MR Imaging with Metal-suppression Sequences for Evaluation of Total Joint Arthroplasty.

Metallic artifact at orthopedic magnetic resonance (MR) imaging continues to be an important problem, particularly in the realm of total joint arthroplasty. Complications often follow total joint arthroplasty and can be expected for a small percentage of all implanted devices. Postoperative complications involve not only osseous structures but also adjacent soft tissues-a highly problematic area at MR imaging because of artifacts from metallic prostheses. Without special considerations, susceptibility artifacts from ferromagnetic implants can unacceptably degrade image quality. Common artifacts include in-plane distortions (signal loss and signal pileup), poor or absent fat suppression, geometric distortion, and through-section distortion. Basic methods to reduce metallic artifacts include use of spin-echo or fast spin-echo sequences with long echo train lengths, short inversion time inversion-recovery (STIR) sequences for fat suppression, a high bandwidth, thin section selection, and an increased matrix. With care and attention to the alloy type (eg, titanium, cobalt-chromium, stainless steel), orientation of the implant, and magnetic field strength, as well as use of proprietary and nonproprietary metal-suppression techniques, previously nondiagnostic studies can yield key diagnostic information. Specifically, sequences such as the metal artifact reduction sequence (MARS), WARP (Siemens Healthcare, Munich, Germany), slice encoding for metal artifact correction (SEMAC), and multiacquisition with variable-resonance image combination (MAVRIC) can be optimized to reveal pathologic conditions previously hidden by periprosthetic artifacts. Complications of total joint arthroplasty that can be evaluated by using MR imaging with metal-suppression sequences include pseudotumoral conditions such as metallosis and particle disease, infection, aseptic prosthesis loosening, tendon injury, and muscle injury.

Cumulative Radiation Exposure to Patients Undergoing Arthroscopic Hip Preservation Surgery and Occupational Radiation Exposure to the Surgical Team.

PURPOSE: To quantify cumulative radiation exposure in patients undergoing arthroscopic hip preservation surgery and occupational exposure to operating room (OR) personnel during such surgery; a secondary objective of this study was to identify factors affecting radiation exposure in patients undergoing hip arthroscopy. METHODS: Radiation exposure from all preoperative and intraoperative imaging studies was determined for 52 patients undergoing hip arthroscopy. Cumulative and effective radiation doses were calculated and correlated with pathology and body mass index (BMI). Badge dosimeters were worn by OR personnel to measure cumulative occupational exposure. A highly sensitive portable ion chamber was used to evaluate the radiation scatter during surgery performed on a high-BMI patient and a low-BMI patient to reflect a "worst-case scenario" and "best-case scenario," respectively. RESULTS: Forty-three patients underwent procedures for femoroacetabular impingement (FAI) and 9 underwent procedures for soft-tissue pathologies (ST). The median cumulative exposure was 8.6 mGy and 5.0 mGy for FAI patients and ST patients, respectively (P = .01). The cumulative effective radiation dose was 490 mrem and 350 mrem for FAI patients and ST patients, respectively (P = .47). BMI significantly correlated with cumulative exposure (P = .0004) and trended toward significance with cumulative effective dose (P = .073). OR staff cumulative occupational exposure was low (9 mrem for the surgeon). Ion chamber data showed that increasing patient BMI resulted in increased occupational exposure. CONCLUSIONS: The median cumulative effective radiation dose to patients undergoing arthroscopic hip preservation surgery is 490 mrem and results in an excess lifetime risk of death from cancer of 0.025%. Greater BMI correlates with increased cumulative radiation exposure and may increase risk to OR personnel. Occupational exposure to the surgical team from hip arthroscopy ranges from 7 to 9 mrem per 50 hip arthroscopies (+0.0005% excess lifetime risk of death from cancer). LEVEL OF EVIDENCE: Level IV, diagnostic.

Early-stage COVID-19 pandemic observations on pulmonary embolism using nationwide multi-institutional data harvesting.

