Biomedical subjects

T L Chenevert

Publications and source records attributed to T L Chenevert.

At least 37 records · Page 2Linked to original sources

PubMed1998

Acute ethanol effects on focal cerebral ischemia in fasted rats.

The effects of acute ethanol intoxication were investigated in a rat model of unilateral middle cerebral artery occlusion. Groups of 5 to 8 male Sprague-Dawley rats were subjected to 4 hr of left middle cerebral artery occlusion. All groups were deprived of food overnight and were pretreated intraperitoneally with 5% dextrose solution (10 ml/kg), 20% ethyl alcohol in 5% dextrose solution (2 g/kg), or 30% ethyl alcohol in a 5% dextrose solution (3 g/kg) 1 hr before middle cerebral artery occlusion. Regional cerebral blood flow during ipsilateral occlusion was approximately 9.1 to 10% of baseline in all groups. The mean % brain water content in control, 2 g/kg ethanol-treated groups, and 3 g/kg ethanol-treated groups were: in the ischemic core--81.6, 81.2, and 82.4; intermediate zone--80.5, 80.6, and 81.7; and outer zone--79.7, 79.7, and 80.8, respectively. Brain Na+ and K+ content in the three groups was related to water content, but much greater with ethanol pretreatment. The water content of the intermediate zones in the 3 g/kg ethanol-treated animals was significantly greater than in the control (p < 0.01 and 0.001) and the 2 g/kg ethanol-treated groups. One-way analysis of variance indicated a significant dose-effect relationship in which the lower dose of ethanol tended to reduce ischemic core water content, and the larger dose increased ischemic core water, compared with the control. None of the overnight fasted groups had any significant hyperglycemia. The group given 3 g/kg i.p. ethanol 1 hr before had exacerbated edema formation with a mean whole blood level of ethanol of approximately 230 mg/dl. The neurotoxic effects of high concentrations of ethanol were unrelated to any change in plasma glucose concentrations.

Alcoholic Intoxication↗

PubMed1997

Diagnosis of pulmonary embolism with magnetic resonance angiography.

BACKGROUND: Diagnosing pulmonary embolism may be difficult, because there is no reliable noninvasive imaging method. We compared a new noninvasive method, gadolinium-enhanced pulmonary magnetic resonance angiography, with standard pulmonary angiography for diagnosing pulmonary embolism. METHODS: A total of 30 consecutive patients with suspected pulmonary embolism underwent both standard pulmonary angiography and magnetic resonance angiography during the pulmonary arterial phase at the time of an intravenous bolus of gadolinium. All magnetic resonance images were reviewed for the presence or absence of pulmonary emboli by three independent reviewers who were unaware of the findings on standard angiograms. RESULTS: Pulmonary embolism was detected by standard pulmonary angiography in 8 of the 30 patients in whom pulmonary embolism was suspected. All 5 lobar emboli and 16 of 17 segmental emboli identified on standard angiograms were also identified on magnetic resonance images. Two of the three reviewers reported one false positive magnetic resonance angiogram each. As compared with standard pulmonary angiography, the three sets of readings had sensitivities of 100, 87, and 75 percent and specificities of 95, 100, and 95 percent, respectively. The interobserver correlation was good (k=0.57 to 0.83 for all vessels, 0.49 to 1.0 for main and lobar vessels, and 0.40 to 0.81 for segmental vessels). CONCLUSIONS: In this preliminary study, gadolinium-enhanced magnetic resonance angiography of the pulmonary arteries, as compared with conventional pulmonary angiography, had high sensitivity and specificity for the diagnosis of pulmonary embolism. This new technique shows promise as a noninvasive method of diagnosing pulmonary embolism without the need for ionizing radiation or iodinated contrast material.

Adult↗

PubMed1997

Contrast-enhanced abdominal MR angiography: optimization of imaging delay time by automating the detection of contrast material arrival in the aorta.

