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Biomedical subjects

D H Grönemeyer

Publications and source records attributed to D H Grönemeyer.

18 recordsLinked to original sources
PubMed2001

Reproducibility of two coronary calcium quantification algorithms in patients with different degrees of calcification.

PURPOSE: To evaluate the reproducibility of coronary calcium quantification algorithms by electron beam CT (EBT) in patients with different amounts of calcified plaque using the conventional (Agatston) score and an area score and to demonstrate a potential application of these results for evaluation of follow-up scans. METHODS: In 50 consecutive patients. the conventional calcium score (CCS = Agatston score) and the area score (AS) were summed for each artery and patient. Data were analyzed in four groups according to degrees of calcification: 0 (absent-minimal): CCS 0-9, I (mild): CCS 10-99, II (moderate): CCS 100-399, III (severe): CCS > or = 400. We determined and compared the reproducibility for each algorithm within and among groups. RESULTS: Median percent reproducibility improved with increasing amounts of calcified plaque for the CCS and the AS (p = 0.002 and p = 0.004, respectively). We demonstrate how these reproducibility values can be used to evaluate long-term follow-up studies. The reduction of median reproducibility per patient using the AS vs. the CCS was 32% (13 vs. 19%, respectively). On a vessel-by-vessel basis, the reduction of median reproducibility was 7% (24.3 vs. 22.6%, CCS vs. AS, p < 0.02), which was attributable to a 45% reduction in reproducibility in arteries with mild scores (46.1 vs. 25.5%, CCS vs. AS, p < 0.005). CONCLUSION: The AS has an improved reproducibility compared with the CCS, especially in patients with small amounts of coronary calcifications which may prove clinically useful. Different reproducibility values in different degrees of calcification can be used for an individual assessment of changes in amounts of coronary calcification.

Adult↗
PubMed2001

Prevalence and clinical significance of accidental findings in electron-beam tomographic scans for coronary artery calcification.

AIMS: To analyse the prevalence, and diagnostic and therapeutic consequences, of accidental findings in electron-beam tomographic scans performed for evaluation of coronary artery calcification. METHODS AND RESULTS: A total of 1812 consecutive patients with known or suspected coronary artery disease underwent electron-beam tomography. In 583 (32%) of the patients, i.v. contrast was also administered for non-invasive coronary angiography. A total of 2055 non-coronary pathological findings were observed in 953 (53%) of the patients. The prevalence of extra-cardiac disease, as shown in native scans and contrast studies, was assessed separately. In 583 (32%) patients, cardiac structures or the pericardium were affected, in 423 (23%) aortic disease was found. Lung disease was found in 357 (20%), and pathology of other organs in 273 patients (15%). The most frequent findings were aortic calcium in 423 (23%) patients and heart valve calcification in 317 patients (17%). Malignant disease could be detected in three patients. Further diagnostic investigations were done in 191 (11%) patients, 141 (74%) of which concerned the heart. In 22 (1.2%) patients, specific therapy was initiated following electron-beam tomographic findings. CONCLUSION: Accidental non-coronary pathology is a frequent finding in electron-beam tomographic calcium scanning, and often requires diagnostic or therapeutic action. Profound knowledge of the radiological differential diagnosis of the thoracic organs is necessary for reporting electron-beam tomographic scans, in order to avoid misdiagnosis and to receive a high quality interpretation.

Adult↗
PubMed2000

New aspects of image distribution and workflow in radiology.

The progressive use of digital image-generating devices and digital communication technology in clinical and practice environments implies changes in radiological workflow and asks for adequate quality assurance in the whole process of radiology report preparation. This improvement potential has to be rigorously reinvestigated with regard to up-to-date procedures and the full exploitation of supporting technologies like linguistic analysis, help desk and trouble ticket systems, competitive allocation algorithms, time-and-event monitoring, and intelligent agents. These approaches are to be evaluated in combination with business process analysis and shall help to reduce turnaround times for radiology reports while maintaining or even increasing quality-assurance levels.

