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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
PubMed1999

Effective contrast use in CT angiography and dual-phase hepatic CT performed with a subsecond scanner.

OBJECTIVE: To deduce an optimal injection protocol for CT angiography and fast dual-phase hepatic CT. METHODS: Fifty-two patients underwent fast dual-phase hepatic CT using one of three different injection protocols: A (0.9 g/sec iodine injection rate, 36 g dose); B (1.35 g/sec, 30 g); C (1.6 g/sec, 40 g). Aortic attenuation time curves as well as aorta-to-liver contrast and hepatic enhancement time curves obtained by region of interest measurements along the helical axis were analyzed. RESULTS: Protocol C revealed a significantly higher peak in aortic attenuation and hepatic enhancement than the other protocols. Approximately 50 seconds after the bolus injection, hepatic enhancement declined to a plateau similar to that seen with the other protocols. In terms of the areas under the curves of the aorta-to-liver contrast and hepatic enhancement dynamics, protocol C was significantly superior to the other protocols. CONCLUSIONS: A high iodine injection rate realized by a high iodine concentration in conjunction with fast dual-phase scanning (total scan time < 50 seconds) promises to enhance CT angiography and contrast of liver lesions.

Angiography↗
PubMed1999

New formula for quantification of pleural effusions from computed tomography.

The authors develop a method to accurately and easily estimate the volume of pleural effusions with computed tomography (CT). In 15 patients with either simple or loculated pleural effusions (14 right-sided and 11 left-sided), routine helical CT examinations of the thorax were obtained. Two experienced radiologists visually estimated the volume of the effusions. Three-dimensional reconstructions of the pleural effusions were performed from the helical CT examinations, and the volumes of the effusions were calculated. Effusion volumes were also estimated using the formula d2 x l (d = greatest depth of the effusion on a single CT image, l = greatest length of the effusion). The computer calculated the estimated volumes and they were then statistically compared. The coefficient of correlation between the estimation by measurement and calculated volumes of all effusions was 0.908 (p<0.0001) for the right side, and 0.849 for the left side (p<0.002). Excluding the loculated effusions, the coefficient of correlation was 0.969 for the right side and 0.949 for the left side (p<.001). The volume estimation by visual inspection was also correlated to the calculated volumes (0.84 on the left and 0.85 on the right, p<0.008), but resulted in a consistent overestimation by 300 ml to 500 ml. Although pleural effusion volumes can be estimated by visual inspection with good correlation, some overestimation is consistently seen. Use of the formula d2 x l readily enables estimation of pleural effusion volume from CT, from two simple measurements. This formula-based method of volume estimation provides an accurate and easily measured means of estimation that is readily obtained from routine CT of the chest.

Humans↗
PubMed1999

Electrocardiographically gated thin-section CT of the lung.

PURPOSE: To determine whether electrocardiographic (ECG) gating improves image quality of thin-section computed tomographic (CT) scans of the lung obtained with a subsecond CT scanner. MATERIALS AND METHODS: Thin-section CT was performed in 35 patients by using standard techniques. Three additional sections were obtained in each patient with prospective ECG gating at corresponding levels of the paracardiac lung parenchyma. Non-ECG-gated and ECG-gated sections were then rated in blinded fashion by three experienced radiologists for overall image quality, spatial resolution, and diagnostic value and for different types of respiratory and cardiac motion artifacts. RESULTS: ECG gating helped significantly reduce artifacts caused by cardiac motion (i.e., distortion of pulmonary vessels, double images, or blurring of the cardiac border) (P < .05). ECG gating did not reduce respiratory motion artifacts. In patients with heart rates of less than 76 beats per minute, ECG gating significantly improved overall image quality (P = .041). ECG gating was not perceived to increase the diagnostic value of thin-section CT scans. CONCLUSION: ECG gating improves image quality of thin-section CT scans of the lung by reducing cardiac motion artifacts that may mimic disease. It must be established whether ECG gating can help increase the diagnostic accuracy of thin-section CT for the evaluation of subtle parenchymal disease.

Adult↗
PubMed1998

Comparison of sequences for depicting bone marrow alterations in osteomyelitis applied in a low field strength magnetic resonance imaging system.

