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Biomedical subjects

T Helmberger

Publications and source records attributed to T Helmberger.

At least 55 records · Page 3Linked to original sources
PubMed1998

Breath-hold MR cholangiography with snapshot techniques: prospective comparison with endoscopic retrograde cholangiography.

PURPOSE: To compare findings with magnetic resonance (MR) cholangiography with rapid acquisition with relaxation enhancement (RARE) and half-Fourier acquisition with single-shot turbo spin-echo (hereafter, half Fourier RARE) snapshot imaging techniques to those with endoscopic retrograde cholangiography (ERC). MATERIALS AND METHODS: Heavily T2-weighted thick-section (RARE) and thin-section (half-Fourier RARE) MR cholangiography were performed prospectively, on a 1.5-T imager, in the biliary tree of 61 consecutive patients before ERC. Findings at ERC were considered the standard of reference. The radiologist and endoscopist were blinded to each other's report. On- and off-site MR cholangiographic readings were performed to detect stones (n = 24), biliary dilatation (n = 34), or stenosis (n = 36). RESULTS: The sensitivity and specificity of MR cholangiography, respectively, calculated on a lesion-by-lesion basis, were 92.3% and 95.8% for cholangiolithiasis, 94.1% and 92.6% for duct dilatation, and 88.8% and 84.0% for stenosis. With snapshot MR cholangiography, on a patient-by-patient basis, differentiation between normal (n = 15) and abnormal (n = 46) results yielded a sensitivity of 92.4%, a specificity of 83.4%, and a positive predictive value of 95.6%. Pitfalls were caused by flow artifacts, compression by vessels, and low contrast between calculi and surrounding parenchyma. CONCLUSION: Snapshot MR cholangiography allowed noninvasive, accurate detection of biliary stones, strictures, and dilatation similar to that with ERC. Discrepancies regarding low-grade dilatation and strictures had no clinical relevance at retrospective review.

Bile Duct Diseases↗
PubMed1998

Three-dimensional volumetric assessment of abnormally low attenuation of the lung from routine helical CT: inspiratory and expiratory quantification.

OBJECTIVE: The purpose of this investigation was to quantitatively assess abnormally low attenuation of the lung by use of three-dimensional volumetric reconstructions from routine helical CT and to assess their correlation with pulmonary function tests. MATERIALS AND METHODS: Helical CT was performed in 100 patients in full inspiration. Examination was also performed in full expiration in 53 of these patients. Three-dimensional volumetric reconstructions were performed for total lung volumes at inspiration and at expiration, with a threshold of -896 H on inspiratory CT and -790 H on expiratory CT, to quantify emphysematous change. Correlation was made with pulmonary function tests in 79 patients. RESULTS: CT volumetric assessments of abnormally low attenuation of the lung at inspiration and expiration had a high correlation (r2 = .84, p < or = .0001). In comparison with pulmonary function tests, both inspiratory low attenuation of the lung and expiratory low attenuation of the lung correlated well with the logarithm of the ratio of the forced expiratory volume in 1 sec (FEV1) to the forced vital capacity (r2 = .74, p < or = .0001 and r2 = .74, p < or = .0001, respectively) and with the percentage of predicted ratio of the FEV1 to the forced vital capacity (r2 = .69, p < or = .0001 and r2 = .69, p < or = .0001, respectively). Linear correlations were also seen with FEV1, residual volume, and forced residual capacity. CONCLUSION: Three-dimensional volumetric reconstructions of hypoattenuating lung correlate well with pulmonary function tests. In addition, inspiratory and expiratory data are also correlative, suggesting that a dedicated expiratory examination is not needed. This easily obtainable information will prove useful for patients with obstructive lung disease from emphysema, providing a measure of pulmonary function status in this population.

Adolescent↗
PubMed1998

[Preoperative marking of non-palpable mammary lesions on the magnetic resonance image using a body coil].

