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Maximilian Reiser

Publications and source records attributed to Maximilian Reiser.

At least 37 records · Page 2Linked to original sources
PubMed2005

CT of the normal temporal bone: comparison of multi- and single-detector row CT.

PURPOSE: To evaluate multi- and single-detector row computed tomographic (CT) depiction of anatomic landmarks of temporal bone. MATERIALS AND METHODS: Institutional review board approval and written informed consent were obtained. In 50 temporal bones, transverse and coronal single-detector row CT images were compared with transverse and reformatted coronal multi-detector row CT images obtained of additional 50 temporal bones. Two radiologists evaluated images. Visibility of 50 landmarks was scored with a five-point quality rating scale. Fisher exact test, kappa statistics, and Mann-Whitney U test were used to evaluate imaging technique and landmark visibility. RESULTS: In delineating landmarks, total interobserver agreement was higher (P < .001) for transverse multi- than for single-detector row CT images. In 60% of landmarks, interobserver agreement was higher (P < .001) for transverse multi- than for single-detector row CT images. In 20% of landmarks, there was no difference, and in another 20% of landmarks, interobserver agreement was higher (P < .01) for single-detector row CT. Total interobserver agreement was higher (P < .01) for coronal multi-detector row reformations than for coronal single-detector row images. In 58% of landmarks, interobserver agreement was higher (P < .001) for coronal multi-detector row reformations than for coronal single-detector row images, while there was no difference in 8%. In 34% of landmarks, interobserver agreement was higher (P < .001) for coronal single-detector row images. Frequency of detected landmarks was higher for transverse (82%) and coronal (88%) multi-detector row images than for corresponding single-detector row images. In 72% of landmarks, transverse multi-detector row images were (P < .05) superior to corresponding transverse single-detector row images in landmark delineation. In 56% of landmarks, reformatted coronal multi-detector row images were (P < .05) superior to coronal single-detector row images in landmark delineation. CONCLUSION: Multi-detector row CT images, including reformations, better delineate temporal bone anatomy than do single-detector row CT images.

Female↗
PubMed2005

Visualising noncalcified coronary plaques by CT.

Due to a rapid improvement of the new generation submillimetre multislice CT-technology noninvasive tomographic imaging of the coronary vessel wall has become reality. First clinical studies have shown the ability in particular of 16-slice CT to determine plaque burden, plaque composition and compensatory vessel-wall remodelling. These novel findings already constitute an important step forward to assess coronary atherosclerosis noninvasively in a detailed manner which opens promising new opportunities for a better understanding and riskstratification of coronary atherosclerosis. Current limitations, mainly the insufficient accuracy to detect small lesions in distal coronary segments, might be overcome by improved spatial and temporal resolution of the new generation scanners operating with 64 and more detectors.

Contrast Media↗
PubMed2005

Role of MRI for the diagnosis and prognosis of multiple myeloma.

For the correct staging of patients with multiple myeloma sensitive detection is mandatory in order to estimate prognosis and to decide for adequate therapy. Magnetic resonance imaging (MRI) is superior to radiography for both, focal and diffuse involvement. Five different infiltration patterns can be differentiated: (1) normal appearance of bone marrow despite minor microscopic plasma cell infiltration, (2) focal involvement, (3) homogeneous diffuse infiltration, (4) combined diffuse and focal infiltration, (5) "salt-and-pepper"-pattern with inhomogeneous bone marrow with interposition of fat islands. For the fast and complete assessment of all patterns a combination of a T1-weighted spin echo sequence and a fat suppression technique should be employed. The focal involvement is clearly demonstrated as areas of high signal intensity on, e.g. STIR images. Diffuse involvement is best detected on unenhanced T1-weighted SE sequences and it manifests as homogeneous signal reduction. It can be quantified objectively by calculation of the percentage of signal intensity increase after contrast material injection. With parallel imaging and special coil devices, such as total imaging matrix (Siemens systems, Avanto) a "screening" of the whole red bone marrow as for myeloma infiltration is possible within a reasonable time. Patients without bone marrow infiltration have a significantly longer survival than patients with bone marrow infiltration in MRI at the time of diagnosis. However, even in stage I disease (Durie and Salmon) and negative X-ray films bone marrow infiltration in MRI may be detected in 29-50% of patients. Those patients typically show an earlier disease progression. Recently, MRI has been implemented in the clinical staging of patients with multiple myeloma. MRI may also monitor response to therapy. Signs of good response in cases with focal involvement are: reduction of signal intensity on T2-weighted spin echo images, lack or rim-like enhancement after contrast material injection or even a normalisation of bone marrow signal. In case of diffuse involvement a partly patchy reconversion to fatty marrow can be seen.

