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Biomedical subjects

M Strotzer

Publications and source records attributed to M Strotzer.

At least 37 records · Page 2Linked to original sources
PubMed2001

Frequency of benign hepatic lesions incidentally detected with contrast-enhanced thin-section portal venous phase spiral CT.

PURPOSE: To evaluate the frequency of benign focal hepatic lesions incidentally detected at contrast-enhanced thin-section portal venous phase spiral CT. MATERIAL AND METHODS: Between January 1998 and February 1999, contrast-enhanced hepatic spiral CT examinations were performed in 1,892 patients. Out of these, only 100 patients fulfilled the following inclusion criteria: No underlying malignant disease, no liver cirrhosis, no suspected or known focal liver lesions. Standardized spiral CT parameters were applied. All CT studies were reviewed retrospectively by one radiologist. Any focal lesion was recorded and classified. Lesion size and number were noted. RESULTS: A total of 108 hepatic lesions were reported in 33 out of 100 patients (80 cysts; 18 hemangiomas; 3 focal fatty infiltrations; 2 focal non-tumorous perfusion defects; 1 calcification; and 4 non-classified lesions). The average lesion size was 9.4 mm (< or =5 mm: n=40; 6-10 mm: n=30; 11-15 mm: n=28; >15 mm: n=10). CONCLUSION: Benign liver lesions are probably a frequent incidental finding at abdominal spiral CT.

Adult↗
PubMed2001

[The PACS concept of the University of Regensburg].

AIM: Planning a PACS (Picture Archiving and Communication System) with the aim of a filmless hospital. The service for the referring physicians should be optimised. METHODS: Statistical analysis of data from the RIS (Radiological Information System), customer survey, workflow analysis and cost effectiveness analysis was the basis for planning the PACS. RESULTS: The calculated data quantity of the institute is 6.2 gigabyte per day or 1.7 terabyte per year. The referring physicians wanted to have the examination in 93% of the cases on the same day. For 53% of the cases remote studies were necessary for reading. Only 2.3% of these pictures were older than two years. The organisation of the department makes it necessary to have access to the examination of all modalities from each diagnosis workstation. CONCLUSIONS: Due to specific attributes of the institute, a fast nearline archive, a clustering of the diagnosis workstations and a DiCOM based picture distribution were planned.

Cost-Benefit Analysis↗
PubMed2001

[Dynamic MR defecography for diagnosis of combined functional disorders of the pelvic floor in proctology].

PURPOSE: Evaluation of magnetic resonance defecography in the diagnosis of pelvic floor disorders were examined prospectively. MRI was performed on a 1.5 T scanner. The rectum was opacified with 200 ml of ultrasound transmission gel. A sagittal single section T2-weighted gradient echo sequence with a temporal resolution of 1.1 second was performed. Changes of the anorectal angle and the position of the pelvic organs in relation to the pubococcygeal line were registered at rest, during straining, and during evacuation of the rectum. RESULTS: Patients with obstructed defecation (n = 15) showed prolapse of the rectal mucosa (n = 5), anterior rectocele (n = 8), pelvic floor descent (n = 5), enterocele (n = 2), and anorectal dyscoordination (n = 3). Individuals with stool incontinence (n = 15) had an anterior rectocele (n = 10), pelvic floor descent (n = 11), enterocele (n = 2), prolapse of rectal mucosa (n = 1), and a puborectal insufficiency (n = 1). Urine incontinence was associated with cystocele (n = 10) or normal findings (n = 4). In patients with unspecific symptoms (n = 6), anorectal dyscoordination (n = 4) and prolapse of the rectal mucosa (n = 2) were found. MRI was superior for the detection of enteroceles, cystoceles and pelvic floor descent compared with clinical investigation. CONCLUSION: Dynamic MR imaging supplies complex information in anorectal disease and thus improves proctoscopy.