PURPOSE: To evaluate the efficacy of a MRI localization procedure using a non-dedicated body coil in lesions only visible in MRI. MATERIAL AND METHODS: In 18 patients, we performed a contrast enhanced (i.v. 0.2 mmol Gd-DTPA/kg b.w.) breast MRI on a 1.0 Tesla system (Magnetom Impact, Siemens, Erlangen, Germany) using a body coil and a GRE 3D sequence. In prone position, the patients were placed in a customized positioning device offering lateral access to the breast. The localizations were done with a MRI-compatible wire (n = 21). In addition, all patients underwent the same imaging protocol using a dedicated breast coil (without localization). For both MRI modalities, the signal intensities of the lesion, the normal breast tissue, and the background noise were measured. The lesion-to-fat contrast (LFC), the lesion-to-fat contrast (LFC), the lesion-to-breast tissue contrast (LBC) and the percentage of signal change pre and post contrast administration were calculated and compared. The localisation results were correlated to pathologic findings. RESULTS: There was no difference in lesion detection (lesion size: 0.5 to 1.2 cm) between the body coil and the dedicated breast coil. Regarding the LFC and LBC, the body coil was superior to the dedicated breast coil (no statistical significance). However, the background noise was higher using the body coil. In all cases the localisation was successful. CONCLUSION: In our preliminary experience, detection of breast lesions and wire-localization of the lesion by MRI is efficient and reliable using a non-dedicated body coil.

Adult↗
PubMed1997

A comparison of pulse sequences in the detection of post-traumatic bone marrow abnormalities at low field strength MRI.

OBJECTIVE AND PATIENTS: One hundred and forty-one patients with recent joint trauma, aged 12-71 years, were imaged on a 0.2-T dedicated MRI system and evaluated for bone bruises. The most beneficial sequences were compared. DESIGN: The diagnosis of post-traumatic bone marrow abnormalities was established in 20 of 141 patients on the basis of decreased signal intensity on T1-weighted SE and GRE sequences and increased signal intensity on T2-weighted TSE and fat-suppressed IRGE sequences. Signal changes within the bone marrow were evaluated and statistically correlated with normal bone. RESULTS: The highest signal alteration was found on T1-weighted SE and GRE sequences, followed by IRGE, which detected smaller differences in signal intensity. T2-weighted TSE imaging showed the least contrast. The areas with bone marrow changes were approximately equal in size on T1-weighted SE and T2-weighted TSE sequences. The same areas depicted on IRGE and GRE sequences proved to be significantly larger (P < 0.01). CONCLUSION: Using a 0.2-T dedicated system T1-weighted SE, T1-weighted GRE and IRGE sequences were most effective in detecting conspicuous bone marrow alteration, while the T2-weighted TSE sequence was inferior. GRE and IRGE imaging showed areas about 4 times larger depicting bone marrow changes. On suspicion of bone bruise, a protocol including GRE and IRGE pulse sequences could be most beneficial.

Adolescent↗
PubMed1997

The arterioportal fistula syndrome: clinicopathologic features, diagnosis, and therapy.

BACKGROUND & AIMS: Arterioportal fistulas (APFs) are rare vascular disorders of the mesenteric circulation. The aim of this study was to determine the etiology, anatomical location, and main symptom at presentation of APFs, and analyze the various modes of treatment. METHODS: The etiology, clinical presentation, radiographs, and treatment of 12 patients with APFs are reported in detail, and another 76 cases published since 1980 are reviewed. RESULTS: APFs result from trauma (n = 25, 28%), iatrogenic procedures (n = 14, 16%), congenital vascular malformations (n = 13, 15%), tumor (n = 13, 15%), aneurysm (n = 12, 14%), and other causes (n = 11, 12%). The origin of APFs is the hepatic artery in the majority of patients (n = 56, 65%). The main symptoms at presentation are lower or upper gastrointestinal bleeding (n = 29, 33%), ascites (n = 23, 26%), heart failure (n = 4.5%), or diarrhea (n = 4.5%). Radiological intervention provides definitive treatment in 42% (n = 33) of patients, whereas the remainder are treated by surgery alone (n = 27, 31%) or a combination of radiological intervention and surgery (n = 8, 9%). CONCLUSIONS: APFs result in a protean syndrome variously combining portal hypertension and other hemodynamic imbalances (heart failure, intestinal ischemia). Single or multiple interventional radiological procedures using arterial and/or venous approaches allow definitive treatment of most APFs. With increasing technological advances, it is anticipated that surgery will only be indicated in rare instances after failure of radiological intervention(s).

