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Biomedical subjects

C G Peterfy

Publications and source records attributed to C G Peterfy.

At least 19 recordsLinked to original sources
PubMed2003

Metallic artefacts in MR imaging: effects of main field orientation and strength.

AIM: To determine the effect of metallic implant positioning on magnetic resonance (MR) imaging artefacts, and to determine the optimal imaging parameters for minimization of metallic artefacts. MATERIALS AND METHODS: In a phantom and in three joints with non-ferromagnetic metallic implants imaged at 1.5 and/or at 0.2 T, we examined the influence of the static magnetic field (B(0)) strength and orientation, frequency-encoding direction, and type of imaging sequence on metallic artefacts. RESULTS: The impact of artefacts caused by metallic objects depends mainly on the relationship between the anatomy of interest and the orientation of the object relative to the direction of B(0). The main field strength plays a less important role, but its orientation depends on the type of MR imager. CONCLUSION: MR artefacts can be easily minimized by optimally positioning patients with metallic implants in the magnet. Knowledge of how this influences MR imaging is helpful in patient selection and guiding limb positioning.

Artifacts↗
PubMed2002

Femoral neck and intertrochanteric fractures: radiographic indicators of fracture healing.

Serial hip radiographs from 280 patients with proximal femoral fractures were analyzed retrospectively by 3 radiologists to evaluate conventional radiographic healing patterns. Patients with hemiarthroplasty or insufficient follow-up were excluded. In the remaining 41 patients, the fracture line and callus was assessed. Intertrochanteric fractures demonstrated increasing callus and sclerosis at the fracture site. No such association was seen in femoral neck fractures. Traditional indicators of fracture healing cannot be readily applied at the hip. Radiographic features relate more to fracture type and fixation method.

Adult↗
PubMed2001

Magnetic resonance imaging of rheumatoid arthritis: the evolution of clinical applications through clinical trials.

Powerful techniques are being developed for evaluating rheumatoid arthritis with magnetic resonance imaging (MRI). Much of this development is being driven by the pharmaceutical and biotechnology industries searching for novel therapies for this disease. Accordingly, the imaging tools that ultimately will be used to direct patients to specific therapies and then to monitor treatment effectiveness and safety are currently being refined and validated in rigorous multicenter and multinational clinical trials aimed at gaining regulatory approval of these new therapies. As these trials approach completion, rheumatologists can anticipate an increased demand for expertise and experience in evaluating disease progression and treatment response with these techniques and the emergence of MRI systems specifically designed for this market. The following discussion reviews this novel pathway for evolving imaging techniques for clinical use through clinical drug trials, lists the most promising MRI markers available today for evaluating joint destruction in rheumatoid arthritis, and speculates on how these techniques will find their way into clinical practice.

Arthritis, Rheumatoid↗
PubMed2001

Magnetic resonance imaging of the wrist in rheumatoid arthritis.

Despite the extraordinary advances made in medical imaging over the past two decades and the central role that magnetic resonance imaging (MRI) and other sophisticated technologies now play in routine clinical practice, rheumatology has benefited relatively little from these advances thus far. Over the past few years, however, evidence has accumulated to show that MRI can identify joint damage in patients with rheumatoid arthritis earlier and more sensitively than other techniques can, and that MRI can directly visualize and monitor changes in synovium and bone that precede actual bone erosion. Much of this development is being driven by the pharmaceutical and biotechnology industries as they search for novel therapies to combat this disease. Accordingly, the imaging tools that ultimately will be used to direct patients to specific therapies and then to monitor treatment effectiveness and safety are currently being refined and validated in rigorous multicenter and multinational clinical trials aimed at gaining regulatory approval of these new therapies. As these therapies become available for clinical use, radiologists can anticipate increased demand for expertise and experience in evaluating disease progression and treatment response with these techniques and the emergence of MRI systems specifically adapted for this application. The following discussion reviews the current status of this development, and points to areas where further advances are anticipated in the near future.

Arthritis, Rheumatoid↗
PubMed2001

Role of MR imaging in clinical research studies.

There have been numerous advances in cartilage imaging with magnetic resonance imaging (MRI) over the past several years. However, in the absence of effective treatments for articular cartilage disease, these innovations have had little applicability to clinical practice. Putative new therapies do exist but only in clinical trials aimed at establishing the efficacy and safety of these therapies before they are released into general use. These trials, therefore, represent the earliest opportunity to develop imaging methods specifically for such therapies and the diseases that they treat. Accordingly, it is the commercial, regulatory, and logistical demands of the clinical trials process, rather than those of clinical practice, that ultimately shape the early evolution of these imaging tools. Understanding this process and its priorities is essential to contributing to this development and to keeping radiology in sync with advances in the rest of medicine. The following article reviews this novel pathway for innovation in medical imaging and reflects on how recent advances in cartilage MRI might fit in.

