Biomedical subjects

J Gieseke

Publications and source records attributed to J Gieseke.

At least 19 recordsLinked to original sources

PubMed2007

Double inversion recovery brain imaging at 3T: diagnostic value in the detection of multiple sclerosis lesions.

BACKGROUND AND PURPOSE: To prospectively determine the sensitivity in the detection of multiple sclerosis (MS) lesions by using double inversion recovery (DIR), fluid-attenuated inversion recovery (FLAIR), and T2-weighted turbo spin-echo (T2 TSE) MR imaging at 3T. METHODS: Seventeen patients presenting with a clinically isolated syndrome (CIS) suggestive of MS, 9 patients with definite MS, and 6 healthy control subjects were included. Imaging was performed on a 3T MR system using DIR, FLAIR, and T2 TSE sequences. Lesions were counted and classified according to 5 anatomic regions: infratentorial, periventricular, deep white matter, juxtacortical, and mixed white matter-gray matter. The sensitivity at DIR was compared with the corresponding sensitivity at FLAIR and T2 TSE sequence. The contrast between lesions and normal-appearing gray matter, normal-appearing white matter, and CSF was determined for all sequences. RESULTS: Because of higher lesion-white matter contrast, the DIR showed a higher number of lesions compared with the FLAIR (7% gain, P = 0.04) and the T2 TSE (15% gain, P = 0.01). The higher sensitivity was also significant for the infratentorial region compared with the FLAIR (56% gain, P = 0.02) and the T2 TSE (44% gain, P = 0.02). Compared with the FLAIR, no significant changes of the lesion load measurements were observed in the supratentorial brain: slightly higher numbers of periventricular and mixed gray matter-white matter lesions on the DIR were counterbalanced by a slightly reduced sensitivity regarding juxtacortical lesions. CONCLUSION: DIR brain imaging at 3T provides the highest sensitivity in the detection of MS lesions especially in the infratentorial region.

Adult↗

PubMed2006

Initial experience with lung-MRI at 3.0T: Comparison with CT and clinical data in the evaluation of interstitial lung disease activity.

OBJECTIVES: We evaluated the feasibility of highfield lung-MRI at 3.0T. A comparison with Computed Tomography (CT) and clinical data regarding the assessment of inflammatory activity in patients with diffuse lung disease was performed. MATERIAL AND METHODS: Prospective evaluation of 21 patients (15 males, 6 females, 43-80 y) with diffuse lung diseases who underwent clinical work-up inclusive laboratory tests, lung-function tests and transbronchial biopsy. After routine helical CT (additional 12 HRCT) a lung-MRI (3.0 Intera, Philips Medical Systems, Best, The Netherlands) using a T2-weighted, cardiac and respiratory triggered Fast-Spinecho-Sequence (TE/TR=80/1500-2500 ms, 22 transverse slices, 7/2mm slice-thickness/-gap) was performed. A pneumologist classified the cases into two groups: A=temporary acute interstitial disease or chronic interstitial lung disease with acute episode or superimposed infection/B=burned out interstitial lung disease without activity. Two blinded CT-radiologists graded the cases in active/inactive disease on the basis of nine morphological criteria each. A third radiologist rated the MRI-cases as active/inactive, depending on the signal-intensities of lung tissues. RESULTS: The pneumologist classified 14 patients into group A and 7 patients into group B. Using CT, 6 cases were classified as active, 15 cases as inactive disease. With MRI 12 cases were classified as active and 9 cases as inactive. In the complete group of 21 patients MRI decisions and CT decisions respectively were false positive/false negative/correct in 2/4/15 respectively 0/8/13 cases. Correct diagnoses were obtained in 72% (MRI) respectively 62% (CT). In the subgroup of 12 cases including HRCT, MRI respectively CT were false positive/false negative/correct in 2/1/9 respectively 0/5/7 cases. Correct diagnoses were obtained in 75% (MRI) respectively 58% (CT). CONCLUSION: Highfield MRI of the lung is feasible and performed slightly better compared to CT in the determination of activity in patients with interstitial lung diseases.

Adult↗

PubMed2006

Is the body-coil at 3 Tesla feasible for the MRI evaluation of the painful knee? A comparative study.