Adolescent↗
PubMed2001

[Percutaneous transfemoral implantation of a new, flexible thoracic aorta endoprosthesis using a percutaneous suture system for vascular suture--initial experiences].

PURPOSE: To evaluate the transfemoral placement of a new, flexible stent-graft into the thoracic aorta and the suture-mediated closure of the femoral access. PATIENTS AND METHODS: Five patients were treated endovascularly with a stent-graft for an aneurysm (n = 3) or acute dissection (n = 2) of the thoracic aorta via a femoral 24 F sheath. The femoral access site was closed with two suture-mediated closure devices after placement of the stent-graft. RESULTS: The aneurysm or the false lumen was excluded from perfusion by the placement of the stent-graft in all patients. Hemostasis at the femoral access site was successful in all patients with the percutaneous suture device. A minor stenosis of the femoral artery was found angiographically in four patients after suture-mediated closure. Besides a reversible renal failure due to the medically induced hypotension for the treatment of an acutely ruptured aneurysm, no complications resulted from the stent-graft placement or the percutaneous suture. CONCLUSION: The percutaneous transfemoral placement of stent-grafts in the thoracic aorta using a suture-mediated closure of the access site is technically feasible. Long-term results of the technique have to be awaited.

Aged↗
PubMed2001

[Extravasation of contrast media in brain parenchyma and cerebrospinal fluid space after CT or DSA of thorax or abdomen].

PURPOSE: Analysis of clinical and CT findings in patients with signs of disruption of the blood-brain or blood-CSF barrier after i.v. or i.a. administration of non-ionic contrast media. METHODS: 1. Retrospective analysis of 8 patients with clinical and CT findings of disruption of the blood-brain or blood-CSF barrier after i.v. or i.a. administration of non-ionic contrast media (200-450 ml). 2. Prospective analysis of 30 intensive care patients with sepsis and suspected abscess, who underwent CT of the chest and abdomen with 240 ml of a non-ionic contrast medium followed by cranial CT to rule out septic lesions. RESULTS: The retrospective analysis proved that disruption of the blood-brain barrier may occur in elderly patients with risk factors after injection of higher amounts of contrast media. In the prospective study, equivalent CT phenomena were observed in 3 of 30 patients with sepsis. CONCLUSIONS: Hypoxemic and toxics damage to the blood-brain barrier as well as higher amounts of contrast media may result in extravasation of contrast medium into the CSF space, which can be demonstrated by CT. For differential diagnosis, the clinical symptoms and CT patterns of a disruption of the blood-brain or blood-CSF barrier should be known.

Adult↗
PubMed2001

Quantification of blood flow in the carotid arteries: comparison of Doppler ultrasound and three different phase-contrast magnetic resonance imaging sequences.

RATIONALE AND OBJECTIVES: To compare blood flow velocities in the carotid arteries measured with three different magnetic resonance (MR) phase-contrast imaging techniques and with percutaneous Doppler ultrasound. METHODS: Fourteen healthy male volunteers with a mean age of 33 +/- 3.8 years were studied. Ultrasound and MR phase velocity mapping of both common carotid arteries (n = 28) was performed within 5 hours. A two-dimensional fast low-angle shot sequence with retrospective cardiac gating, a sequence with prospective cardiac triggering, and a breath-hold sequence with prospective cardiac triggering were used. Resistance indexes and pulsatility indexes were calculated for all modalities. RESULTS: The comparison of flow velocities obtained with ultrasound and the different MR techniques led to a moderate correlation of the retrospective gated and prospective triggered MR techniques (eg, r = 0.73 for maximum systolic velocity). The worst correlation was found between the breath-hold technique and retrospective cardiac gating (eg, r = 0.004 for pulsatility index). There was a weak correlation of all three MR sequences compared with ultrasound (r = 0.19-0.60) CONCLUSIONS: A moderate correlation was found between velocities and indexes measured with the prospective cardiac-triggered phase-contrast MR technique and the retrospective cardiac-gated phase-contrast MR technique. A weak correlation was found between the three different MR techniques and ultrasound, as well as between the breath-hold prospective cardiac-triggered MR sequence and both of the other MR sequences. The influence of temporal and spatial resolution on MR phase-contrast velocity mapping was confirmed.

