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Biomedical subjects

W Martel

Publications and source records attributed to W Martel.

123 records · Page 7Linked to original sources
PubMedDate not supplied

Pathogenesis of cervical discovertebral destruction in rheumatoid arthritis.

A review of 20 cases of rheumatoid arthritis strongly supported the concept that the cervico-disco-vertebral destruction seen radiologically is a consequence of cervical instability caused by apophyseal arthritis and ligamentous laxity. It is postulated that such instability results in chronic trauma to the discovertebral joints leading to destruction of the disc cartilage and vertebral endplates. "Rheumatoid inflammation" of the disc has previously been described, but it is uncertain that such inflammation in the disc is the primary cause of these destructive lesions.

Adult↗
PubMedDate not supplied

Hepatic imaging: positron emission tomography, digital angiography, and nuclear magnetic resonance imaging.

Major advances in diagnostic imaging of the human body have been made in recent years. Positron emission tomography, a technique founded on advances in radiopharmaceuticals and radionuclide imaging apparatus, permits imaging regional metabolism, metabolite distribution, and flow. Thus far, its major applications have been in the study of the brain, and to a lesser extent, the heart; however, it is also finding a role in the study of the liver. Digital angiography is being applied to fluoroscopic systems which permits visualization of relatively low doses of intravascular iodinated radiographic contrast media. Imaging of the major arteries is possible using simple intravenously administered contrast media; digital techniques also increase the diagnostic yield in intraarterial studies. Nuclear magnetic resonance (NMR) imaging is an outgrowth of laboratory NMR spectroscopy; the interaction of radiofrequency signals with nuclei in strong magnetic fields permits imaging the distribution and certain chemical properties of various isotopes. Hydrogen NMR imaging is proving most useful for clinical diagnosis. The techniques used to image hydrogen are also being applied to NMR spectroscopy in vivo of various isotopes, including carbon-13, phosphorus-31, and hydrogen-1.

Angiography↗
PubMedDate not supplied

MRI in osteoarthritis of the hip: gradations of severity.

In a prospective study, 10 patients with well-documented osteoarthritis (O.A.) of the hips were imaged using spin-echo pulse sequences (TR = 0.5 to 1.5 s and TE = 28 to 60 ms). After analyzing the changes observed, an MR grading system for assessing severity of O.A. in the hips was developed. Using this grading system and an established grading system for osteoarthritis using roentgenograms (both systems use grades 0-4), two radiologists independently graded the MR studies and plain films separately, twice. The roentgenogram grading system was more accurate in predicting symptoms in the more severe cases, whereas the MR grading system was slightly more useful in the less severe cases. Our results show that MR can demonstrate a spectrum of changes of O.A. in the hips. Its ability to directly image articular cartilage makes it a powerful research and clinical tool.

Adult↗
PubMedDate not supplied

Some commonly unrecognized manifestations of metabolic arthropathies.

The metabolic arthropathies are characterized by the deposition of abnormal substances in or around joints. Certain features of some of these arthropathies and their significance have only recently been recognized and others have been insufficiently emphasized. An important group of conditions are the arthropathies related to renal failure and its treatment, namely, aluminum toxicity, periarticular calcification and crystal deposition, hyperparathyroidism, and dialysis-related amyloidosis. Crystal deposition diseases, specifically, gouty arthritis, calcium pyrophosphate deposition, and calcium hydroxyapatite deposition, are also reviewed.

Aluminum↗
PubMedDate not supplied

Systematic evaluation and increased structure in a radiology elective.

Diagnostic radiology is expanding, playing an increasingly central role in patient care, which heightens the importance of radiology teaching in undergraduate medical education. This study examined the impact of increased structure and systematic evaluation on student performance in a radiology elective. The evaluation protocol included premultiple and postmultiple choice examinations (70 questions each), a film interpretation quiz (ten films, 20 questions), faculty assessment of a student oral case presentation, and student evaluations of the elective experience. The relationships among the evaluation techniques, as well as differences in class level and course ratings were also examined. Two different treatment groups were studied. Group 1 was given general objectives and information regarding availability of recommended resources, including self-learning materials for the elective, didactic seminars, and viewbox exposure. Group 2 was given specific written instructional objectives, a structured schedule for viewing the self-learning materials, and the same seminars and viewbox exposure. The statistically significant higher performance of the structured group suggests that medical students achieve the objectives of an elective better when learning activities are well defined, structured, and systematically evaluated. In addition, those students receiving the structured experience rated the radiology elective more favorably.