PURPOSE: To improve gadolinium-enhanced magnetic resonance (MR) angiogram quality by automatically synchronizing acquisition of central k-space image data with the arterial phase of contrast material bolus infusion. MATERIALS AND METHODS: A spin-echo pulse sequence with orthogonal 90 degrees and 180 degrees pulses was used to monitor signal in a single 4 x 4 x 12-cm voxel that encompassed a segment of aorta. An increase in signal that corresponded to the arrival of gadolinium was used to trigger three-dimensional, spoiled gradient-echo abdominal MR angiography in 50 adult patients. RESULTS: Arterial signal intensity increased 28-fold with automatic compared to 19-fold with manual triggering (P < .05) at an approximate dose of 0.3 mmol/kg. Automatic triggering with a lower dose (approximately 0.2 mmol/kg) resulted in 20-fold arterial enhancement, which is comparable with enhancement after manual triggering at the high dose. In addition, venous enhancement was less (1.5-fold) with automatic than with manual (3.5-fold) triggering at the same dose (P < .05). CONCLUSION: Automatic triggering results in improved arterial-tovenous contrast. It increases arterial enhancement or enables MR angiograms to be obtained with less contrast material. The authors now routinely use this technique for aortorenal imaging with a gadolinium-based contrast material dose of 20 mmol (40 mL) in patients who weigh more than 50 kg and 10 mmol (20 mL) in patients who weigh less than 50 kg.

Abdomen↗

PubMed1997

Automated detection of bolus arrival and initiation of data acquisition in fast, three-dimensional, gadolinium-enhanced MR angiography.

Automatic triggering of magnetic resonance (MR) angiography with detection of a contrast material bolus was evaluated. Signal intensity changes with time were tracked in a prescribed tracking or monitoring volume by a parallel signal processing unit that automatically started data acquisition once user-defined thresholds were exceeded. This technique, referred to as MR Smartprep, was reliable and avoided the inconsistencies of manual timing.

Adult↗

PubMed1997

Effect of gadolinium on phase-contrast MR angiography of the renal arteries.

OBJECTIVE: Our aim was to evaluate the effect of gadolinium chelates on image quality in phase-contrast MR angiography of renal arteries in patients suspected of having renal artery stenosis. MATERIALS AND METHODS: In 24 patients, axial three-dimensional phase-contrast MR angiography of the renal arteries was obtained on a 1.5-T MR imaging system before and after administration of gadolinium contrast agent. The improvement in distal renal artery signal-to-noise ratio after enhancement was measured and correlated with patient age, serum creatinine level, clinical estimation of renal artery flow, and the imaging parameter flip angle. RESULTS: On average, the distal renal artery signal-to-noise ratio increased 2.2-fold after gadolinium administration (p < .001). The increase was greatest in patients more than 60 years old (3.1-fold; p < .001) and in patients with serum creatinine levels greater than 3.0 mg/dl (4.3-fold; p < .01). After enhancement, we found an apparent increase in renal artery diameter (3.5 +/- 1.1 mm before enhancement versus 4.8 +/- 1.4 mm after enhancement [mean +/- SD; p < .001]). We believe this increase reflects improved visualization of slow blood flow along the artery wall. Although the visualization of renal arteries was better in most patients after enhancement, two patients had poorer image quality after enhancement because of increased venous signal obscuring the arteries. CONCLUSION: Gadolinium administration significantly increases distal renal artery signal-to-noise ratio on three-dimensional phase-contrast MR angiography in most patients. The signal-to-noise ratio improvement is greatest in older patients and in patients with impaired renal function. However, in some cases, increased venous signal may obscure arteries.

Adult↗

PubMed1997

Monitoring early response of experimental brain tumors to therapy using diffusion magnetic resonance imaging.

