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Biomedical subjects

B Hamm

Publications and source records attributed to B Hamm.

At least 55 records · Page 3Linked to original sources
PubMed2003

[Dose reduction through gridless technique in digital full-field mammography].

PURPOSE: To determine the role of the scatter grid in digital full-field mammography with respect to image quality and dose and to compare the experimental results with initial clinical experience. MATERIALS AND METHODS: A phantom consisting of 205 fields that enclose gold dots of different thickness and size (CD-Mam phantom, Medical Department, Nijmegen, Netherlands) was used for digital full-field mammography with the conventional grid module and a special gridless module. Four different breast thicknesses were simulated using Plexiglas as scatter material. First, the phantom was exposed at the parameter and dose settings automatically selected in each experimental setup (with and without grid). Subsequently, the phantom was exposed at the different simulated breast thicknesses using the gridless module in combination with the parameters automatically selected for the grid module. This was followed by a series of phantom mammograms obtained with the experimental setup reversed. The 16 mammograms were evaluated by 3 readers and the results compared considering breast thickness, radiation dose, and quality. The gridless module was used for preoperative labeling in 16 patients for comparison of mammograms obtained with and without a grid. RESULTS: For the same entrance dose used in routine mammography, digital mammography without grid is superior to digital mammography with grid when performed on simulated thin breasts (Plexiglas less than 3 cm), with no difference found when performed on simulated large breasts. The advantages of gridless mammography are more pronounced at a markedly reduced entrance dose (identical parenchymal dose without and with grid using the dose automatically selected for the gridless module). This tendency is confirmed by the initial clinical comparison. CONCLUSION: Gridless digital full-field mammography has the potential to reduce the dose further, in addition to already known mechanisms of dose reduction. However, the gridless system must be adjusted (markedly higher "switch-off dose" at the detector) to achieve an overall dose reduction since gridless mammography is inferior to grid mammography for identical doses at the detector plane.

Artifacts↗
PubMed2003

[Sacroiliitis in children with spondyloarthropathy: therapeutic effect of CT-Guided intra-articular corticosteroid injection].

PURPOSE: The prospective investigation of the therapeutic effect of CT-guided intra-articular corticosteroid injection into inflammatory sacroiliac (SI) joints compared to conventional treatment with nonsteroidal anti-inflammatory drugs (NSAIDS) in children with juvenile spondyloarthropathy (jSpA) and the determination of the role of dynamic magnetic resonance imaging (MRI) in establishing the indication and monitoring the therapy. MATERIALS AND METHODS: The study comprises 89 children with known jSpA who were diagnosed by MRI to have a unilateral or bilateral sacroiliitis. Therapy with NSAIDS was initiated or continued in all 89 patients. Four weeks after the diagnostic MRI, two groups were distinguished according to the clinical response to NSAIDS, with group 1 consisting of 33 responders and group 2 of 56 non-responders. The patients of group 2 were treated with CT-guided intra-articular corticosteroid injection (low-dose injection) while the therapy with NSAIDS was continued. A total of 83 SI joints were punctured without complications, 27 bilaterally and 29 unilaterally. The indication for the intervention was based on inflammatory activity as determined by MRI. The therapy was monitored by clinical follow-up every 8 to 12 weeks over a period of 20 months. Follow-up by dynamic MRI was performed in all 56 children of group 2 and in 15 of the 33 children of group 1 within 8 +/- 4 months of the initial examination. RESULTS: A total of 87.5% of the children in group 2 showed a statistically significant decrease in their subjective complaints from 6.9 +/- 3.4 to 1.8 +/- 1.7 (p < 0.05) as measured on a visual analog scale (VAS from 0 to 10). Improvement was seen as early as 1.5 +/- 1.0 weeks after the intervention and lasted for a mean of 12 +/- 6 months. The children in group 1 already showed similar improvement of the VAS from 6.8 +/- 3.2 to 1.5 +/- 1.4 (p < 0.05) during the initial four weeks of NSAIDS therapy, with the improvement lasting for the 20-month observation period. The follow-up dynamic MRI (0.1 mmol/kg body weight) during therapy showed a statistically significant lower contrast-enhancement in both groups (group 1: 117 +/- 43 % versus 38 +/- 24 %, p < 0.05; group 2: 127 +/- 59 % versus 38 +/- 22 %, p < 0.05). One third of the patients of group 2 showed progression of joint destruction despite absence of subjective complaints. CONCLUSION: CT-guided intra-articular corticosteroid injection has proven an effective, symptomatic, and uncomplicated therapy of acute sacroiliitis in patients with jSpA. Dynamic MRI has a role in establishing the indication for intervention but its role for any follow-up is restricted to cases with inconclusive clinical response.

