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Markus Völk

Publications and source records attributed to Markus Völk.

18 recordsLinked to original sources
PubMed2005

Chest radiography with a flat-panel detector: image quality with dose reduction after copper filtration.

PURPOSE: To compare image quality and estimated dose for chest radiographs obtained by using a cesium iodide-amorphous silicon flat-panel detector at fixed tube voltage and detector entrance dose with and without additional 0.3-mm copper filtration. MATERIALS AND METHODS: The study was approved by the institutional ethics committee. All prospectively enrolled patients signed the written consent form. Chest radiographs in two projections were acquired at 125-kVp tube voltage and 2.5-microGy detector entrance dose. The experimental group (38 patients) was imaged with 0.3-mm copper filtration; the control group (38 patients) was imaged without copper filtration. An additional 12 patients were imaged with and without copper filtration and served as paired subject-controls. Three readers blinded to group and clinical data independently evaluated the radiographs for image quality on a digital display system. Twelve variables (six for each radiographic projection) were assigned scores on a seven-point ordinal scale. Scores between experimental and control groups were compared: Logistic regression analysis and Mann-Whitney U test were used for unpaired patients; and Wilcoxon and McNemar test, for paired patients. In all, 72 comparisons were determined (36 [12 variables x three readers] for unpaired patients and 36 for paired patients). In a phantom study, radiation burden of experimental protocol was compared with that of control protocol by using Monte Carlo calculations. RESULTS: For 70 of 72 comparisons, digital radiographs obtained with copper filtration were of similar image quality as radiographs obtained without copper filtration (P = .123 to P > .99). For two of 72 comparisons, one observer judged the experimental protocol superior to the control protocol (P = .043, P = .046). Patient dose reduction estimated with Monte Carlo calculations was 31%. Use of copper filtration increased exposure times by 48% for posteroanterior views and by 34% for lateral views. CONCLUSION: Subjectively equivalent chest radiographic image quality was found with estimated 30% dose reduction after addition of 0.3-mm copper filtration with flat-panel cesium iodide-amorphous silicon technology.

Cesium↗
PubMed2005

Dark lumen magnetic resonance enteroclysis in combination with MRI colonography for whole bowel assessment in patients with Crohn's disease: first clinical experience.

BACKGROUND: Magnetic resonance enteroclysis (MRE) is a recently introduced imaging technique that assesses the small bowel with similar sensitivity and specificity as the fluoroscopically performed conventional enteroclysis. Magnetic resonance imaging colonography (MRC) seems to be a promising technique for polyp assessment in the colon. In this feasibility study, we evaluated the combination of small bowel MRI with unprepared MRC as an integrative diagnostic approach of the whole bowel in patients with Crohn's disease. METHODS: Thirty patients with known Crohn's disease were prospectively examined. No particular colonic preparation was applied. Applying the dark lumen technique in all patients, MRE and MRC were performed within 1 session using an integrative examination protocol. T2-weighted and contrast-enhanced T1-weighted sequences were acquired. Inflammation assessment (grades 0 to 2) of the colon was compared with conventional colonoscopy in 29 patient and with surgery in 1 patient. The entire colon was graded fair to good distended in all patients. In 11 of 210 evaluated colonic segments, feces hindered an adequate intraluminal bowel assessment. Twenty-three of 30 patients had complete colonoscopy as the gold standard. In 7 patients, complete colonoscopy could not be performed because of an inflamed stenosis. RESULTS: Correct grading of colonic inflammation was performed with 55.1% sensitivity and 98.2% specificity in all segments. Considering only more extensive inflammation (grade 2), the sensitivity of MRC increased to 70.2% with a specificity of 99.2%. CONCLUSIONS: The combination of MRE and MRC could improve the diagnostic value of abdominal MRI evaluation in patients with Crohn's disease. However, MRC can not replace conventional colonoscopy in subtle inflammation assessment.