The purpose of this study was to compare the in-built body coil of the 3.0-Tesla (T) scanner with a dedicated surface coil of a 1.5 T system regarding knee imaging. We performed an intraindividual prospective clinical trial on 17 patients with knee pain using magnetic resonance imaging (MRI) at 1.5 and 3.0 T systems equipped with identical gradient systems. Proton-density-weighted turbo spin echo sequences with the same spatial resolution and comparable contrast parameters were used. A quantitative measurement of signal to noise ratio (SNR), relative contrast (RC) and contrast to noise ratio (CNR) between muscle and bone marrow was performed, followed by a qualitative assessment of anatomic/pathologic structures and the extent of artefacts. At 3.0 T, 30 lesions (91%) compared to 33 lesions at 1.5 T were detected. The SNR/CNR/RC were moderately reduced at 3.0 T versus 1.5 T (muscle 42 vs 47 and bone 83 vs 112/46 vs 69/0.33 vs 0.43). Motion artefacts from the pulsating popliteal artery were significantly increased at 3.0 T. A visible and measurable signal loss occurred at 3.0 T using the built-in body coil compared with the dedicated 1.5 T knee coil, but nearly all clinically important information could be obtained.

Adult↗

PubMed2006

[MR techniques for noninvasive diagnosis of prostate cancer].

The diagnosis of prostate cancer is suggested on the basis of an elevated PSA level, abnormal digital exam, and abnormal transrectal ultrasound. US-guided biopsy is used to confirm the diagnosis, but up to 30% of prostate cancer may be missed with this approach. Meanwhile MR imaging and proton MR spectroscopy have emerged as the most sensitive additional tools for the noninvasive evaluation of prostate cancer. This article reviews the clinical indications for MRI of the prostate and summarizes new techniques such as high field strength (3 tesla) and dynamic contrast-enhanced MRI.

Biomarkers, Tumor↗

PubMed2006

Does high-field MR imaging have an influence on the classification of patients with clinically isolated syndromes according to current diagnostic mr imaging criteria for multiple sclerosis?

BACKGROUND AND PURPOSE: Current MR imaging criteria for multiple sclerosis (MS) do not specify the magnetic field strength. The aim of this study was to investigate whether different MR imaging field strengths, specifically high-field MR imaging, have an impact on the classification of patients with clinically isolated syndromes suggestive of MS, according to MR imaging and diagnostic criteria. METHODS: In a prospective intraindividual comparative study, we examined 40 patients with clinically isolated syndromes (CIS) consecutively with a 1.5 T and 3T MR imaging system, including axial sections of T2 turbo spin-echo, fluid-attenuated inversion recovery, and T1 spin-echo, before and after injection of gadolinium-diethylene-triaminepentaacetic acid. Constant resolution parameters were used for both field strengths. High-signal-intensity white matter lesions with a size of >3 mm were counted and categorized according to their anatomic location in infratentorial, callosal, juxtacortical, periventricular, and other white matter areas. Assessment of the fulfilled Barkhof MR imaging and McDonald diagnostic criteria was made separately for both field strengths in every patient. RESULTS: Eleven patients fulfilled more MR imaging criteria at 3T. Two of these patients fulfilled the criterion of dissemination in space (DIS) according to the first definition of McDonald criteria, which is based on imaging criteria alone. Another patient had DIS only at 3T, according to the second definition of the McDonald criteria including CSF parameters. CONCLUSION: MR field strength, specifically high-field MR imaging, has a substantial influence on the classification of patients with CIS according to imaging and a mild influence on the classification according diagnostic criteria for MS, leading to consequences for prognostic classification, imaging guidelines, and clinical trials.

Adolescent↗

PubMed2005

3D motion adapted gating (3D MAG): a new navigator technique for accelerated acquisition of free breathing navigator gated 3D coronary MR-angiography.