Germany↗
PubMed2000

Coronary arterial stent patency: assessment with electron-beam CT.

PURPOSE: To evaluate electron-beam computed tomography (CT) for stent localization and noninvasive assessment of stent patency in patients with coronary arterial stents and coronary bypass stents. MATERIALS AND METHODS: CT in the single-section volume mode was performed in 202 patients with 321 coronary arterial stents in 221 vessels to localize the stents. Patency was evaluated in the multisection flow mode with an intravenous bolus injection of contrast material. All electron-beam CT images were reviewed by an observer who had no knowledge of the coronary angiographic results. Electron-beam CT findings were then compared with coronary angiographic findings. RESULTS: The stents could be visualized and related to the coronary arterial segments in 216 of 221 vessels with electron-beam CT. Of the 221 vessels, 207 were correctly evaluated with electron-beam CT. Compared with coronary angiography, electron-beam CT permitted the detection of 18 of 23 high-grade stenoses (sensitivity, 78%) and correctly depicted the absence of high-grade stenoses in 189 of 193 vessels with stents (specificity, 98%). Altogether, 18 stenoses were detected correctly at electron-beam CT; the interpretation was false-positive in four vessels (positive predictive value, 82% [18/22 vessels]) and false-negative in five (negative predictive value, 97% [189/194 vessels]). CONCLUSION: Electron-beam CT may be helpful in localizing intracoronary stents and assessing stent patency noninvasively to delay the intervals between catheterizations in an increasing number of patients.

Adult↗
PubMed2000

New DICOM extensions for softcopy and hardcopy display consistency.

The DICOM standard defines in detail how medical images can be communicated. However, the rules on how to interpret the parameters contained in a DICOM image which deal with the image presentation were either lacking or not well defined. As a result, the same image frequently looks different when displayed on different workstations or printed on a film from various printers. Three new DICOM extensions attempt to close this gap by defining a comprehensive model for the display of images on softcopy and hardcopy devices: Grayscale Standard Display Function, Grayscale Softcopy Presentation State and Presentation Look Up Table.

Computer Communication Networks↗
PubMed1999

Minimally invasive evaluation of coronary stents with electron beam computed tomography: In vivo and in vitro experience.

We sought to describe the value of electron beam computed tomography (EBCT) to detect stent restenoses at follow-up and to identify characteristic EBCT features of coronary stents. Six coronary stents (GRII, Jostent, NIR, PS, Micro, Wiktor) were scanned in vitro (10 1. 5-mm-thick slices, 15-cm FoV, 100-ms AT) before and after inflation with 3.0-, 3.5-, and 4.0-mm balloons to study intensity values and different stent dimensions in comparison to caliper measurements. In 44 patients (60 +/- 10 years, 4 females) we prospectively compared EBCT findings [eight 8-mm-thick slices in the flow mode, 26-cm field of view (FoV), 50 ms acquisition time (AT)] with 6-month angiographic outcome after placement of 86 stents in 49 vessels. For the detection of significant angiographic luminal narrowing (>/=75%) that occurred in 17/49 vessels (35%), we found a sensitivity of 65%, a specificity of 84%, and a positive and negative predictive value of 69% and 82%, respectively. The in vitro data show significant differences in image intensity between the stents and a significant gradual decrease in image intensity with increasing stent diameters. The mean differences between EBCT and caliper measurements for the length and diameter were 0.17 +/- 0.18 mm and -0.32 +/- 0.25mm, respectively. EBCT is currently the only noninvasive technique that allows the assessment of stent dimensions and stent geometry, which may prove useful in patients when intravascular ultrasound cannot be performed. Contrast-enhanced EBCT is a promising tool for minimally invasive stent patency evaluation at follow-up, especially in patients that are unable to exercise. Cathet. Cardiovasc. Intervent. 48:39-47, 1999.

Coronary Angiography↗
PubMed1999

Magnetocardiography in the diagnosis of fetal arrhythmia.

