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Biomedical subjects

M F Reiser

Publications and source records attributed to M F Reiser.

At least 19 recordsLinked to original sources
PubMed2006

Quantitative and qualitative characterization of vascularization and hemodynamics in head and neck tumors with a 3D magnetic resonance time-resolved echo-shared angiographic technique (TREAT)--initial results.

The purpose of this paper is to characterize and quantify the vascularization and hemodynamic characteristics of head and neck tumors (HNT) with a dynamic 3D time-resolved echo-shared angiographic technique (TREAT) using the regular contrast agent (CA) bolus. Sixteen patients with HNT underwent 3D-TREAT during the CA administration on a 1.5-T magnetic resonance (MR) scanner. Using a parallel imaging acceleration factor of 2, 20 3D data sets at a temporal resolution of 2.3 s/frame were acquired. The quality of tumor delineation, vascularization type, and enhancement pattern were evaluated. Quantitative assessment included measurement of the contrast-to-noise ratio (CNR), determination of signal-intensity-over-time (SIT) curves, time-to-peak enhancement within the carotid arteries and the tumor, and the delay between both. TREAT was compared to conventional digital subtraction angiography (DSA) in six patients. Tumor delineation with TREAT was very good or good in 11/16 patients, and better with TREAT than with DSA in 3/6 cases. The CNR was significantly different for glomus tumors versus hypovascularized malignant tumors with TREAT (p=0.0001), but not on T1-weighted gradient echo (T1w GE) images. Qualitative assessment of tumor vascularization on dynamic TREAT shows good correlation (r=0.75) to quantitative SIT curves. We conclude that TREAT imaging permits the characterization of tumor vascularity and holds promise as a supplementary diagnostic tool in the differential diagnosis of HNT.

Adolescent↗
PubMed2006

Should 3K zoom function be used for detection of pneumothorax in cesium iodide/amorphous silicon flat-panel detector radiographs presented on 1K-matrix soft copies?

The purpose of the study was to evaluate observer performance in the detection of pneumothorax with cesium iodide and amorphous silicon flat-panel detector radiography (CsI/a-Si FDR) presented as 1K and 3K soft-copy images. Forty patients with and 40 patients without pneumothorax diagnosed on previous and subsequent digital storage phosphor radiography (SPR, gold standard) had follow-up chest radiographs with CsI/a-Si FDR. Four observers confirmed or excluded the diagnosis of pneumothorax according to a five-point scale first on the 1K soft-copy image and then with help of 3K zoom function (1K monitor). Receiver operating characteristic (ROC) analysis was performed for each modality (1K and 3K). The area under the curve (AUC) values for each observer were 0.7815, 0.7779, 0.7946 and 0.7066 with 1K-matrix soft copies and 0.8123, 0.7997, 0.8078 and 0.7522 with 3K zoom. Overall detection of pneumothorax was better with 3K zoom. Differences between the two display methods were not statistically significant in 3 of 4 observers (p-values between 0.13 and 0.44; observer 4: p = 0.02). The detection of pneumothorax with 3K zoom is better than with 1K soft copy but not at a statistically significant level. Differences between both display methods may be subtle. Still, our results indicate that 3K zoom should be employed in clinical practice.

Adult↗
PubMed2006

Percutaneous radiofrequency ablation of pulmonary tumors--is there a difference between treatment under general anaesthesia and under conscious sedation?

