Imaging features of soft-tissue infections.

Skin and soft tissues are among the most common sites of infections. Infections can involve the superficial epidermis to deep muscles and bones. Most infections spread through contiguous structures, although hematogenous spread can occur in the setting of an immunocompromised state and with atypical infections. While clinical diagnosis of infections is possible, it often lacks specificity, necessitating the use of imaging for confirmation. Cross-sectional imaging with US, CT, and MRI is frequently performed not just for diagnosis, but to delineate the extent of infection and to aid in management. Nonetheless, the imaging features have considerable overlap, and as such, it is essential to integrate imaging features with clinical features for managing soft tissue infections. Radiologists must be aware of the imaging features of different infections and their mimics, as well as the pros and cons of each imaging technique to properly use them for appropriate clinical situations. In this review, we summarize the most recent evidence-based features of key soft tissue infections.

Spontaneous pancreatic pseudocyst - superior mesenteric vein fistula: A rare complication of chronic pancreatitis.

Pseudocyst formation is common in chronic pancreatitis. A rare subset of these patients may develop fistulization between the pseudocyst and the portal vein system. We report a case of spontaneous pancreatic pseudocyst - superior mesenteric vein fistula in a 61-year-old male with a history of chronic recurrent calcifying pancreatitis. The fistulous connection was correctly identified on both computed tomography and magnetic resonance cholangiopancreatography (MRCP), and the patient was treated successfully with a conservative approach. Our case report aims to educate on this rare and potentially fatal vascular complication of chronic pancreatitis and to discuss the role of modern noninvasive imaging techniques, such as T2-weighted MRI/MRCP, in establishing this diagnosis and making a decision regarding its management.

Soft-Tissue Infections and Their Imaging Mimics: From Cellulitis to Necrotizing Fasciitis.

Infection of the musculoskeletal system can be associated with high mortality and morbidity if not promptly and accurately diagnosed. These infections are generally diagnosed and managed clinically; however, clinical and laboratory findings sometimes lack sensitivity and specificity, and a definite diagnosis may not be possible. In uncertain situations, imaging is frequently performed to confirm the diagnosis, evaluate the extent of the disease, and aid in treatment planning. In particular, cross-sectional imaging, including computed tomography and magnetic resonance imaging, provides detailed anatomic information in the evaluation of soft tissues due to their inherent high spatial and contrast resolution. Imaging findings of soft-tissue infections can be nonspecific and can have different appearances depending on the depth and anatomic extent of tissue involvement. Although many imaging features of infectious disease can overlap with noninfectious processes, imaging can help establish the diagnosis when combined with the clinical history and laboratory findings. Radiologists should be familiar with the spectrum of imaging findings of soft-tissue infections to better aid the referring physician in managing these patients. The aim of this article is to review the spectrum of soft-tissue infections using a systematic anatomic compartment approach. We discuss the clinical features of soft-tissue infections, their imaging findings with emphasis on cross-sectional imaging, their potential mimics, and clinical management. ©RSNA, 2016.

Role of Optimal Quantification of FDG PET Imaging in the Clinical Practice of Radiology.

The combination of fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) and computed tomography (CT) for dual-modality imaging (PET/CT) plays a key role in the diagnosis and staging of FDG-avid malignancies. FDG uptake by the tumor cells offers an opportunity to detect cancer in organs that appear normal at anatomic imaging and to differentiate viable tumor from posttreatment effects. Quantification of FDG uptake has multiple clinical applications, including cancer diagnosis and staging. Dedicated FDG PET/CT-based visual and quantitative criteria have been developed to evaluate treatment response. Furthermore, the level of tumor FDG uptake reflects the biologic aggressiveness of the tumor, predicting the risk of metastasis and recurrence. FDG uptake can be measured with qualitative, semiquantitative, and quantitative methods. Qualitative or visual assessment of PET/CT images is the most common clinical approach for describing the level of FDG uptake. Standardized uptake value (SUV) is the most commonly used semiquantitative tool for measuring FDG uptake. SUV can be measured as maximum, mean, or peak SUV and may be normalized by using whole or lean body weight. SUV measurements provide the basis for quantitative response criteria; however, SUVs have not been widely adopted as diagnostic thresholds for discriminating malignant and benign lesions. Volumetric FDG uptake measurements such as metabolic tumor volume and total lesion glycolysis have shown substantial promise in providing accurate tumor assessment. SUV measurement and other quantification techniques can be affected by many technical, physical, and biologic factors. Familiarity with FDG uptake quantification approaches and their pitfalls is essential for clinical practice and research.

