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M Unterweger

Publications and source records attributed to M Unterweger.

36 records · Page 2Linked to original sources
PubMed2005

Test of radiation detectors used in homeland security applications.

This work was performed as part of the National Institute of Standards and Technology (NIST) program to support the development of the new American National Standards Institute (ANSI) standards N42.32-2003 and N42.33-2003 for hand-held detectors, and personal electronic dosimeters, as well as to support the Office of Law Enforcement Standards (OLES) and the Department of Homeland Security (DHS) in testing these types of detectors for their use by first responders. These instruments are required to operate over a photon energy range of 60 keV to 1.33 MeV and over a wide range of air-kerma rates. The performance and response of various radiation detectors, purchased by the NIST, was recorded when placed in 60Co, 137Cs, and x-ray beams at different air-kerma rates. The measurements described in this report were performed at the NIST x-ray and gamma-ray radiation calibration facilities. The instruments' response (exposure or dose rate readings) shows strong energy dependence but almost no dependence to different air-kerma rates. The data here reported provide a benchmark in support of current protocols that are being developed for radiation detection instrumentation used in homeland security applications. A future plan is to test these devices, plus other commercially available detectors, against ANSI standards N42.32-2003 and N42.33-2003.

Benchmarking↗
PubMed2004

[CME radiology 4].

Explore the source record for details and available documents.

Diagnosis, Differential↗
PubMed2002

[Vaginal granulocytic sarcoma: CT and MR imaging].

A 30-year-old female patient with vaginal bleeding was referred to the gynecological unit of our hospital. Speculum examination showed a lobulated tumor, 5 cm in size, at the vaginal fornix. MRI demonstrated a tumor encompassing the ventral part of the vagina and the entire cervix. Computed tomography diagnosed pathologically enlarged mediastinal lymph nodes. Subsequent examinations revealed an acute myeloic leukemia, synchronous histopathological examination of the vaginal tumor led to the rare diagnosis of a granulocytic sarcoma.

Adult↗
PubMed2002

Three-dimensional dynamic MR-hysterosalpingography; a new, low invasive, radiation-free and less painful radiological approach to female infertility.

BACKGROUND: The purpose of this study was to propose a new method for imaging the uterine cavity and Fallopian tube patency by three-dimensional dynamic magnetic resonance hysterosalpingography (3D dMR-HSG) and to analyse if, by using a higher viscosity contrast solution, direct visualization of the Fallopian tubes may be achieved by this new technique. METHODS: 10 consecutive infertile women underwent 3D dMR-HSG and conventional HSG as gold standard. 3D dMR-HSG consisted of injection of 20 ml of a gadolinium-polyvidone solution into the uterine cavity while acquiring five consecutive three-dimensional (3D) T1-weighted MR-sequences. RESULTS: In three patients the catheter became dislodged during 3D dMR-HSG. However, in one of these patients the examination was still partially diagnostic. Imaging findings of 3D dMR-HSG showed good correlation with conventional hysterosalpingography and allowed 3D imaging of the uterine cavity and of Fallopian tube patency in 8/10 patients and direct visualization of the Fallopian tubes in 5/7 patients. CONCLUSION: 3D dMR-HSG represents a new and promising imaging approach to female infertility causing less pain and avoiding exposure of the ovaries to ionizing radiation. By using a higher viscosity MR-contrast agent it allows not only visualization of uterine cavity and Fallopian tube patency but also direct visualization of Fallopian tubes.

Adult↗
PubMed2001

Bladder outflow obstruction caused by prostate metastasis in a young male.

A 38-year-old male patient presented with symptoms of bladder outflow obstruction. Rectal palpation revealed a giant prostate. Sonography only confirmed the enlarged prostate. Magnetic resonance imaging showed, on both T1- and T2-weighted sequences, a large, inhomogenously hypointense, encapsulated prostate tumor encompassing the entire prostate. No capsular penetration or seminal vesicle invasion was seen. Transurethral biopsy of the prostate was performed. Histology demonstrated a prostate metastasis of colorectal carcinoma.