This study aimed to evaluate the influence of a new navigator technique (3D MAG) on navigator efficiency, total acquisition time, image quality and diagnostic accuracy. Fifty-six patients with suspected coronary artery disease underwent free breathing navigator gated coronary MRA (Intera, Philips Medical Systems, 1.5 T, spatial resolution 0.9x0.9x3 mm3) with and without 3D MAG. Evaluation of both sequences included: 1) navigator scan efficiency, 2) total acquisition time, 3) assessment of image quality and 4) detection of stenoses >50%. Average navigator efficiencies of the LCA and RCA were 43+/-12% and 42+/-12% with and 36+/-16% and 35+/-16% without 3D MAG (P<0.01). Scan time was reduced from 12 min 7 s without to 8 min 55 s with 3D MAG for the LCA and from 12 min 19 s to 9 min 7 s with 3D MAG for the RCA (P<0.01). The average scores of image quality of the coronary MRAs with and without 3D MAG were 3.5+/-0.79 and 3.46+/-0.84 (P>0.05). There was no significant difference in the sensitivity and specificity in the detection of coronary artery stenoses between coronary MRAs with and without 3D MAG (P>0.05). 3D MAG provides accelerated acquisition of navigator gated coronary MRA by about 19% while maintaining image quality and diagnostic accuracy.

Aged↗

PubMed2005

[3D motion adapted gating: a new navigator technique to shorten the acquisition time for coronary MRA].

PURPOSE: A major problem of free breathing coronary MR angiography (MRA) with respiratory navigator gating is low navigator efficiency and prolonged scan time due to irregular breathing patterns. 3D motion adapted gating (MAG) is a new adaptive navigator technique, which adapts in real time to changes of the end-expiratory position of diaphragm. This study evaluates the influence of 3D MAG on coronary MRA. METHODS AND MATERIALS: In 3D MAG, two additional gating windows are grouped around the conventional window. Additionally, each gating window is divided into three bands assigned to different portions of the k-space. The scan is terminated when three consecutive bands are filled and one complete image data set is collected. Free breathing navigator-gated coronary MRA was performed on 48 patients with suspected coronary artery disease. In random order, each patient underwent an ECG-gated, a 3D segmented k-space gradient echo sequence using 3D MAG and a conventional navigator technique. The coronary MRA was evaluated and compared using the following parameters: 1. navigator efficiency and scan time; 2. visualized coronary artery length; 3. qualitative assessment of image quality; and 4. detection of stenoses > 50 % in comparison with catheter angiography. RESULTS: Coronary MRA with 3D MAG had a significant increase in the average navigator efficiency (46 % +/- 12 % vs. 38 % +/- 12 %, p < 0.05), resulting in a significantly shorter scan time (mean: 18 % +/- 4 %, p < 0.05) for coronary MRA with 3D MAG compared to conventional navigator technique. Scans with and without 3D MAG had no significant differences in the continuously visualized vessel lengths, in the assessed image quality and in the sensitivity and specificity (83 % and 89 % vs. 83 % and 88 %, p > 0.05) of detecting coronary artery stenoses > 50 %. CONCLUSION: The 3D MAG technique improves the navigator efficiency and significantly (p < 0.05) shortens the scan time of navigator gated coronary MRA while maintaining image quality and diagnostic accuracy in the detection of coronary artery stenoses.

Adult↗

PubMed2004

3.0-T high-field magnetic resonance imaging of the female pelvis: preliminary experiences.

The purpose of this study was to evaluate if 3.0 T allows for clinically useful pelvic magnetic resonance imaging, i.e. if familiar image quality and tissue contrast can be achieved at 3.0 T as compared with at 1.5 T. Adapting a 1.5-T protocol to the 3.0-T environment is subject to a variety of factors. In order to reduce the number of potential variables, we chose two cornerstones: the 3.0-T sequence should have similar spatial resolution and acquisition time; furthermore, the contrast parameters repetition time (TR) and echo time (TE) were kept identical. Based on this modified 3.0-T T2-weighted turbo spin-echo sequence (TR/TE 2,705/80 ms; 0.7x1.04x4 mm measured voxel size; field of view 360 mm; 4.03-min scan time) we performed an intraindividual study on 19 patients with the 1.5-T sequence as the standard of reference. Two radiologists analyzed the examinations in consensus with regard to tissue contrast (visualization of zonal anatomy of the uterus and/or delineation of pathologic findings) rated on a three-point scale (3 is 3.0 T better; 2 is 3.0 T equal; 1 is 3.0 T worse than 1.5 T). In addition, the signal difference between muscle and bone marrow was measured as a marker for tissue contrast. The analysis of the image quality comprised the level of the artifacts (rated on a five-point scale: 1 is no artifacts; 5 is nondiagnostic study), the visual signal-to-noise ratio (rated on a three-point scale) and detail delineation. Only minor artifacts were observed at both 1.5 and 3.0 T; the difference was not statistically significant. The visual signal-to-noise ratio and the delineation of image details were rated equal for 1.5 and 3.0 T. With regard to image contrast, both qualitative analysis as well as quantitative analysis revealed comparable image contrast for the 1.5- and 3.0-T protocols. Pathological findings were seen equally well with both field strengths. Clinically diagnostic pelvic studies of high image quality can be obtained using a 3.0-T scanner with our modified examination protocol. To fully exploit the capability of the high-field technique, and to point out potential advantages, further intraindividual studies are needed, with the adjustment of other imaging parameters to the high-field environment.

