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Biomedical subjects

H Bosmans

Publications and source records attributed to H Bosmans.

At least 19 recordsLinked to original sources
PubMed2001

Organ radiation dose assessment for conventional spiral tomography: a human cadaver study.

The head of a human cadaver was positioned in a Cranex TOME multifunctional unit (Orion Corporation Soredex, Helsinki, Finland) to measure the organ radiation doses after tomographic examinations of the upper and lower edentulous jaw bone. Five consecutive examinations were carried out in the upper and lower anterior jaw regions to cover the entire frontal area, 2 in the upper and lower left premolar regions, and 3 and 4 in the upper and lower left molar regions, respectively. Each examination consisted of 4 slices with a 2 mm slice thickness. Thermoluminescent dosimeter chips were placed in the thyroid gland and bilaterally in the parotid and submandibular glands. Dosimetric measurements were repeated for the different tomographic examinations mentioned above. For spiral tomography in the maxilla, organ doses for both parotid glands were most elevated, while those for the thyroid glands were the lowest. Average doses per examination reached levels of 0.27 mGy for the right (OS) parotid gland with frontal tomography, and 3.89 mGy and 1.67 mGy for the parotid gland at tube-side (TS) for premolar and molar tomography. For the thyroid gland, a minimal dose of < or = 0.004 mGy was noticed for all examinations. For spiral tomography of the frontal area in the mandible, the OS parotid gland received the highest dose (0.77 mGy), while for an analysis of the premolar and molar areas, doses were more elevated for the TS parotid gland (1.22 mGy and 1.72 mGy, respectively). For the TS submandibular gland, organ doses were also raised, with values of 0.39 mGy for frontal, 1.31 mGy for premolar and 1.61 mGy for molar tomography. This study thus indicates that for conventional spiral tomographic examinations in the maxilla and the mandible, radiation doses for the TS submandibular and parotid glands were significantly more elevated than those to the thyroid gland. These values remain however below the organ doses previously reported for spiral CT involving both a full upper or lower jaw.

Aged↗
PubMed2000

Magnetic resonance imaging in the assessment of urologic disease: an all-in-one approach.

The aim of this study was to evaluate an "all-in-one" MR procedure to examine the kidneys, the renal vascular supply and renal perfusion, and the urinary tract. In 64 patients (58 with urologic disease and 6 healthy volunteers), MR was performed including: (a) T1- and T2-weighted imaging; (b) 3D contrast-enhanced MR angiography (MRA), including the renal arteries, renal veins, as well as renal perfusion; and (c) 3D contrast-enhanced MR urography (MRU) in the coronal and sagittal plane. For the latter, low- and high-resolution images were compared. Prior to gadolinium injection, 0.1 mg/kg body weight of furosemide was administered intravenously. The results were compared with correlative imaging modalities (ultrasonography, intravenous urography, CT), ureterorenoscopy and/or surgical-pathologic findings. Visualization of the renal parenchyma, the vascular supply, and the collecting system was adequate in all cases, both in nondilated and in dilated systems and irrespective of the renal function. One infiltrating urothelial cancer was missed; there was one false-positive urothelial malignancy. Different MR techniques can be combined to establish an all-in-one imaging modality in the assessment of diseases which affect the kidneys and urinary tracts. Continuous refinement of the applied MR techniques and further improvements in spatial resolution is needed to expand the actual imaging possibilities and to create new tracts and challenges in the MR evaluation of urologic disease.

Adult↗
PubMed2000

Remote myocardial dysfunction after acute anterior myocardial infarction: impact of left ventricular shape on regional function: a magnetic resonance myocardial tagging study.