Quantitative magnetic resonance imaging was performed to evaluate water diffusion and relaxation times, T1 and T2, as potential therapeutic response indicators for brain tumors using the intracranial 9L brain tumor model. Measurements were localized to a column that intersected tumor and contralateral brain and were repeated at 2-day intervals before and following a single injection of 1,3-bis(2-chloroethyl)-1-nitrosourea (13.3 mg/kg). Tumor growth was measured using T2-weighted magnetic resonance imaging to determine the volumetric tumor doubling time (Td) before (Td = 64 +/- 13 h, mean +/- SD, n = 16) and after (Td = 75 +/- 9 h, n = 4) treatment during exponential regrowth. Apparent diffusion coefficient of untreated tumors was independent of tumor volume or growth time, whereas relaxation times increased during early tumor growth. Diffusion displayed the strongest treatment effect and increased before tumor regression by 55% 6-8 days following treatment. Changes in relaxation times were also significant with increases of 16% for T1 and 27% for T2. Diffusion and relaxation times returned to pretreatment levels by 12 days after treatment. Histological examination supports the model that the observed increase in diffusion reflects an increase of extracellular space following treatment. Furthermore, the subsequent apparent diffusion coefficient decrease is a result of viable tumor cells that repopulate this space at a rate dependent on the surviving tumor cell fraction and recurrent tumor doubling time. Serial tumor volume measurements allowed determination of log cell kill of 1.0 +/- 0.3 (n = 4). These results suggest that diffusion measurements are sensitive to therapy-induced changes in cellular structure and may provide an early noninvasive indicator of treatment efficacy.

Animals↗

PubMed1996

Effect of the rate of gadopentetate dimeglumine administration on abdominal vascular and soft-tissue MR imaging enhancement patterns.

PURPOSE: To delineate dynamic gadopentetate dimeglumine enhancement profiles within the abdomen as a guide to improve gadolinium-enhanced magnetic resonance (MR) angiography. MATERIALS AND METHODS: Fifteen patients (eight women, seven men; aged 19-80 years) underwent fast three-dimensional spoiled gradient-recalled-echo imaging with the keyhole technique during the administration of 0.1 mmol/kg gadopentetate dimeglumine by means of bolus (10-second) injection (n = 5), 60 second injection (n = 5), or slow (120-230-second) pump injection (n = 5). Injection was initiated 10 seconds after imaging began. Regions of interest were constructed within the aorta, inferior vena cava, liver, spleen, renal cortex, muscle, and fat. Inclusion of phantoms of gadopentetate dimeglumine in tubes allowed estimation of intravascular gadolinium concentration. RESULTS: Maximal arterial enhancement occurred with bolus administration; maximal parenchymal organ enhancement, with 60-second injection. Slow pump injection resulted in a longer time to preferential arterial to venous enhancement (120 seconds +/- 14 [+/-standard deviation]) than did bolus (48 seconds +/- 64) or 60-second (88 seconds +/- 39) injections. The peak arterial to venous enhancement ratio was 6.3 +/- 3.3 for the bolus injection, 4.7 +/- 1.6 for the 60-second injection, and 3.3 +/- 1.3 for the slow pump injection. CONCLUSION: The dynamics and magnitude of abdominal vascular and soft-tissue enhancement are affected by the rate of gadopentetate dimeglumine administration.

Abdomen↗

PubMed1996

Thrombin-soaked gelatin sponge and brain edema in rats.

