Neurovascular, Muscle, and Skin Changes on [18F]FDG PET/MRI in Complex Regional Pain Syndrome of the Foot: A Prospective Clinical Study

A Case Report of Neuroleukemiosis Detected on FDG PET Scan in a Patient of Mixed Phenotype Acute Leukemia Post Bone Marrow Transplantation in Remission

Neuroleukemiosis, an exceedingly rare manifestation of leukemia, is defined as peripheral nerve infiltration by leukemic cells. The typical clinical presentation is with peripheral neuropathy and/or chloromatous masses. The diagnosis of this condition is quite challenging, as symptoms usually appear in patients during remission and there are no other signs of relapse. The diagnosis is supported with electrophysiologic testing and imaging and finally established with histopathology and immunophenotyping. We present a case of multineuritis in a patient with mixed phenotype acute leukemia during remission post allogeneic hematopoietic stem cell transplant, where inflamed thickened nerves were detected on positron emission tomography/computed tomography imaging with fluorine-18 fluorodeoxyglucose. A diagnosis of neuroleukemiosis was established via biopsy and immunophenotyping. The literature is reviewed regarding this interesting and rare clinical condition.

What Role Does PET/MRI Play in Musculoskeletal Disorders?

Musculoskeletal disorders of nononcological origin are one of the most frequent reasons for consultation. Patients suffering from musculoskeletal disorders also consult more than once for the same reason. This results in multiple clinical follow-ups after several radiological and serum examinations, the main ones including X-rays targeting the painful anatomical region and inflammatory serum parameters. As part of their work up, patients suffering from musculoskeletal disorders often require multisequence, multi-parameter MRI. PET/MRI is a promising imaging modality for their diagnosis, with the added advantage of being able to be performed in a single visit. PET/MRI is particularly useful for diagnosing osteomyelitis, spondylodiscitis, arthritis, many pediatric pathologies, and a wide range of other musculoskeletal pathologies. PET/MRI is already used to diagnose malignant bone tumors such as osteosarcoma. However, current knowledge of the indications for PET/MRI in nononcological musculoskeletal disorders is based on studies involving only a few patients. This review focuses on the usefulness of PET/MRI for diagnosing nononcological musculoskeletal disorders.

Multimodal positron emission tomography (PET) imaging in non-oncologic musculoskeletal radiology

Musculoskeletal (MSK) disorders are associated with large impacts on patient's pain and quality of life. Conventional morphological imaging of tissue structure is limited in its ability to detect pain generators, early MSK disease, and rapidly assess treatment efficacy. Positron emission tomography (PET), which offers unique capabilities to evaluate molecular and metabolic processes, can provide novel information about early pathophysiologic changes that occur before structural or even microstructural changes can be detected. This sensitivity not only makes it a powerful tool for detection and characterization of disease, but also a tool able to rapidly assess the efficacy of therapies. These benefits have garnered more attention to PET imaging of MSK disorders in recent years. In this narrative review, we discuss several applications of multimodal PET imaging in non-oncologic MSK diseases including arthritis, osteoporosis, and sources of pain and inflammation. We also describe technical considerations and recent advancements in technology and radiotracers as well as areas of emerging interest for future applications of multimodal PET imaging of MSK conditions. Overall, we present evidence that the incorporation of PET through multimodal imaging offers an exciting addition to the field of MSK radiology and will likely prove valuable in the transition to an era of precision medicine.

Imaging of Pain using Positron Emission Tomography

Positron emission tomography (PET) is a noninvasive molecular imaging technique that utilizes biologically active radiolabeled compounds to image biochemical processes. As such, PET can provide important pathophysiological information associated with pain of different etiologies. As such, the information obtained using PET often combined with MRI or CT can provide useful information for diagnosing and monitoring changes associated with pain. This review covers the most important PET tracers that have been used to image pain including tracers for fundamental biological processes such as glucose metabolism and cerebral blood flow to receptor-specific tracers such as ion channels and neurotransmitters. For tracer type, we describe the structure and radiochemical synthesis of the tracer followed by a brief summary of the available preclinical and clinical studies. By providing a summary of the PET tracers that have been employed for PET imaging of pain, this review aims to serve as a reference for preclinical, translational and clinical investigators interested in molecular imaging of pain. Finally, the review ends with an outlook of the needs and opportunities in this area.