OBJECTIVES: We sought to evaluate regional morphology and function in patients in their first week after having a reperfused anterior myocardial infarction (MI) using magnetic resonance (MR) myocardial tagging. BACKGROUND: The mechanism of myocardial dysfunction in the remote, noninfarct-related regions is an unresolved issue to date. METHODS: Sixteen patients with a first reperfused transmural anterior MI were studied with MR tagging at 5 +/- 2 days after the event, and the results were compared with those of an age-matched control group regions. The left ventricle (LV) was divided into infarct, adjacent and remote regions. Magnetic resonance tagging provided information on the regional ventricular morphology and function. RESULTS: Morphologically, an increase of the circumferential radius of curvature was found in the remote myocardium, whereas the longitudinal radius of curvature was increased in all regions of the LV. A significant increase in apical sphericity was also found. A significant reduction in strain and function was found not only in the infarct region, but also in the adjacent and remote myocardium. The loss in regional ejection fraction in the remote myocardium (61.4 +/- 11.7% in patients vs. 68.7 +/- 10.0% in control subjects, p < 0.0001) was related to a significant reduction of the longitudinal and circumferential strain, whereas systolic wall thickening was preserved. CONCLUSIONS: Remote myocardial dysfunction contributes significantly to the loss in global ventricular function. This could be secondary to morphologic changes in the infarct region, leading to an increased systolic longitudinal wall stress without loss of intrinsic contractility in the remote regions.

Adult↗
PubMed2000

Breath-hold contrast-enhanced three-dimensional MR angiography of the abdomen: time-resolved imaging versus single-phase imaging.

PURPOSE: To evaluate a technique for time-resolved breath-hold contrast material-enhanced three-dimensional magnetic resonance (MR) angiography of the abdomen. MATERIALS AND METHODS: In a prospective study, 43 patients underwent time-resolved MR angiography (acquisition time per data set, 7 seconds). The patients also underwent single-phase high-spatial-resolution MR angiography (acquisition time, 27 seconds) (n = 6), conventional angiography (n = 7), or both (n = 30). No bolus timing study was performed for time-resolved MR angiography. Image quality (presence of artifacts, ability to prevent venous overlap on arterial phase images, contrast enhancement) and demonstration of anatomic variants (renal arterial and venous variants, vena caval anomaly, visceral arterial variants) and vascular diseases were assessed. RESULTS: Time-resolved MR angiographic images were characterized by fewer and less severe artifacts, less overlap of enhancing veins, and better contrast enhancement than were single-phase MR angiographic images (P < .05). The mean sensitivity and specificity were 90% (nine of 10) and 100% (1 73 of 1 73), respectively, for detection of arterial anatomic variants and 93% (28 of 30) and 100% (324 of 325), respectively, for detection of disease. The technique also proved to be reliable for demonstration of venous disease. CONCLUSION: In comparison with current non-time-resolved MR angiographic techniques, time-resolved MR angiography is more robust and easier to perform and allows simultaneous evaluation of arterial and venous disease.

Abdomen↗
PubMed2000

Review of MR mammography techniques.

Many of the new techniques of MRI have promising characteristics for the further improvement of sensitivity and specificity but there remains a large place for clinical trials to evaluate the practical value of the different new approaches. The authors review the general MRI rules that determine image quality and comment on the use-fullness of innovations in MR mammography.

Breast Diseases↗
PubMed1999

The contribution of magnetic resonance imaging to the three-dimensional treatment planning of localized prostate cancer.

PURPOSE: To investigate whether the use of transaxial and coronal MR imaging improves the ability to localize the apex of the prostate and the anterior part of the rectum compared to the use of transaxial CT alone, and whether the incorporation of MR could improve the coverage of the prostate by the radiotherapy field and change the volume of rectum irradiated. METHODS AND MATERIALS: Ten consecutive patients with localized prostate carcinoma underwent a CT and an axial and coronal MR scan in treatment position. The CT and MR images were mathematically aligned, and three observers were asked to contour independently the prostate and the rectum on CT and on MR. The interobserver variability of the prostatic apex location and of the delineation of the anterior rectal wall were assessed for each image modality. A dosimetry study was performed to evaluate the dose to the rectum when MR was used in addition to CT to localize the pelvic organs. RESULTS: The interobserver variation of the prostatic apex location was largest on CT ranging from 0.54 to 1.07 cm, and smallest on coronal MR ranging from 0.17 to 0.25 cm. The interobserver variation of the delineation of the anterior rectum on MR was small and constant along the whole length of the prostate (0.09+/-0.02 cm), while for CT it was comparable to that for the MR delineation at the base of the prostate, but it increased gradually towards the apex, where the variation reached 0.39 cm. The volume of MR rectum receiving more than 80% of the prescribed dose was on average reduced by 23.8+/-11.2% from the CT to the MR treatment plan. CONCLUSION: It can be concluded that the additional use of axial and coronal MR scans, in designing the treatment plan for localized prostate carcinoma, improves substantially the localization accuracy of the prostatic apex and the anterior aspect of the rectum, resulting in a better coverage of the prostate and a potential to reduce the volume of the rectum irradiated to a high dose.