Adolescent↗
PubMed2003

[Quantitative perfusion imaging by multi-slice CT in stroke patients].

OBJECTIVES: Evaluation of a parametric deconvolution algorithm (DA) in the diagnostic assessment of stroke patients by multi- slice spiral computed tomography (MS-CT). MATERIAL AND METHODS: 52 patients (age range 34 - 89 years) with clinically suspected acute ischemia of one hemisphere and no infarct demarcation on plain cerebral CT underwent CT perfusion (CTP), performed on average 3.4 hours after the onset of symptoms by using MS-CT (4 x 8 mm scan volume). Using a DA-based software module, perfusion images of the cerebral blood perfusion (CBP), cerebral blood volume (CBV) and mean transit time (MTT) were calculated and assessed by two readers for visually apparent perfusion abnormalities. Amount and extension of perfusion disturbances were measured and correlated with the outcome. RESULTS: Of 44 patients, in whom perfusion maps could be generated, territorial infarction was confirmed by follow-up in 22 subjects. With a sensitivity of 95 % ischemia could be detected on MTT-maps (CBP 91 %, CBV 77 %). Specificity was highest (100 %) for CBV-maps. Patients with infarction showed significant (p < 0.001) reduction of CBP (10.7 vs. 38.3 ml/100 ml/min), CBV (1.3 vs. 2.3 ml/100 ml) and prolongation of MTT (12.3 vs. 4.3 s) compared to the contralateral hemisphere, whereas in patients without infarction no significant changes were found. Extension of CBV reduction showed the best correlation (r = 0.82) with final infarct volume. CONCLUSION: The DA-based CTP protocol evaluated in this study is a suitable tool for the early identification and quantification of acute cerebral ischemia.

Adult↗
PubMed2003

[MR angiography of the coronary arteries: comparison of the blood pool contrast medium Gadomer and Gd-DTPA in pigs].

AIM: To investigate the signal-enhancing effects of the macromolecular contrast medium Gadomer in MR angiography of the coronary arteries compared to Gd-DTPA. MATERIAL AND METHODS: A total of 15 MRI examinations of the heart were performed in pigs at 1.5 T using a pulse-triggered, segmented 3D FLASH sequence with data acquisition during breathhold before and up to 30 min after contrast medium injection. Gadomer was investigated at two doses (0.05 and 0.1 mmol Gd/kg), Gd-DTPA at one (0.3 mmol Gd/kg) (n = 5 examinations per dose). Standard sequences without magnetization preparation were supplemented by sequences with magnetization saturation applied before data acquisition before and immediately after contrast medium injection. Analysis comprised quantitative determination of blood and myocardium signal to noise (S/N) and contrast to noise (C/N) and qualitative assessment of several parameters of image quality and coronary artery visualization. RESULTS: Gadomer leads to a significant C/N increase between blood and myocardium compared to the unenhanced examination and the increase is longer-lasting than that produced by Gd-DTPA (Gd-DTPA: only directly after injection; Gadomer: up to 5 min post injection at 0.05 mmol Gd/kg, up to 10 min at 0.1 mmol Gd/kg). The qualitative evaluation shows that visualization of the coronary arteries and branch vessels is significantly better with Gadomer at both doses than with Gd-DTPA. Magnetization saturation increases the C/N in combination with Gd-DTPA and at the higher dose of Gadomer with the latter producing a higher increase in C/N values. CONCLUSION: Gadomer is a suitable contrast medium for MR angiography of the coronary arteries with the dose of 0.1 mmol Gd/kg being superior to 0.05 mmol Gd/kg due to a longer imaging window.