Adult↗

PubMed2004

Lung MRI at 3.0 T: a comparison of helical CT and high-field MRI in the detection of diffuse lung disease.

The purpose of this study was to evaluate the feasibility of high-field magnetic resonance imaging (MRI) of the lung using a T2-weighted fast-spin echo (TSE) sequence. Comparison was made with helical computed tomography CT findings in patients with diffuse pulmonary diseases. Prospective segment-wise analysis of high-field MR imaging findings in 15 patients with diffuse pulmonary diseases was made using helical CT and HRCT as the standard of reference. The MR studies were performed on a 3.0-T whole body system (Intera 3T, Philips Medical Systems) using a T2w TSE sequence with respiratory and cardiac gating (TE 80 ms TR 1,500-2,500 ms; turbo factor 17; 22 slices with 7/2-mm slice thickness and gap; 256x192 matrix). MR artifacts were graded on a three-point scale (low, moderate, high). Lung MR studies were prospectively analyzed segment-by-segment and diagnosed as healthy or pathological; results were compared with helical CT findings. In all 15 patients, MR imaging of the lung was successful. All 15 MR studies were compromised by artifacts; however, the severity of these artifacts was classified as low or moderate in 8/15, respectively, 7/15 cases. A total of 143/285 lung segments showed diffuse lung disease in helical CT. With MRI, 133 of these 143 segments (93%) were judged to be diseased. The ten segments that received false negative MR diagnoses displayed non-acute pulmonary lesions with inherently low proton density (scars, granulomas). MRI at 3.0 T can detect diffuse pulmonary disease with a high sensitivity. Based on this experience, further pulmonary studies with high-field systems appear justified and promising.

Adult↗

PubMed2004

Sensitivity encoding (SENSE) for high spatial resolution time-of-flight MR angiography of the intracranial arteries at 3.0 T.

PURPOSE: 1) To evaluate feasibility of sensitivity encoding (SENSE) for high spatial resolution intracranial 3D time-of-flight (TOF) MR angiography at 3.0 T using a 1024 imaging matrix and 2) to compare image quality and diagnostic yield with 3.0 T TOF MRA without SENSE. METHODS: In a prospective study TOF MR angiography of the circle of Willis was performed with SENSE in 24 patients on a clinical whole body 3.0 T MR system (Intera, Philips Medical Systems, NL). In the SENSE protocol (S-MRA), a SENSE factor of 2.5 was used to shorten acquisition time and to increase the anatomic coverage (5:12 min.; 150 slices). A matrix of 832 x 572 was acquired and reconstructed to 1024 yielding a non-zerofilled voxel size of 0.30 x 0.44 x 1.00 mm(3) (0.13 mm(3)). Two readers were asked to review the images regarding the presence of vascular disease, and to rate, in consensus, the quality of the angiograms on a 5-point scale (5 = excellent through 1 = non-diagnostic). Results were compared with the results in 15 subjects who underwent intracranial TOF MRA at 3.0 T without SENSE (NS-MRA: acquisition time, 7:57 min.; 100 slices). Digital subtraction angiography (DSA) served as standard of reference in the 4/24 patients in whom vascular disease was identified. RESULTS: S-MRA at 3.0 T was judged to provide image quality that was adequate for diagnosis or better in 24/24. Median score of image quality of S-MRA and NS-MRA were 5 and 5, respectively. In the 4 patients with DSA correlation, a total of 8 pathologic findings (7 steno-occlusive diseases, 1 aneurysm) were correctly identified on S-MRA. CONCLUSION: The use of SENSE for intracranial TOF MRA at very high imaging matrix is feasible at 3.0 T. Compared to the imaging technique without SENSE, it allows TOF MRA with substantially reduced acquisition time, and with substantially increased anatomic coverage while maintaining image quality of NS-MRA.

