Thomas J Vrieze

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In x-ray computed tomography (CT), the most common parameter used to estimate and minimize patient dose is the CT dose index (CTDI). The CTDI is a volume-averaged measure that is used in situations where the table is incremented in conjunction with the tube rotation. Variants of the CTDI correct for averaging across the field of view and for adjacent beam(More)
OBJECTIVE The purpose of this study was to determine typical radiation dose levels to patients undergoing CT-guided interventional procedures. MATERIALS AND METHODS A total of 571 patients undergoing CT interventional procedures were included in this retrospective data analysis study. Enrolled patients underwent one of five procedures: cryoablation,(More)
A study was conducted to investigate how operator exposure in interventional radiology is affected by various common fluoroscopic imaging conditions. Stray radiation levels surrounding the imaging chain of a C-arm angiographic system were measured with an anthropomorphic abdomen phantom under different imaging conditions, and isodose curves were(More)
OBJECTIVE The purpose of our study was to evaluate the dose and image quality performance of a dedicated cone-beam CT (CBCT) scanner in comparison with an MDCT scanner. MATERIALS AND METHODS The conventional dose metric, CT dose index (CTDI), is no longer applicable to CBCT scanners. We propose to use two dose metrics, the volume average dose and the mid(More)
PURPOSE To assess the z-axis resolution improvement and dose reduction potential achieved using a z-axis deconvolution technique with iterative reconstruction (IR) relative to filtered backprojection (FBP) images created with the use of a z-axis comb filter. METHODS Each of three phantoms were scanned with two different acquisition modes: (1) an ultrahigh(More)
OBJECTIVE To investigate whether the integrated circuit (IC) detector results in reduced noise in computed tomography (CT) colonography (CTC). METHODS Three hundred sixty-six consecutive patients underwent clinically indicated CTC using the same CT scanner system, except for a difference in CT detectors (IC or conventional). Image noise, patient size, and(More)
The purpose of this study was to use three-dimensional (3-D) printing techniques to construct liver and brain phantoms having realistic pathologies, anatomic structures, and heterogeneous backgrounds. Patient liver and head computed tomography (CT) images were segmented into tissue, vessels, liver lesion, white and gray matter, and cerebrospinal fluid(More)
PURPOSE To determine the precision and accuracy of CTDI(100) measurements made using commercially available optically stimulated luminescent (OSL) dosimeters (Landaur, Inc.) as beam width, tube potential, and attenuating material were varied. METHODS One hundred forty OSL dosimeters were individually exposed to a single axial CT scan, either in air, a(More)
Radiographs that must be repeated, which are commonly referred to as "repeats," represent additional, non-billable costs due to increased film, chemistry, and equipment use as well as increased personnel time. Furthermore, patients receive additional radiation exposure from repeats and must remain on the premises until the second exam is completed.(More)
OBJECTIVE A new twin screen-film cassette system optimised for conventional chest radiography was evaluated by four thoracic radiologists. MATERIALS AND METHODS The twin screen-film cassette system produces two film images, the front film optimised for the mediastinal region of the chest, the rear for the lung region. Image degradation on either(More)