Animals↗
PubMed2003

[Imaging of the coronary arteries by means of multislice helical CT: optimization of image quality with multisegmental reconstruction and variable gantry rotation time].

PURPOSE: To evaluate the potential of multisegmental reconstruction and variable gantry rotation time for reducing motion-induced artifacts in coronary artery imaging by multislice helical CT. MATERIALS AND METHODS: The data sets of 20 patients (8 with HR < 60 bpm, 12 with HR > 60 bpm) were analyzed. The patients underwent multislice helical CT (Aquilion 8, Toshiba, Otawara, Japan) using the following parameters: 0.5 mm slice thickness, 250 mA, 120 kV, pitch of 0.25 and variable gantry rotation times of 400, 500, or 600 msec. Images were generated by halfscan and multisegmental reconstruction. In 9 coronary segments of each patient, the presence and severity of motion artifacts were assessed and graded on a scale between 5 (no artifacts) and 1 (heaviest artifacts). RESULTS: Diagnostically relevant motion artifacts were rare at low heart rates (< 60 bpm) for both types of image reconstruction (4 % of all segments). Higher heart rates (> 60 bpm) were associated with an increase in motion artifacts on halfscan reconstructions (33% of all segments, p < 0.05) but not on multisegmental reconstructions (4% of all segments). At low heart rates mean image quality did not differ between multisegmental and halfscan reconstruction (4.28 +/- 0.37 vs. 4.22 +/- 0.41; p > 0.05), whereas at higher heart rates image quality was better for multisegmental reconstruction than for halfscan reconstruction (4.23 +/- 0.47 vs. 3.11 +/- 0.63; p < 0.05). CONCLUSION: Multisegmental reconstruction with variable gantry rotation times suppresses motion artifacts and thus improves assessment of the coronary arteries in patients with higher heart rates.

Artifacts↗
PubMed2003

[Superparamagnetic iron oxide particles: current state and future development].

A wide range of applications for superparamagnetic iron oxide (SPIO) particles as contrast media for MRI has emerged over the last 15 years. SPIO particles can be manufactured with different particle sizes and surface coatings. Large SPIO particles (50-150 nm) predominantly produce a signal decrease or T2 -shortening and are used as contrast media for MRI of the liver and spleen. They have a high accuracy, especially in detecting liver metastases (approved for clinical use: AMI-25 (Endorem or Ferridex), SHU-555A (Resovist)). Smaller particles (about 20 nm in diameter) show a different organ distribution and have a potential for improving noninvasive lymph node assessment or characterizing vulnerable atherosclerotic plaques (in clinical trials: AMI-227 [Sinerem or Combidex]). Particles with an optimized T1-relaxivity and prolonged intravascular circulation time can be used as blood pool contrast media for MR angiography. The currently investigated indications are MR angiography of the trunk, peripheral vessels, and coronary arteries (e.g., SHU-555 C (Supravist), VSOP-C 184). Other applications of small SPIO particles include MRI of the bone marrow and the determination of perfusion parameters in tumors or other tissues like the myocardium. SPIO particles with a modified coat can be used in so-called molecular imaging, such as receptor-directed imaging, cell labeling for in-vivo monitoring of cell migration, e.g., stem cell labeling, and labeling of gene constructs for localization in genetic therapy. In tumor therapy SPIO particles can serve as mediators for hyperthermia. SPIO is a powerful MR contrast medium with manifold applications ranging from diagnostic imaging to molecular medicine.

Animals↗
PubMed2003

[Evaluation of passive cardiomyoplasty using left- and right-ventricular volume measurements by EBCT and MRI in patients with chronic congestive heart failure].

PURPOSE: To evaluate the efficacy of passive cardiomyoplasty with the determination of biventricular volumes, global systolic function as well as left-ventricular muscle mass. MATERIALS AND METHODS: In 19 patients with congestive heart failure of idiopathic or ischemic origin, a polyester mesh-graft was implanted around both ventricles for stabilization and functional support. Before and three months after surgery, 15 patients underwent EBCT and 4 patients with impaired renal function underwent MRI, for the evaluation of the volume and ejection fraction of both ventricles. RESULTS: EBCT demonstrated a decrease from 385 to 310 ml in LV-EDV, from 312 to 242 ml in LV-ESV, from 209 to 160 ml in RV-EDV and from 149 to 87 ml in RV-ESV, and an increase from 20 to 26% in LV-EF and from 37 to 50% in RV-EF as well as a reduction of LV-MM from 300 to 274 g (p < 0.05 each). Similar results were obtained by MRI. CONCLUSION: Following passive cardiomyoplasty, EBCT and MRI revealed an improvement of the global systolic function as well as a reduction of biventricular volumes and left-ventricular muscle mass.

