Biomedical subjects

Lawrence M White

Publications and source records attributed to Lawrence M White.

At least 19 recordsLinked to original sources

PubMed2006

Metal artifact reduction in musculoskeletal magnetic resonance imaging.

Many strategies can be employed to reduce the size and scale of metal susceptibility artifacts in the vicinity of orthopedic hardware; factors include selection of metal hardware material, patient positioning, and MRI sequence adjustments and techniques. The adjustments to sequence parameters include high spatial resolution fast spin echo sequences with minimal interecho spacing and increased receiver bandwidth. Frequency and phase encoding gradients can be orientated so misregistration artifacts arising from the metal are directed away from areas of anticipated clinical diagnostic interest. Complications arising in the vicinity of metallic hardware, including loosening, can be assessed after implication of these metal artifact reduction techniques.

Artifacts↗

PubMed2006

Magnetic resonance imaging of joint replacements.

An increasing number of joint replacements are being performed annually. Complications of joint arthroplasty are diverse and may involve the hardware as well as osseous and soft tissue components. Although modalities such as conventional radiography and scintigraphy remain the mainstay of radiological investigation, in some cases these traditional methods of imaging may be negative or underestimate the extent of disease. Magnetic resonance imaging (MRI) has been considered of limited benefit following arthroplasty because of severe image degradation caused by metallic components. However, with modification of pulse sequences, artifact reduction and improved visualization of periprosthetic tissues are achievable, enabling a comprehensive assessment of articular and nonarticular pathologies. The common artifacts in the presence of orthopedic hardware, optimization of pulse sequences to minimize metal-related artifacts, and the clinical uses of MRI following joint replacement, particularly with regard to total hip arthroplasty, total knee arthroplasty, and shoulder arthroplasty, are reviewed.

Arthroplasty, Replacement↗

PubMed2006

Cartilage T2 assessment: differentiation of normal hyaline cartilage and reparative tissue after arthroscopic cartilage repair in equine subjects.

PURPOSE: To prospectively assess T2 mapping characteristics of normal articular cartilage and of cartilage at sites of arthroscopic repair, including comparison with histologic results and collagen organization assessed at polarized light microscopy (PLM). MATERIALS AND METHODS: Study protocol was compliant with the Canadian Council on Animal Care Guidelines and approved by the institutional animal care committee. Arthroscopic osteochondral autograft transplantation (OAT) and microfracture arthroplasty (MFx) were performed in knees of 10 equine subjects (seven female, three male; age range, 3-5 years). A site of arthroscopically normal cartilage was documented in each joint as a control site. Joints were harvested at 12 (n = 5) and 24 (n = 5) weeks postoperatively and were imaged at 1.5-T magnetic resonance (MR) with a 10-echo sagittal fast spin-echo acquisition. T2 maps of each site (21 OAT harvest, 10 MFx, 12 OAT plug, and 10 control sites) were calculated with linear least-squares curve fitting. Cartilage T2 maps were qualitatively graded as "organized" (normal transition of low-to-high T2 signal from deep to superficial cartilage zones) or "disorganized." Quantitative mean T2 values were calculated for deep, middle, and superficial cartilage at each location. Results were compared with histologic and PLM assessments by using kappa analysis. RESULTS: T2 maps were qualitatively graded as organized at 20 of 53 sites and as disorganized at 33 sites. Perfect agreement was seen between organized T2 and histologic findings of hyaline cartilage and between disorganized T2 and histologic findings of fibrous reparative tissue (kappa = 1.0). Strong agreement was seen between organized T2 and normal PLM findings and between disorganized T2 and abnormal PLM findings (kappa = .92). Quantitative assessment of the deep, middle, and superficial cartilage, respectively, showed mean T2 values of 53.3, 58.6, and 54.9 msec at reparative fibrous tissue sites and 40.7, 53.6, and 61.6 msec at hyaline cartilage sites. A significant trend of increasing T2 values (from deep to superficial) was found in hyaline cartilage (P < .01). Fibrous tissue sites had no significant change with depth (P > .59). CONCLUSION: Qualitative and quantitative T2 mapping helped differentiate hyaline cartilage from reparative fibrocartilage after cartilage repair at 1.5-T MR imaging.

Animals↗

PubMed2006

MRI comparison of periprosthetic structures around zirconium knee prostheses and cobalt chrome prostheses.