OBJECTIVE: This retrospective study aimed to compare feasibility, complication rate and local tumor control after radiofrequency ablation (RFA) of pulmonary tumors under conscious analgo-sedation (AS) versus general anaesthesia (GA). MATERIALS AND METHODS: Within 36 months 21 patients had RFA (36 tumors, 26 treatment sessions). One patient suffered from NSCLC, 20 had metastases (breast (8/20), colorectal (6/20), renal cell (2/20), pharyngeal carcinoma (1/20), malignant melanoma (3/20)). Patients were no surgical candidates due to underlying comorbidities. Eleven of 26 treatments were performed under GA, while in 15 of 26 treatments AS was used. Follow-up was scheduled 24 h, 6 weeks, 3 months, 6 months and then every 6 months after treatment. RESULTS: RFA was feasible in all treatments under GA, while under AS targeting of the lesion was not possible in 2/15. Six adverse events occurred in the GA group (three major, three minor), while seven complications happened in the AS group (three major, four minor) (p=0.57). During follow-up of 3-36 months local recurrence was detected in 3 of 21 tumors in the GA group and in 2 of 15 tumors in the AS group (p=0.79). DISCUSSION: Hospitalization, complication rates and types, and the rate of local tumor control did not differ substantially among both groups. Furthermore, there was no significant difference in technical success and feasibility. CONCLUSION: RFA of pulmonary tumors under GA or AS did not result in different tumor control and complication rates, respectively. Therefore, AS should be used except in anxious or agitated patients.

Adult↗
PubMed2006

Functional renal imaging: nonvascular renal disease.

Functional renal imaging-a fast-growing field of MR-imaging-applies different sequence types to gather information about the kidneys other than morphology and angiography. This update article presents the current status of different functional imaging approaches and presents current and potential clinical applications. Apart from conventional in-phase and opposed-phase imaging, which already yields information about the tissue composition, BOLD (blood-oxygenation level dependent) sequences, DWI (diffusion-weighted imaging) sequences, perfusion measurements, and dedicated contrast agents are used.

Contrast Media↗
PubMed2006

[Oxygen-enhanced MRI of the lung: optimized calculation of difference images].

BACKGROUND: In oxygen-enhanced lung MRI, difference maps of acquisitions during inhalation of room air and pure oxygen are calculated to assess lung function. The purpose of this study was to analyze how the calculation of these difference maps depends on the delayed signal change after switching the gas supply. METHODS: Ten healthy volunteers were examined with an ECG and respiratory-triggered T1-weighting inversion recovery HASTE sequence with parallel imaging. Four blocks with 20 repetitions of up to 6 coronal slices were continuously acquired; in blocks 1 and 3 room air was supplied, in blocks 2 and 4 oxygen. Data were postprocessed, discarding between 0 and 19 repetitions after each change of gas supply before calculating the relative signal difference. RESULTS: The averaged relative signal difference increases from 9.4 to 17.4% when the number of discarded acquisitions increases; the ratio of signal difference and spatial standard deviation reaches a maximum at 5-8 discarded acquisitions. CONCLUSIONS: An optimized ratio of signal difference and statistical error is found if about 5-8 of 20 respiratory-triggered repetitions are discarded after each change of gas supply for the calculation of difference maps.

Adult↗
PubMed2006

[MRI of pulmonary perfusion].

Lung perfusion is a crucial prerequisite for effective gas exchange. Quantification of pulmonary perfusion is important for diagnostic considerations and treatment planning in various diseases of the lungs. Besides disorders of pulmonary vessels such as acute pulmonary embolism and pulmonary hypertension, these also include diseases of the respiratory tract and lung tissue as well as pulmonary tumors. This contribution presents the possibilities and technical requirements of MRI for diagnostic work-up of pulmonary perfusion.

Humans↗
PubMed2006

[Lumbar disc arthroplasty: indications, biomechanics, types, and radiological criteria].