Adolescent↗

PubMed2002

Three-dimensional magnetic resonance cholangiopancreatography with respiratory triggering in the diagnosis of primary sclerosing cholangitis: comparison with endoscopic retrograde cholangiography.

BACKGROUND AND STUDY AIMS: The purpose of this study was to evaluate the accuracy of respiratory-triggered three-dimensional magnetic resonance cholangiopancreatography (3D-MRCP) for the detection of primary sclerosing cholangitis (PSC) and to compare the specific findings of magnetic resonance cholangiography and endoscopic retrograde cholangiography in patients with PSC. PATIENTS AND METHODS: The MRCP findings were evaluated in 150 patients with clinical symptoms (progressive fatigue, pruritus followed by icterus) and/or elevated values for alkaline phosphatase and serum aspartate transaminase, and occasionally an elevated serum concentration of bilirubin as a sign of cholestasis, who were consecutively referred for magnetic resonance imaging. Two observers independently classified bile duct abnormalities and established the MRCP diagnosis in a consensus reading. The results of MRCP were compared with the definitive diagnosis, which was based on the clinical history and laboratory and histological data, as well as on endoscopic retrograde cholangio-pancreatography (ERCP) findings. In a second step, the observers compared the delineation of the biliary system and morphological findings using MRCP and ERCP in patients with confirmed PSC. RESULTS: Diagnostic examinations were obtained in 146 of the 150 MRCPs (97 %). The diagnosis of PSC was confirmed by clinical data and ERCP in 34 of these 150 patients (23 %). The sensitivity and specificity of MRCP for diagnosing PSC were 88 % (29 of 33) and 99 % (108 of 109), respectively. MRCP and ERCP yielded similar scores for the delineation of the biliary system (P = 0.2) in patients with PSC. However, different bile duct abnormalities leading to the diagnosis of PSC were depicted by MRCP and ERCP; more bile duct stenoses and pruning were seen with ERCP and more skip dilatation with MRCP (P < 10(-4)). CONCLUSION: In patients with PSC, MRCP is a highly sensitive method and its diagnostic accuracy is comparable to that of ERCP.

Adolescent↗

PubMed2001

Noninvasive quantification of left-to-right shunt in pediatric patients: phase-contrast cine magnetic resonance imaging compared with invasive oximetry.

BACKGROUND: Blood flow can be quantified noninvasively by phase-contrast cine MRI (PC-MRI) in adults. Little is known about the feasibility of the method in children with congenital heart disease. METHODS AND RESULTS: In 50 children (mean age 6.2 years, range 1.1 to 17.7 years) with an atrial- or ventricular-level shunt, blood flow rate in the great vessels was determined by PC-MRI, and the ratio of pulmonary to aortic flow (Qp/Qs) was compared with Qp/Qs by oximetry. We found a difference of 2% and a range of -20% to +26% (limits of agreement, mean +/-2 SD). In another 7 children with congenital heart disease but no cardiac shunting (mean age 7.9 years, range 1.3 to 13.5 years), Qp/Qs by PC-MRI was 1.02 (SD +/-0.06). No difference between systemic venous and aortic flow volumes was found (range -17% to +20%, n=37). Blood flow through a secundum atrial septal defect as assessed by PC-MRI (n=24) overestimated the shunt compared with the difference between pulmonary and aortic flows. The mean difference between 3 repeated PC-MRI measurements in each location was 5.3% (SD +/-4.0%, n=522), demonstrating good precision. The interobserver variability was low. The accuracy of PC-MRI was confirmed by in vitro experiments. CONCLUSIONS: Determination of Qp/Qs by PC-MRI in children is quick, safe, and reliable compared with oximetry. Systemic venous flow can be quantified by PC-MRI, whereas through-plane shunt measurement within an atrial septal defect is inaccurate.