Previous work from this laboratory has shown that injection of thrombin into rat basal ganglia causes brain edema. This study investigates the effect on rat brain of thrombin-soaked gelatin sponge (used for intraoperative hemostasis in clinical situations) at a concentration similar to that used in humans. Three models were developed to evaluate this effect. In the first model, a gelatin sponge soaked with vehicle or thrombin (100 U/cm3) was placed on the intact pia of the right frontal lobe in rats without cortical lesions. In the second model, frontal cortex was excised (3 mm3) and the exposed brain was cauterized with electrocoagulation. Gelatin sponge was soaked with vehicle or thrombin (1000, 100, 10, or 1 U/cm3) and placed in the lesion site. In the third model, hirudin, a specific thrombin antagonist, was added to the thrombin-soaked gelatin sponge and placed in a similar cortical lesion to determine if the observed effects were specific to thrombin. The dose-response range for thrombin was determined qualitatively by magnetic resonance (MR) imaging and quantitatively by brain edema formation 24 hours after exposure. We found no edema in the cortically intact rats. The rats given cortical lesions developed significant edema when subjected to 1000, 100, and 10 U/cm3 thrombin as seen on MR imaging and at 100 and 10 U/cm3 thrombin as revealed by wet/dry weight and ion studies of brain tissue. Topical hirudin prevented thrombin-induced edema. It is concluded that thrombin-soaked gelatin sponges cause or enhance significant brain edema in rats at concentrations typically used for human neurosurgery.

Administration, Topical↗

PubMed1996

Three-dimensional contrast-enhanced MR angiography.

Three-dimensional contrast-enhanced magnetic resonance (MR) angiography is a relatively new technique that uses the transient shortening in blood T1 following the intravenous injection of gadolinium chelates to image blood vessels irrespective of flow. For many applications, 3D contrast-enhanced MR angiography is developing into a safe, fast, and cost-effective alternative to conventional diagnostic angiography. One of its biggest advantages over other MR angiography techniques (and CT angiography) is the ability to image in a plane parallel to the vessel of interest. This feature, combined with the inherent properties of a 3D gradient refocused sequence, make 3D contrast-enhanced MR angiography intrinsically fast, high resolution and free from saturation and turbulence-related artifacts. This article is designed to familiarize the reader with the theory of 3D contrast-enhanced MR angiography and the application of the technique to different vascular territories. Contrast agents, relaxation effects, contrast bolus effects, pulse sequences, artifacts, and post-processing, as well as the present state of thinking with regard to optimal contrast injection timing/detection and Fourier space mapping are discussed. Patient preparation and techniques and imaging parameters for body applications of gadolinium-enhanced MR angiography, including aorta, renal arteries, mesenteric arteries, portal venous system, pelvis and legs, pulmonary arteries, and carotid arteries are included.

Fourier Analysis↗

PubMed1995

Dynamic three-dimensional imaging with partial k-space sampling: initial application for gadolinium-enhanced rate characterization of breast lesions.

PURPOSE: To evaluate a method to monitor gadolinium enhancement patterns at magnetic resonance (MR) imaging with high temporal resolution and full coverage through both breasts. MATERIALS AND METHODS: In 12 patients with 13 masses, including nine carcinoma, nonenhanced three-dimensional MR imaging was performed with full-matrix resolution. At dynamic imaging, 32 serial passes were made during bolus administration of contrast material, and temporal resolution was reduced to 12 seconds by collecting the central (low spatial frequency) 32 x 16 or 16 x 16 phase-encode views. Full-matrix dynamic images were reconstructed by complementing central phase-encode data with precontrast data from peripheral high-spatial-frequency views. RESULTS: Results at time-course analysis with a mono-exponential saturation model indicated malignant lesions tend to show rapid (< 60 seconds) contrast change relative to benign masses and normal tissues. One cancer displayed an exceptionally slow contrast change (260 seconds). CONCLUSION: The technical objectives of full tissue coverage, rapid temporal sampling, and quantification of enhancement curves are met with this method for certain lesions (> 5 mm in largest diameter).

Adult↗

PubMed1995

Breath-hold gadolinium-enhanced MR angiography of the abdominal aorta and its major branches.