Suture slippage in knotless suture anchors resulting in subacromial-subdeltoid bursitis.

Rotator cuff repair using a suture bridge and knotless suture anchors is a relatively new, but increasingly used technique. The suture bridge technique creates an anatomically similar and more secure rotator cuff repair compared with conventional arthroscopic techniques and the use of knotless anchors eliminates the challenges associated with knot tying during arthroscopic surgery. However, previous in vitro biomechanical tests have shown that the hold of the suture in a knotless suture anchor is far lower than the pullout strength of the anchor from bone. Up until now slippage has been a theoretical concern. We present a prospectively diagnosed case of in vivo suture loosening after rotator cuff repair using a knotless bridge technique resulting in subacromial-subdeltoid bursitis.

Vascular access graft and native arterial branch fistulous formation.

This is the first reported case of an unusual complication of upper extremity swelling of the arm in a patient with an arteriovenous (AV) graft for haemodialysis. A graftogram demonstrated an aberrant fistula formation between the native arterial branch and the AV graft (aberrant arterio-graft fistula). Inadvertent back wall laceration of the AV graft during haemodialysis cannulation was postulated to be the aetiology. Aberrant arterio-graft fistula formation may be hard to diagnose because of the presence of thrill or bruit at the level of the anastomoses and rarity of the complication. Progression of extremity swelling with or without central venous occlusion should raise the suspicion and sought further investigation. Proper cannulation techniques prior to haemodialysis may prevent such complications.

Utility of fluorodeoxyglucose-positron emission tomography in the identification of new lesions in lung cancer patients for the assessment of therapy response.

PURPOSE: Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1) has added positron emission tomography (PET) as an optional complement for the detection of new lesions. In this study, we evaluate the utility of fluorodeoxyglucose (FDG)-PET in the identification of new lesions and progressive disease not recognized on computed tomography (CT) in patients with nonsmall cell lung cancer (NSCLC) undergoing therapy. MATERIALS AND METHODS: Seventy patients (30 female, 40 male; mean age 67±14 years, range, 39-94 years) with NSCLC underwent FDG-PET before and after chemotherapy and/or radiotherapy, whereas 69 patients underwent CT imaging. Overall (OS) and progression-free survivals (PFS) were calculated for RECIST 1.1 with CT alone, RECIST 1.1 with PET for the identification of new lesions, visual PET, and semiquantitative PET using a change in standardized uptake value ranging from -15 to -50%. RESULTS: PET identified new lesions in 26 patients, resulting in 10 patients (14.5%) being upgraded to progressive disease. The combination of CT and PET for the detection of new lesions improved the prediction of survival (OS: P=0.0491 for all stages and P=0.0033 for stage IV; PFS: P=0.0045 for stage IV) compared with CT imaging alone (OS: P=0.1362 for all stages and P=0.1625 for stage IV; PFS: P=0.0632 for stage IV). Furthermore, a change in standardized uptake value of -35% was the most discriminative for the prediction of survival for the semiquantitative PET approach (OS: P=0.0393 for all stages, P=0.0051 for stage IV; PFS: P=0.0092 for stage IV) and more discriminative than the visual PET approach (OS: P=0.2699 for all stages, P=0.0105 for stage IV; PFS: P=0.014 for stage IV). CONCLUSION: FDG-PET is helpful in identifying new lesions in NSCLC patients, resulting in the improved assessment of therapy response with CT imaging combined with FDG-PET compared with CT imaging alone. Although RECIST 1.1 includes FDG-PET only as an optional adjunct, we recommend the implementation of PET imaging in the assessment of therapy response.