Dose-Response Relationship, Radiation↗
PubMed1999

Noninvasive measurements of infarct size after thrombolysis with a necrosis-avid MRI contrast agent.

BACKGROUND: Gadophrin-2 is a new MRI contrast agent with high affinity for necrotic myocardium. The aim of the study was to evaluate whether noninvasive measurements of infarct size after thrombolysis are possible with gadophrin-2-enhanced MRI. METHODS AND RESULTS: Coronary artery thrombosis was induced in 3 groups of dogs by the copper-coil technique. Thrombolytic therapy together with aspirin and heparin was initiated after 90 minutes of occlusion. One day (group A), 2 days (group B), or 6 days (group C) after infarction, gadophrin-2 was injected intravenously (50 micromol. kg-1). In vivo T1-weighted segmented turbo-FLASH, in vivo T2-weighted segmented half-Fourier turbo spin echo (HASTE), and T1- and T2-weighted spin-echo MRI of the excised heart were performed 24 hours after gadophrin-2 injection. Regions of strong enhancement were observed on T1-weighted images. Planimetry of short-axis MR images and of corresponding triphenyltetrazolium chloride (TTC)-stained left ventricular (LV) slices showed a close correlation between the enhanced areas and TTC-negative areas for both in vivo (r2=0.98, P<0.0001; mean difference, 0.9+/-2.0% [SD] of the LV volume [LVV]) and postmortem (r2=0.99, P<0.0001; mean difference, 0.9+/-1.4% of LVV) measurements. T2-weighted images overestimated the infarct size by 8.1+/-5.4% of LVV. The mean infarct size was 10.8+/-11.6% of LVV (group A), 22.4+/-11.7% (group B), and 5.1+/-9.3% (group C). CONCLUSIONS: In this animal model, in vivo gadophrin-2-enhanced MRI could precisely determine infarct size after thrombolytic therapy. This technique may be very useful for the noninvasive evaluation of infarct size after reperfusion for AMI.

Animals↗
PubMed1999

Comparison of iron oxide particles (AMI 227) with a gadolinium complex (Gd-DOTA) in dynamic susceptibility contrast MR imagings (FLASH and EPI) for both phantom and rat brain at 1.5 Tesla.

The goal of the study was to compare, in phantom and normally perfused rat brain tissue, a superparamagnetic iron oxide particle-based contrast agent (AMI 227) with a low-molecular-weight gadolinium chelate, gadolinium tetraazacyclododecanetetraacetic acid (Gd-DOTA), in two susceptibility contrast magnetic resonance imaging (MRI) modes [fast low-angle shot sequence (FLASH) and echoplanar imaging (EPI)]. A phantom consisting of dilution series of both contrast agents was manufactured. Dilutions were obtained with isotonic serum from the available agent solutions (0.5 mmol Gd/mL Gd-DOTA; 350 mumol Fe/mL AMI 227). Eighteen rats were studied. Contrast agent (0.1 mL) was bolus injected in each rat, and dynamic MRI was performed (first pass of the contrast agent) in rat brain. The doses of AMI 227 injected were extrapolated from the phantom experiment: 0.2 mmol/kg body weight of Gd-DOTA and 7, 14, and 28 mumol Fe/kg body weight of AMI 227 were injected. For both sequences, signal-to-noise ratios (S/N) were measured on each tube of the phantom and on rat brain from each image of the dynamic imaging. S/N was plotted versus contrast dilution (phantom) and versus time (rats). In the FLASH sequence, a well-shaped curve (S/N decrease, S/N peak decrease, S/N increase) of the first pass of the contrast agent was demonstrated for Gd-DOTA and for AMI 227 (7 mumol Fe/kg body weight). In the EPI sequence, a well-shaped curve was demonstrated for Gd-DOTA, and a plateau effect was noted for both concentrations of AMI 227. With the FLASH technique, dynamic susceptibility contrast imaging of rat brain can be performed with very low concentrations of AMI 227 compared with the Gd-DOTA concentration (0.2 mmol Gd/kg body weight) used in clinical practice. This could be of interest in perfusion imaging, because it may allow for first-pass susceptibility imaging after administration of a small volume in a narrow bolus.