Biomarkers↗
PubMed2001

Automated measurement of radiographic hip joint-space width.

Radiographic joint-space narrowing (JSN) is the principle indicator of cartilage loss in osteoarthritis (OA). JSN is usually assessed qualitatively by visual inspection or in clinical research, is measured manually with a graduated handheld lens directly applied to the x-ray film, or from digitized radiographs by hand tracing the joint margins with a mouse. The minimum joint-space width (mJSW) and joint-space area (JSA) are recorded as the indices of OA progression in epidemiological studies and clinical drug trials. We present a computerized method that automatically finds the articular margins of the hip to improve determination of mJSW and JSA. The algorithm requires that three seed points are manually identified on the femoral head and uses three steps to process each digitized hip x-ray. First, a Hough transform finds the center and radius (R) of a circle that approximates the femoral head. Finding R indicates whether magnification differences must be corrected on repeat exams. Second, a gradient algorithm finds the edge of the femoral head and acetabulum. Third, the mid-line of the femoral neck is automatically found and used to define the joint portion (theta) that is assessed for narrowing. theta is fixed for follow-up exams of the same subject. The algorithm was evaluated in three ways to determine its performance characteristics. First, the inter-reader and intra-reader variability for mJSW and JSA associated with the selection of the seed points was found to be negligible (< 1%) compared to the variability associated with manual scoring with a lens or by tracing the joint margins with a mouse. Second, from duplicate hip x-rays of 19 subjects with OA, the Root Mean Square Standard Deviation and coefficient of variation for mJSW and JSA defined by the algorithm was determined to be better than manual techniques by at least a factor of 2. Third, the algorithm correctly identified the joint margin in more than 85% of the 105 cases tested. Automated measures of radiographic hip joint-space narrowing is less subjective than manual methods and may be applicable for monitoring OA progression in clinical research.

Acetabulum↗
PubMed2001

Magnetic resonance imaging in rheumatoid arthritis: current status and future directions.

The performance of alternative imaging endpoints in clinical trials can be compared in terms of validity, rate of change, measurement precision, and convenience and cost. With respect to technical performance, magnetic resonance imaging (MRI) appears to show greater sensitivity than radiography for detecting bone abnormalities in rheumatoid arthritis (RA). In addition to monitoring changes in the bones, cartilage, and synovium, MRI can directly visualize the full spectrum of tendon pathology, and has been shown to identify tendonitis and tendon rupture with greater accuracy than clinical examination. MRI is currently regarded to be the most sensitive imaging technique for identifying trauma, infection, ischemia, and primary and secondary neoplasia of bone. Several studies have also shown MRI to be highly sensitive for detecting what appear to be bone erosions in the hands and wrists of patients with RA. MRI shows remarkable promise as a tool for identifying and monitoring structural damage in the joints of patients with RA. MRI appears to be able to identify bone erosions with greater sensitivity than radiography, and to disclose edema-like changes in the marrow, which may precede actual erosion formation. As new therapies with structure modifying capabilities enter the clinic, the ability to identify patients appropriate for those therapies and then to monitor the effectiveness and safety of treatment become increasingly important.

Arthritis, Rheumatoid↗
PubMed2000

Trainable rule-based algorithm for the measurement of joint space width in digital radiographic images of the knee.

The progression of osteoarthritis (OA) can be monitored by measuring the minimum joint space width (mJSW) between the edges of the femoral condyle and the tibial plateau on radiographs of the knee. This is generally performed by a trained physician using a graduated magnifying lens and is prone to the subjectivity and variation associated with observer measurement. We have developed software that performs this measurement automatically on digitized radiographs. The test data consisted of 180 digitized radiographs of the knee (90 duplicate acquisitions) from 18 normal (nonarthritic) subjects and 38 images from 10 subjects with OA. These were digitized and manually cropped so that the images were free of nonanatomical structures and the knee was approximately centered. The software first determined the edge of the femoral condyle on 400 microm pixel subsampled images. Contours marking the location of the tibial plateau in the medial compartment were found on 100 microm images using the femoral edge as a reference. The algorithm was trained using an independent but similar data set and using a jackknife approach with the test data. The results were compared to contours drawn by a trained reader and the duplicate acquisitions were used to measure the reproducibility of the mJSW measurement. The reproducibility was 0.16 mm and 0.18 mm for normal and osteoarthritic knees, respectively, representing an improvement of approximately a factor of 2 over manual measurement. The algorithm also showed excellent agreement with the hand-drawn contours and with mJSW determined by the manual method.