Lumbar total disc replacement (TDR) was developed to treat a painful degenerative lumbar motion segment while avoiding the disadvantages of fusion surgery, such as adjacent segment instabilities. Early clinical results with TDR have shown a significant reduction in low back pain and a significant improvement in disability scores. When compared to fusion, the results with TDR tend to be superior in the short-term follow-up and initial rehabilitation is faster. The radiological assessment is an integral part of the preoperative work-up. Plain X-rays of the lumbar spine should be complemented by flexion - extension views in order to assess residual segmental mobility. Computed tomography is used to exclude osteoarthritis of the zygapophyseal joints, Baastrup's disease (kissing spines) and other sources of low back pain. Magnetic resonance imaging is useful to exclude substantial disc protrusions; it allows for the detection of disc dehydration and bone marrow edema in the case of activated spondylochondrosis. If osteoporosis is suspected, an osteodensitometry of the lumbar spine should be performed. Postoperative plain X-rays should include antero-posterior and lateral views as well as flexion - extension views in the later postoperative course. Measurements should determine the disc space height in the lateral view, the segmental and total lumbar lordosis as well as the segmental mobility in the flexion - extension views. The ideal position of a TDR is exactly central in the ap-view and close to the dorsal border of the vertebral endplates in the lateral view. Malpositioning may cause segmental hyperlordosis and unbalanced loading of the endplates with the risk of implant subsidence and migration.

Adult↗
PubMed2006

[Vertebroplasty in the treatment of back pain].

BACKGROUND: Percutaneous vertebroplasty (PVP) represents a minimally invasive option which is gaining in importance for the treatment of vertebral compression fractures (VCF) and osteolysis of the spine. This article describes the indications for its use, peri-interventional imaging, technique, and results of PVP. MATERIAL AND METHODS: The current guidelines for performance of PVP are explained in accordance with the "Interdisciplinary Consensus Paper on Vertebroplasty and Kyphoplasty" of the German Professional Associations and the 2005 CIRSE Guidelines. The results of our own study carried out in 2002 are compared to the complication rates and clinical outcomes reported in the literature. RESULTS: Painful osteoporotic VCF and osteolysis within the vertebral body due to metastases and multiple myeloma are indications for PVP. Absolute contraindications are, in particular, asymptomatic VCF, alleviation of pain by drug treatment, therapy-refractory coagulopathies, allergies to cement components, and active infections. MRI or CT is indicated before undertaking PVP to assess the fracture age, to exclude other causes of pain, and to evaluate the posterior edge of the vertebral body. High-quality mono- or biplanar fluoroscopy--preferably in combination with CT (fluoroscopy)--is necessary for PVP to minimize the risk of cement leakage. A clear reduction in pain [mean reduction of 6.1 points (VAS)] is achieved in 86-92% of the patients with PVP. Our own study treating 58 patients (mean follow-up 323+/-99 days) revealed a clear alleviation of pain in 77% [-5.7 points (VAS)]. CONCLUSION: PVP constitutes a safe and effective minimally invasive treatment approach to stabilize and reduce acute and chronic back pain due to osteoporotic VCF and tumor-associated osteolysis.

Back Pain↗
PubMed2006

[Quantification of right ventricular function in congenital heart disease: correlation of 3D echocardiography and MRI as complementary methods].

PURPOSE: In congenital heart disease, the exact determination of the right ventricular function is of high importance for therapeutic and especially surgical planning. The aim of this study was to correlate the parameters of the right ventricular function in MRI and 3D echocardiography to determine the agreement of both modalities. MATERIALS AND METHODS: In 18 patients suffering from congenital heart disease, 3D echocardiography was performed using a Philips Sonos 7500 system. In MRI short axis slices with a 4-mm distance were acquired using an SSFP sequence on a Siemens Sonata or Symphony System. Volumetry for both modalities was performed on an external workstation (Tomtec) using the EchoView software. RESULTS: Enddiastolic and endsystolic volumes showed a highly significant correlation with coefficients of 0.996 and 0.990, respectively. In echocardiography there was a systematic slight underestimation of enddiastolic volumes and overestimation of endsystolic volumes. The Wilcoxon test did not show significant differences between the volumes and ejection fractions assessed by both modalities. CONCLUSION: There is an excellent correlation in the quantification of right ventricular volumes in MRI and 3D echocardiography, which allows a comparison of acquired volumes in clinical follow-up.

