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Biomedical subjects

Derek R Armfield

Publications and source records attributed to Derek R Armfield.

11 recordsLinked to original sources
PubMed2007

Assessment of normal ACL double bundle anatomy in standard viewing planes by magnetic resonance imaging.

Anatomical studies show that the native ACL consists of two distinct functional bundles, termed the anteromedial (AM) and posterolateral (PL) bundles. The utility of using routine magnetic resonance imaging (MRI) to distinguish the individual bundles of the ACL has not been evaluated. The purpose of this study was to evaluate the intra- and inter-observer agreement for assessment of the AM and PL bundles using MRI in the axial, coronal, and sagittal viewing planes. We identified a series of patients seen in the senior author's clinic during a 16-month period. Images were independently evaluated in blinded fashion at two separate time points by a musculoskeletal radiologist and two orthopaedic residents. The AM bundle was detected in most planes of view with high frequency and reliability, while detection of the PL bundle was less frequent and had a lower associated reliability. Our results indicate that it is difficult to reliably detect both the AM and PL bundles using a low-field strength magnet with standard planes of view. It has been demonstrated that the ACL may be imaged effectively in planes that are based on the natural course of the ligament, and it is likely that this will also facilitate visualization of the individual AM and PL bundles. The use of additional oblique planes of view offers a potential approach for improved evaluation of the ACL, even with low field strength magnets. Future work in this area may assist in the pre-operative assessment of isolated AM or PL bundle injuries, facilitating a more anatomic approach to ACL reconstruction.

Adult↗
PubMed2006

Arthroscopic capsulolabral reconstruction for posterior instability of the shoulder: a prospective study of 100 shoulders.

BACKGROUND: There are few reports in the literature detailing arthroscopic treatment of unidirectional posterior shoulder instability. HYPOTHESIS: Arthroscopic capsulolabral reconstruction is effective in restoring stability and function and alleviating pain in athletes with symptomatic unidirectional posterior instability. This population has significant differences in glenoid and chondrolabral versions when compared with controls. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Ninety-one athletes (100 shoulders) with unidirectional recurrent posterior shoulder instability were treated with an arthroscopic posterior capsulolabral reconstruction and evaluated at a mean of 27 months postoperatively. A subset of 51 shoulders in contact athletes were compared with the entire group of 100 shoulders. Patients were evaluated prospectively with the American Shoulder and Elbow Surgeons scoring system. Stability, strength, and range of motion were evaluated preoperatively and postoperatively with standardized subjective scales. Forty-eight shoulders had magnetic resonance arthrograms performed and were available for review. The posterior inferior chondrolabral and bony glenoid versions were measured and compared with controls. RESULTS: At a mean of 27 months postoperatively, the mean American Shoulder and Elbow Surgeons score improved from 50.36 to 85.66 (P < .001). There were significant improvements in stability, pain, and function based on standardized subjective scales (P < .001). The contact athletes did not demonstrate any significant differences when compared with the entire cohort for any outcome measure. The results in the 71 shoulders followed for at least 2 years were similar to the overall group. On magnetic resonance arthrography, the shoulders with posterior instability were found to have significantly greater chondrolabral and osseous retroversion in comparison with controls (P < .001 and P = .008, respectively). CONCLUSION: Arthroscopic capsulolabral reconstruction is an effective, reliable treatment for symptomatic unidirectional recurrent posterior glenohumeral instability in an athletic population. Overall, 89% of patients were able to return to sport, with 67% of patients able to return to the same level postoperatively.

Adolescent↗
PubMed2006

Radiographic and MR imaging of the athletic hip.

Imaging of the athletic hip has changed significantly over the past 10 years to address clinical concerns of intra-articular pathology and femoroacetabular impingement. Currently, high-resolution direct MR arthrography of the hip provides the best means for evaluating intra-articular pathology. However, radiography remains important for the diagnosis of subtle bony irregularities associated with femoroacetabular impingement. Therefore, a comprehensive imaging strategy requires conventional radiographs and MRI to evaluate intra- and extra-articular sources of pain. Because of newer surgical techniques, MR interpretations should provide description of labral tears and assessment of cartilage defects, as well as, capsule/iliofemoral ligament injury, femoroacetabular impingement, and tears of the ligamentum teres to aid preoperative planning and help provide prognostic information.