Animals↗
PubMed1999

Time-resolved MR angiography of the upper abdomen: initial clinical experience.

In this study, thirty-eight patients with a variety of upper abdominal diseases were examined with three-dimensional time-resolved MR angiography (7 sec/data set). Visualisation of arterial and venous anatomy was excellent in the majority of patients. Moreover, subtraction images could be calculated and organ perfusion could be assessed. It is concluded that this technique opens new perspectives for a comprehensive evaluation of vascular and parenchymal disease.

Abdomen↗
PubMed1999

Screening applications for MRI in the detection of upper abdominal disease: comparative study of non-contrast-enhanced single-shot MRI and contrast-enhanced helical CT.

PURPOSE: To compare the value of 'push-button' single-shot non-contrast-enhanced MRI and contrast-enhanced helical CT for detection of upper abdominal disease. METHODS: In 120 patients, images obtained with non contrast-enhanced single-shot MRI (T2: double echo HASTE, and T1: turbo FLASH) and contrast-enhanced helical CT were compared. Lesions or abnormalities were divided in 8 anatomical categories (1: liver; 2: pancreatobiliary; 3: kidney/adrenal gland; 4: retroperitoneum; 5: vascular; 6: spleen; 7: gastrointestinal tract and peritoneum; 8: base of thorax) and classified as follows: 2: seen at MRI only; 1: better seen at MRI; 0: no difference; -1: better seen at CT; -2: seen at CT only. Also recorded were the 'door-to-door' examination times. RESULTS: Of a total of 629 abnormalities, 594 were detected at MRI (94 %) and 536 at CT (85 %). CT offered better results in two categories only: retroperitoneum (mean score: -0.68) and vascular (mean score -0.87). Mean examination times were 19 min for CT and 14.8 min for MRI. CONCLUSION: Unenhanced single-shot MRI is a valuable first step of a comprehensive upper abdominal MR exam and may even be the final step in many patients.

Abdomen↗
PubMed1999

MRI of non-ischemic vascular disease: aneurysms and vascular malformations.

Due to flow-void phenomena, MRI is of great value in the demonstration of cerebral aneurysms and vascular malformations as well as of related parenchymal changes and hemorrhagic complications. Magnetic resonance angiography can produce vascular images which are of importance in the diagnosis and follow-up of the lesions.

Brain↗
PubMed1999

Three-dimensional MR angiography in the evaluation of thoracic outlet syndrome.

OBJECTIVE: The objective is to present our initial experience with the combination of three-dimensional time-resolved contrast-enhanced MR angiography and T1-weighted spin-echo imaging for investigation of vascular compression related to thoracic outlet syndrome. CONCLUSION: In patients with clinical signs of thoracic outlet syndrome suggesting vascular elongation or compression, this technique proves to be robust, and its results are comparable to those of conventional catheter angiography. Our results allow precise identification of the anatomic structure(s) responsible for the clinical symptoms and show the effect of arm hyperabduction on the patency of the subclavian vessels.

Adult↗
PubMed1999

Confrontation of mammography systems in flanders with the European Guidelines for Quality Assurance in mammography screening. Analysis of initial results.

From May 1997 to April 98, 30 radiological centers made an agreement with the Leuvens Universitair Centrum voor Kankerpreventie (LUCK) for the work out of physical and technical quality control in mammography screening. A protocol was used based on the European Guidelines for Quality Assurance. The reports of all 30 acceptance tests were retrospectively reviewed. The following parts showed to be most critical: alignment of radiation field and film in the bucky, tube voltage precision, automatic exposure controller, average optical density of a standard exposure, dark room and its safe lights. The mean film gradient was in the majority of the centers higher than what is prescribed in the European document. This is acceptable and even desirable whenever daily quality control shows that the development system is sufficiently stable. Although it is difficult to compare the scores for the specific tests with results in other countries, there is evidence that the tendencies are very similar.

Absorptiometry, Photon↗
PubMed1998

Fast FLAIR MRI in childhood white-matter abnormalities.