Adult↗
PubMed2001

Appearance of vascular stents in computed tomographic angiography: in vitro examination of 14 different stent types.

RATIONALE AND OBJECTIVES: To evaluate the appearance of the vessel lumen after implantation of different vascular stents with the use of a computed tomographic (CT) angiography model. METHODS: A vascular phantom was studied with helical CT and different slice thicknesses (2 and 3 mm) and pitch values (1.0, 1.5, and 2.0). Original transverse CT images and coronal reformations were evaluated. Fourteen different stents were analyzed with regard to changes in the stent lumen (attenuation values, noise, and artificial lumen narrowing). RESULTS: Some stents caused artifacts resulting in potential errors during evaluation of their patency. Assessment of the lumen was impaired in two stents (Strecker tantalum and Passager). Increased attenuation values were measured in all stents (increase of 8%-145%). The degree of artificial lumen narrowing was 4.4% to 77.8%. CONCLUSIONS: In most stents, reliable evaluation of the stent lumen seems possible. However, knowledge of the artifacts caused by different stent types is useful for the assessment of stent patency with CT angiography.

Angiography↗
PubMed2001

Comparison between magnetic resonance phase contrast imaging and transcranial Doppler ultrasound with regard to blood flow velocity in intracranial arteries: work in progress.

OBJECTIVE: The authors evaluate blood flow velocities in the medial cerebral artery (MCA) and the basilar artery using magnetic resonance (MR) phase contrast technique in comparison with transcranial Doppler ultrasound (TCD). Eleven healthy male volunteers were studied. TCD of the MCA (n = 22) and basilar artery (n = 11) was performed. MR phase velocity mapping was done in each vessel at the same location where the TCD signal had been acquired. A 2-dimensional FLASH sequence with retrospective cardiac gating and an average temporal resolution of 45 ms was used. Resistance indices (RIs) and pulsatility indices (PIs) were calculated for both modalities. The TCD insonation angle was measured retrospectively with MR, and TCD velocities were corrected based on these measurements. The comparison of flow velocities obtained with TCD and MR led to a low correlation coefficient with regard to the basilar artery and the MCA: maximum systolic velocity, r = 0.02 and r = 0.50, respectively; enddiastolic velocity, r = 0.47 and r = 0.65, respectively; mean velocity, r = 0.52 and r = 0.66, respectively. The average PIs in the basilar artery and the MCA were 0.80 and 0.81 with MR and 0.65 and 0.85 with TCD, respectively. The average RIs in the basilar artery and the MCA were 0.52 and 0.54 with MR and 0.52 and 0.55 with TCD, respectively. The TCD insonation angle differed significantly from the ideal value in the basilar artery (mean value = 32.6 degrees) and the MCA (mean value = 26.5 degrees). The authors find a low correlation between velocities measured with MRI and TCD but similar results with regard to the PIs and RIs. Several sources of error, such as a nonideal TCD insonation angle, were identified.

Adult↗
PubMed2001

Visualization of the IXth to XIIth cranial nerves using 3-dimensional constructive interference in steady state, 3-dimensional magnetization-prepared rapid gradient echo and T2-weighted 2-dimensional turbo spin echo magnetic resonance imaging sequences.