PURPOSE: To develop and evaluate a sequence for breath-hold three-dimensional gadolinium-enhanced magnetic resonance (MR) angiography of the abdominal aorta. MATERIALS AND METHODS: In 63 patients, the abdominal aorta and its branches were imaged for 29, 43, or 58 seconds with breath holding. A fast spoiled gradient-echo sequence was used at 1.5 T during infusion of 42 mL of a gadolinium chelate. Correlation with conventional angiography was performed in 19 patients. MR image quality (signal-to-"total" noise ratio [S/N*]) with breath holding was compared with that with free breathing (104 patients). RESULTS: With breath-hold gadolinium-enhanced MR angiography, renal, celiac, and superior mesenteric artery occlusive disease was graded appropriately in 15 of 19 patients, and 10 of 11 accessory renal arteries were depicted correctly. Renal artery branches were visualized in 86 of 95 kidneys on breath-hold images compared with only 84 of 236 kidneys with free breathing (P < .001). Distal renal artery S/N* was 3.1 with breath holding and 2.1 with free breathing (P < .001). CONCLUSION: Breath holding statistically significantly improves three-dimensional gadolinium-enhanced MR angiography of the renal, celiac, and superior mesenteric arteries.

Adult↗

PubMed1995

Intracerebral infusion of thrombin as a cause of brain edema.

Purified thrombin from an exogenous source is a hemostatic agent commonly used in neurosurgical procedures. The toxicity of thrombin in the brain, however, has not been examined. This study was performed to assess the effect of thrombin on brain parenchyma, using the formation of brain edema as an indicator of injury. Ten microliters of test solution was infused stereotactically into the right basal ganglia of rats. The animals were sacrificed 24 hours later, and the extent of brain edema and ion content were measured. Concentrations of human thrombin as low as 1 U/microliter resulted in a significant increase in brain water content. Rats receiving 10 U/microliters had a mortality rate of 33% compared to no mortality in the groups receiving smaller doses. Thrombin-induced brain edema was inhibited by a specific and potent thrombin inhibitor, hirudin. A medical grade of bovine thrombin commonly used in surgery also caused brain edema when injected at a concentration of 2 U/microliters. Edema formation was prevented by another highly specific thrombin inhibitor, N alpha-(2-Naphthalenesulfonylglycyl)-4-DL-phenylalaninepiperidid e (alpha-NAPAP). Thrombin-induced brain edema was accompanied by increases in brain sodium and chloride contents and a decrease in brain potassium content. Changes in brain ions were inhibited by both hirudin and alpha-NAPAP, corresponding to the inhibition of brain water accumulation. This study shows that thrombin causes brain edema when infused into the brain at concentrations as low as 1 U/microliter, an amount within the range of concentrations used for topical hemostasis in neurosurgery.

Animals↗

PubMed1995

In vivo MR determination of water diffusion coefficients and diffusion anisotropy: correlation with structural alteration in gliomas of the cerebral hemispheres.

PURPOSE: To determine whether a relationship exists between water diffusion coefficients or diffusion anisotropy and MR-defined regions of normal or abnormal brain parenchyma in patients with cerebral gliomas. METHODS: In 40 patients with cerebral gliomas, diffusion was characterized in a single column of interest using a motion-insensitive spin-echo sequence that was applied sequentially at two gradient strength settings in three orthogonal directions. Apparent diffusion coefficients (ADCs) were derived for the three orthogonal axes at 128 points along the column. An average ADC and an index of diffusion anisotropy (IDA = diffusion coefficientmax-min/diffusionmean) was than calculated for any of nine MR-determined regions of interest within the tumor or adjacent parenchyma. RESULTS: In cerebral edema, mean ADC (all ADCs as 10(-7) cm2/s) was 138 +/- 24 (versus 83 +/- 6 for normal white matter) with mean IDA of 0.26 +/- 0.14 (versus 0.45 +/- 0.17 for normal white matter). Solid enhancing central tumor mean ADC was 131 +/- 25 with mean IDA of 0.15 +/- 0.10. Solid enhancing tumor margin mean ADC was 131 +/- 25, with IDA of 0.25 +/- 0.20. Cyst or necrosis mean ADC was 235 +/- 35 with IDA of 0.07 +/- 0.04. CONCLUSION: In cerebral gliomas ADC and IDA determinations provide information not available from routine MR imaging. ADC and IDA determinations allow distinction between normal white matter, areas of necrosis or cyst formation, regions of edema, and solid enhancing tumor. ADCs can be quickly and reliably characterized within a motion-insensitive column of interest with standard MR hardware.