Bone Marrow↗
PubMed2005

Comparison of spiral multidetector CT angiography and myocardial perfusion imaging in the noninvasive detection of functionally relevant coronary artery lesions: first clinical experiences.

UNLABELLED: Compared with conventional coronary angiography, spiral multidetector CT (MDCT) angiography has delivered promising accuracy in the detection and validation of coronary lesions. Myocardial perfusion imaging (MPI) using SPECT is an established method for noninvasively assessing the functional significance of coronary stenoses and delivers valuable information for risk stratification. This retrospective analysis compared the accuracies of MDCT angiography and MPI in the detection of hemodynamically relevant lesions of the coronary arteries. METHODS: Twenty-five patients with suspected or known coronary artery disease were studied. Electrocardiographically gated MPI and 16-MDCT angiography were performed. Myocardial perfusion images were analyzed by 2 experienced observers, and reversible and fixed perfusion defects were detected and allocated to their corresponding coronary vessels. For the evaluation of MDCT angiography, image quality was determined, and lesions > or = 50% and luminal narrowing < 50% were visually assessed and characterized by 2 independent observers unaware of the results of MPI. RESULTS: Ninety-nine coronary vessels were analyzed, and the quality of MDCT angiography images was assessed for 330 coronary segments. Coronary artery diameter was interpretable for 231 (70%) of 330 segments, whereas in 99 (30%) of 330 segments, vessel diameter could not be evaluated because of heavy calcifications, blurring, motion artifacts, or intracoronary stents. MDCT angiography detected stenoses > or = 50% in 15 of 100 coronary arteries. Eight (53%) of 15 stenoses > or = 50% showed reversible or fixed perfusion defects in the corresponding myocardial areas on MPI. Sensitivity, specificity, and negative and positive predictive values were 100%, 87%, 100%, and 29%, respectively, for the ability of MDCT angiography to detect reversible perfusion defects in the corresponding myocardial areas. CONCLUSION: MDCT angiography detected myocardial ischemia, as defined by reversible perfusion defects on MPI, with a positive predictive value of 29% in a nonselected study cohort. Compared with MPI alone, MDCT angiography added important morphologic information, but MPI remains mandatory for evaluating the functional relevance of coronary artery lesions.

Coronary Angiography↗
PubMed2005

18F-FDG PET/CT for staging of penile cancer.

UNLABELLED: The value of PET or PET/CT with (18)F-FDG for the staging of penile cancer has yet to be determined. The objective of this study was to investigate the pattern of (18)F-FDG uptake in the primary malignancy and its metastases and to determine the diagnostic value of (18)F-FDG PET/CT in the staging and restaging of penile cancer. METHODS: Thirteen patients (mean +/- SD age, 64 +/- 14.0 y) with suspected penile cancer or suspected recurrent disease were examined with a Gemini PET/CT system (200 MBq of (18)F-FDG). The reference standard was based on histopathologic findings obtained at biopsy or during surgery. RESULTS: Both the primary tumor and regional lymph node metastases exhibited a pattern of (18)F-FDG uptake typical for malignancy. Sensitivity in the detection of primary lesions was 75% (6/8), and specificity was 75% (3/4). On a per-patient basis, sensitivity in the detection of lymph node metastases was 80% (4/5), and specificity was 100% (8/8). On a nodal-group basis, PET/CT showed a sensitivity of 89% (8/9) in the detection of metastases in the superficial inguinal lymph node basins and a sensitivity of 100% (7/7) in the deep inguinal and obturator lymph node basins. The mean +/- SD maximum standardized uptake value for the 8 primary lesions was 5.3 +/- 3.7, and that for the 16 lymph node metastases was 4.6 +/- 2.0. CONCLUSION: According to our results, the main indication for (18)F-FDG PET in the primary staging or follow-up of penile cancer patients may be the prognostically crucial search for lymph node metastases. With the use of a PET/CT unit, the additional information provided by CT may be especially useful for planning surgery. Implementing (18)F-FDG PET and PET/CT in future staging algorithms may lead to a more precise and stage-appropriate therapeutic strategy. Furthermore, invasive procedures with a high morbidity rate, such as general bilateral lymphadenectomy, may be avoided.