Adolescent↗
PubMed2005

Magnetic resonance-guided percutaneous angioplasty of femoral and popliteal artery stenoses using real-time imaging and intra-arterial contrast-enhanced magnetic resonance angiography.

OBJECTIVE: The aim of this study was to demonstrate the possibility of performing magnetic resonance (MR)-guided interventional therapy for femoral and popliteal artery stenoses with commercially available materials supported by MR real-time imaging and intra-arterial MR angiography. MATERIALS AND METHODS: A total of 15 patients suffering from symptomatic arterial occlusive disease of the lower limbs with 19 stenoses were included. Interventional intra-arterial digital subtraction angiography was performed before and after angioplasty on each patient as standard of reference. MR images were acquired on a 1.5-T MR scanner. A fast-low-angle shot (FLASH) 3D sequence was applied for a contrast enhanced MR-angiography (ceMRA). A total of 5 mL of diluted gadodiamide was injected via the arterial access. Maximum intensity projections (MIPs) were used as roadmaps and localizers for the interactive positioning of a continuously running 2D-FLASH sequence with a temporal solution of 2 images/second. The lesion was crossed by a balloon-catheter, which was mounted on a guidewire. The visibility was provided by the radiopaque markers on the balloon and was improved by injection of 1 mL of gadolinium into the balloon. Postinterventional control was performed by intra-arterial MR angiography and catheter angiography. RESULTS: Stenoses were localized by intra-arterial MR angiography. The guidewire/balloon combination was visible, and the balloon was placed correctly to cover the entire stenoses. Balloon dilation reduced the degree of stenosis by approximately 57% on average. No complications were observed. CONCLUSION: MR-guided balloon dilation of femoral and popliteal artery stenoses supported by real-time MR imaging and intra-arterial MR angiography is feasible with commercially available materials.

Aged↗
PubMed2004

Dose reduction in skeletal and chest radiography using a large-area flat-panel detector based on amorphous silicon and thallium-doped cesium iodide: technical background, basic image quality parameters, and review of the literature.

The two most frequently performed diagnostic X-ray examinations are those of the extremities and of the chest. Thus, dose reduction in the field of conventional skeletal and chest radiography is an important issue and there is a need to reduce man-made ionizing radiation. The large-area flat-panel detector based on amorphous silicon and thallium-doped cesium iodide provides a significant reduction of radiation dose in skeletal and chest radiography compared with traditional imaging systems. This article describes the technical background and basic image quality parameters of this 43 x 43-cm digital system, and summarizes the available literature (years 2000-2003) concerning dose reduction in experimental and clinical studies. Due to its high detective quantum efficiency and dynamic range compared with traditional screen-film systems, a dose reduction of up to 50% is possible without loss of image quality.

Cesium↗
PubMed2004

Abdominal MRI after enteroclysis or with oral contrast in patients with suspected or proven Crohn's disease.

BACKGROUND & AIMS: Diagnostic results of magnetic resonance (MR) enteroclysis correlate highly with those from conventional enteroclysis; nevertheless, intubation of the patient and positioning of an intestinal tube is still necessary for the examination, which is often remembered as the most embarrassing part of the examination by the patient. A more comfortable and highly sensitive examination of the small bowel therefore would increase patient acceptance for recurring examinations, which are often necessary, for example, in patients with Crohn's disease. This study evaluates the diagnostic efficacy of abdominal MR imaging (MRI) of the small bowel after drinking contrast agent only compared with conventional enteroclysis and abdominal MRI performed after enteroclysis in patients with suspected or proven Crohn's disease. METHODS: Twenty-one patients with Crohn's disease referred for conventional enteroclysis underwent abdominal MRI after enteroclysis. Additionally, 1 to 3 days before or after these examinations, abdominal MRI was performed using only orally administered contrast. All MRI examinations were performed using a 1.5T scanner. RESULTS: All pathological findings on conventional enteroclysis were shown correctly with MRI after enteroclysis and MRI after oral contrast only. Additional information by MRI was obtained in 6 of 21 patients. No statistically significant differences were found in assessing the diagnostic efficacy of the 3 examinations. CONCLUSIONS: Abdominal MRI with oral contrast only can be used as a diagnostic tool for evaluation of the small bowel in patients with Crohn's disease and has the potential to replace conventional enteroclysis as follow-up.

