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Biomedical subjects

M Reiser

Publications and source records attributed to M Reiser.

At least 433 records · Page 24Linked to original sources
PubMed1996

[Dynamic MR mammography: is the course of signal intensification suitable for the differentiation of different forms of mastopathy?].

PURPOSE: The capacity of dynamic contrast-enhanced MR mammography to distinguish between different forms and grades of mastopathy according to Prechtel's classification was evaluated in a retrospective study. PATIENTS AND METHODS: MR mammograms of 51 patients with histologically proven mastopathy were retrospectively evaluated in areas subsequently biopsied. RESULTS: Mean values of regressive and hyperplastic types of mastopathy differed significantly no significant differences were found between proliferating and non-proliferating mastopathies or Prechtel grades I-III mastopathy when MRI data obtained with a FLASH 3 D sequence (TR = 8.4 ms, TE = 3 ms, flip angle = 30 degrees at 1.0 T) were compared one minute, three, 5 and 8 minutes after i.v. bolus administration of contrast media (Gd-DTPA, 0.1 mmol/kg body weight). CONCLUSION: Our data indicate that dynamic contrast-enhanced MR mammography does not allow the differentiation of proliferating and non-proliferating mastopathy according to the Prechtel classification. Dynamic MR mammography assessment of breast cancer risk does not seem to be feasible.

Breast↗
PubMed1996

[Technics for the preoperative marking of nonpalpable breast lesions in MRT].

We describe a method of localizing suspicious breast lesions only visible by MRI that does not require additional hardware and can be carried out on any MRI-scanner suited for MR-mammography. We have performed a total of 48 localizations with different techniques: 28 charcoal/Gd-DTPA, 18 with wires and two skin markings. All localizations have been successful; wire localizations provided the best results, since the position of the wire could be corrected under MR-guidance. Until suitable localization- and biopsy coils become available the methods employed by us provide a satisfactory alternative which allows radiologists who perform diagnostic MR-mammography with techniques to carry out precise pre-operative localisations of breast lesions.

Breast↗
PubMed1996

[Initial experiences with pulsed fluoroscopy on a multifunctional fluoroscopic unit].

PURPOSE: Comparison of radiation doses in pulsed and continuous fluoroscopy to quantify the dose reduction by pulsed fluoroscopy. Further, the applicability of pulsed fluoroscopy in clinical routine has been evaluated. MATERIALS AND METHODS: In a human pelvic phantom, the radiation dose (skin entry dose in cGycm2) was measured at two pulses per second (pps), 3 pps, 6 pps, 12 pps and continuous fluoroscopy mode, respectively, using image-intensifier entries of 38 cm, 25 cm, and 17 cm. 300 examinations were carried out, and the results of the different fluoroscopy modes were registered. RESULTS: Dose reduction depends on the image-intensifier entry. Compared to the radiation dose in continuous fluoroscopy, with 12 pps fluoroscopy the radiation dose can be reduced at a minimum of 51%, with 6 pps fluoroscopy to 40%, with 3 pps fluoroscopy to 20%, and with 2 pps fluoroscopy to a minimum of 14.5%. Clinical routine has shown that 78% of all examinations can be performed with 2 or 3 pps fluoroscopy mode. In 12.7% of the cases pulsed fluoroscopy of diverse frequencies was used, in an additional 2% combined with continuous fluoroscopy. Exclusively, continuous fluoroscopy has been employed in 2% of the cases. CONCLUSIONS: Using pulsed fluoroscopy, an 80% reduction of the radiation dose compared to continuous fluoroscopy is possible. About 96% of all examinations can be performed with pulsed fluoroscopy of different pulse rate and without using continuous fluoroscopy.

Diagnostic Tests, Routine↗
PubMed1996

MRI-guided laser interstitial thermal therapy (LITT) of head and neck tumors: progress with a new method.