OBJECTIVE: To examine the possible use of magnetocardiography in the diagnosis of fetal arrhythmias. DESIGN: Investigation of routinely examined pregnant women, as well as women referred because of arrhythmias or other reasons. PARTICIPANTS: Sixty-three women between the 13th and 42nd week of pregnancy. METHODS: Recording of 189 fetal magnetocardiograms, of which 173 traces (92%) demonstrated sufficient fetal signal strength to permit evaluation. After digital subtraction of the maternal artefact, all fetal complexes were identified and the recording was examined for arrhythmic events. RESULTS: Short bradycardic episodes, not associated with any pathological condition, were found in 26% of all recordings, usually in mid-pregnancy. In 12 cases, isolated extrasystoles of no clinical importance could be identified. There were nine traces which revealed multiple arrhythmias including ventricular and supraventricular ectopic beats, bigeminy and trigeminy, sino-atrial block and atrio-ventricular conduction disturbances. Furthermore, two cases with tachycardia were found. CONCLUSION: Magnetocardiography offers a simple noninvasive method for examination of the fetal cardiac electrophysiological signal. It may thus be useful in the identification and classification of clinically relevant arrhythmia and aid in decisions concerning treatment.

Adult↗
PubMed1996

Two- and three-dimensional imaging for interventional MRI and CT guidance.

Minimally invasive techniques using endoscopes for image guided therapy are common in the surgical field and in internal medicine. Interventional procedures in the past were performed with either fluoroscopic, sonographic or CT-guidance, but now MRI-guided interventional procedures are being developed. Combining these technologies will improve surgical access and reduce complications. Today, tomographic 2 D and 3 D imaging (CT, EBT, MRI) can be used for precise and transparent guidance of endoscopes and surgical instruments inside the body for the field of minimally invasive therapy. 3 D imaging is helpful for anatomical, but not for morphological understanding. It has to be used interactively with actual cross sectional imaging for instrument guidance. This will offer a safe and effective access into the body, especially in high risk areas and lead to the new field of "Surgical Tomography".

Endoscopes↗
PubMed1994

[Pelvimetry using various magnetic resonance tomography techniques vs. digital image enhancement radiography: accuracy, time requirement and energy exposure].

In 50 patients with suspected or proven cephalo-pelvine disproportion pelvimetry was performed with MR-tomography using a gradient-echo-sequence (FLASH 2D) before or after labour. Results were compared with measurements using digital radiography. In principle, both methods are exchangeable. The sagittal pelvic in- and outlet bispinous diameters are well reproducible. On the other hand, the transverse pelvic inlet and the distance between the ischiatic tubera are not so reliably reproduced. The accuracy of measurement does not depend on individual pelvic distances. Critical statistical analysis demonstrates, that in the worst case differences between the two methods might become unacceptable. Our results indicate two major reasons: 1. there are interobserver problems which cannot be neglected, and 2. the anatomical definition of referential landmarks for the measurements is unsafe. In 10 volunteers, a comparison was made between a T1-weighted spin-echo sequence (SE), a fast gradient echo sequence (FLASH-2D) and an ultrafast gradient echo technique (Turbo-FLASH). For the examination techniques presented here, the high-frequency exposure load or specific absorption rate (SAR loc and SAR total) is below the values permitted by the German Federal Health Bureau (Bundesgesundheitsamt). Whereas the exposure load in case of spin-echo takes (SE) is 22fold higher than with the gradient echo technique (GHE), the load values of ultra-fast GE (usGE) are only about 16% of the 2D-FLASH sequence or about 0.007% of SE. The difference in image quality does not affect the accuracy of measurement.

Adolescent↗
PubMed1993

[Microinvasive CT-controlled tumor therapy of soft tissue and skeletal metastases].