Administration, Oral↗
PubMed2004

Contrast-enhanced magnetic resonance angiography of the carotid arteries: influence of injection rates and volumes on arterial-venous transit time.

RATIONALE AND OBJECTIVES: To assess the influence of injection rates and volumes on the arrival time of contrast material (CM) in the common carotid artery, the jugular vein and the resulting arterial-venous transit time. Additionally the relationship between injection parameters and the extent of a CM plateau was evaluated. MATERIALS AND METHODS: In 60 patients a CM injection was necessary to investigate suspected cranial disease. All patients were prospectively assigned to 6 protocol groups with varying volumes of gadolinium dimeglumine (2, 10, 20 mL) and injection rates (0.5, 1, 2, 4 mL/s). Simultaneously to the CM injection, 50 repetitive transverse measurements (1/s) were acquired at the level of the common carotid artery. Based on the resulting signal-time curves, the arrival time of the contrast material in the common carotid artery and the jugular vein, the resulting arterial-venous transit time, the peak enhancement and the extent of a CM-plateau were calculated as a function of the injection parameters. RESULTS: Smaller flow rates (0.5 mL/s) resulted in a longer arrival time in the common carotid artery (mean value 22,6 seconds +/- 2.3) and the jugular vein (mean value 32.6 seconds +/- 2.6) and resulted in longer arterial-venous transit time (mean value 10.1 second +/- 1.9). The volume showed no effect on these parameters. The peak arterial and venous signal intensity and a consistent CM-plateau after 50 seconds were dependent on the volume, but not on the injection rate. CONCLUSION: The injection rate showed an influence to the arrival time in the common carotid artery and the jugular vein and also to the arterial-venous transit time. The injected volume only affected the extent of the contrast plateau. A flow rate of 1 to 2 mL/s and a minimum of 20 mL gadolinium dimeglumine are recommended to achieve optimal image quality without venous overlay.

Adolescent↗
PubMed2004

Amorphous silicon, flat-panel, x-ray detector: reliability of digital image fusion regarding angle and distance measurements in long-leg radiography.

RATIONALE AND OBJECTIVES: To evaluate composed long-leg images acquired with a large-area, flat-panel x-ray detector with regard to angle and distance measurements. METHODS: Radiographs of a long-leg phantom were acquired at 13 different angle settings with a 43-cm x 43-cm digital x-ray detector based on cesium iodide (CsI) and amorphous silicon (a-Si) technology. Three overlapping single images of the phantom were reconstructed at a workstation using a generalized correlation method. Four blinded observers were instructed to determine the angle of the axis of the long-legs as well as the length of "femur" and "tibia" on soft-copy displays. For that, the angle and distance measurement software integrated in the workstation was used. The images were analyzed with and without prior manual fine tuning of the primary composition result according to a mapped scale. Standard of reference was angle and distance determination at the phantom. RESULTS: On average, the difference between the observers' angle measurements and the standard of reference was 0.4 degrees for both images with and without prior manual correction. Regarding distance measurements, the average discrepancies to the standard were 0.2 cm (femur) and 0.1 cm (tibia) when analyzing images that had undergone manual fine tuning and 0.5 cm and 0.7 cm, respectively, for images without manual correction. CONCLUSIONS: The evaluated image fusion algorithm in conjunction with a 43-cm x 43-cm flat-panel detector is feasible regarding angle and distance measurements on long-leg images. In the case of inaccurate primary composition, results can be corrected easily by manual fine tuning.

Algorithms↗
PubMed2004

Contrast-detail phantom study for x-ray spectrum optimization regarding chest radiography using a cesium iodide-amorphous silicon flat-panel detector.