Adult↗
PubMed2003

Double contrast MRI of thermally ablated liver metastases.

PURPOSE: To investigate the ability of double contrast MRI (enhancement with iron oxide and gadopentetate dimeglumine) to increase the difference in contrast between various tissues after thermal ablation of liver metastases. MATERIALS AND METHODS: 12 patients were imaged after MR-guided laser-induced thermotherapy (LITT). Imaging was performed with a 1.5T MR system. Nonenhanced, iron oxide-enhanced and double contrast images were acquired using T (1)-weighted GRE and T (2)-weighted TSE sequences. Iron oxide imaging was performed 10 min after injection of 1.4 ml ferucarbotran (Resovist(R), Schering AG Berlin, Germany) and double contrast imaging 60 sec after the additional injection of 0.1 mmol/kg body weight gadopentetate dimeglumine (Magnevist(R), Schering AG Berlin, Germany). Qualitative and quantitative assessment was performed on induced necroses, residual or recurrent tumor tissue and metastatic tissue untreated at the time of the study. RESULTS: Iron oxide-enhanced T (1) GRE images demonstrated the highest contrast between ablated hyperintense tissue and iron accumulating and resultant hypointense liver parenchyma. Due to Gd enhancement, double contrast T (1)-weighted GRE images displayed the highest change in signal intensity in vital tumor tissue compared to ablated tissue and iron oxide accumulating liver parenchyma (p < 0.01). CONCLUSIONS: First observations indicate that LITT of hepatic metastases can be better followed with double contrast MRI, which displays increased contrast due to Gd enhancement of perfused tumor tissue and signal intensity loss in iron oxide accumulating hepatic parenchyma. Induced necrosis does not change its signal intensity at all after injection of iron oxide and Gd-containing contrast media.

Aged↗
PubMed2003

Visualization of the pulmonary valve using cine MR imaging.

PURPOSE: To evaluate the capability of bright-blood cine MR to directly visualize the leaflets of the valve replacement in pulmonary position following Ross operation. MATERIAL AND METHODS: Long and short axis views of the pulmonary valve were obtained in 10 normal subjects and 14 patients after Ross operation. Valve morphology and function were analyzed and signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were calculated. Flow measurements were performed in the pulmonary trunk to assess pulmonary regurgitation. RESULTS: In all subjects, tricuspid morphology of the pulmonary valve was visualized. SNR of the leaflets in normal subjects (9.8 +/- 3.0) and in patients after Ross operation (7.5 +/- 2.2) differed significantly from blood (12.6 +/- 3.2 and 11.3 +/- 2.5, respectively, p < 0.05). Valvular regurgitation was seen in 5 patients as an insufficient closure of the valve which was confirmed by flow measurements. CONCLUSION: Cine MR enables in-plane visualization of the pulmonary valve and allows for functional and morphological evaluation in patients after pulmonary valve surgery.

Adult↗
PubMed2002

Results of the safety and efficacy of iobitridol in more than 61,000 patients.