Adenocarcinoma↗
PubMed2001

Ultrafast MR imaging of the pelvic floor.

OBJECTIVE: The aim of this study was to compare pelvic floor anatomy and laxity at rest and on straining (Valsalva's maneuver) using dynamic ultrafast MR imaging in women who were continent versus those with stress incontinence differing in obstetric history. MATERIALS AND METHODS: Thirty continent women were divided into three equal groups (nulliparous, previous cesarean delivery, previous vaginal delivery) and compared with 10 women with stress-incontinence with a history of at least one vaginal delivery. MR imaging of the pelvic floor at rest and on maximal strain was performed, using axial T2-weighted fast spin-echo images followed by sagittal ultrafast T2-weighted single-shot fast spin-echo sequences. Mean population age (age range, 22-45 years; mean +/- SD, 36 +/- 5.4 years), was similar in the four groups, as was parity in the three parous groups. RESULTS: Mean distances between the bladder floor and pubococcygeal line at rest did not differ between the four groups. On straining, bladder floor descent was 1.1 +/- 0.9, 1.0 +/- 1.1, and 1.9 +/- 0.9 cm in continent nulliparous, cesarean delivery, and vaginal delivery women, respectively, versus 3.2 +/- 1.0 cm in incontinent women (p = 0.0005). Cervical descent was greater in incontinent versus nulliparous women (p = 0.0019). Bladder floor descent was greater in the continent vaginal delivery group than in continent cesarean delivery control patients (p = 0.04). In patients with stress incontinence, symptoms did not correlate with amplitude of descent. The right levator muscle was thinner overall than the left, regardless of frequency direction (p = 0.001). CONCLUSION: Ultrafast MR imaging using the T2-weighted single-shot fast spin-echo sequence allows dynamic evaluation of the pelvic compartments at maximal strain with no need for contrast medium. Pelvic floor laxity and supporting fascia abnormalities were most common in patients with stress incontinence followed by continent women with a history of vaginal delivery. The results are therefore compatible with the hypothesis of vaginal delivery as a contributory factor to stress incontinence in older parous women.

Adult↗
PubMed2000

[Breast imaging after augmentation with homologous adipose tissue implant].

The implantation of cadaveric fat for breast augmentation, which has been performed up to the Seventies, is nowadays considered obsolete. Since complications frequently arise many years later, we are, however, occasionally confronted with the problematic consequences of the technique. The present case report describes the clinical, mammographic and for the first time to our knowledge MR-mammographic findings of a mammoplasty with cadaveric fat in a 57-year-old patient with a history of breast cancer.

Adipose Tissue↗
PubMed2000

Spiral CT in an acute spontaneous aorto-caval fistula.

A patient with a known infrarenal atherosclerotic aneurysm measuring 8 cm presented with sudden dyspnoe, lower back pain and enormous venous congestion of the lower extremities. Spiral CT rendered precise diagnosis and localisation of a large and acute spontaneous aorto-caval fistula and made early surgical intervention possible. Abdominal aorto-caval fistulas are rare complications and can occur after surgery, trauma or spontaneously in an atherosclerotic or inflammatory aneurysm. Spiral CT enables a rapid and precise diagnosis facilitating the planning of the therapeutic approach to this complication.

Acute Disease↗
PubMed1999

[Krukenberg syndrome in metastatic gallbladder adenocarcinoma with unknown primary tumor].

The casuistic describes a female patient, in whom a metastatic adenocarcinoma of the ovary was diagnosed 3 years after cholecystectomy due to cholecystolithiasis, which was compatible with metastases of a carcinoma of the gallbladder or the bile ducts. While clinical and imaging results suggested a primary ovarian carcinoma with inapparent primary tumor, the final diagnosis was obtained on the basis of histological findings. The case demonstrates that an ovarian metastasis can simulate a primary tumor according to clinical and imaging results. This fact can be of serious therapeutic consequences for the respective patient. Therefore, in the presence of a clinically inapparent primary tumor, the differential diagnosis of unclear ovarian masses should include metastatic adenocarcinoma in addition to primary ovarian carcinoma and other ovarian lesions.