Adult↗
PubMed2004

Neovascularization of bone marrow in patients with diffuse multiple myeloma: a correlative study of magnetic resonance imaging and histopathologic findings.

BACKGROUND: The goal of the current study was to assess the correlation between bone marrow histology and contrast enhancement in infiltrative diffuse myeloma. METHODS: Forty-four patients with homogeneous diffuse infiltration of bone marrow by multiple myeloma were examined using magnetic resonance imaging of the spine. The sequence protocol included T1-weighted spin-echo (pre- and post-gadolinium dimeglumine administration) and short-inversion time inversion recovery sequences. The percent increase in signal after intravenous gadolinium administration was calculated in bone marrow from patients with myeloma and from a control group of 86 patients who did not have bone marrow disease. Grade of infiltration with plasma cells, fat cell content, and hematopoietic marrow content were evaluated via histologic assessment of bone marrow, and microvessel density was evaluated via anti-CD34-positive immunostaining. RESULTS: Increased microvessel density was observed in association with increasing plasma cell content (Kruskall-Wallis test: P < 0.0001). Contrast enhancement increased in a stepwise manner according to grade of microvessel density (Mann-Whitney U test: P < 0.05 and P < 0.001 for increases from low to intermediate and intermediate to high grade) and was significantly higher in patients with myeloma compared with control patients (Mann-Whitney U test: P < 0.001). A significant correlation also was found between histologic extent of tumor infiltration and contrast enhancement (Mann-Whitney U test: P < 0.0001). The mean level of contrast enhancement was 18% in the control group, 26% in patients with low-grade infiltration, 49% in patients with intermediate-grade infiltration, and 90% in patients with high-grade infiltration. In addition, fat cell content was found to be inversely correlated with contrast enhancement (chi-square test: P < 0.01). CONCLUSIONS: As a consequence of increased microvessel density, decreased fat cell content, and increased cellularity, the presence of diffuse bone marrow infiltration in patients with multiple myeloma can be verified using gadolinium-enhanced magnetic resonance imaging.

Adipocytes↗
PubMed2004

Cross-sectional imaging of biliary tumors: current clinical status and future developments.

Extrahepatic cholangiocarcinoma, including hilar cholangiocarcinoma, is a relatively rare diagnosis. However, it frequently has been associated with major problems in diagnostics and clinical management from its first comprehensive description by Klatskin up until today. In this article, cholangiocarcinoma, representing the most common biliary tumor, as well as the differential diagnoses of benign and malignant biliary obstruction, will be discussed. The latest improvements of cross-sectional imaging modalities (sonography, CT, MRI and PET) and their diagnostic values for detection and staging will be displayed. A practical imaging-based diagnostic approach to obstructive biliary disease will be proposed.

Bile Duct Neoplasms↗
PubMed2004

Accuracy of multidetector spiral computed tomography in identifying and differentiating the composition of coronary atherosclerotic plaques: a comparative study with intracoronary ultrasound.