Adolescent↗
PubMed2006

Perforation of the colon: a rare complication of hepatocellular carcinoma.

Direct infiltration of the colon by hepatocellular carcinoma (HCC) is a rare condition. Only a few reports can be found in the literature. Here we present a case of direct infiltration of the ascending colon by an exophytic growing HCC of the right posterior liver lobe, in which treatment with transarterial chemoembolization (TACE) had been performed. Tumor invasion became evident by abdominal pain and lower gastrointestinal bleeding. Diagnosis was established by contrast-enhanced multidetector computed tomography (CE-MDCT), demonstrating the direct tumor invasion with concomitant perforation of the infiltrated colon segment. Based on these findings, rapid and effective surgical treatment could be achieved.

Abdominal Pain↗
PubMed2006

Cluster analysis of dynamic cerebral contrast-enhanced perfusion MRI time-series.

We performed neural network clustering on dynamic contrast-enhanced perfusion magnetic resonance imaging time-series in patients with and without stroke. Minimal-free-energy vector quantization, self-organizing maps, and fuzzy c-means clustering enabled self-organized data-driven segmentation with respect to fine-grained differences of signal amplitude and dynamics, thus identifying asymmetries and local abnormalities of brain perfusion. We conclude that clustering is a useful extension to conventional perfusion parameter maps.

Algorithms↗
PubMed2006

Dose reduction and image quality in MDCT colonography using tube current modulation.

OBJECTIVE: The purpose of our study was to evaluate the dose reduction potential of combined online (x- and y-axes) and topogram-based (l) X-ray tube current modulation in CT colonography in a screening population. MATERIALS AND METHODS: Eighty asymptomatic individuals underwent CT colonography screening for colon polyps. A 16-MDCT scanner (Somatom Sensation 16) was used. Forty patients were examined at 120 kVp and 120 effective mAs (supine) and 40 effective mAs (prone) using online x- and y-axis tube current modulation. Another 40 patients were scanned using combined x-, y-, and z-axis tube current modulation. Individual patient radiation exposure was determined using the dose-length product. Image noise was determined by Hounsfield unit measurements in the colonic lumen at four anatomic levels. Image quality was rated on a 5-point confidence scale by two independent reviewers. The unpaired Student's t test (for radiation dose, image noise) and Wilcoxon's test (for image quality) were used to test for statistically significant differences between these values. RESULTS: Radiation dose was significantly lower in the patient group scanned with x-, y-, and z-axis tube current modulation than in the group scanned with x- and y-axis tube current modulation (supine: 4.24 vs 6.50 mSv, p < 0.0001; prone: 1.61 vs 2.38 mSv, p < 0.0001). Radiation dose was reduced by 35% (supine) and 33% (prone). No statistically significant difference was seen in overall image noise (supine: 15.9 vs 16.3 H, p = 0.13; prone: 23.5 vs 24.8 H, p = 0.44) or image quality (supine: 4.6 vs 4.5, p = 0.62; prone: 3.5 vs 3.6, p = 0.54). CONCLUSION: Combined x-, y-, and z-axis tube current modulation leads to a significant reduction of radiation exposure in CT colonography without loss of image quality.

Aged↗
PubMed2006

Relative value of sliding-thin-slab multiplanar reformations and sliding-thin-slab maximum intensity projections as reformatting techniques in multisection CT angiography of the cervicocranial vessels.