We present results of a postmarketing surveillance study with iobitridol (Xenetix, Sulzbach, Germany) in more than 61,000 patients from 1996 until 2000. The purpose of this study was the assessment of safety and diagnostic efficacy of the non-ionic contrast agent iobitridol in the setting of a post-marketing surveillance study. Iobitridol (Xenetix) has been registered in Germany since 1996. Between 1996 and 2000 207 radiologists have documented in a questionnaire the routine use of Xenetix in 61,754 patients that have received Xenetix for diagnostic procedures. On each questionnaire parameters regarding demographic data, safety, and diagnostic efficacy were assessed. The data were statistically evaluated and analysed. The examination allowed for a diagnosis in 99% of cases. Image quality was rated as "excellent" or "good" in 89.8% of cases. In obese patients there was a significantly higher percentage ( p<0.001) of poor image quality. In 0.1% poor contrast was noted. Of patients, 28.8% had at least one risk factor, and 3.1% had three or more. Adverse events were noted in 2.3% of the examinations, but nearly half of them (1.1%) presented with "feeling of warmth" as the only symptom. Of adverse events, 0.2% were non-transient, and 1 patient died. In 0.2% of patients the procedure was stopped due to adverse events. In 0.9% of patients the causal relationship with the contrast agent was rated as probable (probable+possible=1.1%). The percentage of adverse events (excluding warmth) was independent of iodine concentration and of dose, and was higher in young patients. Xenetix is an efficient contrast agent for radiological procedures and is associated with a low rate of adverse events.

Contrast Media↗
PubMed2002

[Digital full field mammography after breast augmentation].

PURPOSE: The use of digital full field mammography for imaging augmented breasts. METHODS: Images of a sponge, as a tissue equivalent, partly covered with one of three different implants (silicone, silicone/saline, saline) were obtained using digital and film-screen technique. The visualisation of the sponge structure covered by the implant and next to the implant was evaluated by two radiologists. Results were compared to clinical results from 35 patients with implants. RESULTS: Two images with different parameter settings have to be obtained to visualize the covered sponge structure and the structure around the implant with film-screen technique. Digital mammography allows assessment of both areas using one image at different window settings. The assessability of covered structures depends on the type of implant. These results are in keeping with our clinical experiences. CONCLUSION: Digital mammography allows equal or better assessment of covered and non-covered tissue in augmented breasts without the need for additional exposures.

Breast Diseases↗
PubMed2002

[Cross-sectional imaging of endometrial carcinoma: MR imaging and CT].

Magnetic resonance (MR) imaging has superseded computed tomography (CT) in the diagnostic assessment of cancer of the uterus (endometrial and cervical carcinoma). Contrast-enhanced MR imaging is highly accurate in staging endometrial carcinoma, in particular in terms of the depth of myometrial invasion. MR imaging will in the future provide a good basis for preoperative therapeutic decision making, especially to answer the question whether or not lymphadenectomy is necessary based on myometrial infiltration depth. - This article outlines the potential of MR imaging for staging endometrial cancer, provides a brief description of the imaging strategies, and discusses the role of MR imaging in the diagnostic assessment of endometrial cancer.

Cervix Uteri↗
PubMed2002

[Multislice CT of the abdomen--current indications and future trends].

Multislice CT systems allow the simultaneous acquisition of multiple slices per gantry rotation. In combination with faster gantry rotation times of 0.5 seconds, the abdominal structures can be displayed in higher spatial and temporal resolution. In MS-CT of the liver it is possible to scan the entire organ with an optimal slice thickness of 2 - 3 mm within a defined perfusion phase in less than 10 seconds. This results in an improved detection and characterization of focal liver lesions. A high-quality, 3-dimensional reconstruction of the hepatic arterial and portalvenous system is obtained with the same data set. The diagnostic use of the simultaneously acquired perfusion data will lead to a better characterization of focal liver lesions in the future. The diagnostics of the pancreas also profits from MS-CT, especially for the detection of small tumors and the evaluation of resectability of a pancreatic carcinoma. All abdominal structures can be displayed in a coronal view without loss of image quality because of the almost isotropic voxels obtained. This proves to be beneficial for the preoperative diagnostics of renal cell carcinomas, especially if the tumor extension into adjacent organs (e. g., liver or spleen) in the longitudinal direction has to be evaluated. The multiplanar display and the sophisticated 3-dimensional reconstruction tools have a substantial value for the abdominal CT angiography. It proves to have a major diagnostic impact on acute abdominal aortic and visceral arterial diseases because even large distances in the z-direction can be covered with high spatial resolution.

Abdominal Neoplasms↗
PubMed2002

[Comparing the visualization of microcalcifications with direct magnification in digital full-field mammography vs. film-screen mammography].