We introduce a multi-institutional data harvesting (MIDH) method for longitudinal observation of medical imaging utilization and reporting. By tracking both large-scale utilization and clinical imaging results data, the MIDH approach is targeted at measuring surrogates for important disease-related observational quantities over time. To quantitatively investigate its clinical applicability, we performed a retrospective multi-institutional study encompassing 13 healthcare systems throughout the United States before and after the 2020 COVID-19 pandemic. Using repurposed software infrastructure of a commercial AI-based image analysis service, we harvested data on medical imaging service requests and radiology reports for 40,037 computed tomography pulmonary angiograms (CTPA) to evaluate for pulmonary embolism (PE). Specifically, we compared two 70-day observational periods, namely (i) a pre-pandemic control period from 11/25/2019 through 2/2/2020, and (ii) a period during the early COVID-19 pandemic from 3/8/2020 through 5/16/2020. Natural language processing (NLP) on final radiology reports served as the ground truth for identifying positive PE cases, where we found an NLP accuracy of 98% for classifying radiology reports as positive or negative for PE based on a manual review of 2,400 radiology reports. Fewer CTPA exams were performed during the early COVID-19 pandemic than during the pre-pandemic period (9806 vs. 12,106). However, the PE positivity rate was significantly higher (11.6 vs. 9.9%, p < 10-4) with an excess of 92 PE cases during the early COVID-19 outbreak, i.e., ~1.3 daily PE cases more than statistically expected. Our results suggest that MIDH can contribute value as an exploratory tool, aiming at a better understanding of pandemic-related effects on healthcare.

Multiparametric Magnetic Resonance Imaging of Recurrent Prostate Cancer.

Multiparametric magnetic resonance (MR) imaging of the prostate combines both morphological and functional MR techniques by utilizing small field of view T1-weighted, T2-weighted, diffusion-weighted imaging, dynamic contrast-enhanced imaging, and MR spectroscopy to accurately detect, localize, and stage primary and recurrent prostate cancer. Localizing the site of recurrence in patients with rising prostate-specific antigen following treatment affects decision making regarding treatment and can be accomplished with multiparametric prostate MR. Several different treatment options are available for prostate cancer including radical prostatectomy, external beam radiation therapy, brachytherapy, androgen deprivation therapy, or a number of focal therapy techniques. The findings of recurrent prostate cancer can be different depending on the treatment the patient has received, and the radiologist must be able to recognize the variety of imaging findings seen with this common disease. This review article will detail the findings of recurrent prostate cancer on multiparametric MR and describe common posttreatment changes which may create challenges to accurate interpretation.

Imaging of the spine in sports medicine.

Much controversy exists surrounding the utility of plain film, computed tomography, magnetic resonance imaging (MRI), and bone scintigraphy in the evaluation of sports-related spine injuries. The articles reviewed here offer several different perspectives. Cervical spine radiography, return-to-play criteria following cervical trauma, lumbar pain and pars injuries, utility of MRI in acute sports injuries, and sports-specific injuries are reviewed. The relationship between bone mineral density and sports activity is also reviewed.

Stress reactions of the lumbar pars interarticularis: the development of a new MRI classification system.

STUDY DESIGN: In a retrospective study, multiple examiners reviewed lumbar magnetic resonance imaging scans to develop a new grading system for lumbar pars interarticularis stress reaction and spondylolysis. The resulting system can be used as a mechanism for classifying patients, and as a measurement tool for future studies assessing the outcome efficacy of lumbar magnetic resonance imaging in patients with abnormalities of the pars interarticularis. OBJECTIVE: To determine the reliability of patient assignment to five different grades of bone stress reaction involving the lumbar pars interarticularis. SUMMARY OF BACKGROUND DATA: Injury to the lumbar pars interarticularis (spondylolysis) is reported to be a common cause of low back pain in young patients. High-field-strength magnetic resonance imaging using fat saturation techniques and dedicated coil technology is sensitive in detecting bone stress injuries of the lumbar pars interarticularis, and thus is an excellent method for diagnosis. It also may be useful in prognostic decision making for these patients. A reliable classification system is a fundamental requirement for performing the research assessing the relationship between lumbar MRI findings and prognosis. METHODS: For this study, 55 young athletic patients undergoing evaluation for low back pain with suspected stress injury to the lumbar pars interarticularis underwent standardized lumbar magnetic resonance imaging using a 1.5-T scanner. Magnetic resonance images were reviewed by three readers using a new magnetic resonance classification system developed for lumbar spondylolysis. The findings were assessed for both interobserver and intraobserver reliability for five possible combinations in a 5-grade classification system. RESULTS: On magnetic resonance imaging, 42% of the patients demonstrated signal abnormalities of the lumbar pars interarticularis. The intraobserver and interobserver reliability coefficients for assigning the grade of pars interarticularis abnormality ranged, respectively, from 0.766 (95% confidence interval [CI], 0.62-0.91) to 0.906 (95% CI, 0.80-1), and from 0.706 (95% CI, 0.55-0.86) to 1. CONCLUSIONS: Magnetic resonance findings of stress reactions and spondylolysis of the lumbar pars interarticularis can be reliably classified into five grades by experienced readers. Further study is needed to determine the role of these findings in the management of young athletic patients with low back pain.