Adult↗
PubMed2003

Performance change of mammographic CAD schemes optimized with most-recent and prior image databases.

RATIONALE AND OBJECTIVES: The authors evaluated performance changes in the detection of masses on "current" (latest) and "prior" images by computer-aided diagnosis (CAD) schemes that had been optimized with databases of current and prior mammograms. MATERIALS AND METHODS: The authors selected 260 pairs of matched consecutive mammograms. Each current image depicted one or two verified masses. All prior images had been interpreted originally as negative or probably benign. A CAD scheme initially detected 261 mass regions and 465 false-positive regions on the current images, and 252 corresponding mass regions (early signs) and 471 false-positive regions on prior images. These regions were divided into two training and two testing databases. The current and prior training databases were used to optimize two CAD schemes with a genetic algorithm. These schemes were evaluated with two independent testing databases. RESULTS: The scheme optimized with current images produced areas under the receiver operating characteristic curve of (0.89 +/- 0.01 and 0.65 +/- 0.02 when tested with current images and prior images, respectively. The scheme optimized with prior images produced areas under the receiver operating characteristic curve of 0.81 +/- 0.02 and 0.71 +/- 0.02 when tested with current images and prior images, respectively. Performance changes for both current and prior testing databases were significant (P < .01) for the two schemes. CONCLUSION: CAD schemes trained with current images do not perform optimally in detecting masses depicted on prior images. To optimize CAD schemes for early detection, it may be important to include in the training database a large fraction of prior images originally reported as negative and later proven to be positive.

Algorithms↗
PubMed2003

Biomechanical basis of common shoulder problems.

Balancing mobility and stability, the biomechanics of the shoulder provides optimal use of the thumb and hand. More than a glenohumeral joint, the shoulder complex consists of four joints and numerous muscles and ligaments. Injuries to the shoulder result from overuse, extremes of motion, and excessive forces. This review describes basic shoulder biomechanics, their role in impingement and instability, and how imaging can detail shoulder function and dysfunction.

Biomechanical Phenomena↗
PubMed2003

Hip biomechanics: importance to functional imaging.

Although well recognized the hip joint is not well understood. In many respects knowledge of the hip is similar to that of the knee several decades ago. Increased understanding of the hip's structure and function will improve our ability to diagnose and treat pre-end-stage hip joint disease. This article describes relevant anatomy and mechanics and details the crucial role that imaging plays in current assessments of hip function.

Biomechanical Phenomena↗
PubMed2003

Knee joint biomechanics: relevance to imaging.

Over the past 2 decades our understanding of the anatomy and biomechanics of the knee joint has dramatically increased. The translation of this knowledge into clinical practice has greatly improved athletic training and medical treatment when injury occurs. Advances in imaging techniques have played a role in this improvement. The next step for imaging is to move beyond merely providing morphology and to assess the functional mechanics of the knee. This article focuses on the biomechanics of the femorotibial joint and its relevance to imaging.

Biomechanical Phenomena↗
PubMed2003

Prevalence effect in a laboratory environment.

PURPOSE: To measure observer performance at various levels of prevalence. MATERIALS AND METHODS: A multiobserver multiabnormality receiver operating characteristic (ROC) study to assess the effect of prevalence on observer performance was conducted. Fourteen observers, including eight faculty members, two fellows, and four residents, interpreted 1,632 posteroanterior chest images with five prevalence levels by using a nested study design. Performance comparisons were accomplished by using a multireader multicase approach to assess the effect of prevalence from 28% (69 of 249) to 2% (31 of 1,577) on diagnostic accuracy. The mean times required to review and report a case were analyzed and compared for different levels of prevalence and readers' experience. RESULTS: Area under the ROC curve demonstrated that, with the study experimental conditions, no significant effect could be measured as a function of prevalence (P >.05) for any abnormality, group of cases, or readers. There were no significant differences (P >.05) in the mean times required to review and report cases at different prevalence levels and with different groups of readers. CONCLUSION: The consistency in the results and the size of this study suggest that with laboratory conditions, if a prevalence effect exists, it is quite small in magnitude; hence, it will not likely alter conclusions derived from such studies.