RATIONALE AND OBJECTIVES: The purpose of this study evaluating a cesium iodide-amorphous silicon-based flat-panel detector was to optimize the x-ray spectrum for chest radiography combining excellent contrast-detail visibility with reduced patient exposure. MATERIALS AND METHODS: A Lucite plate with 36 drilled holes of varying diameter and depth was used as contrast-detail phantom. For 3 scatter body thicknesses (7.5 cm, 12.5 cm, 21.5 cm Lucite) images were obtained at 113 kVp, 117 kVp, and 125 kVp with additional copper filter of 0.2 and 0.3 mm, respectively. For each setting, radiographs acquired with 125 kVp and no copper filter were taken as standard of reference. On soft-copy displays, 3 observers blinded to the exposure technique evaluated the detectability of each aperture in each image according to a 5-point scale. The number of points given to all 36 holes per image was added. The scores of images acquired with filtration were compared with the standard images by means of a multivariate analysis of variance. Radiation burden was approximated by referring to the entrance dose and calculated using Monte Carlo method. RESULTS: All 6 evaluated x-ray spectra resulted in a statistically equivalent contrast-detail performance when compared with the standard of reference. The combination 125 kVp with 0.3 mm copper was most favorable in terms of dose reduction (approximately 33%). CONCLUSION: Within the constraints of the presented contrast-detail phantom study simulating chest radiography, the CsI/a-Si system enables an addition of up to 0.3 mm copper filtration without the need for compensatory reduction of the tube voltage for providing constant image quality. Beam filtration reduces radiation burden by about 33%.

Cesium↗
PubMed2004

Intraarterial contrast material-enhanced magnetic resonance angiography of the aortoiliac system.

In a period of 4 months, 10 patients were examined prospectively with intraarterial magnetic resonance (MR) angiography after digital subtraction angiography. Intraarterial MR angiography was performed with use of a 1.5-T MR imaging system. Contrast agent (gadodiamide) was injected with a conventional angiography catheter placed in the proximal abdominal aorta. The increase in vascular signal intensity was determined and the diagnostic value of the MR angiograms was scored according to a five-point scale by four investigators. The MR angiograms were judged good to excellent, and all were scored as diagnostic. In conclusion, this study shows that intraarterial MR angiography is feasible. Intraarterial MR angiography is appropriate to support MR-guided vascular intervention.

Adult↗
PubMed2004

Iliac artery stent placement: clinical experience and short-term follow-up regarding a self-expanding nitinol stent.

PURPOSE: To evaluate the effectiveness, safety, and short-term patency rates of a self-expandable nitinol stent (JostentSelfX; Abbott Laboratories, Chicago, IL) for treatment of iliac artery stenoses. MATERIALS AND METHODS: In a prospective study, 34 chronic iliac artery stenoses were primarily treated in 27 patients (mean age, 61.7 years +/- 9.4) by placement of a JostentSelfX. Handling and visibility of the stent was scored on a 4-point scale. Before stent placement, within 3 days after stent placement and at 6 months follow-up, the clinical history, clinical stage according to the Rutherford classification, and the ankle-brachial index (ABI) were assessed. Intra-arterial digital subtraction angiography including measurement of the mean pressure gradient was performed at the time of stent placement and at 6 months follow-up or in case of recurrence of symptoms. The Wilcoxon signed rank test and Kaplan-Meier method were applied for statistical analysis. RESULTS: The immediate technical success rate was 94%. The clinical success rate immediately after the procedure was 96% and 85% at 6 months follow-up. Stent placement significantly decreased the severity of stenoses as well as the mean pressure gradients and significantly increased the ABI. Handling of the stent was judged good. No misplacement occurred. Foreshortening during deployment was negligible and no stent migration was seen. However, visibility of the stent during fluoroscopy was ranked as moderate to bad. Follow-up at 6 months revealed the cumulative angiographic primary patency rate (<50% restenosis and <10 mm Hg mean pressure gradient) to be 0.96. CONCLUSION: The evaluated self-expandable nitinol stent is an effective tool in treating iliac artery stenoses. Apart from poor visibility, handling was good. The angiographic patency rate is comparable with data reported in other stent trials.