OBJECTIVE: The purpose of this study was to evaluate the visibility of the IXth to XIIth cranial nerves using different magnetic resonance sequences. Thirty healthy volunteers underwent magnetic resonance imaging at 1.5 T using 3-dimensional constructive interference in steady state (CISS) sequence (TR = 17 ms, TE = 8.08 ms, alpha = 70 degrees), 3-dimensional magnetization-prepared rapid gradient echo (MP-RAGE) sequence (TR = 11.08 ms, TE = 4.3 ms, alpha = 15 degrees), and T2-weighted (w) 2-dimensional turbo spin echo (TSE) sequence (TR = 4000 ms, TE = 102 ms, alpha = 180 degrees, slice thickness = 2 mm). Visibility of the IXth to XIIth cranial nerves in each sequence was evaluated by consensus of 2 radiologists using an evaluation scale from 1 (excellently visible) to 5 (not visible). A correlation with anatomic specimens was made. The 3-dimensional CISS sequence provides best resolution of the IXth to XIIth cranial nerves and their relation to surrounding structures. Additional information is given by the 3-dimensional MP-RAGE when nerves are surrounded by soft tissues. Using the T2w 2-dimensional TSE sequence, even whole nerves cannot be visualized due to intersection gap and partial volume effects. However, even in 3-dimensional high-resolution sequences, segments of nerves are not always visualized. A combination of 3-dimensional CISS and 3-dimensional MP-RAGE proved to be useful to visualize the IXth to XIIth cranial nerves, whereas the 2-dimensional technique failed. Further investigations using 3-dimensional MP-RAGE with contrast medium should be performed in the case of abnormality.

Accessory Nerve↗
PubMed2001

MR imaging-guided stent placement in iliac arterial stenoses: a feasibility study.

PURPOSE: To assess the feasibility of magnetic resonance (MR) imaging-guided stent placement in iliac arterial stenoses. MATERIALS AND METHODS: Thirteen patients with 14 iliac arterial stenoses were examined prospectively. Angioplasty was performed through a femoral sheath by using a conventional 1.5-T MR imaging system. Stents and catheters were visualized on the basis of their artifacts. Nitinol stents were placed with gradient-echo MR imaging guidance. Angioplasty balloons were inflated with gadolinium-based contrast material. Results were evaluated clinically and with both digital subtraction angiography (DSA) and contrast material-enhanced MR angiography. RESULTS: Ten of 13 patients were treated with technical success by using MR imaging-guided intervention alone. Three patients were treated with additional fluoroscopic guidance, because complications (ie, panic attack, subintimal recanalization, and stent misplacement) occurred with MR guidance. The quality of the postinterventional contrast-enhanced MR angiograms of three of 12 lesions with stents was limited owing to stent-induced signal loss of the lumen. The mean stenosis degree after stent placement was significantly higher at contrast-enhanced MR angiography than at DSA (24.6% vs 6.2%). The mean MR imaging-guided procedure time was 74 minutes. CONCLUSION: MR imaging-guided stent placement in iliac arteries is feasible in select patients. The presented technique has limitations-that is, long procedure times, lack of real-time monitoring, and stent artifacts-that necessitate further modifications before it can be recommended for clinical use.

Aged↗
PubMed2001

Renal time-resolved MR angiography: quantitative comparison of gadobenate dimeglumine and gadopentetate dimeglumine with different doses.

PURPOSE: Results with different doses of gadobenate dimeglumine and gadopentetate dimeglumine were compared at magnetic resonance (MR) angiography of the renal arteries. The signal-to-noise ratio (SNR) was evaluated as a quantitative measure of image quality. MATERIALS AND METHODS: Sixty consecutive patients (age range, 24-81 years; mean age, 65 years) underwent intraarterial digital subtraction angiography (DSA) and contrast material-enhanced time-resolved MR angiography. DSA was the standard of reference. Fifteen patients received gadopentetate dimeglumine at doses of 0.2 or 0.1 mmol per kilogram of body weight. Fifteen patients received gadobenate dimeglumine at doses of 0.05 or 0.1 mmol/kg. The SNR was calculated in the aorta and both main renal arteries. The number and degree of stenoses of the renal arteries and accessory vessels were evaluated by four observers. RESULTS: SNRs with gadobenate dimeglumine at a dose of 0.1 mmol/kg were significantly superior to those with gadopentetate dimeglumine at a dose of 0.1 mmol/kg. Differences were not statistically significant between the SNRs in the other groups. Eleven (85%) of 13 hemodynamically significant renal artery stenoses were detected correctly with MR angiography as were 22 (85%) of 26 accessory renal arteries. CONCLUSION: SNRs with gadobenate dimeglumine were higher than those with gadopentetate dimeglumine, but in most cases the differences in SNRs were not statistically significant.