Adolescent↗
PubMed1997

[Lymph node staging in cervix carcinomas: the results of high-resolution magnetic resonance tomography (MRT) with a phased-array body coil].

PURPOSE: To determine the diagnostic value of high resolution MR imaging with a circularly polarised (c.p.) body phased-array coil for the staging of pelvic lymph nodes in cervical carcinoma. MATERIAL AND METHODS: 42 patients with histologically proven carcinoma of the cervix were studied on a 1.5 T scanner by using a c.p. body phased-array coil. The imaging protocol included T2-weighted turbo-spin-echo (TSE) and T1-weighted spin-echo sequences pre and post i.v. application of Gd-DTPA; slice thickness was 5-7 mm and pixel size 0.53 mm2. Lymph nodes with a diameter of > or = 8 mm were considered to have metastatic involvement. MR imaging results were compared with histopathologic findings. RESULTS: MR imaging showed enlarged lymph nodes (> or = 8 mm) in 16 of 18 patients with histologic proof of lymph node metastases (sensitivity 89%). In 22 of 24 cases MR findings were true negative (specificity 92%). Diagnostic accuracy was 91%. CONCLUSION: High-resolution MR imaging with a c.p. body phased-array coil provides high sensitivity, specificity, and diagnostic accuracy for pelvic lymph node staging in cervical carcinoma.

Adult↗
PubMed1997

Pathologic conditions in the small bowel: findings at fat-suppressed gadolinium-enhanced MR imaging with an optimized suspension of oral magnetic particles.

Depiction of small-bowel pathologic conditions was optimized with use of a negative luminal contrast agent, spectral fat suppression, and gadolinium enhancement in an excised gut phantom. The method was applied in nine patients in conjunction with standard enteroclysis examinations. Bulk susceptibility effects of oral magnetic particles were canceled with use of a diamagnetic methylcellulose suspension. In the ileum, fat suppression and contrast between bowel wall and lumen was judged good or excellent in eight and nine patients, respectively. In eight of nine patients, additional mesenteric findings were depicted.

Administration, Oral↗
PubMed1997

[Abdominal arteriovenous and arterio-portal fistulas: etiology, diagnosis, therapeutic possibilities].

PURPOSE: Arterioportal and arteriovenous fistulas (APF, AVF) are rare vascular disorders occurring as a result of congenital vascular malformation, trauma, iatrogenic causes or neoplasms. The clinical spectrum of presentation ranges from symptom-free individuals to patients with severe portal hypertension or congestive heart failure. While the majority of patients have been treated surgically in the past, interventional radiological procedures are being performed with increasing frequency. To prove this trend we reviewed the international literature. REVIEW: We reviewed the clinical presentation and management of 79 cases reported between 1980 and 1996 in the literature and six own patients. RESULTS: Review of the literature and our own six cases show that these fistulas can be divided in intrahepatic (n = 49, 75%) and extrahepatic fistulas (n = 20, 25%). The most important causes are trauma (n = 29, 37%), iatrogenic induced by procedures (n = 21, 27%) and congenital vascular malformations (n = 10, 13%). APFs and AVFs can be diagnosed by ultrasound, computed tomography and magnetic resonance imaging. Angiography confirms the diagnosis and in many cases allows definitive interventional radiologic treatment. CONCLUSION: Management of AVFs and APFs remains a challenge. However, interventional radiologic procedures provide a safe, low-cost, and effective method for treatment. Due to these facts in the last three years we notice an increasing part of interventional procedures for treatment.

Arteriovenous Fistula↗
PubMed1996

[MRI of the pancreas: value, technique and applications].