OBJECTIVE: The purpose of our study was to compare reviewer confidence and interobserver agreement in the evaluation of MR images of periprosthetic structures around zirconium total knee prostheses and cobalt chrome prostheses. MATERIALS AND METHODS: Three board-certified radiologists blinded to prosthesis type used identical MRI protocols to independently evaluate 21 total knee prostheses: 14 zirconium prostheses and seven cobalt chrome prostheses. The radiologists evaluated the following eight parameters: integrity of the medial and lateral collateral ligaments, the quadriceps and the patellar tendons, presence of a joint effusion, and for evidence of periprosthetic osseous signal abnormality around each of the three components. The reviewers gave their degree of confidence in evaluating each of the findings on a five-point scale, 0 being no confidence and 4 being high confidence in the finding. The degree of confidence was used as the vehicle for comparing the two groups of patients. RESULTS: The confidence ratings for all MRI variables were significantly higher for the zirconium group than for the cobalt chrome group. The confidence ratings varied less for the zirconium group than for the cobalt chrome group with an SD of 0.45 versus 0.95, respectively. There was greater interobserver agreement in the zirconium group (coefficient of interobserver agreement, 0.82 vs 0.35). The reviewers had the highest degree of confidence when examining for joint effusion in both groups (3.9 for the zirconium group; 3.7 for the cobalt chrome group). The greatest discrepancies between the two groups were in evaluation of periprosthetic osseous signal changes with the greatest difference being between the femoral component of each group with an average confidence rating of 3.3 for the zirconium group and 0.8 for the cobalt chrome group. CONCLUSION: Reviewers had significantly more confidence, less variability, and greater interobserver agreement in MRI evaluation of periprosthetic structures around zirconium knee prostheses than those around cobalt chrome knee prostheses.

Adult↗

PubMed2005

Increased subcortical patellar signal intensity at T2-weighted MR imaging: a subacute finding after knee injury.

PURPOSE: To investigate the temporal prevalence of a rim of increased signal intensity in the subcortical part of the patella at T2-weighted magnetic resonance (MR) imaging after arthroscopic knee surgery or knee injury. MATERIALS AND METHODS: The prospective and retrospective components of the study were performed after receiving approval from the institutional research ethics board. Written informed consent was obtained for the prospective component of the study. The need for informed consent was waived for the retrospective component of the study. The authors performed a prospective evaluation of serial MR images of the knee of four patients (three men and one woman; age range, 28-53 years; mean age, 36.8 years) after arthroscopic anterior cruciate ligament (ACL) reconstruction. They also performed a retrospective review of MR images of the knee from 90 consecutive patients (59 male and 31 female patients; age range, 13-66 years; mean age, 34.6 years) referred for the evaluation of an ACL injury. All imaging studies were evaluated in consensus by two musculoskeletal radiologists for the presence of a rim of increased signal intensity in the subcortical part of the patella at T2-weighted imaging. The presence of this signal intensity pattern was correlated with the time to imaging from surgery or joint injury. Logistic regression modeling was performed with increased subcortical signal intensity as the outcome and a second-degree polynomial for elapsed time as the predictor. RESULTS: All four patients who underwent imaging prospectively after ACL surgery showed increased T2-weighted signal intensity in the subcortical part of the patella 12 weeks after surgery. None of the patients showed these signal intensity changes at 6 or 24 weeks. A subcortical rim of increased T2-weighted signal intensity was seen in the patella in 24 (27%) of the 90 consecutive patients who underwent imaging for the assessment of possible ACL injury. Significant independent differences were seen in the prevalence of increased T2-weighted signal intensity in the subcortical part of the patella when related to time between injury and MR imaging (P = .002), with an increase in prevalence as time since injury increased and a decrease in prevalence in patients who underwent MR imaging more than 20 weeks after injury (P = .013). CONCLUSION: Increased T2-weighted signal intensity in the subcortical part of the patella appears to be a subacute transient MR finding seen after knee surgery or injury.

Adult↗

PubMed2005

Granular cell tumor of the extremity: magnetic resonance imaging characteristics with pathologic correlation.

OBJECTIVE: The purpose of this study is to delineate the magnetic resonance (MR) appearance of a granular cell tumor (GrCT) of the extremity and to correlate the imaging appearance with the microscopic findings. DESIGN AND PATIENTS: A retrospective review of five patients with a histopathologic diagnosis of GrCT and pre-operative MR imaging of the neoplasm was done. The images were reviewed by two musculoskeletal radiologists in a consensus fashion. Lesion location, size, shape, margination, and signal intensity characteristics were assessed. MR findings were correlated with histopathological examination. RESULTS: The benign subtype of GrCT is usually isointense or brighter than muscle on T1-weighted sequences, round or oval in shape, superficial in location, and 4 cm or less in size. On T2-weighted sequences, benign lesions may demonstrate a high peripheral signal, as well as a central signal intensity that is isointense to muscle or suppressed fat. A significant stromal component in the tumor and, hypothetically, a ribbon-like arrangement of tumor cells may influence the signal intensity demonstrated on the T1 and T2-weighted sequences. The malignant subtype may demonstrate signal intensity characteristics and invasion of adjacent structures often seen with other aggressive neoplasms; sizes larger than 4 cm and association with major nerve trunks can be seen. CONCLUSION: Benign GrCT has imaging characteristics which may distinguish this tumor from other soft tissue neoplasms, as well as the malignant type of this tumor.