Child↗

PubMed2001

A new method of MR total spine imaging for showing the brace effect in scoliosis.

Bracing is a method of early, nonsurgical treatment for scoliosis, but a hypokyphotic effect on the thoracic spine is reported. We developed a magnetic resonance tomography (MR) procedure presenting an image of the whole spine in the coronal and sagittal planes (MR total spine imaging), and studied the brace effect, using this technique. We examined 26 female patients with idiopathic scoliosis treated with a Cheneau brace (mean age, 13.2 years; mean duration of brace treatment at the time of investigation, 1.5 years). The MR examinations were performed with the patient in the supine position with and without the brace in direct sequence. As measured on the coronal MR images, the thoracic curve was corrected, on average, from 29 degrees to 22 degrees (mean correction, 24%). There was a slight reduction in the sagittal Cobb angle measured between T4 and T12 (mean sagittal Cobb angle without brace, 14 degrees; with brace, 12 degrees ), which was still a significant change. MR total spine imaging could be a useful tool for studying the brace effect in scoliosis in two planes. Using this technique, we found reduced sagittal Cobb angles for the thoracic kyphosis with brace. Because there is no radiation exposure, the MR procedure has a potential use in the monitoring of brace treatment.

Adolescent↗

PubMed2000

Ultra-fast three-dimensional MR perfusion imaging of the entire brain in acute stroke assessment.

We sought to evaluate a three-dimensional (3D) whole-brain perfusion technique based on echo-shifting (PRESTO) for its performance in evaluation of acute stroke. Twenty-six patients were scanned within 6 hours after onset of hemispheric symptoms, and the results were compared with results of diffusion-weighted imaging (DWI) and digital subtraction angiography (DSA). The signal-to-noise ratio of the images was 61 +/- 3 pre-contrast and 47 +/- 3 at the bolus peak. Brain coverage on perfusion parameter maps was 95% +/- 2% compared with that displayed on T2-weighted images, with only minor artifacts related to susceptibility at the skull base. Measured regional cerebral blood volume (rCBV) reduction closely correlated to lesion size on initial DWI and to final clinical outcome (P = 0.006), consistent with results previously reported for 2D perfusion methods. Mismatches between DWI and perfusion imaging characterized the total extent of tissue at risk, and the contrast timing correlated with the amount of collateral circulation as shown on DSA. In conclusion, 3D imaging using the PRESTO technique permits high-quality perfusion imaging of the entire brain.

Adolescent↗

PubMed2000

[Pulse triggering for improved diffusion-weighted MR imaging of the abdomen].

PURPOSE: The aim of this work was to reduce the influence of motion on diffusion-weighted MR images of the abdomen by pulse triggering of single-shot sequences. METHODS: Five healthy volunteers were examined both without and with finger pulse-triggering of a diffusion-weighted single-shot echo planar MR imaging sequence at 1.5 T. Series of diffusion-weighted images were acquired at different phases of the cardiac cycle by varying the time delay between finger pulse and sequence acquisition. The measurements were repeated three times. The diffusion weighted images were analysed by measuring the signal intensities and by determining the ADC values within the spleen, kidney and liver. RESULTS: The magnitude of motion artifacts on diffusion weighted images shows a strong dependence on the trigger delay. The optimum trigger delay is found to be between 500 and 600 ms. For these values the abdominal organs appear homogeneous on all diffusion weighted images and the strongest signal intensities are detected. At optimum triggering the accuracy of the apparent diffusion coefficients is up to 10 times better than without triggering. Moreover, the standard deviation of the repeated measurements is smaller than 12% for all volunteers and for all organs. Without triggering the standard deviation is larger by a factor of 4 on average. CONCLUSION: Pulse triggering of single-shot sequences leads to significant reduction of motion related artifacts on diffusion weighted images of the abdomen and provides more accurate and reproducible ADC values.

Abdomen↗

PubMed2000

Middle cerebral artery (MCA) susceptibility sign at susceptibility-based perfusion MR imaging: clinical importance and comparison with hyperdense MCA sign at CT.