Alloys↗
PubMed2003

[28-Year-Old Patient with Elevated Serum IgE Levels and Multiple Refractory Epidural and Paravertebral Abscesses. Clinical manifestation of a Job's Syndrome?].

BACKGROUND: The hyper-IgE syndrome is a rare primary immunodeficiency characterized by recurrent staphylococcal infections and high levels of serum IgE. CASE REPORT: The case of a 28-year-old man with epidural and paravertebral abscesses and a markedly elevated serum IgE level of 2,609 U/ml is reported. There was no allergic diathesis, nor had the patient a history of other diseases, which might explain the high serum IgE level. In a blood culture, Staphylococcus aureus was detected. Since early childhood, the patient has suffered from recurrent skin infections. CONCLUSION: The presented study case discusses the diagnosis of a Job's syndrome in this patient and reviews previously published cases. It also summarizes the current knowledge about pathogenesis and diagnostic criteria of this rare syndrome.

Adult↗
PubMed2003

Amorphous silicon, flat-panel, x-ray detector versus storage phosphor-based computed radiography: contrast-detail phantom study at different tube voltages and detector entrance doses.

RATIONALE AND OBJECTIVES: Evaluation of the contrast-detail performance of an active-matrix flat-panel x-ray detector in comparison with a storage phosphor system with special regard to the potential of dose reduction. METHODS: A digital x-ray detector based on cesium iodide (CsI) and amorphous silicon (a-Si) technology was compared with a fifth-generation storage phosphor system. A lucite plate with 36 drilled holes of varying diameters and depths was used as contrast-detail phantom. At 45 kVp, 70 kVp, and 113 kVp, images at 8 different detector entrance doses ranging between 0.3 microGy and 40 microGy were obtained. On soft-copy displays, 3 masked observers evaluated the detectability of each aperture in each image according to a 5-point scale. The mean sum scores of corresponding images were compared. RESULTS: For all tube voltages and detector entrance doses, the images obtained with the CsI/a-Si detector resulted in better observer contrast-detail performance as compared with the images of the storage phosphor system. The CsI/a-Si system allowed a calculated dose reduction of 39% at 45 kVp, 68% at 70 kVp, and 81% at 113 kVp as compared with the storage phosphor system, without loss of contrast-detail detectability. CONCLUSIONS: Under the conditions of the chosen experimental design, the CsI/a-Si system provided a superior contrast-detail performance as compared with the storage phosphor system. The potential of dose reduction increased with rising tube voltage.

Cesium↗
PubMed2003

Routine skeleton radiography using a flat-panel detector: image quality and clinical acceptance at 50% dose reduction.

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate image quality and clinical acceptance of a large-area, flat-panel X-ray detector for routine skeleton examinations at 50% dose reduction. METHODS: A total of 153 examinations (307 images) of 100 consecutive patients were evaluated. The cesium iodide-amorphous silicon active-matrix imager had a panel size of 43 x 43 cm, a matrix of 3000 x 3000, and a pixel pitch of 143 microm. All images were obtained with a kilovoltage setting identical to conventional radiographies of speed class 400. The amperage values were reduced by 50% compared with standard dose. Images were presented to 3 radiologists, who subjectively rated image quality on a 4-point scale according to 5 criteria (bone cortex, bone trabecula, soft tissue, overall contrast, and overall impression). Three trauma surgeons rated the clinical acceptance on a 4-point scale. Clinical acceptance was defined as directly derived consequences or therapy based on the presented image quality. For both evaluations, 1 represented excellent, 2 represented good, 3 represented moderate, and 4 represented nondiagnostic image quality/clinical acceptance. Intermediate scores at 0.5 intervals were allowed. RESULTS: The mean values for all 5 image quality criteria were rated good or excellent (< or = 2). A total of 4.2% (13 of 307) of the images were rated 2.5 to 3.5 concerning the overall impression. None of the imaging features was ranked more than 3.5 by any radiologist. The mean value of the clinical acceptance was between good and excellent (1.47). A total of 98.7% (151 of 153) of the examinations were rated < or = 2.5; 1.3% (2 of 153) of examinations were of moderate clinical acceptance (< or = 3.5). None of the examinations was of nondiagnostic image quality or clinical acceptance (>3.5); therefore, no study had to be repeated. CONCLUSION: Routine skeleton images with 50% dose reduction yield good image quality and good clinical acceptance. In cases with abundant soft tissue, less dose reduction or standard dose is required.

