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Biomedical subjects

H Greess

Publications and source records attributed to H Greess.

At least 19 recordsLinked to original sources
PubMed2007

[How to cope with the demands of the new "Approbation Regulation" (AR) by radiology-related interdisciplinary courses. The Erlangen model].

BACKGROUND: To create radiology-related interdisciplinary programs for the undergraduate education in terms of the new "Approbation Regulation". MATERIAL AND METHODS: Medical students developed in collaboration with radiologists and clinical partners virtual, radiology-related interdisciplinary training courses for different fields. Students and teachers evaluated the acceptance of the programs' structure and content as well as the possibility to replace the radiologist partly during interdisciplinary lessons. RESULTS: Six target group oriented virtual, radiology-related interdisciplinary training courses were developed which will relieve the implementation of the new AR's demands for more interdisciplinary education in small groups and the dreaded shortage of personnel. CONCLUSION: By the use of web- and CDRom-based interdisciplinary course models different fields of medicine and diagnostic radiology can be bridged in the sense of the new AR's demands as well as manpower in radiology can be saved.

CD-ROM↗
PubMed2006

[Orthorad--the online reference database of skeletal plain film radiography].

PURPOSE: It is evident that there is a growing need for Internet-based reference databases for reasons of practicability and due to the increasing use of reporting on digital workstations. The main advantages of online databases are expected with respect to plain film radiography and cross-sectional imaging. A reference database of skeletal plain film radiography was to be created using the Orthorad program. MATERIALS AND METHODS: The most important standard settings and special images of young and healthy adults in plain film radiography were collected over one year. All samples were approved for the Orthorad database by a board qualified radiologist. Based on the workflows of radiographers and radiologists, the records were organized by body part ( http://www.idr.med.uni-erlangen.de/orthorad/orthorad.htm ). This logical data structure will ensure that the tool serves as a source of information in two ways: On the one hand, the radiographer can access information on positioning, tube voltage and cassette format. On the other hand, the radiologist receives important knowledge regarding X-ray anatomy, reference data regarding the human skeleton, and information about the correct reporting for an image. RESULTS AND CONCLUSION: Orthorad is used as an online reference database for traumatologic plain film radiography to support radiographers and radiologists in their daily working routines. To date, user feedback has been positive.

Adult↗
PubMed2006

Retrospective interactive rigid fusion of (18)F-FDG-PET and CT. Additional diagnostic information in melanoma patients.

AIM: This study investigates whether interactive rigid fusion of routine PET and CT data improves localization, detection and characterization of lesions compared to separate reading. For this purpose, routine PET and CT scans of patients with metastases from malignant melanoma were used. PATIENTS, METHODS: In 34 patients with histologically confirmed malignant melanoma, FDG-PET and spiral CT were performed using clinical standard protocols. For all of these patients, gold standard was available. Clinical and radiological follow-up identified 82 lesions as definitely pathological. Two board-certified nuclear medicine physicians and two board-certified radiologists analyzed PET and CT images independently from each other. For each patient up to 32 anatomical regions (24 lymph node regions, 8 extranodular regions) were systematically classified. Discordant areas were interactively analyzed in manually and rigidly registered images using a commercially available fusion tool. No side-by-side reading was performed. RESULTS: Image fusion disclosed that the evaluation of the PET images alone led to a mislocalization in 26 of 91 focally FDG enhancing lesions. The overall sensitivities of PET, CT, and image fusion were 85, 88, and 94%, respectively; the overall specificities of PET, CT and image fusion were 98, 95 and 100%, respectively. Image fusion exhibited statistically significant higher specificity values as compared with CT. Ten definitely malignant sites were false-negative in CT, but could be detected by PET. On the other hand, twelve metastases were false-negative in PET, but could be detected by CT. These included two lesions, which had a clear correlate on the PET image when the fused images were evaluated. On the whole, registration of the PET and CT images yielded additional diagnostic information in 44% of the definitely malignant lesions. CONCLUSION: Retrospective image fusion of independently obtained PET and CT data is particularly valuable in exactly localizing foci of abnormal FDG uptake and improves the detection of metastases of malignant melanoma.

Adult↗
PubMed2005

[HNORAD].

BACKGROUND: New media are gaining importance in undergraduate as well as postgraduate and continued medical education. We aimed to create an interactive educational program for imaging diseases of the ear, nose and throat (ENT). MATERIALS AND METHODS: Cases and images representing clinical routine were collected, arranged by content and graphically presented according to instructional criteria. Undergraduate students participating in the project used an authoring system to generate case studies, which were then published at http://www.HNORAD.de. RESULTS: HNORAD is an interdisciplinary teaching program offering more than 100 classical disease presentations. Three systematic indices offer a choice of instructional approach. Apart from typical images, the information presented includes patient history, clinical findings, imaging findings as described by a board-qualified radiologist, diagnosis, differential diagnosis and internet links. Elements of the radiologist's report are linked with the images in such a way that the structure or finding described can be interactively highlighted. An evaluation index allows proficiency testing in self study and as a part of taught courses. CONCLUSION: HNORAD is a valuable resource for students, ENT surgeons and radiologists at the undergraduate, postgraduate and CME level for self study as well as for course work.