OBJECTIVES: We evaluated the accuracy of contrast-enhanced multidetector spiral computed tomography (MDCT) for the noninvasive detection and classification of coronary plaques and compared it with intracoronary ultrasound (ICUS). BACKGROUND: Noninvasive determination of plaque composition and plaque burden may be important to improve risk stratification and to monitor progression of coronary atherosclerosis. METHODS: We included 46 consecutive patients with a distinctive risk profile, who were investigated by ICUS (Goldvision, 20 MHz, Jomed Inc., Rancho Cordova, California). Due to the inability to slow the heart rate below 65 beats/min (n = 7) and due to renal insufficiency (n = 2), nine of 46 consecutive patients could not be studied by MDCT (Sensation 16, Siemens, Forchheim, Germany). RESULTS: In the remaining 37 patients, 68 vessels were investigated by ICUS, and 58 of these vessels were visualized by MDCT with image quality sufficient for analysis. In these vessels that were divided in 3-mm sections, MDCT correctly classified 62 of 80 (78%) sections containing hypoechoic plaque areas, 87 of 112 (78%) sections containing hyperechoic plaque areas, and 150 of 158 (95%) sections containing calcified plaque tissue. In 484 of 525 (92%) sections, atherosclerotic lesions were correctly excluded. The MDCT-derived density measurements within coronary lesions revealed significantly different values for hypoechoic (49 HU [Hounsfield Units] +/- 22), hyperechoic (91 HU +/- 22), and calcified plaques (391 HU +/- 156, p < 0.02). CONCLUSIONS: This study demonstrates that, in the case of diagnostic image quality, contrast-enhanced MDCT permits an accurate identification of coronary plaques and that computed tomography density values measured within plaques reflect echogenity and plaque composition.

Aged↗
PubMed2004

3D imaging with an isocentric mobile C-arm comparison of image quality with spiral CT.

The purpose of this study was to evaluate the image quality of the new 3D imaging system (ISO-C-3D) for osteosyntheses of tibial condylar fractures in comparison with spiral CT (CT). Sixteen human cadaveric knees were examined with a C-arm 3D imaging system and spiral computed tomography. Various screws and plates of steel and titanium were used for osteosynthesis in these specimens. Image quality and clinical value of multiplanar (MP) reformatting of both methods were analyzed. In addition, five patients with tibial condylar fractures were examined for diagnosis and intra-operative control. The image quality of the C-arm 3D imaging system in the cadaveric study was rated as significantly worse than that of spiral CT with and without prostheses. After implantation of prostheses an increased incidence of artifacts was observed, but the diagnostic accuracy was not affected. Titanium implants caused the smallest number of artifacts. The image quality of ISO-C is inferior to CT, and metal artifacts were more prominent, but the clinical value was equal. ISO-C-3D can be useful in planning operative reconstructions and can verify the reconstruction of articular surfaces and the position of implants with diagnostic image quality.

Artifacts↗
PubMed2004

Reduced hippocampal volumes associated with the long variant of the serotonin transporter polymorphism in major depression.

BACKGROUND: Substantial evidence supports a role for dysfunction of the serotonin transporter in the pathogenesis of major depression. Several studies have found reciprocal interactions between the serotonergic system and both brain-derived neurotrophic factor and glutamate, which are known to modulate or affect hippocampal morphologic characteristics. OBJECTIVE: To examine the influence of a polymorphism (5-HTTLPR) in the promoter region of the serotonin transporter gene on hippocampal volumes in patients with major depression and healthy controls. DESIGN: Baseline investigation of a prospective magnetic resonance imaging study with a 4-year follow-up period. PATIENTS: We examined 40 inpatients with major depression as well as 40 healthy controls matched for age, sex, and handedness. MAIN OUTCOME MEASURES: Subjects underwent high-resolution magnetic resonance imaging. Furthermore, genotyping for the 5-HTTLPR biallelic polymorphism was performed, which consists of a 44-base pair insertion (L allele) or deletion (S allele). RESULTS: Patients with the L/L homozygous genotype had significantly smaller hippocampal gray matter (left hemisphere: P=.003; right hemisphere: P=.01) and white matter volumes (left hemisphere: P=.001; right hemisphere: P=.002) than controls with this genotype. No significant differences were found between patients and controls with the L/S or S/S genotype. Moreover, patients with the L/L genotype had significantly smaller hippocampal white matter volumes than those with the L/S or S/S genotype (P=.03). CONCLUSIONS: These findings suggest that homozygosity for the L allele is associated with decreased hippocampal volumes in patients with major depression but not in healthy controls. A possible explanation is that the interaction between the serotonergic system and neurotrophic factors as well as excitatory amino acid neurotransmission may affect hippocampal morphologic characteristics.