PURPOSE: To describe the radiologic findings of susceptibility changes in acute middle cerebral artery (MCA) thromboembolism detected with three-dimensional (3D) susceptibility-based perfusion magnetic resonance (MR) imaging and to compare the detectability and clinical value of this sign with those of the hyperdense MCA sign at computed tomography (CT). MATERIALS AND METHODS: Twenty-three patients (mean age, 55 years) underwent CT and MR imaging within the first 6 hours after the onset of acute MCA stroke. The hyperdense MCA sign at CT and the presence of susceptibility changes in acute thromboembolism as depicted on T2*-weighted 3D perfusion MR images were assessed. The presence of each sign was correlated with clinical presentation. RESULTS: The sensitivity of the hyperdense MCA sign at CT was 54% (negative predictive value, 71%) compared with 82% (negative predictive value, 86%) for the susceptibility changes at MR imaging. There were no false-positive CT or MR readings. The presence of the MCA susceptibility sign correlated positively with the initial clinical presentation (chi(2) = 7.987, P =.009, Spearman rho = 0.589). However, neither of the signs was a predictor for clinical outcome in cases of spontaneous MCA stroke. CONCLUSION: In addition to the information traditionally provided with reconstructed perfusion parameter maps, 3D susceptibility-based perfusion MR images allow the identification of acute MCA thromboembolism with a sensitivity higher than that of CT.

Acute Disease↗

PubMed2000

MR imaging and cardiac pacemakers: in-vitro evaluation and in-vivo studies in 51 patients at 0.5 T.

PURPOSE: To evaluate the safety and feasibility of magnetic resonance (MR) imaging at 0.5 T in patients with implanted cardiac pacemakers. MATERIALS AND METHODS: Twenty-one models of pacemakers and 44 pacemaker electrodes were exposed to in vitro MR imaging with continuous registration of pacemaker output and temperature at the lead tip. Prior to MR imaging examination, pacemakers were programmed to an asynchronous mode (A00, V00, or D00). Pacemakers were examined before and after MR imaging. Forty-four patients with implanted pacemakers underwent 51 MR imaging examinations under cardiologic surveillance, continuous electrocardiography, pulse oximetry, and capnographic monitoring. RESULTS: MR imaging was safely performed in all patients. None of the pacemakers displayed a pacing dysfunction at MR imaging. No changes occurred in the programmed parameters in any device tested in vivo or in vitro. Maximum increases in the temperature at the lead tips were 8.90 degrees C at a specific absorption rate (SAR) of 0.6 W/kg and 23.50 degrees C under a worst-case radio-frequency (RF) heating condition with an SAR of 1.3 W/kg. CONCLUSION: MR imaging at 0.5 T can be safely performed in patients with implanted pacemakers in carefully selected clinical circumstances when appropriate strategies (programming to an asynchronous mode, adequate monitoring techniques, limited RF exposure) are used.

Capnography↗

PubMed2000

Detection of thrombosis in the portal venous system: comparison of contrast-enhanced MR angiography with intraarterial digital subtraction angiography.

PURPOSE: To determine whether intraarterial digital subtraction angiography (DSA) can be replaced by contrast material-enhanced magnetic resonance (MR) angiography in the assessment of patency or thrombosis of the portal venous system in patients with portal hypertension. MATERIALS AND METHODS: Thirty-six patients with portal hypertension underwent contrast-enhanced MR angiography and intraarterial DSA for assessment of the portal venous system. The images were evaluated for vessel patency or thrombosis of the portal, splenic, or superior mesenteric vein. RESULTS: Of the 101 vessels evaluated, 42 were thrombosed. Overall sensitivity, specificity, and accuracy for the detection of thrombosis were 100%, 98%, and 99%, respectively, for MR angiography and 91%, 100%, and 96%, respectively, for DSA; differences between the imaging methods were not statistically significant. Only in four patients with six vessels (6%) were there discordant findings between MR angiography and DSA. CONCLUSION: Noninvasive contrast-enhanced MR angiography has the potential to replace intraarterial DSA as the standard method to assess the whole portal venous system.

Adolescent↗