A less invasive method for treatment of tumors is being tested based on interstitial photothermal ablation via infrared Nd:YAG laser fiber optics. The technique can be applied safely and effectively for therapy of common tumors in humans. In the current study five patients were treated by interstitial laser palliation with the Nd:YAG laser using special fiberoptic applicator tips, which distribute laser energy efficiently throughout the tumor volume. Magnetic resonance imaging (MRI) scanning was employed to locate the tumor, position the fibers correctly, and monitor the development of thermal necrosis in the tumors. Two patients were diagnosed with adenoid cystic carcinoma of the paranasal sinuses, one with a recurrent carcinoma of the tongue and oropharynx, one with a recurrent carcinoma limited to the oropharynx, and one patient with a carcinoma of the epi- and oropharynx. The maximum follow-up without recurrence was 2 years in a patient with an adenoid cystic carcinoma tumor of the paranasal sinuses. There were no immediate or delayed complications. Anatomical structures including eyes, brain, and important vessels were recognized by MRI during laser therapy. MRI-guided interstitial laser photothermal ablation appears to be a safe and effective method for treatment of selected tumors of the head and neck region with particular applications in palliation of inoperable tumor recurrences.

Aged↗
PubMed1996

Diffusion measurements in the ischemic human brain with a steady-state sequence.

RATIONALE AND OBJECTIVES: The authors evaluate the clinical usefulness of a diffusion-weighted steady-state free-precession (SSFP) sequence to detect acute and subacute ischemic changes. METHODS: Twenty-four patients were examined on a 1.5-tesla scanner, using a SSFP-sequence (repetition time [TR]/ echo time [TE] = 22/3-8 mseconds). The slice thickness was 5 mm, 10 averages, 57 seconds per slice. The diffusion gradient strength was 23 millitesla/m, with b-values from 165 to 598 seconds/mm2. Diffusion-weighted images (DWI) were compared with T2-weighted images. RESULTS: The diffusion-weighted SSFP sequence produced diagnostic quality images in 23 of 24 patients. Diffusion depicted (group 1: 0-12 hours) more acute lesions (3 of 6) than T2-weighted images (2 of 6); the mean lesion diameter depicted by diffusion was 10.9 mm (standard deviation [SD], 12.3) and in T2-weighted images was 4.7 mm (SD 6.8). A significant correlation (P < 0.017) in subacute lesions was found when diffusion was compared with turbo spin echo (mean size difference/T2 = 18.5/17.5 mm, SD 13.2/12.2). CONCLUSIONS: The diffusion-weighted SSFP-sequence is more sensitive in acute ischemia and delineates likewise in subacute ischemia, when compared with T2-weighted imaging.

Adult↗
PubMed1996

Temporal constraints in processing of nonverbal rhythmic patterns.

This study investigates the effect of a mental content of presented stimuli, normal aging and individual differences in cognitive abilities on temporal limits of an integration mechanism. Younger and older subject grouped together the beats generated by a metronome. Subjects were asked to listen to the beats of a metronome and to accentuate mentally every second, third, fourth...etc. beat, to create a subjective rhythm. This rhythm exists, in fact, only in subjects' mind and not objectively. Subjects reported verbally how many clicks they were able to integrate into a perceptual unit. On this basis, the time interval during which subjects were able to integrate temporally separated stimuli was calculated (number of beats reported as being integrated x time distance between beats) for different metronome frequencies. The results show, firstly, that the length of integration periods significantly depends on the frequency of presented metronome beats. When the frequency of metronome beats is high, the time interval during which the subjects integrate beats into a single perceptual unit is shorter. Secondly, older adults integrate information during a longer time interval than younger ones. Thirdly, the length of an integration period is related to a subjects' level of cognitive ability. These results suggest that the length of an integration period is not a constant, stable feature, but varies across the life span depending on the mental content of the information presented and individual factors.

Acoustic Stimulation↗
PubMed1996

13 MHz high-frequency sonography of the lateral ankle joint ligaments and the tibiofibular syndesmosis in anatomic specimens.

In this study, the ligaments of the ankle joint and the tibiofibular syndesmosis were examined in formalin-fixed anatomic specimens using a 13 MHz sonographic scanner. For this purpose, 48 specimens of the ankle joint were examined, and the anterior tibiofibular, anterior talofibular, and calcaneofibular ligaments were marked by sonographically guided dye injection. The markings were checked during the subsequent dissection. The number of identifications reached 89.6% for the anterior tibiofibular and talofibular ligaments and 87% for the calcaneofibular ligament. The results show that the most frequently injured ligaments of the ankle joint can be visualized reliably by use of 13 MHz high-frequency sonography.