MR imaging of the pancreas is compromised by several problems: motion artifacts from breathing, cardiac and vascular pulsation, and bowel peristalsis. These limitations can be overcome by modern scanner- and software technology. In the meantime, MRI of the pancreas can compete with well established methods as ultrasound and computed tomography (CT). In addition, new sequences provide imaging modalities comparable to angiography and ERCP. In the future, the value and the efficacy of MRI in comparison to CT, and its clinical impact has to be evaluated in clinical studies. In this article, we review the technical development of MRI of the pancreas, and discuss its clinical use.

Artifacts↗
PubMed1996

[MRI of the pancreas: radiologic-pathologic correlation].

The typical MRI features of the most common pancreatic diseases, such as pancreatitis and adenocarcinoma of the pancreas, have been established. However, even in these common pancreatic disorders, MRI correlation with the underlying pathology is limited for clinical reasons. We emphasize MR-pathological correlation of inflammatory and neoplastic pancreatic changes, including pancreatitis, adenocarcinoma, acinar cell carcinoma, rare cystic and solid pancreatic neoplasms, and islet cell tumors. By highlighting the correlation of key pathological features with MR findings, a better understanding of the MR appearance of pancreatic pathology can be provided. In addition, MRI may prove a powerful tool in detection and characterization of pancreatic tumors.

Adenocarcinoma↗
PubMed1996

[Techniques and applications of MR pancreatography in comparison with endoscopic retrograde pancreatography].

Using heavily T2 weighted sequences, magnetic resonance tomography allows the delineation of the pancreatic duct system with high contrast. The development of fast and ultrafast imaging sequences results in a variety of different technical approaches already published. Aim of this article is the review of the different approaches and results published. In addition, we compare MRP in 34 patients with results of ERP using a snap-shot sequence approach. In this study, MRP has a sensitivity of 83.3% a specifity of 90.9% and accuracy of 83.3% regarding detection of duct changes like stenosis, occlusion and duct dilatation. Our results indicate, that MR-pancreaticography can be a valuable adjunct to MR-imaging of the pancreas.

Adult↗
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

Ring enhancement in ultrasmall superparamagnetic iron oxide MR imaging: a potential new sign for characterization of liver lesions.

OBJECTIVE: We performed this study to evaluate the incidence and significance of ring enhancement after i.v. administration of an ultrasmall superparamagnetic iron oxide (USPIO) particle (Code 7227), a reticuloendothelial contrast agent with potential use as a blood-pool agent, for characterizing focal hepatic lesions. SUBJECTS AND METHODS: Conventional T1-weighed imaging, fat-suppressed T1-weighted imaging, conventional T2-weighted imaging, and fast T2-weighted imaging of the liver were obtained in 27 patients with 43 liver lesions before and after i.v. administration of a USPIO preparation. All lesions were larger than 1 cm; 29 were malignant and 14 were benign. Diagnosis was confirmed in all cases, either pathologically (19 patients) or by follow-up examination (eight patients). Two readers independently evaluated each pulse sequence for the presence of ring enhancement of hepatic lesions. RESULTS: Ring enhancement was noted only on T1-weighted images, with no ring enhancement evident on T2-weighted images. Twenty of 43 (47%) lesions showed ring enhancement, including 18 of 29 (62%) malignant lesions and two of 14 (14%) benign lesions (p < .011); Wilcoxon signed rank test). Fat-suppressed T1-weighted imaging showed ring enhancement better than or equal to conventional T1-weighted imaging in all cases, with ring enhancement of 15 of 18 (83%) malignant lesions and two of two benign lesions better demonstrated on fat-suppressed T1-weighted imaging sequences (p < or = .025). CONCLUSION: Ring enhancement after i.v. administration of Code 7227 is a frequent finding seen more often with malignant than benign lesions, potentially identifying a new MR imaging feature for the characterization of liver lesions. The identification of ring enhancement on T1-weighted images attests to the significant blood-pool effects of USPIO particles.

Contrast Media↗