Algorithms↗
PubMed2000

Scratching the surface: articular cartilage disorders in the knee.

Powerful techniques with MR imaging are being developed for evaluating articular cartilage. Pharmaceutical and biotechnology development is driven largely by the search for novel therapeutic solutions to the growing problem of arthritis in our aging society. Accordingly, imaging tools that will be used to direct patients to specific therapies and then to monitor treatment effectiveness and safety presently are being refined and validated in rigorous multicenter and multinational clinical trials aimed at gaining regulatory approval. As trials approach completion, radiologists can anticipate an increased demand for expertise and experience in evaluating articular cartilage disorders. This article reviews this novel mechanism for evolving imaging techniques for clinical use through clinical drug trials, lists the most promising MR imaging markers available for evaluating cartilage integrity, and speculates on how these techniques will find their way into clinical practice.

Cartilage Diseases↗
PubMed1999

MR imaging of the arthritic rabbit knee joint using albumin-(Gd-DTPA)30 with correlation to histopathology.

The purpose of this study was to demonstrate a technique, in a pilot study, for measuring abnormal capillary permeability in synovial tissue of rabbit arthritic knees using dynamic MRI with a gadolinium-based blood pool agent. Arthritis, simulating rheumatoid arthritis, was induced in knees of 8 rabbits by intra-articular injection of carrageenan (n = 4) or ovalbumin (n = 4). Sequential fat presaturated T1-weighted Spoiled Grass images were obtained before and up to 30 min after intravenous administration of albumin-(Gd-DTPA)30. Estimates of synovial tissue plasma-volume (PV), fractional-leak-rate (FLR), and permeability-surface-area-product (PS) were computed. Histologic correlation was obtained in the corresponding regions. Dynamic MRI showed extravasation of albumin-(Gd-DTPA)30 into hypertrophic synovium in six of the eight arthritic knees. Histologic examination of these six knees showed markedly inflamed synovium. The two knees that did not show abnormal vascular permeability contained non-hypertrophic synovium. None of the rabbits showed abnormal permeability in muscle. MRI derived microvascular characteristics (PV, FLR and PS) correlated positively (r2 = 0.51, 0.97 and 0.86) with the histology. Factors involving the structural and functional microvascular characteristics of synovial tissue can be estimated non-invasively using albumin-(Gd-DTPA)30. This technique may be useful for monitoring disease progression and treatment response in rheumatoid arthritis.

Albumins↗
PubMed1999

Accuracy of T2-weighted fast spin-echo MR imaging with fat saturation in detecting cartilage defects in the knee: comparison with arthroscopy in 130 patients.

OBJECTIVE: The purpose of this study was to assess the accuracy of routine T2-weighted MR imaging in detecting and grading articular cartilage lesions in the knee compared with arthroscopy. SUBJECTS AND METHODS: We examined 130 consecutive patients who underwent MR imaging and arthroscopy of the knee for suspected internal derangement. MR imaging consisted of axial and coronal T2-weighted fast spin-echo sequences with fat saturation and sagittal T2-weighted spin-echo sequences. Each single plane was evaluated and graded for the presence and appearance of articular cartilage defects using a standard arthroscopic grading scheme adapted to MR imaging. RESULTS: Of the 86 arthroscopically proven abnormalities, 81 were detected on MR imaging. Sensitivity of the T2-weighted fast spin-echo sequence with fat saturation was 61% for the coronal plane alone and 59% for the axial plane alone. Specificity for each plane was 99%. Sensitivity for the sagittal T2-weighted spin-echo sequence was 40%, and specificity was 100%. Sensitivity of the combination of axial and coronal T2-weighted fast spin-echo sequences with fat saturation and sagittal T2-weighted spin-echo sequence compared with arthroscopy for revealing cartilage lesions was 94%, specificity was 99%, and accuracy was 98%. Sensitivity of coronal and axial T2-weighted fast spin-echo sequences with fat saturation was 93%, and specificity was 99%. Fifty-five lesions (64%) were identically graded on MR imaging and arthroscopy. Seventy-eight lesions (90%) were within one grade using MR imaging and arthroscopy, and 84 lesions (97%) were within two grades using MR imaging and arthroscopy. CONCLUSION: T2-weighted fast spin-echo MR imaging with fat saturation is an accurate and fast technique for detecting and grading articular cartilage defects in the knee. The combination of the axial and coronal planes offers sufficient coverage of articular surfaces to provide a high sensitivity and specificity for chondral defects.