Adult↗
PubMed2001

Spinal metastases from renal cell carcinoma: effect of preoperative particle embolization on intraoperative blood loss.

BACKGROUND AND PURPOSE: Surgical repair of spinal metastases from renal origin is often complicated by excessive bleeding. The purpose of this study was to assess the effect of preoperative particulate embolization on intraoperative blood loss. METHODS: Twenty spinal metastases from renal origin (17 patients) treated by preoperative embolization with polyvinyl alcohol particles were analyzed retrospectively. Surgical decompression was performed within 2 days after embolization. A control group of 10 patients with 11 spinal metastases of renal origin underwent surgery without embolization. The effect of preoperative embolization, of completeness of embolization, and of particle size on the estimated intraoperative blood loss was analyzed using nonparametric statistical tests. RESULTS: Complete embolization was achieved in 10 cases and partial embolization in the other 10. The estimated blood loss of 19 embolized and 11 control cases was available from the surgical report. Median intraoperative blood loss in 19 embolized lesions was 1500 mL (range, 300-8000 mL), compared with 5000 mL (range, 1440-15000 mL) in the control group. Even after partial embolization, blood loss (median, 2000 mL) was significantly lower than in the control group. No significant differences in estimated blood loss were noted between the use of particles smaller than 250 microm and those larger than 250 microm. No embolization-related permanent neurologic deficit or skin or muscle necrosis occurred. CONCLUSION: Preoperative embolization of spinal metastases of renal origin with polyvinyl alcohol particles is safe and might reduce intraoperative blood loss significantly. Even partial embolization seems to be effective.

Aged↗
PubMed2001

Value of high-resolution MR in patients scheduled for cochlear implantation.

OBJECTIVE: To determine sensitivity and specificity of high-resolution MR imaging and of high-resolution axial CT (HRCT) and to compare the two modalities in predicting the surgical and functional success of cochlear implantation. MATERIAL AND METHODS: The presurgical MR images (2D T2W TSE, 3D T2*W CISS, plain and contrast-enhanced 3D T1W MP-RAGE) and axial HRCT findings of 26 patients were evaluated with regard to the predictive value concerning the success of cochlear implantation. RESULTS: We found a high correlation between MR and HRCT and the success of cochlear implantation. In all 26 patients, the MR-based predictions concerning the success of cochlear implantation were correct. In 10 patients, MR gave additional information to HRCT. In all patients, MR gave sufficient information about the status of the inner ear, inner auditory canal and cochlear nerve to aid the surgeon during the operation. CONCLUSION: A high-resolution MR protocol consisting of coronal 2D T2W TSE, 3D T2*W axial CISS, plain and contrast-enhanced sagittal T1W 3D MP-RAGE is recommended for the evaluation of candidates scheduled for cochlear implantation. It provides information which cannot be obtained by HRCT.

Adolescent↗
PubMed2000

Intraoperative ultrasonography versus helical computed tomography and computed tomography with arterioportography in diagnosing colorectal liver metastases: lesion-by-lesion analysis.