Adolescent↗

PubMed1995

Growth kinetics and treatment response of the intracerebral rat 9L brain tumor model: a quantitative in vivo study using magnetic resonance imaging.

We report the use of magnetic resonance imaging (MRI) for in situ tumor growth rate studies of experimental intracranial 9L tumors. T2-weighted spin-echo coronal magnetic resonance images of rat brains with 9L tumors were obtained every 2 days beginning at 8-11 days postimplantation using a 7 tesla MRI system. Tumors were clearly delineated in the images as a hyperintense region with a relatively well-demarcated border and minimal peritumoral edema. Tumor volumes from individual slices were summed together to yield the total tumor volume. The accuracy of this methodology for volumetric determination was verified by MRI phantom studies. Tumor growth rates determined from sequential MRI measurements of tumor volumes were quantitated in terms of volumetric doubling time. Tumor doubling times were found to range from 50 to 81 h, with an average of 66 +/- 8 h (n = 10). Intracranial 9L tumors were found to grow exponentially over the entire life span of the animal, allowing treated animals to serve as their own controls since the volumetric doubling time could be determined from three to four MRI scans before treatment administration. The intracerebral tumor growth delay following a single injection of 1, 3-bis(2-chloroethyl)-1-nitrosourea (13.3 mg/kg i.p.) allowed for noninvasive determination of in vivo log cell kill. A 2.0 +/- 0.2 (n = 3) log cell kill from 1,3-bis(2-chloroethyl)-1-nitrosourea treatment was found from post-treatment MRI volume measurements. These results demonstrate that MRI provides a powerful and sensitive method for assessing the growth and treatment response of intracranial 9L tumors in the rat.

Animals↗

PubMed1994

Medical physics.

Explore the source record for details and available documents.

Diagnosis, Computer-Assisted↗

PubMed1994

Experimental intracerebral hemorrhage: relationship between brain edema, blood flow, and blood-brain barrier permeability in rats.

There have been few investigations of brain edema formation after intracerebral hemorrhage (ICH), despite the fact that mass effect and edema are important clinical complications. The present study was designed to investigate the time course for the formation and resolution of brain edema and to determine how changes in cerebral blood flow (CBF) and blood-brain barrier (BBB) permeability are temporally related to edema formation following ICH. Anesthetized adult rats received a sterile injection of 100 microliters of autologous blood into the caudate nucleus. Water and ion contents were measured immediately, at 4 and 12 hours, and daily to Day 7 (10 time points, six rats at each time) after experimental ICH. The water content of the ipsilateral basal ganglia increased progressively (p < 0.002) over the first 24 hours, then remained constant until after Day 5, when the edema began to resolve. Edema was most severe in the tissue immediately surrounding the hemorrhage; however, it was also present in the ipsilateral cortex, the contralateral cortex, and the basal ganglia. Measurements of local CBF (using [14C]-iodoantipyrine) and BBB permeability (using [3H]-alpha-aminoisobutyric acid) were obtained in separate groups of six to eight rats at various time intervals between 1 and 48 hours after ICH. Cerebral blood flow was reduced to 50% of control at 1 hour, returned to control values by 4 hours, but then decreased to less than 50% of control between 24 and 48 hours after ICH. The BBB permeability increased significantly prior to the occurrence of significant edema in the tissue surrounding the clot. However, BBB permeability in the more distant structures remained normal despite the development of edema. These results demonstrate a time course for the formation and resolution of brain edema following ICH similar to that observed during focal ischemia. Brain edema forms in the immediate vicinity of the clot as a result of both BBB disruption and the local generation of osmotically active substances and then spreads to adjacent structures. While local ischemia, due to the mass effect of the hemorrhage, may play a role in producing cytotoxic and vasogenic edema, the release of toxic substances from the clot should also be considered. Since edema is nearly maximal by 24 hours after ICH, therapy directed at reducing edema formation must be instituted within the 1st day.