Adolescent↗

PubMed2005

MR imaging evaluation of the postoperative knee: ligaments, menisci, and articular cartilage.

The surgical management of knee injuries has increased in recent years. Postoperative magnetic resonance (MR) imaging of the knee following surgical intervention serves an important role in the diagnostic evaluation of patients with recurrent or residual symptoms following surgical intervention. MR imaging additionally assists in the noninvasive documentation of temporal changes at the surgical site potentially reflective of procedural success, or failure. Background understanding of the common surgical procedures performed, their normal postoperative MR imaging appearance, and imaging features of potential procedural complications are essential in the accurate evaluation of patients following prior knee surgery. The focus of the following article is to review the clinical and MR imaging features of the postoperative knee following prior surgical treatment of ligamentous, meniscal, and articular cartilage injuries of the joint.

Cartilage, Articular↗

PubMed2005

Histologic assessment of peritumoral edema in soft tissue sarcoma.

PURPOSE: To evaluate whether satellite tumor cells can be identified histologically in the tissues surrounding a soft tissue sarcoma and whether their presence correlates with increased T(2)-weighted signal intensity on MRI. METHODS AND MATERIALS: Fifteen patients with a high-grade extremity or truncal soft tissue sarcoma underwent preoperative MRI. The extent of high T(2)-weighted signal changes in the tissues surrounding tumor, thought to represent peritumoral edema/reactive changes, was determined. Twelve patients received i.v. gadolinium, and contrast enhancement was determined. All patients underwent surgical resection in the absence of preoperative chemotherapy or radiotherapy. The presence of tumor cells in the surrounding tissues was determined histologically in representative paraffin-embedded sections and correlated with the MRI findings. RESULTS: The extent of peritumoral T(2)-weighted MRI signal changes ranged from 0 to 7.1 cm (mean, 2.5 cm); contrast enhancement ranged from 0 to 5.3 cm (mean, 1.1 cm). Sarcoma cells were identified histologically in the tissues beyond the tumor in 10 of 15 cases. In 6 cases, tumor cells were located within 1 cm of the tumor margin, and in 4 cases, malignant cells were found at a distance >1 cm and up to a maximum of 4 cm. The location of tumor cells beyond the margin did not correlate with tumor size nor did it correlate with the location or extent of peritumoral changes. CONCLUSION: The ability to identify tumor cells beyond the margin of a soft tissue sarcoma has important implications in planning appropriate targets for treatment. This could influence the use of new radiotherapy technologies such as intensity-modulated radiotherapy that aim to minimize treatment volumes through conformal planning.

Adult↗

PubMed2005

Periprosthetic bone remodeling around a prosthesis for distal femoral tumors: longitudinal follow-up.

Serial measurements using dual-energy x-ray absorptiometry (DEXA) were undertaken to evaluate progressive periprosthetic bone loss in patients treated for primary bone tumors of the distal femur using an uncemented tumor prosthesis. Twelve patients underwent sequential DEXA analysis on average 26.5 and 90.9 months postsurgery. Changes in bone mineral density were measured in regions of interest (ROIs) around the prosthesis stem. The test-retest reliability coefficient (r) ranged from 0.92 to 0.99 for all ROI. In the most distal ROI (ROI1), 10 of 11 patients with 2 measurements showed no change or a small increase in absolute bone mineral density. The results in other ROIs were similar. This longitudinal DEXA data suggest that progressive bone resorption is not problematic with an uncemented distal femur endoprosthesis at intermediate follow-up. Key words: DEXA, stress shielding, uncemented endoprothesis, tumor, bone loss.

Absorptiometry, Photon↗

PubMed2005

Imaging the post-operative meniscus.