Computer-Assisted Instruction↗
PubMed2004

Dose reduction in subsecond multislice spiral CT examination of children by online tube current modulation.

The potential of online tube current modulation in subsecond multislice spiral CT (MSCT) examinations of children to reduce the dose without a loss in image quality is investigated in a controlled patient study. The dose can be reduced for oval patient sectional view without an increase in noise if the tube current is reduced where the patient diameter and, consequently, attenuation are small. We investigated a product version of an online control for tube current in a SOMATOM Sensation 4 (Siemens, Forchheim). We evaluated image quality, noise and dose reduction for examinations with online tube current modulation in 30 MSCT of thorax/abdomen and abdomen and compared mA s for tube current modulation to the mA s in standard weight-adapted children protocols. Image quality was rated as "very good," "good," "diagnostic" and "poor" in a consensus by three radiologists. Noise was assessed in comparison to 24 MSCT examinations without tube current modulation measured as SD in ROIs. The dose was reduced from 26 to 43% (mean 36%), depending on the patient's geometry and weight. In general, no loss of image quality was observed. Measured noise showed a decrease up to 26% and an increase up to 36%, although there was no decrease of image quality. Online tube current modulation is now used as a standard in MSCT at our institution. Dose in MSCT examinations of children can be reduced substantially in routine examinations by online tube current modulation without a loss of image quality.

Child↗
PubMed2004

[Automatic exposure control to reduce the dose in subsecond multislice spiral CT: phantom measurements and clinical results].

PURPOSE: To investigate the potential of dose reduction in multislice spiral CT (MSCT) with automatic exposure control. MATERIALS AND METHODS: The study was performed on a Sensation 4 multislice scanner. This prototype implementation analyzed the distribution of the attenuation along the z-axis in the lateral and sagittal directions of the digital radiogram. Depending on this distribution of the attenuation, the tube current (mA) is defined for every tube rotation. In addition, the tube current was modulated during each tube rotation. First, a three step oval water phantom was measured to evaluate the potential of this method with respect to dose reduction and image quality. In a patient study (n = 26), four different scan regions (shoulder, thorax, abdomen, pelvis) were examined and dose (mAs) and image quality evaluated in comparison to examinations with a standard protocol for these regions in adults and a weight-adjusted standard protocol in children. The image quality was classified in consensus as good, sufficient and poor image quality. RESULTS: By adapting and modulating the tube current, we substantially reduced the variation of noise in one spiral scan and in one scan region of our patient collective. The dose (average mAs) was reduced by 31 % to 66 % in children (mean 44 %) and between 35 % and 64 % in adults (mean 53 %), depending on the scan region. The image quality was substantially improved in regions with high attenuation and did not suffer in low attenuation regions. CONCLUSION: The dose can be reduced substantially by an automatic exposure control including angular tube current modulation with the same or improved image quality.

Abdomen↗
PubMed2002

[Indications and diagnostic sensitivity of CT and MRI in the otorhinolaryngology field].

Of all malignant tumors, 4-5% affect the head and neck region. Computed tomography (CT) and magnetic resonance imaging (MRI) provide the means for us to determine the precise extent and depth of infiltration of space-occupying lesions, detect submucosal growth, stage lymph nodes preoperatively, and thus facilitate better preoperative planning. Thinner collimations of sections and shorter examination times are possible with modern multilayer spiral CT. Two-dimensional and three-dimensional images can be calculated from the volume specifications to assess the skull base (coronal and sagittal sections) and the midline crossover of tumors as well as staging of lymph nodes (coronal section). Examination of laryngeal and hypopharyngeal function as well as determination of tumor perfusion are also possible. Detection of tumors that do not absorb any contrast medium (approximately 15%) is more difficult with CT. In addition to providing a high degree of tissue contrast, MRI makes it possible to directly acquire images in any number of planes. In contrast to CT, metallic artefacts hardly come into play. Infiltration of the dura and the cerebrum can be depicted better with MRI than with CT. The long examination time with MRI carries the risk of movement artefacts. In the head and neck region, it is important to suppress fat in T2-weighted sequences and in T1-weighted sequences after administration of contrast media. Inflammations in the head and neck region are only exceptionally clarified with CT or MRI. It is imperative that CT be performed before functional endoscopic operations of the paranasal sinuses. Further indications for CT and MRI in cases of inflammation are the diagnosis of retrotonsillar and parapharyngeal abscesses and ensuing complications as well as the diagnosis of osteomyelitis. Since conventional sialography is contraindicated in acute inflammation in sialolithiasis, magnetic resonance sialography can be employed.

Humans↗
PubMed2002

[CT and MRI of the petrous bone].