Adult↗
PubMed1997

Arthritic temporomandibular joint: correlation of macromolecular contrast-enhanced MR imaging parameters and histopathologic findings.

PURPOSE: To assess the utility of macromolecular contrast material-enhanced magnetic resonance (MR) imaging parameters for determining the histopathologic severity of temporomandibular joint (TMJ) arthritis. MATERIALS AND METHODS: Ovalbumin was used to induce arthritis in the TMJs of 10 previously sensitized adult white rabbits. Five rabbits composed the sham-treated control group. Dynamic spin-echo imaging was performed immediately before and for 30 minutes after injection of macromolecular contrast medium. Histologic specimens of TMJ were assessed quantitatively for arthritis. Changes in MR signal intensity were derived from the synovial and subsynovial tissues of the TMJ, and plasma volume (PV) and permeability surface area product (PS) were calculated. These MR parameters and the arthritic scores were compared between sham-treated and antigen-challenged TMJs. The relationships between MR parameters and histopathologic indexes were also determined. RESULTS: Arthritic TMJs showed marked enhancement of the synovial and subsynovial tissues over the imaging period. PS and all histopathologic indexes of arthritis were significantly greater (P < .005) in antigen-challenged than in sham-treated TMJs. PS demonstrated strong positive relationships with all histologic parameters of arthritis, indicating its utility for assessing the severity of joint inflammation. CONCLUSION: Macromolecular contrast-enhanced MR imaging enables quantification of PS and PV in inflamed joints. This technique may provide insights into the pathogenesis of joint inflammation and noninvasive monitoring of disease severity and treatment response in arthritis.

Albumins↗
PubMed1997

Dedicated extremity MR imaging. An emerging technology.

Dedicated extremity MR imaging represents a radical departure from conventional whole-body scanning. Extremity MR imaging offers such advantages as reduced cost, more convenient and inexpensive setting, greater patient comfort and safety, and high diagnostic power. This article examines some of the features of extremity MR imaging and how this technology is affecting musculoskeletal imaging in today's environment of cost containment and health care reform.

Arm↗
PubMed1996

Magnetic resonance imaging of labral cysts of the hip.

OBJECTIVE: To present the magnetic resonance (MR) imaging findings in patients with labral cysts adjacent to the acetabulum and to examine their association with hip pathology. DESIGN: MR images and conventional radiographs of seven patients with paralabral cysts were retrospectively reviewed by three musculoskeletal radiologists. PATIENTS: The patients included three men and four women with hip pain, ranging in age from 29 to 82 years. Two patients had developmental dysplasia of the hip and six had a history of remote trauma/dislocation. Clinical history and follow-up were obtained in all patients. Surgery was performed on one patient. RESULTS AND CONCLUSIONS: Paralabral cysts were located in the posterosuperior aspect of the hip joint in five patients and in the anterior aspect in two patients. A tear of the adjacent acetabular labrum was confirmed surgically in one patient, and in all patients the MR features suggested the presence of an abnormal labrum. Osteoarthritis was observed in three patients and there was associated subchondral cyst formation in the acetabulum adjacent to the cyst in three patients. The paralabral cyst of the hip is well visualized on MR imaging and is seen in patients with a predisposition to labral pathology.

Acetabulum↗
PubMed1996

MR imaging.

MRI is a tool of unprecedented capabilities for evaluating arthritis and its progression. Not only can it non-invasively delineate the anatomy of all components of a joint with unparalleled clarity, MRI is also capable of probing important functional and compositional parameters of disease in these tissues. Particularly intriguing is MRI's potential for identifying very early changes of joint disease when clinical symptoms may be minimal or absent. Early detection of patients who are at risk for developing progressive disease may allow appropriate treatment to be initiated earlier, when there may be a greater chance of favourable outcome. MRI can, furthermore, provide objective and quantitative measures of disease progression and treatment response. Certain parameters, such as articular cartilage volume, have been validated cross-sectionally; however, their longitudinal performance has yet to be established. Further work is, therefore, necessary to thoroughly validate and optimize some of these measures so that they can begin to be used in more powerful ways to explore the pathophysiology and potential therapies of arthritic disorders.

Arthritis↗