Up-and-coming Radiotracers for Imaging Pain Generators

Chronic musculoskeletal pain is among the most highly prevalent diseases worldwide. Managing patients with chronic pain remains very challenging because current imaging techniques focus on morphological causes of pain that can be inaccurate and misleading. Moving away from anatomical constructs of disease, molecular imaging has emerged as a method to identify diseases according to their molecular, physiologic, or cellular signatures that can be applied to the variety of biomolecular changes that occur in nociception and pain processing and therefore have tremendous potential for precisely pinpointing the source of a patient's pain. Several molecular imaging approaches to image the painful process are now available, including imaging of voltage-gated sodium channels, calcium channels, hypermetabolic processes, the substance P receptor, the sigma-1 receptor, and imaging of macrophage trafficking. This article provides an overview of promising molecular imaging approaches for the imaging of musculoskeletal pain with a focus on preclinical methods.

Value of Edema-like Marrow Signal Intensity in Diagnosis of Joint Pain: Radiologists' Perspective

Musculoskeletal pain is a significant contributor to disability. The mechanism and target of the treatment should be optimized by imaging, but currently no accepted gold standard exists to image pain. In addition to end-organ pathology, other mediators also contribute to nociception, such as angiogenesis, axonal extension, immunologic modulation, and central sensitization. Recent research indicates that local inflammation is a significant contributor to pain in the extremities; therefore, we focus here on edema-like marrow signal intensity (ELMSI). We examine both the relevance of ELMSI for pain and novel imaging techniques.

A Practical Guide to Sigma-1 Receptor Positron Emission Tomography/Magnetic Resonance Imaging: A New Clinical Molecular Imaging Method to Identify Peripheral Pain Generators in Patients with Chronic Pain

Accurately identifying the peripheral pain generator in patients with chronic pain remains a major challenge for modern medicine. Millions of patients around the world suffer endlessly from difficult-to-manage debilitating pain because of very limited diagnostic tests and a paucity of pain therapies. To help these patients, we have developed a novel clinical molecular imaging approach, and, in its early stages, it has been shown to accurately identify the exact site of pain generation using an imaging biomarker for the sigma-1 receptor and positron emission tomography/magnetic resonance imaging. We hope the description of the work in this article can help others begin their own pain imaging programs at their respective institutions.

Update on Positron Emission Tomography/Magnetic Resonance Imaging: Cancer and Inflammation Imaging in the Clinic

Hybrid PET/MRI is highly valuable, having made significant strides in overcoming technical challenges and offering unique advantages such as reduced radiation, precise data coregistration, and motion correction. Growing evidence highlights the value of PET/MRI in broad clinical aspects, including inflammatory and oncological imaging in adults, pregnant women, and pediatrics, potentially surpassing PET/CT. This newly integrated solution may be preferred over PET/CT in many clinical conditions. However, further technological advancements are required to facilitate its broader adoption as a routine diagnostic modality.

Determinants of Complex Regional Pain Syndrome Type I among Radial Head Fracture Patients with Unilateral Arthroplasty

OBJECTIVE

This study aims to assess the proportions of complex regional pain syndrome type I (CRPS I) in radial head fracture patients undergoing unilateral arthroplasty and to explore associated factors.

METHODS

This is a prospective observational study. From March 2016 to May 2019, a total of 221 adult patients with radial head fracture patients were included in consecutive studies and completed the 1-year follow-up. All patients were treated by unilateral arthroplasty. At each follow-up visit, the visual analogue scale was used to measure patients' pain level. Occurrence of CRPS I, which was diagnosed by Budapest criteria, was the main outcome collected at baseline and the 1-, 3-, 6-, and 9-month follow-ups. The baseline data were collected before surgery and included demographic and clinical data. Independent t-tests and χ² tests were used as univariate analyses to compare the baseline data of patients with and without CRPS I. Multivariate analysis (Backword-Wald) was used to identify factors independently associated with CRPS I.

RESULTS

The proportion of CRPS I cases among radial head fracture patients undergoing unilateral arthroplasty was 11% (n = 24). A total of 19 (79%) patients were diagnosed with CRPS I within 1 month after surgery. Multivariable logistic regression analysis revealed that female gender (odds ratios [OR]: 1.537; 95% confidence interval [CI]: 1.138-2.072), age younger than 60 years (OR: 1.682; 95% CI: 1.246-2.267), moderate and severe Mayo Elbow Performance Score (MEPS) pain (OR: 3.229; 95% CI: 2.392-4.351) and anxiety (OR: 83.346; 95% CI: 61.752-112.320) were independently associated with CRPS I.

CONCLUSIONS

This exploratory study reported that the incidence of CRPS I developing after radial head arthroplasty was 11%. Female sex, younger age, moderate and severe MEPS pain and anxiety patients seems more likely to develop CRPS I.