Adult↗
PubMed2002

Ultrasound-guided decompression of the spinal canal in traumatic stenosis.

The purpose of this study was to examine the efficacy of ultrasound (US)-guided decompression of the myelon in the surgical treatment of spinal fractures. Intraoperative ultrasonography was performed in 22 patients with traumatic stenosis of the spinal canal during spinal cord surgery with removal of retropulsed bony fragments. US imaging requires a posterior approach and an enlarged foramen interarcuale. The posterior vertebral facet and the myelon can accurately be distinguished from small bony fragments by ultrasonography. Pre- and postoperative computed tomography was compared with intraoperative US imaging. Complete decompression of the spinal canal was controlled by US imaging of the restored ventral epidural space, as seen after repositioning of displaced fragments. Thus, the required extent of the surgical procedure was determined by intraoperative ultrasonography. We conclude that intraoperative US imaging is an important tool to monitor the restoration of the spinal canal and decompression of the spinal cord in case of fracture. The repositioning of stenosing bony fragments using surgical instruments can be monitored. US imaging as a real-time method intraoperatively provides the surgeon with additional information and significantly influences treatment options.

Decompression, Surgical↗
PubMed2002

Time-resolved contrast-enhanced magnetic resonance angiography of the carotid arteries: diagnostic accuracy and inter-observer variability compared with selective catheter angiography.

RATIONALE AND OBJECTIVES: To assess the diagnostic accuracy and interobserver variability of contrast-enhanced magnetic resonance angiography (CE-MRA) in a time-resolved technique compared with digital subtraction angiography (x-ray DSA) in patients with suspected stenoses of the internal carotid artery. MATERIALS AND METHODS: A total of 43 patients were enrolled in this prospective study. All patients underwent selective x-ray DSA involving a total of 84 carotid arteries. CE-MRA was performed in a time-resolved technique with a fast gradient-echo sequence on a 1.5 T MR scanner: TR 3.8 milliseconds, TE 1.49 milliseconds. Four consecutive measurements, each a duration of 10 seconds, were performed with omission of measuring bolus transit time. Four independent radiologists scored the degree of stenosis. The interobserver variability was calculated for CE-MRA and x-ray DSA. RESULTS: In the 43 cases, at least one MRA measurement showed arterial contrast without venous degradation. Compared with x-ray DSA the mean sensitivity and specificity for grading stenosis > or = 70% were 98% and 86%, respectively. The interobserver agreement was substantial with no significant difference between CE-MRA (kappa value 0.794) and x-ray DSA (kappa value 0.786). CONCLUSIONS: The short acquisition time of a fast CE-MRA sequence allows a selective visualization of the internal carotid arteries without degradation from venous enhancement. It is a reliable method with a good interobserver agreement.

Adult↗
PubMed2002

Magnetic resonance imaging in patients diagnosed with papilledema: a comparison of 6 different high-resolution T1- and T2(*)-weighted 3-dimensional and 2-dimensional sequences.