Proximal tibial osteophytes and their relationship with the height of the tibial spines of the intercondylar eminence: paleopathological study.

OBJECTIVE: Tibial spiking (i.e., spurring of tibial spines), eburnation, and osteophytes are considered features of osteoarthritis. This investigation employed direct inspection of the medial and lateral tibial plateaus in paleopathological specimens to analyze the frequency and morphological features of osteoarthritis and to define any relationship between the size of osteophytes and that of the intercondylar tibial spines. MATERIALS AND METHODS: A total of 35 tibial bone specimens were evaluated for the degree of osteoarthritis and presence of eburnation. Each plateau was also divided into four quadrants and the presence and size of bone outgrowths were recorded in each quadrant. The "medial/lateral tibial intercondylar spine index" for each specimen was calculated as follows: (medial/lateral intercondylar tibial spine height)/(anteroposterior width of the superior tibial surface). The relationships between medial and lateral tibial height indexes with the degree of osteoarthritis were then tested. RESULTS: Osteophytes were observed more frequently in the anterior quadrants of both tibial plateaus than in the posterior quadrants (29 vs 16 for the medial tibial plateau [p = 0.01] and 28 vs 20 for the lateral tibial plateau [p = 0.04]). Eburnation was seen more frequently in the posterior regions of both tibial plateaus than in the anterior regions (17 vs 5, p < 0.01). In specimens with no signs of osteoarthritis the lateral intercondylar tibial index was significantly lower than that in specimens with some degree of osteoarthritis (p = 0.02). The medial intercondylar tibial index of the specimens with no signs of osteoarthritis was not significantly different from that of the specimens with some degree of osteoarthritis (p = 0.45). There was a positive correlation between the lateral spine height index and the overall grading of osteoarthritis, (r = 0.6, p < 0.01). In the anteromedial and posteromedial quadrants of the lateral tibial plateau, the association between the lateral intercondylar tibial spine index and the grade of osteophytes was 0.5 (p < 0.01) and 0.7 (p < 0.01) respectively. CONCLUSION: Spiking of the lateral tibial intercondylar spine is associated with osteophyte formation and osteoarthritis. Eburnation occurs mainly in the posterior parts of the tibial plateaus while osteophytes arise mainly in the anterior parts. These findings suggest that stresses occurring in the flexed knee may contribute to many of the morphological abnormalities of osteoarthritis.

Anterior ankle impingement and talar bony outgrowths: osteophyte or enthesophyte? Paleopathologic and cadaveric study with imaging correlation.

OBJECTIVE: Bony "spurs" are a major component of anterior ankle impingement syndrome. The two major accepted hypotheses on the origin of these bony spurs are osteophyte formation due to repetitive microtrauma and enthesophyte development because of recurrent capsular or ligamentous traction. The purpose of this study was to provide a detailed evaluation of the bony outgrowths that arise on the anterior aspect of the talus and correlate them with the sites of capsular attachment. MATERIALS AND METHODS: Twenty-eight well-preserved talus bones from the San Diego Museum of Man were assessed regarding the presence of outgrowths on the anterior aspect of the talus. The distance of the outgrowths from the talar head was measured. The results were correlated with measurements of capsular attachment on the anterior aspect of the talus derived from MR arthrographic images in 13 cadaveric ankles. RESULTS: The average distance of capsular attachment from the talar head in the medial aspect of the bone was 10.63 mm and in the lateral part was 12.04 mm. The mean distance of bony spurs from the talar head in the medial and lateral parts of the talus was 17.2 and 12.5 mm, respectively. Medially, the talar spurs developed more proximally on the neck compared to the capsular attachment (p < 0.01). Laterally, this difference was not significant (p = 0.26). CONCLUSION: On the medial part of the anterior talus, bone development appears to occur in an intraarticular location (i.e., osteophytes). Laterally, the outgrowths develop extraarticularly and appear to result from capsular and ligamentous traction (i.e., enthesophytes).