the ankle (7,9,10). Indeed, in clinical examination, it can be challenging to find the origin of the pain (10) even for the most experienced of clinicians (4), mainly because of the variety of etiologies producing similar patient complaints and clinical abnormalities (8). The foot and the ankle comprise a complex anatomy of small structures (1,9,10), including bones, ligaments, and tendons (11), which can be subject to inflammatory and degenerative diseases producing severe disability (12).To make specific diagnoses and deliver appropriate treatments, small or focal pathologic changes must be well localized (7). Currently, MR imaging is the most widely used technique in evaluating chronic foot and ankle pain, although SPECT/CT can play an important role in assessing the origin of pain (4,10) and early stages of disease (13). On the other hand, in early degenerative changes in the varus and valgus misaligned hind foot, SPECT/CT is use...

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