Education, Medical, Undergraduate↗
PubMedDate not supplied

MR evaluation of liver iron overload.

Children and young adults with hemolytic anemias requiring frequent transfusions develop increased liver iron content. We evaluated 15 chronically transfused children with sickle cell disease to determine whether spin-echo magnetic resonance (MR) imaging was useful in assessing the degree of iron overload. Quantitative MR parameters were correlated with liver biopsy iron determinations and serum ferritin levels. The best predictor of liver iron was the ratio of the intensities between the liver and paraspinal musculature on somewhat T1 weighted sequence (repetition time 0.5 s, echo time 28 ms), R2 = 0.58. Magnetic resonance was able to separate those patients with liver iron levels greater than 100 micrograms/mg (intensity ratios approximately 0.4), from those with levels less than 100 micrograms/mg (intensity ratios near 1). However, MR was unable to quantitate liver iron in patients with values ranging from 100 to 400 micrograms/mg since similar intensity ratios were present in this range. Thus, MR provides a qualitative rather than quantitative assessment of liver iron overload.

Anemia, Sickle Cell↗
PubMedDate not supplied

MR imaging of early fibrodysplasia ossificans progressiva.

Fibrodysplasia ossificans progressiva is a rare disorder characterized by progressive heterotopic bone formation in connective tissue and muscle in association with congenital skeletal anomalies. The disease usually leads to extensive immobility and eventual disability. We report the magnetic resonance findings in a boy prior to ossification of his soft tissue masses.

Child, Preschool↗
PubMedDate not supplied

Automated analysis of multiple performance characteristics in magnetic resonance imaging systems.

As with other digital imaging systems in heavy medical use, it is desirable with magnetic resonance imaging (MRI) to obtain extensive, rigorous system performance measures from a small set of images of one or two relatively simple test objects. Digital analysis of the parallel square rod (PSR) test object introduces digital image system self-evaluation to MRI and extends automated image evaluation to include rigorous measures throughout the imaging volume rather than just average measures over the image. Precise comparisons with theory and between systems can be performed as well as quality control and corrections for nonuniformities. The PSR test object consists of an 18 X 18 X 36 cm rectangular acrylic container enclosing 60 parallel square acrylic rods running the entire length. The inter-rod space is filled with a liquid or gel that produces strong, tissuelike signals in MRI and high contrast relative to the rods for computed tomography (CT). For profiles of slice thickness and separation, the rods are tilted in the test object to intersect the image plane at a 45 degree angle when the test object sides are parallel and perpendicular to the image plane. The test object itself is rotated 6-12 degrees about its major axis so that the sides of the rods make a small angle to the rows and columns of pixels. This allows digital sampling at finer spacing than the pixels for determination of edge response functions.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMedDate not supplied

Magnetic resonance imaging of knee hyaline cartilage and intraarticular pathology.

Injuries to the hyaline cartilage of the knee joint are difficult to diagnose without invasive techniques. Even though these defects may be the most important prognostic factors in assessing knee joint injury, they are usually not diagnosed until arthrotomy or arthroscopy. Once injuries to hyaline cartilage are found and/or treated, no technique exists to follow these over time. Plain radiographs, arthrograms, and even computed tomography fail to detail most hyaline cartilage defects. We used magnetic resonance imaging (MRI) to evaluate five fresh frozen cadaver limbs and 10 patients whose pathology was known from arthrotomy or arthroscopic examination. Using a 0.35 Tesla superconducting magnet and spin-echo imaging technique with a head coil, we found that intraarticular fluid or air helped to delineate hyaline cartilage pathology. The multiplane capability of MRI proved to be excellent in detailing small (3 mm or more) defects on the femoral condyles and patellar surface. Cruciate ligaments were best visualized on sagittal oblique projections while meniscal pathology was best seen on true sagittal and coronal projections. MRI shows great promise in providing a noninvasive technique of evaluating hyaline cartilage defects, their response to treatment, and detailed anatomical information about cruciate ligaments and menisci.

Adolescent↗