Laboratories↗
PubMed2003

Multi-detector row CT of the left atrium and pulmonary veins before radio-frequency catheter ablation for atrial fibrillation.

Radio-frequency catheter ablation (RFCA) of the distal pulmonary veins and posterior left atrium is increasingly being used to treat recurrent or refractory atrial fibrillation that resists pharmacologic therapy or cardioversion. Successful RFCA of atrial fibrillation requires resolution of abnormal rhythms while minimizing complications and can be achieved with precise, preprocedural, three-dimensional (3D) anatomic delineation of the target, the atriopulmonary venous junction. Three-dimensional multi-detector row computed tomography (CT) of the pulmonary veins and left atrium provides the necessary anatomic information for successful RFCA, including (a) the number, location, and angulation of pulmonary veins and their ostial branches unobscured by adjacent cardiac and vascular anatomy, and (b) left atrial volume. The 3D multi-detector row CT scanning and postprocessing techniques used for pre-RFCA planning are straightforward. Radiologists must not only understand these techniques but must also be familiar with atrial fibrillation and the technical considerations and complications associated with RFCA of this condition. In addition, radiologists must be familiar with anatomic variants of the left atrium and distal pulmonary veins and understand the importance of these variants to the referring cardiac interventional electrophysiologist.

Atrial Fibrillation↗
PubMed2002

Radiologists' performance in the diagnosis of liver tumors with central scars by using specific CT criteria.

PURPOSE: To determine the performance of radiologists with differing levels of expertise in the diagnosis of the most common types of liver tumors with central scars (ie, focal nodular hyperplasia [FNH], fibrolamellar hepatocellular carcinoma [HCC], and large hepatic hemangioma) by using specific computed tomographic (CT) findings. MATERIALS AND METHODS: Review of medical records at the University of Pittsburgh Medical Center identified patients with a total of 64 liver tumors that had central scars-including 29 cases of FNH, 20 fibrolamellar HCCs, and 15 large (>3.5 cm in diameter) hemangiomas-and with CT scans available for review. Retrospective review of these scans was performed individually by six radiologists who were blinded to the diagnosis, including two faculty abdominal radiologists, one abdominal imaging fellow, and three radiology residents. Individual performance was evaluated by means of receiver operating characteristic analysis, and interobserver agreement was measured by using the Cronbach alpha. Individual CT findings that may allow differentiation of tumor types were identified with the Kruskal-Wallis test. RESULTS: CT allowed good to excellent interobserver agreement in the diagnosis of tumor type and in recognition of differential findings among the three types. The individual accuracy of diagnosis was very good, with the average area under the receiver operating characteristic curve ranging from 0.81 to 0.90. Although the faculty radiologists performed the best, the differences in performance between the subgroups of readers and the levels of confidence in diagnosis were not statistically significant. The diagnosis of fibrolamellar HCC was the most accurate and had the highest sensitivity, followed by FNH and large hemangioma. Clinical and CT findings that were found to be statistically significant in differentiating tumor types were patient age and sex, tumor size larger than 10 cm, width of tumor scars, invasion of vessels, nodular centripetal enhancement, marked hyperattenuation on arterial phase images, lymphadenopathy, heterogeneity, extrahepatic metastases, surface lobulation, calcification, and isoattenuation with liver tissue on portal venous phase images. CONCLUSION: CT allows accurate differentiation of the most common types of liver tumors with central scars, including FNH, fibrolamellar HCC, and large hemangioma.

Adolescent↗