Diseases of the petrous bone should now be diagnosed by means of high-resolution multislice spiral computed tomography (MSCT) and/or magnetic resonance imaging (MRI). The first step in the process of diagnosis, however, must be conventional X-ray photographs (according to Schüller, Mayer, Stenvers) for screening purposes, because of the high cost of the other procedures mentioned. Because of the excellent imaging of bone structures with MSCT, this technique is especially suitable for the diagnosis both of acquired pathologies and of congenital abnormalities of the external auditory meatus, the middle ear and the mastoid, of trauma-induced pathologies of the entire petrous bone, and of osteogenic diseases. MRI is the method of choice for examination of the labyrinthine system, the interior auditory meatus and the cerebellopontine angle because it gives much the best depiction of soft tissue. Sometimes when questions remain unsolved after computed tomography (CT) examination of the middle ear MRI can be applied to complement CT, and it can yield additional information. Lesions affecting the apex of the petrous pyramid should be examined by MRI. High-resolution CT through the bone window and thin-layer MRI are both components of the presurgical diagnosis before cochlear implant (CI) surgery. For postoperative monitoring a conventional transorbital X-ray of the petrous bone is sufficient; CT is indicated only in complicated cases, and MRI is absolutely contraindicated after CI.

Artifacts↗
PubMed2001

[Rapid interactive 3-D imaging of the temporal bone with "direct volume rendering"].

INTRODUCTION: For the first time, the relatively new method of interactive direct volume rendering (dVR) allows for a fast and direct three-dimensional visualization of spiral CT data without any manual, explicit segmentation. This study was performed to prove whether dVR is capable of providing a meaningful three-dimensional visualization of the structures within the temporal bone. PATIENTS AND METHODS: In ten patients a three-dimensional visualization of the structures of the inner and middle ear was performed from spiral CT data on a commercially available graphics workstation. RESULTS: The cochlea and semicircular canals were visualized in good quality in all patients. The ossicles and bony facial canal were visualized in good or fair quality in most cases. The time needed for the visualization of the data and all target structures was less than 15 min in all cases. CONCLUSIONS: Three-dimensional visualization of the structures within the temporal bone from high-resolution spiral CT data using dVR is easily performed in a very short time on standard graphics workstations. This allows integrating three-dimensional visualizations into routine clinical work.

Computer Graphics↗
PubMed2001

The role of angiography in the lower extremity using free vascularized fibular transplants for mandibular reconstruction.

BACKGROUND: Fibular osteocutaneous free tissue transfer represents the work horse procedure in the reconstruction of large oromandibular defects. Before the fibula is harvested the blood supply of the lower leg and foot should be examined, as the perfusion may be based predominantly on the peroneal artery and venae comitantes. To avoid postoperative ischaemia of the lower leg, adequate perfusion must be guaranteed before sacrificing the peroneal vessels. Anatomical variations and peripheral arterial occlusive disease add to the risk of ischaemia. Various methods of evaluating the blood supply have been described. MATERIAL AND METHODS: Fifty-two consecutive cases of fibular flaps were evaluated to study the arterial blood supply of the lower extremity. For angiography, the right femoral artery was punctured using the Seldinger technique and a total of 20-25 ml contrast medium (Imeron 300) was infused and images required at a rate of 0.5/sec. RESULTS: A patent three-vessel supply to both feet could only be detected in 21 patients. Thirty-one angiograms revealed anatomic and/or arteriosclerotic alterations. Angiography provided accurate information in all patients and allowed successful fibular transfer in those patients who were found preoperatively to have regular conditions. CONCLUSION: Preoperative assessment of the blood supply of the lower extremity is important before fibular osteocutaneous free tissue transfer. We advocate angiography as interpretation is not examiner dependent.

Adult↗
PubMed2001

[Dose reduction in spiral-CT: detection of pulmonary coin lesions with and without anatomically adjusted modulation of tube current].

PURPOSE: To investigate the potential of projection angle-dependent anatomical adaptation of tube current to reduce dose in spiral CT examinations of the thorax without loss in detectability of pulmonary nodules and image quality. PATIENTS AND METHODS: Dose can be reduced for non-circular patient cross-sections without an increase in noise if the tube current is reduced at those angular positions where the patient diameter and, consequently, attenuation are small. The examinations were dose with SOMATOM Plus 4 (Siemens AG). CT projection data were analysed to determine the optimum tube current for each projection angle in real time. We compared image quality, done, and detection rates of pulmonary nodules for thoracic spiral CT examinations with and without online anatomically adapted tube current control in a group of 38 patients. Three radiologists counted all intrapulmonary nodules in consensus separated in three different groups (< 5 mm, 5-10 mm, > 10 mm). Image quality was evaluated in a scale from 1-3 (1 = very good, 2 = good, 3 = worse). RESULTS: On average, the dose was reduced by 21% (15-34%). With a constant tube current, 704 pulmonary nodules were detected, with tube current modulation 707 pulmonary nodules. For three patients we saw more pulmonary nodules (five) with tube current modulation, for two patients we saw less pulmonary nodules (two). In a direct comparison, the missed intrapulmonary nodules were also detected in the respective method. Thus, the detection rate of intrapulmonary nodules was uninfluenced. In general, no deterioration of image quality was observed. CONCLUSION: On average, 21% dose reduction was achieved by an anatomically adapted tube current modulation in spiral CT examinations of the thorax without a loss in detectability of pulmonary nodules and image quality. This method is an important contribution to dose reduction in spiral CT.

Diagnosis, Differential↗