OBJECTIVE/PATIENTS: To investigate the efficacy of standard sequences of a low field system for the detection of osteomyelitis, we tested T1wI pre and post i.v. contrast, T2w and fat suppressed IR sequences. DESIGN: On the basis of clinical and laboratory evidence, pathology reports, and three phase granulocyte scintigraphy, osteomyelitis was diagnosed in 18 of 21 patients with Charcot's joints. A consecutive low and high field magnetic resonance (MR) scan confirmed osteomyelitic bone marrow changes in the same osseous regions. These 18 diabetic patients were then studied on a 0.2 Tesla dedicated MR system (Esaote ArtoScan) using T1wI (SE: relaxation time (TR) 520/echo time (TE) 24: axial and coronal) before and after i.v. application of 0.1 mmol/l Gd-DTPA/kg BW, T2w imaging (TSE: TR 3500/TE 80 or TR 2000/TE 120: axial), and fat suppressed inversion recovery (IR) imaging (short tau inversion recovery (STIR): TR 3000/TE 30/TI 80 or inversion recovery gradient echo (IRGE)/fat suppressed IRGE (GEFS): TR 1000/TE 16m 80: coronal). RESULTS: The SE T1w sequence showed a significantly higher contrast-to-noise ratio (CNR) before administration of i.v. contrast. The TSE T2w pulse sequence demonstrated bone marrow changes superiorily utilizing a TE of 120 ms (CNR = 16.5+/-2.7 compared to 5.5+/-2.5 with TE = 80 ms). The IRGE showed a higher CNR than the standard STIR (CNR = 19.2+/-2.5 compared to 12.4+/-2.9). CONCLUSION: Fat suppressed IRGE imaging and longer TE in T2w TSE sequences result in a significantly better CNR in osteomyelitis. This way, using optimized sequences, low field systems are apt to depict bone marrow changes in the course of osteomyelitis.

Adolescent↗
PubMed1998

[MRI of the small intestine with rapid MRI sequences in Crohn disease after enteroclysis with oral iron particles].

PURPOSE: To evaluate the efficacy of breathhold MRI following enteroclysis with addition of oral magnetic particles to study the extension, detection of stenoses and extraluminal manifestations in Crohn's disease. MATERIAL AND METHODS: 18 patients with Crohn's disease and potential of surgical intervention were studied with enteroclysis with addition of oral magnetic particles. T1-/T2-weighted breathhold MRI w/o spectral fat suppression w/o i.v. Gd-DTPA was applied. RESULTS: Typical findings were marked bowel wall thickening with strong contrast enhancement. 95.8% of affected small bowel segments and 94.7% of stenoses were correctly detected by MRI. All four fistulas were detected and important extraluminal findings were seen in 6/18 patients. Additionally, one ileoileal and two ileosigmoidal adhesions, two extraluminal abscesses and affection of the right ureter were delineated. CONCLUSION: MRI in Crohn's disease offers the potential to avoid radiation exposure in this relatively young patient group. Important additional findings relevant to indication of surgery are seen in approximately one third of cases. The replacement of transduodenal intubation by oral contrast application remains to be further studied.

Administration, Oral↗
PubMed1998

[Focal liver diseases].

INTRODUCTION: Advanced therapies are improving significantly the survival of patients with malignant focal liver disease. For efficient implementation of these surgical and interventional techniques a clear concept of the diagnostic procedure is mandatory. METHODS: Based on a review of the current literature, the different imaging modalities, including ultrasound, computed tomography, magnetic resonance tomography, nuclear medicine and angiography, are discussed and evaluated for their diagnostic efficacy in focal hepatic disease. RESULTS: Considering clinical, diagnostic, and economical appropriateness, recommendations for diagnostic strategies in different clinical scenarios regarding focal heptic disease are presented. CONCLUSION: If the power of specific imaging methods are relevant clinical information is known, problem-based diagnostic strategies help to avoid unnecessary, expensive and time-consuming studies in the work-up of focal liver lesions.

Carcinoma, Hepatocellular↗
PubMed1998

[Vena cava filter. Indications, complications, clinical evaluation].