Ankle Joint↗
PubMed1996

[Dynamic MR colpocystorectography. A new methods for evaluating pelvic floor descent and genital prolapse].

AIM: Introduction of a new method for the dynamic evaluation of genital prolapse by using fast magnetic resonance imaging. METHODS: Dynamic fast magnetic resonance imaging with pelvic floor contraction, relaxation and straining manoeuvres were performed with volunteers and patients presenting with pelvic descent. The urethra, bladder, vagina and rectum were opacified by using a water or Magnevist enteral solution. RESULTS: Delineation and movement of the urethra, bladder, uterus, vagina, rectum and small bowel can be shown in a reliable manner. In comparison to dynamic fluoroscopy an equal or superior diagnosis has been achieved in all cases. CONCLUSION: In comparison to dynamic fluoroscopy MR-Colpocystorectography is a promising new method in assessing pelvic floor descent and prolapse in women. Further studies will have to focus on standardisation and clinical implication.

Aged↗
PubMed1996

[Gadolinium-enhanced magnetic resonance angiography with ultra-short echo times. Initial experiences].

Magnetic resonance angiography (MRA) using three-dimensional (3D) gradient-echo sequences with ultra-short echotimes (USTE; 2 ms) and luminal enhancement of vessels with a gadolinium bolus affords the depiction of extended vascular territories with high spatial resolution within 20-60 s. Because of the ultra-short echo and repetition times, filling of the vascular lumen with gadolinium is depicted; the latter is relatively independent of the complex flow effects on which conventional MRA is based. MRA typical flow voids caused by turbulence or slow flow are thus significantly reduced and allow more reliable depiction of stenoses. After implementing the sequences on our scanner, we evaluated the potential of USTE-MRA for the delineation of various vascular territories in 56 patients. A total of 70 vascular territories were depicted and evaluated by two independent radiologists for image quality and obscuring the arteries because of the contrast of veins. Out of the 56 (4%) diagnostic angiographic quality could not be obtained in only 2 cases. In 13 patients (23%) the studies were judged suboptimal, but diagnostic. In only 3 cases (5%) was venous filling judged to obscure the arteries completely on MIPs (maximum intensity reconstructions), although the studies were diagnostic when evaluated with MRPs (multiplanar reconstructions). Venous superimposition occurred significantly more frequently in the neck than else-where. The greatest improvement over conventional MRA was obtained in the abdomen and thorax where USTE-MRAs can be obtained within a breath-hold without motional artifact.

Adolescent↗
PubMed1996

[The value of ultrafast computerized tomography in detection of the patency of coronary bypasses].

Bypass graft patency with ultrafast computed tomography (= Electron Beam Tomography, EBT) was examined in 72 bypass grafts (47 saphenous veins, 25 internal mammary arteries) in 30 patients and compared with coronary angiography. Angiography was performed a mean of 4.4 +/- 3.5 months (range 1-13) from the EBT examination. Contrast material (120 ml) was continuously administered via a peripheral vein and 40 axial slices (3 mm slice thickness, 110 ms scan time) without overlap sequences were obtained, ECG triggered with the single slice scanner mode. Imaging of internal mammary artery grafts began at the thoracic inlet, for saphenous vein grafts, at the undersurface of the aorta. Sixty of 63 angiographically patent bypass grafts were determined patent by EBT (sensitivity 95%), 8 bypass grafts could not be detected by EBT, and 9 were angiographically occluded (specificity 89%). Twenty-four of 25 internal mammary artery grafts were patent at EBT and coronary angiography, one was occluded. In 27 of the 30 patients (90%), all of the angiographically patent grafts could be confirmed as open with EBT. Obstructions of 10 grafts could not be visualized with EBT. Graft insertion into native coronary vessels could be visualized in axial slices, although morphologic quantification of graft insertion stenosis (75-90%) in two cases was not possible. Three dimensional reconstruction of the 40 axial slices allowed graft anatomy to be delineated. Visualization of bypass insertion into the native coronary vessel was less successful because of opacification of the left and right ventricle. Electron beam computed tomography is a minimally invasive procedure capable of evaluating the patency of saphenous vein and internal mammary artery grafts. The morphologic quantification of graft obstruction and visualization of the insertion of the bypasses into the native coronary vessels is less successful with present technology and imaging modalities.

Aged↗