SPECT/CT in Imaging Foot and Ankle Pathology—The Demise of Other Coregistration Techniques

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Disorders of the ankle and foot are common and given the complex anatomy and function of the foot, they present a significant clinical challenge. Imaging plays a crucial role in the management of these patients, with multiple imaging options available to the clinician. The American College of radiology has set the appropriateness criteria for the use of the available investigating modalities in the management of foot and ankle pathologies. These are broadly classified into anatomical and functional imaging modalities. Recently, single-photon emission computed tomography and/or computed tomography scanners, which can elegantly combine functional and anatomical images have been introduced, promising an exciting and important development. This review describes our clinical experience with single-photon emission computed tomography and/or computed tomography and discusses potential applications of these techniques.

Section snippets

Conventional Radiography (X-Ray)

This remains the most widely used, accessible, and cost-effective imaging modality for evaluation and management of acute and chronic foot pain. This has a particularly important role in the management of acute trauma, while its role in chronic injuries remains limited and at best complementary to the other techniques.

CT

CT is an established technique that has been widely available for 2 decades and the advent of multidetector computed tomography (MDCT) has expanded its utility. MDCT helically acquires data that may be reconstructed in any plane, and advances in technology allows submillimeter resolution which aid the clinician to better evaluate the bones, image hardware and related complications, articular cartilage lesions, and even limited assessment of tendon disease.7 The complex anatomy of the hind- and

MRI

MRI has rapidly become the preferred modality for evaluating a variety of musculoskeletal disorders, including diseases of the foot and ankle. Advances in MRI [ultrahigh field strength magnets (>1.5 T)] and in the imaging protocols offer the potential of better signal-to-noise ratio, improved resolution, and faster scan times.11 Improved resolution permits more accurate depiction of small structures, such as the articular cartilage in small joints. MRI is routinely used in the evaluation of

Ultrasonography

Ultrasound is used in patients with foot pain, to examine the soft tissue, and is often the preferred imaging modality when Morton's neuroma or Achilles tendinosis is suspected.12 Sonographic evaluation of the ankle has distinct advantages and disadvantages. Advantages include direct correlation of sonographic findings with the patient's symptoms in comparison with the asymptomatic ankle, dynamic imaging of the foot in multiple planes and positions, wide availability of sonographic equipment,

Nuclear Medicine

A bone scan is a highly sensitive technique that has been used in the diagnosis and management of skeletal pathology for nearly 3 decades.15 Groshar et al16 in their review article have described the role of bone scintigraphy in specific conditions resulting in foot pain. Although the sensitivity of the bone scan in the diagnosis of bony pathology in the foot remains high, specificity remains suboptimal. This coupled with relatively poor resolution compared with MRI and CT remains the main

Method

Standard 2 phase bone scintigraphy after intravenous injection of 800 MBq 99mTc-methylene diphosphonate (as specified in the “Notes for Guidance on Clinical Administration of Radiopharmaceuticals and Use of Sealed Radioactive Sources −2006”) is carried out in accordance with the department bone scintigraphy protocol. This includes early blood pool imaging at 5 minutes postinjection of tracer followed by the standard delayed planar images at 3 hours postinjection. Anterior, posterior, lateral,

Postoperative Evaluation of Joint Fusion

Joint arthrodesis has long been used for the treatment of painful malalignment or arthritis of the hindfoot.22, 23, 24 Successful osseous union after joint arthrodesis is usually expected to occur within 6 months of the procedure25, 26, 27 and is confirmed if no joint motion is detected on clinical examination and there is evidence of trabeculation across the arthrodesis site as observed on plain film radiographs. Delayed union is defined as a successful fusion 6-9 months after surgery.

In

Our Experience

We have assessed the additional value of SPECT/CT in 16 patients referred from a specialist orthopedic clinic, and it was observed that SPECT/CT provided additional information in 13 of 16 (81%) patients and was unhelpful in 3 (19%) cases. A specific diagnosis was made in 6 of 13 (46%) patients, which included malunion, OCD, osteomyelitis, and inflammatory arthritis. More accurate localization of degenerative or postsurgical changes was observed in the remaining 7 patients. When compared with

Conclusion

Imaging of chronic foot pain remains complex and challenging. Currently MR remains the favored modality although with gradually increasing evidence, SPECT/CT shows promise as a valuable addition to the imaging armamentarium available to the clinician, particularly in the evaluation of pathology after surgery or in patients not suitable for MR, and may also play a role in guiding intra-articular injections.

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