Considerable developments have occurred in meniscal surgery, and consequently in the imaging of post-operative menisci, over the last 15 years. A drive to preserve meniscal physiologic function for as long as possible, in order to delay osteoarthrosis, has resulted in limited partial meniscectomies, meniscal repairs and meniscal transplants. Each of these techniques affects the imaging appearance of the meniscus, reducing the accuracy of conventional MRI in predicting recurrent tears. The specificity of conventional MRI can be improved by employing at least two T2-weighted sequences, but this still leaves a shortfall in sensitivity. In an attempt to increase the diagnostic accuracy of cross-sectional imaging, MR arthrography (MRA) and CT arthrography (CTA), have been applied to the post-operative meniscus. Sensitivities and specificities for these two techniques approach 90% in predicting recurrent meniscal tears. In the setting of clinical symptoms and gross meniscal deficiency, meniscal allografts are being transplanted with increasing frequency. In these transplants meniscal degeneration, fragmentation and separation are common findings, but the role of imaging in the management of these patients has not yet been well defined. This review explores the imaging techniques available for the evaluation of the post-operative meniscus, their strengths and weaknesses, and the reasons that they may find a place in a rational strategy for imaging of the symptomatic post-operative knee.

Arthrography↗

PubMed2005

Imaging of the Achilles tendon.

The Achilles tendon is the most commonly injured tendon in the foot and ankle; injuries commonly are related to sports/athletic activities. Imaging modalities that are used most commonly in the diagnostic assessment of the Achilles tendon include conventional radiography, ultrasonography, and MRI. This article reviews the normal and pathologic imaging features of the Achilles tendon, and highlights the potential usefulness and limitations of various imaging techniques in the noninvasive assessment of the tendon and the potential impact of imaging findings on clinical patient care.

Achilles Tendon↗

PubMed2005

The biomechanics and imaging of soccer injuries.

Soccer is one of the most popular sports worldwide and requires the player to have considerable stamina while superimposing sprinting, jumping, tackling, rapid changes of direction, and kicking. This contact sport carries a significant risk for acute and overuse injuries, with the lower limb the region most frequently injured. This article discusses the biomechanics and current role of imaging in the management of several specific soccer injuries highlighting injuries of the ankle, pelvis, and groin and specific muscle and tendon injuries commonly encountered in this athletic population.

Athletic Injuries↗

PubMed2005

MRI of articular cartilage: revisiting current status and future directions.

OBJECTIVE: The purpose of this article is to review the current understanding of the MRI appearance of articular cartilage and its relationship to the microscopic and macroscopic structure of articular cartilage, the optimal pulse sequences to be used in imaging, the appearance of both degenerative and traumatic chondral lesions, the appearance of the most common cartilage repair procedures, and future directions and developments in cartilage imaging. CONCLUSION: Articular cartilage plays an essential role in the function of the diarthrodial joints of the body but is frequently the target of degeneration or traumatic injury. The recent development of several surgical procedures that hold the promise of forming repair tissue that is hyaline or hyalinelike cartilage has increased the need for accurate, noninvasive assessment of both native articular cartilage and postoperative repair tissue. MRI is the optimal noninvasive method for assessment of articular cartilage.

Cartilage Diseases↗

PubMed2004

Epidemiology and natural history of acute patellar dislocation.

BACKGROUND: The goals of this study were to (1) define the epidemiology of acute patellar dislocation, (2) determine the risk of subsequent patellar instability episodes (subluxation and/or redislocation) during the study period, and (3) identify risk factors for subsequent instability episodes. STUDY DESIGN: Prospective cohort study. METHODS: The authors prospectively followed 189 patients for a period of 2 to 5 years. Historical data, injury mechanisms, and physical and radiographic measurements were recorded to identify potential risk factors for poor outcomes. RESULTS: Risk was highest among females 10 to 17 years old. Patients presenting with a prior history of instability were more likely to be female (P < .05) and were older than first-time dislocation patients (P < .05). Fewer first-time dislocators (17%) had episodes of instability during follow-up than patients with a previous history of instability (49%) (P < .01). After adjusting for demographics, patients with a prior history had 7 times higher odds of subsequent instability episodes during follow-up than first time dislocators (adjusted odds ratio = 6.6, P < .001). CONCLUSIONS: Patellar dislocators who present with a history of patellofemoral instability are more likely to be female, are older, and have greater risk of subsequent patellar instability episodes than first-time patellar dislocators. Risk of recurrent patellar instability episodes in either knee is much higher in this group than in first-time dislocators.

Acute Disease↗

PubMed2004

Primary synovial osteochondromatosis of the hip: extracapsular patterns of spread.