Adult↗
PubMed2004

[Comparison of gradient echo and echo planar imaging measurements for the calculation of regional blood volume maps].

The purpose of this study was to evaluate relative regional blood volume (rCBV) in meningioma and compare the utility of reconstruction using both gradient-echo sequence and echo-planar-imaging (EPI) sequence. Eighteen patients with meningiomas were studied on a Siemens 1.5-T scanner. During the gradient-echo sequence (n=12) and EPI sequence (n=6), a bolus (0.2 mmol/kg) of Gd-DTPA was injected mechanically with a flow rate of 5 ml/second. Image processing of dynamic data was performed on a pixel-by-pixel basis. The ratio of tumor rCBV/gray matter rCBV was 3.01 +/- 1.18 (3.07 +/- 1.39 in gradient sequence and 2.84 +/- 0.94 in EPI sequence). The ratio of gray matter/white matter as the reference tissue had a mean of 2.79 +/- 0.76 using the FLASH sequence, and a mean of 3.04 +/- 1.31 using EPI. These differences were not statistically signifcant (P>0.5, t-test). According to the ratio of tumor rCBV/gray matter rCBV, a mean value, 14.5 ml/100 g, of rCBV in meningiomas was calculated. Compared with gray matter, increased inhomogeneous rCBV was observed in meningioma. Based on the two different sequences, no bias can be observed in our rCBV reconstruction.

Adult↗
PubMed2004

The septum pellucidum and its variants. An MRI study.

PURPOSE: Increased prevalence of cavum septi pellucidi (CSP) in schizophrenic patients in comparison to healthy subjects was reported previously. Our purpose was to evaluate the prevalence of variants of the septum pellucidum in healthy subjects in three different age groups. METHODS: 151 healthy subjects, including 46 children (age 6 +/- 4 years), 72 young adults (age 31 +/- 8 years) and 33 elderly adults (age 59 +/- 7 years) were examined with high-resolution MRI. Three observers analysed the images using a standardised protocol. We evaluated the incidences of CSP, cavum vergae (CV) and their length. RESULTS: CSP was detected in 80% of the cases in the paediatric group and 68% of young adults and in 72% of the elderly adults. A cavum vergae (CV) was noted in 22% of the children, in 39% of the young adults and in 36% of the elderly subjects. There was no significant difference between the age-related groups. CONCLUSION: We detected a high prevalence of cavum septi pellucidi without a significant age dependence. Enlarged cava septi pellucidi are rare in healthy subjects.

Adolescent↗
PubMed2004

T2 quantitation of human articular cartilage in a clinical setting at 1.5 T: implementation and testing of four multiecho pulse sequence designs for validity.

RATIONALE AND OBJECTIVES: Evaluation of the T2 relaxation time of articular cartilage holds great potential for quantitative assessment of internal changes of the cartilage matrix. The purpose of the present study was to assess the validity of multiecho-based cartilage T2 quantitation in a clinical MRI setting at 1.5 T. METHODS: Four multisection multiecho sequence variants dedicated for quantitative T2 mapping of human articular cartilage were implemented on a 1.5 T whole-body imager and tested for accuracy in CuSO4-agarose gel phantoms and human patellar cartilage. Sequence design was varied to minimize errors in T2 quantitation due to stimulated echoes. RESULTS: As compared with single spin-echo experiments, the apparent T2 values calculated from the multiecho sequence variants showed mean deviations ranging from +26% to -32% (phantoms) and from +42% to -18% (cartilage). The patellar cartilage T2 covered a range from about 25 milliseconds to 55 milliseconds, with longer T2 values observed in the more superficial layers. In cartilage, best results were obtained from the sequence design using improved section profiles and a spoiler gradient scheme for suppression of stimulated echoes. CONCLUSIONS: Our results revealed a clear dependence of apparent T2 relaxation times on the pulse sequence design, emphasizing that the "true" T2 is hard to find. In addition, the effect on the apparent T2 values resulting from the specific modification of any sequence variant varied according to the respective tissue's properties. Therefore, the acquisition technique in conjunction with the specific tissue on which T2 mapping is performed need to be reported in detail and should kept consistent to allow large-scale comparisons and monitoring of treatment strategies, e.g., in osteoarthritis.