Adenocarcinoma↗
PubMed1996

MR venography of the calf: value of flow-enhanced time-of-flight echoplanar imaging.

OBJECTIVE: Release of a tourniquet on the thigh and termination of Valsalva's maneuver result in a transient increase in venous blood flow in the leg. The purpose of this study was to determine the value of time-of-flight echoplanar imaging performed with these flow-enhancing methods to image the veins of the calf. SUBJECTS AND METHODS: Flow volumes in the femoral veins in eight volunteers were determined with a two-dimensional phase-contrast MR imaging technique before and immediately, 20, 40, and 60 sec after termination of Valsalva's maneuver and thigh vein occlusion. Subsequently, the calf veins of 11 healthy volunteers were imaged with a two-dimensional four-shot echoplanar MR imaging technique. Forty-one 5-mm-thick sections were obtained over 10 sec immediately after termination of venous occlusion. Visibility of the three venous bundles was analyzed in the proximal, middle, and distal portions of the calf on the basis of a four-point scale. Finally, the calf of a single patient with documented DVT was imaged by the same MR imaging technique. RESULTS: Both Valsalva's maneuver and venous occlusion caused significant increases in venous flow (p < .05) only during the first 20 sec after termination of the maneuver and the occlusion. Venous occlusion had a significantly greater effect than did Valsalva's maneuver (p < .05). Flow augmentation by venous occlusion of the thigh improved calf vein visualization with time-of-flight echoplanar MR imaging (p < .0001). Of the 99 calf vein segments examined, 93 were clearly seen. Thrombi were seen in the patient study. CONCLUSION: Multishot time-of-flight echoplanar imaging can exploit the short-lived effect of mechanical flow-enhancing measures, resulting in good visualization of calf veins. The true diagnostic impact of this technique needs to be evaluated in a patient study.

Adult↗
PubMed1994

Cardiac volumetry. Comparison of echoplanar and conventional cine-magnetic resonance data-acquisition strategies.

RATIONALE AND OBJECTIVES: Ejection fraction (EF) measurements obtained using conventional cine-magnetic resonance imaging (MRI) are accurate but time-consuming. With echoplanar imaging (EPI), these data can be acquired much faster. In this study, EF and cardiac output (CO) measurements based on EPI data are compared with those measurements based on cine-MRI images. METHODS: Twelve subjects were examined on a 1.5-T imager equipped with a special EPI gradient system. The entire heart was imaged with contiguous axial 10-mm sections using cine-MRI and EPI techniques. With cine-MRI, 20 frames were acquired over 256 cardiac cycles; with EPI, 24 frames were obtained over four RR intervals using an electrocardiogram-triggered four-shot acquisition strategy. Ejection fraction and CO were calculated based on the summation of the individual end-systolic and end-diastolic volumes. Ejection fraction and CO measurements based on the two different data sets were compared. RESULTS: Multishot EPI was 50 times faster than cine-MRI. The short acquisition time permitted breath-hold imaging. The high temporal (16 to 24 frames/RR interval) and spatial resolution (1.56 x 1.56 mm in plane) of the multishot EPI images enabled delineation of the ventricular lumen at end-systole and end-diastole in a fashion similar to cine-MRI. Echoplanar imaging EF and CO measurements correlated well with cine-MRI EF measurements, with correlation coefficients of 0.96 and 0.94, respectively. The 95% confidence interval of the EF measurement differences between the two techniques was narrow, ranging from -5.2 to 5.7 EF percentage points. CONCLUSIONS: Accurate volumetric EF and CO measurements are possible based on ultrafast multishot EPI data sets as part of an integrated MRI-based cardiac evaluation.

Adult↗