PURPOSE: To evaluate visualization and signal characteristics of macroscopic changes in patients with ophthalmologically stated papilledema and to find a suitable high-resolution magnetic resonance imaging (MRI) protocol. METHOD: Nine consecutive patients with 12 ophthalmologically stated papilledemas underwent MRI of the head and orbits, which consisted of the following high-resolution sequences: 3-dimensional (3D), T2*-weighted (T2*w) constructive interference in steady-state sequence (CISS); 3D, T1-weighted (T1w) magnetization prepared-rapid gradient echo sequence (MP-RAGE) (with and without intravenous contrast medium); transverse 3D and 2-dimensional (2D) (2 mm), T2-weighted (T2w) turbo spin echo (TSE); transverse 2D (2 mm), contrast-enhanced T1w TSE with fat-suppression technique; and transverse 2D (5 mm), T2w TSE. A quantitative and qualitative evaluation of the papilla, optic nerve, optic nerve sheath, optic chiasm, and the brain was performed. The 6 high-resolution sequences were compared. RESULTS: The elevation of the optic disc into the optic globe in ophthalmologically stated papilledema was best visualized in T2w, 3D CISS sequence. The pathological contrast enhancement was best seen in T1w contrast-enhanced 2D TSE sequence with fat-suppression technique. The mean width of the optic nerve sheath directly behind the globe was 7.54 mm (+/- 1.05 mm) in the pathological eyes, compared to 5.52 mm (+/- 1.11 mm) in the normal eyes. In all patients, the cerebral indices calculated showed no signs of increased intracranial pressure or other abnormalities changing the volume of the brain or ventricles. The contrast of the orbital fat versus the optic nerve sheath, the optic nerve sheath versus the surrounding cerebrospinal fluid (CSF), the surrounding CSF versus the optic nerve, the optic chiasm versus the CSF, and the optic papilla versus the optic globe were best visualized in the 3D, T2*w CISS sequence. An enhancement of the swollen optic nerve head was best seen in all 12 cases in the T1w contrast-enhanced 2D TSE sequence with fat-suppression technique. CONCLUSION: An MRI protocol consisting of a 5-mm transverse T2w TSE sequence; a T2*w, 3D CISS sequence; a T1w, 3D MP-RAGE sequence with and without contrast medium; and a transverse T1w, (2-mm) 2D TSE sequence with fat-suppression technique with intravenous contrast medium is suitable to visualize the macroscopic changes in papilledema. In addition, this combination is an excellent technique for the examination of the orbits and the brain.

Adolescent↗
PubMed2002

Routine chest radiography using a flat-panel detector: image quality at standard detector dose and 33% dose reduction.

OBJECTIVE: The purpose of this study was to evaluate the effectiveness of a large-area, flat-panel X-ray detector for performing routine chest radiography at two different detector doses. MATERIALS AND METHODS: The chest radiographs of 50 patients (age range, 16-79 years; mean age, 57 years) were obtained at two different detector dose levels. Digital images were taken from the same patients in posteroanterior and lateral views with detector doses of 2.5 microGy and 1.8 microGy, respectively, at 125 kVp tube voltage. The cesium iodide-amorphous silicon active-matrix imager had a panel size of 43 x 43 cm, a matrix of 3000 x 3000, and a pixel pitch of 143 microm. Images were presented in a random order to three independent radiologists who were unaware of the dose level at which the images had been obtained. They subjectively rated image quality on a 4-point scale, according to six criteria (presentation of obscured lung, unobscured lung, airways, mediastinum and hilum, bony thorax, and overall impression). Statistical significance of differences was evaluated with Student's t test for paired samples (confidence level, 95%). RESULTS: Digital radiographs obtained at 2.5 and 1.8 microGy were equivalent on all quality criteria. No statistically significant differences and no tendency toward a preference for images obtained at one or the other dose level were observed. According to the registered mAs values, the average difference in patient dose was 33%. CONCLUSION: Use of flat-panel digital imagers based on the cesium iodide-amorphous silicon technique allows a considerable dose reduction during routine chest radiography without loss of image quality.

Adolescent↗