INTRODUCTION: Pulmonary embolism is the third leading cause of death in the western countries. If anticoagulation fails or is contra-indicated, or if the risk for pulmonary embolism is increased for other reasons, the percutaneous implantation of a vena cava filter should be considered. METHODS: The available filters can be differentiated by the design (cone, basket, net-types), by the material, and by their removability. The rate of complications (caval thrombosis, fracture of filter) and the in vitro efficacy in trapping thrombotic clots is dependent on the specific filter type. RESULTS: In clinical practice there is no evidence for significant differences in trapping efficacy among the different filters. About 4% of all patients treated by caval filters still can have pulmonary embolism, and 1% will have a fatal outcome. Dependent on the filter type, the most common complication is caval thrombosis, in up to 25% of cases. CONCLUSION: The percutaneous implantation of caval filters can readily be performed by interventional radiologists. However, randomized clinical studies failed to clearly document efficacy of caval filters. Therefore, indication has to be considered carefully.

Humans↗
PubMed1998

[Diagnosis of pulmonary embolism with spiral and electron-beam CT].

PURPOSE: To compare spiral (SCT) and electron-beam CT (EBT) for the diagnosis of pulmonary embolism (PE). MATERIALS AND METHODS: From June 1997 to June 1998 188 patients with suspected acute or chronic thromboembolism of the pulmonary arteries were examined. A total of 108 patients were scanned using SCT and 80 patients using EBT. On each scanner two different scan protocols were evaluated. RESULTS: PE was diagnosed in 38 patients using EBT and in 49 patients using SCT. Especially with EBT, isolated peripheral emboli could be confidently diagnosed. When EBT and SCT were compared for the analysis of peripheral pulmonary arteries, some paracardiac segmental and subsegmental vessels were significantly better analyzable with EB. Additional or diseases other than PE were diagnosed in 112 patients. Other diagnoses included bronchial carcinoma and aortic dissection. CONCLUSIONS: Advanced CT scanning techniques allow the highly accurate diagnosis of central and peripheral PE. Other potentially life-threatening underlying diseases are also readily recognized.

Aortic Dissection↗
PubMed1998

[The filmless hospital--a legal challenge].

PURPOSE: This article concerns the legal aspects of digital archiving of radiological images, in particular with regard to the resolution passed by the 37th Committee meeting of the Federal Board of "RöV" (x-ray ordinance). Concepts of filmless hospitals must therefore be tested for compliance with all present legal requirements. MATERIAL AND METHODS: The literature concerning the legal aspects of digital medical archiving of x-ray documents is reviewed. The concept of a digital archive was compared with these aspects and tested for compliance with the respective legal rules. RESULTS: There are no legal obstacles to realizing our concept of a filmless hospital. However, there are no civil court rulings on record, since there have not been any legal proceedings to date. CONCLUSIONS: There are no legal objections to a complete digital archiving in a hospital in the absence of any court rulings to the contrary.

Confidentiality↗
PubMed1998

[Differential diagnosis of erosive osteochondrosis and bacterial spondylitis: magnetic resonance tomography (MRT)].

PURPOSE: To evaluate retrospectively criteria in the differential diagnosis of erosive osteochondrosis (EO) and infectious spondylitis (IS) on the basis of MRI. METHODS: T1-weighted sagittal images before and after Gd-DTPA application, T2-weighted TSE or T-STIR images of 23 patients with proven 15 and 41 patients with EO were evaluated. Criteria for this evaluation were morphology and extension of bone marrow edema, visibility of the low-intensity vertebral endplate, contrast enhancement and signal intensity in the disc space on T2-weighted and T-STIR images. RESULTS: Bone marrow edema was more extensive in IS than in EO. The mean rated value for bone marrow edema on a four-level scale (0-3) was for IS 2.91 (+/- 0.29), for EO 1.32 (+/- 0.76, p < 0.001). In 37/41 cases of EO and in 22/23 cases of IS Gd-DTPA enhancement was found in the disc space (n.s.). In EO the low intensity endplate was visible in all parts in 36/41 cases (87.8%) on T1-weighted images, in IS not in a single case (0%). On T2-weighted or STIR images signal intensity of the discs was decreased in 82.1% of EO, 82.6% of segments in IS had water-equivalent signal intensity (p < 0.001). CONCLUSION: If all the criteria are taken into consideration differential diagnosis of EO and IS on the basis of MRI findings is possible.

Adult↗
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↗