Cartilage, Articular↗
PubMed2004

Magnetic resonance angiography in the follow-up of distal lower-extremity bypass surgery: comparison with duplex ultrasound and digital subtraction angiography.

PURPOSE: The danger of limb loss as a consequence of acute occlusion of infrapopliteal bypasses underscores the requirement for careful patient follow-up. The objective of this study was to determine the agreement and accuracy of contrast material-enhanced moving-table magnetic resonance (MR) angiography and duplex ultrasonography (US) in the assessment of failing bypass grafts. In cases of discrepancy, digital subtraction angiography (DSA) served as the reference standard. MATERIALS AND METHODS: MR angiography was performed in 24 consecutive patients with 26 femorotibial or femoropedal bypass grafts. Each revascularized limb was divided into five segments--(i) native arteries proximal to the graft; (ii) proximal anastomosis; (iii) graft course; (iv) distal anastomosis; and (v) native arteries distal to the graft-resulting in 130 vascular segments. Three readers evaluated all MR angiograms for image quality and the presence of failing grafts. The degree of stenosis was compared to the findings of duplex US, and in case of discrepancy, to DSA findings. Two separate analyses were performed with use of DSA only and a combined diagnostic endpoint as the reference standard. RESULTS: Image quality was rated excellent or intermediate in 119 of 130 vascular segments (92%). Venous overlay was encountered in 26 of 130 segments (20%). In only two segments was evaluation of the outflow region not feasible. One hundred seventeen of 130 vascular segments were available for quantitative analysis. In 109 of 117 segments (93%), MR angiography and duplex US showed concordant findings. In the eight discordant segments in seven patients, duplex US overlooked four high-grade stenoses that were correctly identified by MR angiography and confirmed by DSA. Percutaneous transluminal angioplasty was performed in these cases. In no case did MR angiography miss an area of stenosis of sufficient severity to require treatment. Total accuracy for duplex US ranged from 0.90 to 0.97 depending on the reference standard used, whereas MR angiography was completely accurate (1.00) regardless of the standard definition. CONCLUSION: Our data strongly suggest that the accuracy of MR angiography for identifying failing grafts in the infrapopliteal circulation is equal to that of duplex US and superior to that of duplex US in cases of complex revascularization. MR angiography should be included in routine follow-up of patients undergoing infrapopliteal bypass surgery.

Adult↗
PubMed2004

Multislice computed tomography of the distal radius metaphysis: relationship of cortical bone structure with gender, age, osteoporotic status, and mechanical competence.

We explore the relationship of region-specific densitometric and geometry-based (cortical) parameters at the distal radial metaphysis with gender, age, and osteoporotic status, using multislice computed tomography (CT). We specifically test the hypothesis that these parameters can improve the prediction of mechanical strength of the distal radius vs bone mass (bone mineral content [BMC]). The BMC was determined in 56 forearm specimens with peripheral dual-energy X-ray absorptiometry (DXA). Trabecular and cortical density and geometric properties of the metaphyseal cortex were determined using multislice CT and proprietary image analysis software. Specimens were tested to failure in a fall simulation, maintaining the integrity of the elbow joint and hand. Women displayed significantly lower failure strength (-34%), BMC (-35%), trabecular density (-26%), and cortical area (-12%) than men. The reduction of trabecular density with age and osteoporotic status was stronger than that of cortical density or thickness. DXA explained approx 50% (r2) of the variability in bone failure loads. This proportion was slightly increased (55%) when adding geometry-based parameters. The study suggests that high-resolution tomographic measurements with current clinical imaging methodology can marginally improve the prediction of mechanical failure strength. Further efforts are required to improve spatial resolution for determining metaphyseal cortical properties clinically.

Aged↗