OBJECTIVE: To identify patterns of extracapsular extension of synovial osteochondromatosis of the hip. DESIGN AND PATIENTS: Seven cases of synovial osteochondromatosis of the hip were retrospectively reviewed. Imaging performed included conventional radiography ( n=7), arthrography ( n=1), CT ( n=3) and MR imaging ( n=3). Disease extent on imaging was assessed for each patient and the presence of intra-articular effusion, capsular abnormality and osteochondral bodies recorded. The presence and distribution of extra-articular spread was also assessed and correlated with the surgical findings. In all cases diagnosis was confirmed by biopsy, with all patients undergoing tumor resection with or without synovectomy. RESULTS: In five cases (5/7) disease extended beyond the hip capsule, while the remaining two cases (2/7) were confined to the hip joint. These findings were confirmed at surgery. Two distinct patterns of extracapsular spread were identified. The first pattern, noted in three cases, involved tumor extension along iliopsoas. The second pattern, noted in five cases, involved tumor extension along the obturator externus fat plane. In three cases both patterns were present. CONCLUSIONS: Extra-articular spread of synovial osteochondromatosis is common. Patterns of extra-articular spread may be predictable based on involvement of recognized periarticular bursae of the hip joint. Bursal patterns of extra-articular spread include extension into the iliopsoas bursa as well as communication along the obturator externus bursa of the hip.

Adult↗

PubMed2004

Cruciate and posterolateral corner injuries in the athlete: clinical and magnetic resonance imaging features.

With an increasing number of people participating in recreational and competitive sporting activities, sports-related injuries of the knee and knee ligaments have increased in incidence. The extent and severity of such injuries may have important implications with regard to potential return to athletic pursuits as well as impacting upon activities of daily life. This article discusses the MR imaging and clinical features of sports-related injuries of the cruciate ligaments and posterolateral corner of the knee, highlighting the implications of such injuries on joint function. MR imaging has the potential to accurately identify these ligamentous injuries, as well as other potential associated combined injuries of the knee, with information from MR imaging examination assisting in decision-making and planning with regard to potential clinical and/or surgical patient management.

Anterior Cruciate Ligament Injuries↗

PubMed2004

Lymph node metastasis in soft tissue sarcoma in an extremity.

For patients with soft tissue sarcoma in an extremity, the outcome is thought to be poor if lymph node metastasis develops. The purpose of this study was to examine the impact of lymphatic involvement from soft tissue sarcoma on patient survival. Thirty-nine (3.7%) of 1066 patients who had surgery for soft tissue sarcoma in an extremity had lymph node metastases develop. Three (20%) of 15 patients with epithelioid sarcoma, four (19%) of 21 patients with rhabdomyosarcoma, two (11.1%) of 18 patients with clear cell sarcoma, and two (11.1%) of 18 patients with angiosarcoma had lymphatic involvement. Thirty patients who had resection of involved lymph nodes had an estimated 5-year survival of 57%, whereas nine patients treated without surgery all died within 30 months. An estimated 4-year survival of 71% for patients with isolated lymph node metastases was significantly better than 21% for patients with synchronous systemic and lymph node involvement. There was no difference in outcome for patients with isolated lymphatic involvement compared with patients with American Joint Committee on Cancer Stage III extremity sarcomas. These results suggest that long-term survival is possible after surgical resection of lymphatic metastases from soft tissue sarcoma. The American Joint Committee on Cancer should consider separating isolated nodal metastases from systemic involvement in patients with Stage IV sarcoma.

Adolescent↗

PubMed2003

Obturator externus bursa: anatomic origin and MR imaging features of pathologic involvement.

PURPOSE: To investigate the anatomy of the obturator externus bursa of the hip and describe the magnetic resonance (MR) imaging features of pathologic involvement. MATERIALS AND METHODS: The authors dissected eight cadaver hemipelvises to assess for the presence of periarticular bursae of the hip and bursal communication with the fascial plane of the obturator externus muscle. In addition, 10 consecutive patients with obturator externus bursa enlargement were prospectively identified with MR imaging. A bursa was considered present when a fluid collection was seen extending along the obturator externus muscle, continuous with the posterior inferior hip joint. The direction, extent, contour, and thickness of the bursa and hip capsule were recorded. Surgical findings were available for eight of the 10 patients, with histopathologic correlation between the bursal lining and hip capsule. RESULTS: At cadaveric dissection, one specimen showed a bursa communicating with and extending from the posteroinferior aspect of the hip joint deep to the obturator externus tendon. In all 10 patients, MR images showed a hip joint effusion with a continuous bursa extending medially and displacing the obturator externus inferiorly. At surgery, a bursa was seen displacing the obturator externus muscle inferiorly and originating from the posteroinferior aspect of the hip joint in all eight patients. Results of pathologic analysis confirmed disease identical to the primary hip abnormality in all eight patients. CONCLUSION: The obturator externus bursa is a potential posteroinferior communication of the hip joint capsule, can be a site of disease spread from the hip joint, and can be accurately identified with MR imaging.

Adult↗