Micro-invasive CT-guided intratumoral therapy (MIC-ITT) when used in combination with sympathectomy can be an excellent palliative treatment with little impairment of the patient. Rapid as well as complete reduction of pain without systemic side effects can be achieved under local anesthesia in patients in advanced tumor stages by the direct instillation of 50 to 96% alcohol and/or a locally efficacious low toxic cytostatic (Mitoxantron) under CT guidance. CT enables not only exact puncture without injuring endangered structures but also a controlled application of medication. The interventions can be performed with special probes with a diameter of 18 to 25 G. The study population consisted of 145 patients who received a total of 434 treatments. Repeated micro invasive intratumoral treatment was performed on 110 patients with bone and soft tissue metastases (Group I, 335 single treatments) and on 35 patients with vertebral metastases (Group II, 109 single treatments). In all patients conventional therapeutic strategies had been exhausted or were no longer applicable on the basis of a reduced Karnofsky Index. Treatment was performed in combination with sympathetic neurolysis at the upper tumor pole in all cases. The maximum follow-up time was 30 months. Pain reduction was estimated on a visual analogic scale. In Group I up to time of death a pain reduction of 75% or better was achieved in 88 patients (80%). A reduction in tumor size concomitant with a stabilization of the tumor region could be shown in 25% in this group, no change in 62% and progression in 13%. In Group II a pain reduction greater than 75% was achieved in 84% as well as a reduction in tumor size (< 50%) in 18% of the patients. Necrotic zones could be shown in 27% and calcification of tumor area in 35%. No change in tumor size was found in 66% of the patients, progression in 16%. All treatments were free of complications. On the whole the results of this therapeutic approach are encouraging. In particular one aspect should be mentioned: with respect to palliative treatment the reduction of tumor size is not crucial. The decisive factor is the improvement in quality of life of the patient using an intervention which impairs the patient only minimally. Furthermore this micro invasive approach should always involve the combination of local tumor treatment with treatment or lysis of the autonomic sympathetic nervous system in tumor vicinity.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Percutaneous nucleotomy with CT and fluoroscopic guidance.

Automated percutaneous diskectomy was performed with use of computed tomographic (CT) and fluoroscopic monitoring. Degenerative disease of the intervertebral disk was treated with local administration of anesthesia and use of a nucleotome. One hundred ten patients with neurologic symptoms and morphologic changes of one segment were selected for treatment. Previous conservative therapy had been unsuccessful. Patients with completely prolapsed and sequestered fragments of herniated disks ("uncontained disk"), narrow intervertebral spaces, posterior osteophytes, diseased facet joints, and spinal stenoses were not considered candidates for percutaneous nucleotomy (PNT). After PNT, 82% of the patients had complete remission of their neurologic symptoms; Lasègue sign was negative or improved in 92%. In 18% (20 patients), the symptoms did not improve sufficiently; 11% (12 of 110) of these patients underwent surgical nucleotomy. There were no serious complications, in particular, no injuries to vital structures (nerves, thecal sac, arteries, veins), except for one case of spondylodiskitis. Guiding PNT with CT and fluoroscopy provides a safe procedure with good clinical results. The addition of CT has shortened the operation but increased over-all procedure time. In the future, a shift to outpatient treatment may offset the additional time and cost of including CT guidance.

Adult↗
PubMed1989

[New possibilities and aspects of low-field magnetic resonance tomography].

Worldwide, MRI is going up to higher field-strength. For imaging, magnets with field-strength between 0.2 and about 2.5 Tesla are installed. Below 0.2 Tesla, Low-Field-systems have been used in research-projects to optimize image quality. New developments of 0.064 Tesla Permanent-Magnet-MRI are hopeful for clinical work. Future possibilities of Low-Field-MRI are shown. The advantages of this system are good image quality by low initial start-up and operating costs as well as ease of sitting and lack of need for cryogens. The open design has excellent patient acceptance and allows to examine patients with claustrophobia feelings. It allows easier monitoring during the examination-especially children and patients with cancer or polytraumatic diseases. The introduction of more affordable MRI-systems of low-field-strength may decrease the cost of MRI to the point where it is competitive with computer tomography.

Costs and Cost Analysis↗