BACKGROUND AND PURPOSE: To investigate image quality and vascular delineation of multisection CT (MSCT) angiography of the cervicocranial vessels with sliding-thin-slab (STS) maximum intensity projections (MIP) and multiplanar reformations (MPR). MATERIALS AND METHODS: Ten patients examined with a standardized protocol on a 16-section MSCT were included in the study. The data were reformatted as MIP and MPR in 3 planes for each subject; both reformatting techniques were applied in an STS technique with an increment of 3 mm. Images were evaluated independently by 3 blinded readers grading image quality parameters and vascular delineation of supra-aortic arteries and veins. An extension of the Mantel-Haenzel row mean score test was used to compare the distribution of scores for vascular delineation and image quality between STS MIP and STS MPR. RESULTS: STS MIP reformations were significantly superior to STS MPR in the delineation of all extra- and intracranial arteries and arterial segments and in the delineation of the cavernous sinus and the internal cerebral veins (P < .05). No significant differences were found for the large venous vessels, the visual assessment of vascular contrast, or the impact of imaging artifacts. CONCLUSION: Because STS MIP reformations were preferred to or equal to STS MPR in all aspects, we recommend STS MIP as the primary reformatting technique in MSCT angiography of the cervicocranial vessels in addition to viewing the source images.

Aged↗
PubMed2005

High-resolution diffusion tensor imaging of human patellar cartilage: feasibility and preliminary findings.

MR diffusion tensor imaging (DTI) was used to analyze the microstructural properties of articular cartilage. Human patellar cartilage-on-bone samples were imaged at 9.4T using a diffusion-weighted SE sequence (12 gradient directions, resolution = 39 x 78 x 1500 microm(3)). Voxel-based maps of the mean diffusivity, fractional anisotropy (FA), and eigenvectors were calculated. The mean diffusivity decreased from the surface (1.45 x 10(-3) mm(2)/s) to the tide mark (0.68 x 10(-3) mm(2)/s). The FA was low (0.04-0.28) and had local maxima near the surface and in the portion of the cartilage corresponding to the radial layer. The eigenvector corresponding to the largest eigenvalue showed a distinct zonal pattern, being oriented tangentially and radially in the upper and lower portions of the cartilage, respectively. The findings correspond to current scanning electron microscopy (SEM) data on the zonal architecture of cartilage. The eigenvector maps appear to reflect the alignment of the collagenous fibers in cartilage. In view of current efforts to develop and evaluate structure-modifying therapeutic approaches in osteoarthritis (OA), DTI may offer a tool to assess the structural properties of cartilage.

Anisotropy↗
PubMed2005

[Hereditary motor and sensory neuropathy (HMSN) with hypertrophy of the cauda equina and concomitant demyelinating white matter lesions].

Hereditary motor and sensory neuropathy (HMSN) is thought to almost exclusively affect the peripheral nervous system. We report the case of a 48-year-old patient with a longstanding history of HMSN type I who developed signs and symptoms of a cauda equina compression and of a central nervous system relapsing-remitting demyelinating white matter disease. Gross enlargement of the cauda equina fibers was detected by MR imaging of the lumbar spine. Cranial MR imaging revealed demyelinating white matter lesions. This case suggests that peripheral neuropathic mechanisms may also affect the central myelin in HMSN type I.

Charcot-Marie-Tooth Disease↗
PubMed2005

[Comparison of 2D and 3D sequences for MRCP. Clinical value of the different techniques].

Magnetic resonance cholangio-pancreaticograpy (MRCP) is a non-invasive imaging modality of the pancreatico-biliary system which plays an increasingly important role in the clinical and diagnostic workup of patients with biliary or pancreatic diseases. The present review is designed to give an overview of the currently available and appropriate sequences, their technical background, as well as new developments and their relevance to the various clinical issues and challenges. The impact of the latest technical innovations, such as integrated parallel imaging techniques and navigator-based respiratory triggering, on the diagnostic capacities of MRCP is discussed. In this context, the individual value of RARE, T2w single shot turbo/fast spin echo (SSFSE) and the recently introduced 3D T2w turbo/fast spin echo sequences (T2w 3D-T/FSE) is reviewed. RARE imaging may be preferred in severely ill patients with limitations in cooperation, SSFSE is particularly effective in differentiating benign and malignant stenosis, and 3D-FSE offers additional advantages in the detection of small biliary concrements.

Adult↗