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Biomedical subjects

Stefan Tigges

Publications and source records attributed to Stefan Tigges.

7 recordsLinked to original sources
PubMed2006

Effect of contrast concentration, tube potential and reconstruction kernels on MDCT evaluation of coronary stents: an in vitro study.

INTRODUCTION: To evaluate effect of different kVp, reconstruction kernels and contrast concentrations on stent luminal diameter measurements and luminal contrast attenuation values. METHODS: Two metallic coronary stents (2.75 mm and 3.0 mm) were deployed in silicone tubes and tubes were filled with diluted iodinated contrast (1:20 dilution of Iohexol 350 mg% to achieve an attenuation value of 550 HU at 120 kVp). The tubes were scanned at 80, 100, 120 and 140 kVp. Each scan acquisition was reconstructed using B10f, B25f, B31f, B36f, B41f, B46f, B60f, and B80f kernels. Scans were repeated using 1:35 contrast dilution (350 HU at 120 kVp). Luminal diameter was measured at mid stent level for each stent, in datasets acquired at different kVp, contrast concentrations, and reconstruction kernels. Luminal attenuation values (HU) were measured at the mid stent level and at a distance of 1 cm from the stent entrance within the tube lumen. RESULTS: kVp did not have a significant effect on the visualization of stent luminal diameter (P > 0.277). The change in kernel significantly affected the difference in luminal HU values at stent and non-stent levels (P < 0.001), with B46f showing the least difference in HU values. The lower contrast concentration (350 HU) showed substantially less artifactual stent stenosis compared to high contrast concentration (550 HU) (P < 0.001). There was excellent inter-observer agreement for stent luminal diameters and attenuation value measurements (r (2)=0.971, P < 0.001). CONCLUSIONS: For lower spatial resolution kernels, 120 kVp or 140 kVp provides better estimate of stent lumen. Reconstruction kernels and contrast concentration (HU) have significant effect on visualization of in-stent luminal diameter and artifactual stenosis. In clinical practice, B46f kernel and lower contrast enhancement value ( approximately 350 HU) may be optimal for evaluating the stent lumen.

Analysis of Variance↗
PubMed2005

MDCT pulmonary angiography: image processing tools.

The postprocessing of multidetector row computed tomography (MDCT) data sets is best termed "volume interrogation." Most techniques are best applied as problem-solving tools rather than as preset protocols, and radiologist involvement is essential. The ability to interact with an isotropic or nearly isotropic data set in near real-time is a tremendous advance, but is one that radiologists must rapidly embrace and master. This review begins with a discussion of the basic postprocessing tools relevant to the analysis of the pulmonary vasculature and proceeds to illustrate the clinical application of these techniques to the MDCT of acute and chronic thromboembolic disease. It is clear that in the era of MDCT, axial image review alone is rapidly becoming not only impractical, but also suboptimal. Reformatted images are also beneficial as communication tools for our referring colleagues and can enhance the role of the radiologist as part of the clinical team.

Angiography↗
PubMed2004

Routine chest radiography in a primary care setting.

PURPOSE: To determine the frequency, diagnostic yield, outcomes, cost, and rate of false-positive results of routine chest radiography performed in asymptomatic patients in the primary care setting. MATERIALS AND METHODS: Radiography reports on all patients who underwent routine or screening posteroanterior and lateral chest radiography at a university-affiliated primary care clinic in 2001 were reviewed. Radiographic results were coded as normal or minor findings or as major abnormalities, such as pulmonary nodules, requiring further diagnostic evaluation. Outcomes of patients with major abnormalities were established by using chart reviews or reviewing additional radiographs. Costs were estimated by using 2002 Medicare reimbursement rates. The main measures assessed were frequency, costs, and rate of false-positive results of routine chest radiography. RESULTS: Of 3812 radiographs obtained at the primary care clinic, 1282 (34%) were ordered for routine or screening purposes by the referring physician. Nine hundred twenty-two radiographs were obtained in male patients and 360 were obtained in female patients; their mean and median age was 49 years (age range, 4-87 years). Fifteen chest radiographs showed major abnormalities. No patient younger than 40 years had a major abnormality. Fourteen of the 15 findings of major abnormalities proved to be false-positive. No disease requiring treatment was diagnosed as a result of radiographic findings. The total cost for follow-up radiography and computed tomography was US dollar 46,609.49. CONCLUSION: Routine chest radiography has low diagnostic yield in asymptomatic primary care patients.

Adolescent↗
PubMed2002

Is there need for thoracic spine radiographs following a negative chest CT in trauma patients?

The purpose of this study was to assess the need for conventional radiographs of the thoracic spine for routine clearance of trauma patients in whom chest CT has revealed no spinal trauma. The study was in the form of a retrospective review of trauma patients over the previous five years who underwent conventional radiographs of the thoracic spine following a chest CT that revealed no spinal trauma. Two hundred thirty-five trauma patients were found to have undergone conventional thoracic spine series following a chest CT that showed no spinal trauma. In 234 of the cases, the thoracic spine series was also negative. In one case, the thoracic spine series revealed mild anterior compression of the T7 vertebral body. This injury was stable and required no specific intervention. CT of the chest is an adequate evaluation of the thoracic spine in trauma patients who require routine thoracic spine clearance, making subsequent conventional radiographs of the thoracic spine unnecessary.

Journal Article↗
PubMed2002

Incremental benefit of maximum-intensity-projection images on observer detection of small pulmonary nodules revealed by multidetector CT.

OBJECTIVE: Our purpose was to assess the incremental effect of maximum-intensity-projection (MIP) image processing on the ability of various observers to detect small (<1 cm in diameter) central and peripheral lung nodules revealed by multidetector CT. MATERIALS AND METHODS: We retrospectively identified 25 patients with metastatic disease, each having from two to nine nodules that were 3-9 mm in diameter. Two senior and three junior reviewers interpreted all images on a workstation. The observers first reviewed axial images (3.75-mm collimation, 3-mm reconstruction interval, multidetector acquisition) in cine and sequential fashion and recorded the size, lobe, and central or peripheral (within 1 cm of the edge of lung) location of each nodule. MIP images (10-mm slab, 8-mm interval) were then reviewed, and additional nodules detected were recorded. Final counts were established by consensus. RESULTS: The reviewers found 122 nodules (71 peripheral, 51 central) in the 25 patients. The addition of MIP slabs significantly enhanced reviewer detection of central nodules (p < 0.001) and junior reviewer detection of peripheral nodules (p < 0.001). MIP slabs also reduced the effects of reviewer experience, particularly for peripheral nodules. CONCLUSION: MIP processing reduces the number of overlooked small nodules, particularly in the central lung. Observer nodule detection remains imperfect even when lesions are clearly depicted on images.

Adult↗
PubMedDate not supplied

Visualization techniques in computed tomographic coronary angiography.

Cardiac computed tomography (CT) scans can produce enormous datasets (>3,000 images), making traditional axial image interpretation un-workable. Previously existing and new techniques including multiplanar reformats, volume rendering, maximum intensity projections, curved multiplanar reformats, and "4D" (time-resolved) methods have all been used to increase diagnostic accuracy and reduce interpretation times. The methods and applications of these techniques to cardiac anatomy will be reviewed and discussed with an eye toward practical film interpretation.

Contrast Media↗