Helical computed tomography with arterioportography (CTAP) and intraoperative sonography (IOUS) are both recognized to be extremely sensitive in the detection of liver metastases measuring <2 cm in diameter. As sensitivity and specificity values for both techniques differ significantly in the literature and in default of sufficient published data regarding this subject, a lesion-by-lesion analysis was considered necessary. Accuracy of IOUS was compared with helical computed tomography (CT) and portal-phase contrast enhancement (CTAP) in the preoperative detection of liver metastases from colorectal carcinoma projected as a prospective blinded study. Cost efficiency should be determined. Liver CTAP and IOUS were evaluated in 33 patients with colorectal carcinoma. Metastases were resected in 10 cases, and the remaining 23 patients were observed for follow-up with CT investigations every 3 months for a period of 1 year. CTAP and IOUS detected all 13 lesions measuring 5-10 mm (13/13). One metastasis measuring >10 mm was missed by IOUS. CTAP presented an ideal sensitivity of 100%, but specificity was as low as 68%. IOUS sensitivity was 98% and specificity was 95%. IOUS and CTAP are of comparable value regarding the detection of liver metastases <10 mm. Both techniques may be used if resections of synchronous or metachronous metastases are planned in order not to miss limiting small lesions and to prevent superfluous liver surgery. Helical CT scan with dynamic intravenous contrast enhancement is considered the most cost-effective preoperative staging method, although local staging may not be achieved because of insufficient intraabdominal survey.

Adult↗
PubMed2000

Digital radiography of the skeleton using a large-area detector based on amorphous silicon technology: image quality and potential for dose reduction in comparison with screen-film radiography.

AIM: The purpose of this study was to evaluate a large-area, flat-panel X-ray detector (FD), based on caesium-iodide (CsI) and amorphous silicon (a-Si) with respect to skeletal radiography. Conventional images were compared with digital radiographs using identical and reduced radiation doses. MATERIALS AND METHODS: Thirty consecutive patients were studied prospectively using conventional screen-film radiography (SFR; detector dose 2.5 microGy). Digital images were taken from the same patients with detector doses of 2.5, 1.25 and 0.625 microGy, respectively. The active-matrix detector had a panel size of 43 x 43 cm, a matrix of 3 x 3K, and a pixel size of 143 microm. All hard copies were presented in a random order to eight independent observers, who rated image quality according to subjective quality criteria. Results were assessed for significance using the Student's t -test (confidence level 95%). RESULTS: A statistically significant preference for digital over conventional images was revealed for all quality criteria, except for over-exposure (detector dose 2.5 microGy). Digital images with a 50% dose showed a small, statistically not significant, inferiority compared with SFR. The FD-technique was significantly inferior to SFR at 75% dose reduction regarding bone cortex and trabecula, contrast and overall impression. No statistically significant differences were found with regard to over- and under-exposure and soft tissue presentation. CONCLUSION: Amorphous silicon-based digital radiography yields good image quality. The potential for dose reduction depends on the clinical query.

Aged↗
PubMed2000

[3D CISS, 3D MP-PAGE and 2D TSE for the preoperative MRI prior to cochlear implantation].

PURPOSE: The aim of this study was to determine the presurgical predictive value of high resolution MRI in patients scheduled for cochlear implantation. METHOD AND MATERIAL: The presurgical MRI (3D CISS, 3D MP-RAGE with and without i.v. contrast medium, 2D TSE) findings of 54 patients and the intraoperative situation reported by the surgeon were compared retrospectively. The surgical and functional success of the cochlear implantation was evaluated. RESULTS: We found a high degree of correlation between MRI and intraoperative findings concerning the patency of the whole cochlea and anomalies as well as in the diagnosis of pathology of the cochlear, vestibular and facial nerves and in anomalies of the internal auditory canal. However, in four out of 54 patients there was a false negative prediction regarding the patency of the cochlea. The sensitivity was 50% (4/8), the specificity 100% (46/46). Concerning the surgical success the accuracy was 100%. In all patients MRI gave sufficient anatomical information to the surgeon concerning the jugular bulb and the facial nerve. CONCLUSION: A high-resolution MRI protocol consisting of coronal 2D T2w TSE, 3D T2*w transverse CISS; plain and contrast enhanced sagittal T1w 3D MP-RAGE is recommended for the evaluation of candidates scheduled for cochlear implantation.

Adolescent↗