Emphysematous Osteomyelitis: Novel Use of PET-MRI and a Review of Characteristic Imaging Findings.

INTRODUCTION: Emphysematous Osteomyelitis (EO) is an extremely rare bone infection caused by gas-forming bacteria with few documented cases in the literature. Our study aims to highlight characteristic imaging features, including the novel use of positron emission tomographymagnetic resonance imaging (PET-MRI) in diagnosing this potentially fatal entity. CASE: Radiography and computed tomography (CT) of the pelvis were performed due to complaints of persistent back pain in a 36-year-old male with a history of recent abdominal aorta surgery. Sacroiliac joint aspiration was performed, and a follow-up PET-MRI was subsequently performed. RESULTS: Radiography and CT demonstrated bilateral sacroiliitis, osteonecrosis and EO in the bony pelvis. Left sacroiliac joint aspiration identified Staphylococcus aureus as the causative organism. PET-MRI revealed EO with left iliopsoas abscess and abdominal aortic graft infection. The patient's symptoms resolved following antibiotic therapy and image-guided abscess drainage. CONCLUSION: EO is a lethal variant of osteomyelitis with a dearth of published cases. Pertinent imaging characteristics of EO on radiography, CT and PET-MRI are discussed here, along with a review of the literature surrounding this rare condition.

"Low Dose MR" Dixon Technique for Imaging FDG PET-MR Lymphoma.

Introduction Hybrid PET-MR is a relatively new imaging modality with its major strength being the MR component offering superior soft tissue contrast. While PET/MRI offers the inherent advantage of reduced radiation dose, it has been shown to result in a markedly prolonged examination time becoming a challenge in children and sick patients. "Low dose MRI" is a term used in the nuclear medicine community to describe fast acquired PET-MR scan protocols that rely heavily on PET images for diagnosis. In this study, we sought to determine if the Dixon sequences obtained for attenuation correction could be used as a diagnostic sequence for interpreting PET-MRI lymphoma cases, potentially reducing scan time. Materials and Methods We retrospectively identified 40 patients who underwent 88 FDG PET-MR body imaging studies for staging or restaging lymphoma. A radiologist and nuclear medicine physician initially reviewed top of the head to mid thigh PET images, attenuation correction coronal Dixon MRI sequences, and PET-MR fusion with Dixon sequence. The same physicians reviewed the PET images, multi-sequence MR including the attenuation correction Dixon, and multi-sequence PET-MR fusion images The lesions were further characterized based on their imaging characteristics, size, SUVmax, and malignant potency. A consensus read followed. Results All patients were adults with an average study age of 43.8 years. Our study consisted of 40 females and 48 males out of which 7 were for staging and 81 were for re-staging. All patients had systemic lymphoma. Thirty-seven of the studies had active lymph nodes on Dixon PET-MR that agreed with multi-sequence PET-MR which identified 33 positive cases (89.1%) having an average SUV 10.2 ± 7.74 SD. Four Dixon PET-MR cases did not detect lesions, with an average SUV 2.3 ± 0.55 SD, which was read as minimal residual activity. Multi-sequence MR identified 11 patients with enlarged lymph nodes without FDG uptake, which were not seen on Dixon MR. All 5 studies with bones lesions were detected by Dixon PET-MR as well as 2 soft tissue organ lesions. Multi-sequence MR identified 1 patient with non-active, healed bone lesion. Fifty-five of these studies were true negatives. Compared to multi-sequence PET-MR, Dixon PET-MR demonstrated 89.2% sensitivity, 100% specificity with no false positive studies. Conclusion The present study investigated the diagnostic potential of a fast protocol for integrated PET/MRI used for dedicated tumor staging of patients with lymphoma. In this retrospective study, Dixon PET-MR was shown to be sensitive and specific compared to multi-sequence PET-MR in the detection of lymphoma. The low number of these cases not detected had minimally active lymph nodes that resolved on subsequent imaging and probably were not clinically important.

Shoulder adhesive capsulitis in cancer patients undergoing positron emission tomography - computed tomography and the association with shoulder pain.