Aminoisobutyric Acids↗

PubMed1993

Signal-to-noise measures for magnetic resonance imagers.

The signal-to-noise ratio (SNR) in magnetic resonance imaging represents one of the system operating variables that must be determined both for evaluating the performance of different imaging protocols on a particular machine, and for monitoring machine performance as part of a routine quality control (QC) program. Utilizing a phantom and set of automated analysis programs currently under development, this study evaluated several ways of measuring image signal and noise and demonstrated the importance of utilizing measured voxel volumes as opposed to nominal volumes in the calculation of SNR. The NEMA proposed standard for SNR is compared with several other SNR measures and is recommended as the measure to be used in routine SNR reporting. The importance of utilizing other SNR measures in addition to the NEMA proposed standard for routine QC is discussed.

Magnetic Resonance Imaging↗

PubMed1993

MR imaging in children with dermatomyositis: musculoskeletal findings and correlation with clinical and laboratory findings.

OBJECTIVE: The purpose of this study was to describe the musculoskeletal MR findings in childhood dermatomyositis and to correlate MR findings with indicators of disease activity such as muscle strength and serum levels of muscle enzymes. SUBJECTS AND METHODS: This prospective study included 24 children: 19 children with dermatomyositis and five control subjects. The diagnosis of dermatomyositis was established by clinical findings and serum levels of muscle enzymes in all patients, electromyography in six patients, and biopsy in four patients. At the time of the initial MR evaluation, patients were classified on the basis of clinical findings as having active (n = 15) or inactive (n = 4) disease. A total of 44 MR evaluations of patients with dermatomyositis were included in the study: 19 initial MR examinations and 12 examinations repeated after 4-6 months of therapy in patients with active disease. An additional 13 examinations were performed on five patients. Conventional T1-weighted (SE 600/20) and T2-weighted (SE 2500/80) spin-echo and fat-suppressed MR images were obtained. The T2-weighted images (TE = 80) were used for comparison. In addition to the visual assessment, ratios between the signal intensity of muscles (gluteus, adductors, quadriceps, and hamstrings) and the signal intensity of subcutaneous fat in the same tomographic section were calculated. RESULTS: All patients with clinically active disease (n = 15) had abnormal findings on MR studies, whereas those with inactive disease (n = 4) had normal MR findings. Signal-intensity ratios of patients with active disease were greater than those in control subjects, whereas the ratios in patients with inactive disease were not different from those in control subjects. After 4-6 months of therapy, the average signal-intensity ratios of treated patients with repeated MR evaluations (n = 12) differed from ratios obtained before therapy in the same patients, but were not different from the ratios in control subjects. Other MR findings observed were perimuscular edema, enhancement of the chemical-shift artifact, and inflammatory changes of subcutaneous fat. Fat-suppressed imaging enhanced visualization of abnormalities. Markedly abnormal signal intensities of muscle were associated with marked elevations of serum levels of muscle enzymes; however, abnormal MR findings were visualized with normal serum levels of muscle enzymes. CONCLUSION: Findings of active childhood dermatomyositis on T2-weighted MR images include increased signal intensity in affected muscle, perimuscular edema, enhanced chemical-shift artifact, and increased signal intensity in subcutaneous fat. After therapy, signal intensity of muscle returns to normal. These MR findings are enhanced on fat-suppressed images.(ABSTRACT TRUNCATED AT 400 WORDS)

Adipose Tissue↗