We compared a fast fluid-attenuated inversion recovery (FLAIR) pulse sequence with a dual-echo short tau fast inversion-recovery (DESTTIR) sequence in 20 children with white matter abnormalities. Although the overall image quality of DESTTIR images was better, the lesion-to-background contrast was significantly higher with the fast FLAIR pulse sequence and lesion detection was more accurate.

Adolescent↗
PubMed1998

T2-weighted MR imaging of the uterus: comparison of optimized fast spin-echo and HASTE sequences with conventional fast spin-echo sequences.

OBJECTIVE: Our objective was to compare the value of a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence with optimized fast spin-echo and conventional fast spin-echo techniques in evaluation of the uterus. SUBJECTS AND METHODS: Optimized fast spin-echo imaging was compared with fast spin-echo and HASTE imaging, for both image quality and ability to assess the zonal anatomy of the uterus, in 40 volunteers. In optimized fast spin-echo imaging, the imaging time was reduced using partial-Fourier reconstruction, reducing the echo spacing, and increasing the echo train length. RESULTS: HASTE imaging offered the least motion artifact of all techniques. On optimized fast spin-echo imaging, motion artifacts were moderate to severe in 10% of patients. On fast spin-echo imaging, motion artifacts were moderate to severe in 40% of patients. Optimized fast spin-echo imaging was superior to the other two techniques in terms of anatomic sharpness and overall image quality. CONCLUSION: Although HASTE imaging offers the unique feature of providing images free of motion artifacts, optimized fast spin-echo imaging appears to be the preferred technique for T2-weighted imaging of the uterus.

Adolescent↗
PubMed1997

Preliminary experience with a new double-echo half-Fourier single-shot turbo spin echo acquisition in the characterization of liver lesions.

A new double-echo half-Fourier single-shot turbo spin echo technique has been implemented in which two images are obtained per excitation pulse, one with an echo time (TE) of 60 ms and another with a TE of 438 ms. The acquisition window per image is 380 ms and is determined by the echo spacing of 4.3 ms and the echo train length of 88 for images with resolution of 160 x 256. No breath holding was performed. The aim of the study was to test whether the additional information of the late TE image improves the characterization of liver lesions. Twenty-eight patients with 39 focal liver lesions (9 cysts, 11 hemangiomas, and 19 solid lesions) were imaged with the new technique, and signal intensity (SI) ratios of lesion and liver were obtained. A t-test analysis showed that in the TE 60 ms image, SI ratios of cysts and hemangiomas were not significantly different, whereas in the TE 438 ms images the two types of lesions can be classified. Signal intensity ratios of solid lesions were in both images clearly lower than those of cysts and hemangiomas. The technique, therefore, seems a promising and straightforward new tool for the characterization of liver lesions.

Cysts↗
PubMed1997

Follow-up of aortic dissection: contribution of MR angiography for evaluation of the abdominal aorta and its branches.

Spin-echo MR is an established method to evaluate thoracic aortic dissections, but is not well suited to study the abdominal aorta. In this study we evaluated whether MR angiography could provide a complete examination of the abdominal aorta. In 28 patients (40 MR studies) with suspected (n = 6) or known (n = 34) aortic dissection, MR studies were performed. Thoracic aorta was evaluated with spin-echo and gradient-recalled-echo MR imaging. Axial two-dimensional time-of-flight MR angiography with thin overlapping slices was used to study the abdominal aorta. Intermediate and high signal intensity on MR angiography was interpreted as patent flow, and low signal was interpreted as thrombus. The presence of an intima flap and the re-entry site could be depicted in all MR studies. Thrombus in the false channel was seen in 8 studies. The origin of the abdominal visceral branches and their relation to the false-true channel could be depicted, except in 4 of 80 renal arteries studied. Extension of the dissection into the coeliac trunk was seen in 2 and in the superior mesenteric artery in 10 studies. Dilatation of the suprarenal abdominal aorta was seen in 20 studies, and of the infrarenal aorta in 9 studies. MR angiography provides valuable information about the abdominal aorta and its branches in patients with aortic dissection. This makes MR imaging appealing as the preferred imaging modality for the diagnosis and follow-up of aortic dissection.

Aortic Dissection↗