PURPOSE: To evaluate the conspicuity of microcalcifications in magnified mammographic views of preparations obtained with full field digital mammography (FFDM), film-screen mammography (FSM), and the DIMA technique. MATERIAL AND METHODS: Twelve preparations were examined by FFDM and FSM using 1.8 x magnification and DIMA using 7 x magnification. Parameter settings were identical for all three techniques. The number of visible microcalcifications was then determined for each modality by three radiologists. As far as possible, all preparations were X-rayed at 22 kV and 10 mAS. RESULTS: Altogether 9705 calcifications were counted (DIMA: 1609/1542/1534; FFDM: 1020/753/881; FSM: 901/643/822). The total number of microcalcifications identified with the DIMA technique was 4685 as compared to 2654 with FFDM and 2366 with FSM. The calcifications counted with FFDM and FSM thus corresponded to 56.6 % and 50.5 %, respectively, of those identified with DIMA. The differences between the groups were statistically significant (F-Test, p < 0.05). CONCLUSION: Significantly more calcifications are identified when magnified mammographic views of preparations containing microcalcifications are obtained with the DIMA technique compared to FFDM or FSM. FFDM depicts markedly more calcifications than FSM. This means one should increase spatial resolution. Digital mammography offers the potential for improved visualization of microcalcifications with advanced applications.

Breast Neoplasms↗
PubMed2002

[Diagnostic value of secretin injections in dynamic MR pancreatography].

PURPOSE: To evaluate the effect of intravenous injections of secretin during MRP procedures. MATERIAL AND METHODS: From 1998 to 2001, 340 patients were examined with MRP. Depending on the native MRI/MRP diagnosis, 110 of them received an injection of secretin followed by multiple MRP's (every 2 minutes) up to 10 min after injection. Diagnosis included healthy persons (n = 23), pancreas divisum (n = 11), chronic pancreatitis (n = 68), and pancreatic tumors (n = 22); some patients had more than 1 diagnosis. Visibility of duct structures and amount of fluid filling of the duodenum after secretin injection were evaluated (dynamic examination) based on a five-point scale. Differences were tested statistically by means of Mc Nemar's test and ROC analysis. RESULTS: The visibility of the pancreatic duct could be increased significantly after secretin injection in all subgroups (p < 0.05). Statistically, it turned out not to be important at what time point after injection the MRP was taken. It was possible to evaluate the excretion rate of the pancreas. In healthy persons and those with pancreas divisum, the fluid filling of the duodenum was significantly higher than in those with chronic pancreatitis or pancreatic tumors. However, this finding alone did not suffice in differentiating between both groups (sensitivity 0.68 and specificity 0.59, respectively). CONCLUSION: The i. v. injection of secretin improves the ability of MRP to evaluate the pancreas by increasing the visibility of the pancreatic duct structures and provides a method to assess the excretion rate of the gland.

Adolescent↗
PubMed2002

[Incidence and distribution pattern of pulmonary saddle emboli: Diagnosis by electron beam tomography (EBT)].

PURPOSE: To determine the incidence of acute pulmonary emboli extending across the bifurcation of the main pulmonary artery, lobar arteries or segmental arteries (interpulmonary, interlobar or intersegmental saddle emboli, respectively). METHODS: 128 patients with clinically suspected acute pulmonary embolism underwent electron beam tomography (EBT). 140 scans were acquired in the continuous volume scanning mode (3 mm slice thickness). 100 ml of contrast material were intravenously administered. Studies were reviewed for the presence of acute pulmonary embolism and the number and location of interpulmonary, interlobar or intersegmental saddle emboli. Saddle emboli were defined as emboli extending across the bifurcation of a vessel into both branches by at least 5 mm each. RESULTS: 30 of 128 (23.4 %) patients (15 men; mean age 59 +/- 17 years) had acute pulmonary embolism. One or more saddle emboli were present in 20 of 30 patients (66.7 %), a total of 77 saddle emboli were detected ranging from 1 to 10 per patient. Distribution of the saddle emboli in the 20 patients was as follows: 5 interpulmonary, 28 interlobar and 44 intersegmental. CONCLUSIONS: Pulmonary saddle emboli are present in the majority of patients with acute pulmonary embolism. They are often multiple and may be found at different levels of the pulmonary arterial vasculature.

Acute Disease↗