BACKGROUND: Adhesive capsulitis is a relatively common condition that can develop in cancer patients during treatment. Positron emission tomography - computed tomography (PET-CT) is routinely performed as a follow-up study in cancer patients after therapy. Being aware of PET-CT findings to suggest shoulder adhesive capsulitis may help to alert clinicians for the diagnosis of unsuspected shoulder capsulitis. AIM: To assess the association of shoulder adhesive capsulitis with cancer/therapy type and symptoms in cancer patients undergoing PET-CT. METHODS: Our prospective study received Institutional Review Board approval. Written informed consent was obtained from all patients, who answered a questionnaire regarding shoulder pain/stiffness at the time of PET-CT study, between March 2015 and April 2019. Patients with advanced glenohumeral arthrosis, metastatic disease or other mass in the shoulder, or shoulder arthroplasty were excluded. Patterns of shoulder capsule 18F-fluorodeoxyglucose (FDG) uptake were noted. Standard Uptake Value (SUV)max and SUVmean values were measured at rotator interval (RI) and deltoid muscle in bilateral shoulders. Normalized SUV (SUV of RI/SUV of deltoid muscle) was also calculated. We assessed if SUV values are different between symptomatic and asymptomatic patients in both shoulders. Covariates were age, gender, and therapy type (surgery, chemotherapy, radiation). Wilcoxon rank sum tests were used to compare unadjusted marginal differences for age, SUV measurements between symptomatic and asymptomatic patients. Multiple linear regression models were used to examine the relationship between right or left shoulder SUV measurements and symptom status, after adjusting for covariates. Statistical significance level was set at P < 0.05. RESULTS: Of 252 patients initially enrolled for the study (mean age 66 years, 67 symptomatic), shoulder PET-CT data were obtained in 200 patients (52 were excluded due to exclusion criteria above). The most common cancer types were lymphoma (n = 61), lung (n = 54) and breast (n = 53). No significant difference was noted between symptomatic and asymptomatic patients in terms of age, gender, proportion of patients who had surgical therapy and radiation therapy. A proportion of patients who received chemotherapy was higher in patients who were asymptomatic in the right shoulder compared to those symptomatic in the right shoulder (65% vs 48%, P = 0.012). No such difference was seen for the left shoulder. In both shoulders, SUVmax and SUVmean were higher in symptomatic shoulders than asymptomatic shoulders (Left SUVmax 2.0 vs 1.6, SUVmean 1.6 vs 1.3, both P < 0.002; Right SUVmax 2.2 vs 1.8, SUVmean 1.8 vs 1.5, both P < 0.01). For lung cancer patients, bilateral RI SUVmax and SUVmean values were higher in symptomatic shoulders than asymptomatic shoulders. For other cancer patients, symptomatic patients had higher left RI SUVmax/mean than asymptomatic patients after adjustment. CONCLUSION: In symptomatic patients metabolic activities in RI were higher than asymptomatic patients. Adhesive capsulitis should be considered in cancer patients with shoulder symptoms and positive FDG uptake in RI.

Severity of heterotopic ossification in patients following surgery for hip fracture: a retrospective observational study.

BACKGROUND: Heterotopic ossification (HO) is a relatively common complication following hip surgery treated with open reduction and internal fixation, total arthroplasty or hemiarthroplasty. Development of HO after hip surgery is an important clinical issue as it can affect functional status. We aimed to determine whether there was association between severity of heterotopic ossification about the hip and the interval between the time of hip fracture and surgery. MATERIALS AND METHODS: Our retrospective study included 151 patients (age range 33-95 years) treated for hip fractures by hemiarthroplasty. Medical records were reviewed for time interval to surgery, laterality, surgical approach, and patient age. Patients who had any post-operative complications were excluded. Radiographs were semiquantitatively assessed for the degree of heterotopic ossification based on Brooker Classification (5-point scale). Statistical analysis was performed utilizing Chi-square, Kruskal-Wallis, and Score tests, and also a proportional odds model (significance level set at 0.05). RESULTS: Thirty eight patients had no heterotopic ossification, 43 had class 1, 55 had class 2, and 15 had class 3 or greater heterotopic ossification. The majority of patients (59.6%) had surgery within 2 days of acute injury. Severe heterotopic ossification (HO 3+) was associated with the longer interval between the time of acute hip fracture and surgery (median 6 days) vs. median 2 days in all other groups (HO classes 0-2) (p = 0.0015). The odds ratio and 95% CI for one level higher HO class was 1.296 (1.152, 1.459), which meant that the odds of having HO class one level higher increased by about 29.6% for every one-day increase in the days to surgery. No significant association was found for other variables. CONCLUSION: Class 3 or greater HO was associated with longer time interval between time of acute hip fracture and surgery compared to all other groups (HO class 0-2).

Herpes zoster ophthalmicus caught in the (Tr)act!

To emphasize the utility of contrast enhanced MRI for identifying the extent of disease in herpes zoster ophthalmicus with intracranial extension to help determine proper management. We present a rare case of herpes zoster ophthalmicus (HZ/HZO) with intracranial extension and MRI demonstration of involvement of the trigeminal nerve, the trigeminal nucleus, and the spinal trigeminal nucleus and tract. Herpes zoster is caused by reactivation of varicella zoster virus. Herpes zoster ophthalmicus with involvement of the ophthalmic division of the trigeminal nerve has been estimated to account for 10-20% of the cases (Yawn et al. in Mayo Clin Proc 88:562-570, 2013). While postherpetic neuralgia is the most common complication, HZ/HZO can rarely manifest in a more sinister manner resulting in multi-dermatomal involvement, disseminated disease, cranial arteritis (Walker in Radiology 107:109-110, 1973), cranial nerve paresis (O.d in Clinical Eye and Vision Care 11:75-80, 1999), hemiplegia (Cavaletti in The Italian Journal of Neurological Sciences 11:297-300, 1990), ocular/dysfunction (Kocaoglu in Türk Oftalmoloji Dergisi 48:42-46, 2018), and intracranial extension (Chen in BMC Infectious Diseases 17:213, 2017; Yawn in Mayo Clin Proc. 88:562-570, 2013). Contrast enhanced MRI (CE-MRI) can be of great benefit to elucidate the extent of disease and intracranial involvement for institution of more aggressive management to prevent further complications.