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Peter M A van Ooijen

Publications and source records attributed to Peter M A van Ooijen.

10 recordsLinked to original sources
PubMed2006

User questionnaire to evaluate the radiological workspace.

Over the past few years, an increase in digitalization of radiology departments can be seen, which has a large impact on the work of the radiologists. This impact is not only demonstrated by the increased use of digital images but also by changing demands on the whole reading environment. In this study, we evaluated the satisfaction of our radiologists with our digital Picture Archival and Communication System environment and their workspace. This evaluation was performed by distribution of a questionnaire consisting of a score sheet and some open questions to all radiologists and residents. Out of 25 questionnaires, 12 were adequately answered and returned. Results clearly showed that most problems were present in the area of reading room design and layout and comfort and ergonomics. Based on the results from this study, adaptations were made and the results were also used in the planning of the redesign of the entire department of radiology.

Analog-Digital Conversion↗
PubMed2006

Correction of error in two-dimensional wear measurements of cemented hip arthroplasties.

The irregularity of individual wear patterns of total hip prostheses seen during patient followup may result partially from differences in radiographic projection of the components between radiographs. A method to adjust for this source of error would increase the value of individual wear curves. We developed and tested a method to correct for this source of error. The influence of patient position on validity of wear measurements was investigated with controlled manipulation of a cadaveric pelvis. Without correction, the error exceeded 0.2 mm if differences in cup projection were as small as 5 degrees. When using the described correction method, cup positioning differences could be greater than 20 degrees before introducing an error exceeding 0.2 mm. For followup of patients in clinical practice, we recommend using the correction method to enhance accuracy of the results.

Arthroplasty, Replacement, Hip↗
PubMed2005

Comparison of analog and digital preoperative planning in total hip and knee arthroplasties. A prospective study of 173 hips and 65 total knees.

INTRODUCTION: Digital correction of the magnification factor is expected to yield more accurate and reliable preoperative plans. We hypothesized that digital templating would be more accurate than manual templating for total hip and knee arthroplasties. PATIENTS AND METHODS: Firstly, we established the interobserver and intraobserver reliability of the templating procedure. The accuracy and reliability of digital and analog plans were measured in a series of 238 interventions, which were all planned using both techniques. RESULTS: Interobserver reliability was good for the planning of knee arthroplasties (e-values 0.63-0.75), but not more than moderate for the planning of hip arthroplasties (e-values 0.22-0.54). Analog plans of knee arthroplasties systematically underestimated the component sizes (1.1 size on average), while the digital procedure proved to be accurate (0.1-0.4 size too small on average). The following figures show percentage of cases receiving a correct implant, allowing an error of one size. Digital templating of the hip arthroplasty was less frequently correct (cemented cup and stem: 72% and 79%; uncemented cup and stem: 52% and 66%) than analog planning (cemented cup and stem: 73% and 89%; uncemented cup and stem: 64% and 52%). INTERPRETATION: Planning of component sizes for total knee arthroplasties is an accurate procedure when performed digitally. Our digital preoperative plans which were performed by someone other than the surgeon were less accurate than the analog plans prepared by the surgeon.

Arthroplasty, Replacement, Hip↗
PubMed2004

Detection, visualization and evaluation of anomalous coronary anatomy on 16-slice multidetector-row CT.

Early identification and evaluation of relatively frequent anomalous coronary anatomy is quite relevant because of the occurrence of sudden cardiac death or related symptoms of myocardial ischemia. Selective coronary angiography (CAG) is invasive, expensive and cannot always provide the required information adequately. Recently, non-invasive imaging techniques such as magnetic resonance imaging and multidetector-row computed tomography (MDCT) have been shown to provide a good anatomical view of the coronary artery tree. This study aims to demonstrate the value of 16-MDCT for evaluation of anomalous coronary anatomy. In 13 patients scanned using 16-MDCT, six different coronary anomalies were diagnosed [two absent left main, one single vessel left coronary artery (LCA), three LCA originating from the right (two with interarterial course), six right coronary artery originating from the left, one double left anterior descending (LAD)]. Mean diagnostic quality, recorded by two observers using a 5-point scale (1= non-diagnostic to 5= excellent diagnostic quality), resulted in a mean score of 3.73 (SD 1.19) without any non-diagnostic result. MDCT offers an accurate diagnostic modality to visualize the origin and course of anomalous coronary arteries by a three-dimensional display of anatomy. Shortcomings in CAG can be overcome by the use of contrast-enhanced MDCT.

Adult↗
PubMed2004

Influence of scoring parameter settings on Agatston and volume scores for coronary calcification.

Current multi-detector CT and electron beam tomography (EBT) technology enables the evaluation of coronary calcification. Multiple software packages are available to quantify calcification using several scoring algorithms implementing user-definable scoring parameters. We investigated the effect of scoring parameters on the calcium score outcome. Three parameters (four-connected or eight-connected, lesion size threshold and interpolation) are evaluated. Their theoretical influence on the scoring outcome is shown using simplified examples. To evaluate the effect in real data, we performed calcium scoring on randomly chosen EBT scans from 50 participants in an epidemiological study. Both the Agatston and volume scores were calculated. Changing from eight-connected to four-connected connectivity decreased both Agatston and volume scores (mean variability Agatston 3.15% and volume score -3.52%). Decreasing the threshold from 4 to 2 pixels increased the calcium scores because smaller lesions were also selected as calcified plaques (mean variability Agatston 16.23% and volume score 18.66%). Finally, the use of interpolation had a large negative effect on the volume score (mean variability -29.67%) and almost no effect on the Agatston score. Parameter settings in software for quantification for coronary calcification affect the calcium score outcome. Therefore, parameter settings for calcium scoring should be standardized.

Aged↗
PubMed2003

Coronary artery imaging with multidetector CT: visualization issues.

Noninvasive imaging of the coronary arteries has attracted growing interest in the past few years. One of the possible acquisition techniques is multidetector computed tomography (CT) that produces large three-dimensional (3D) data sets that require visualization techniques for data evaluation. The objective of this article is to increase knowledge of possible 3D visualization techniques together with their advantages and disadvantages for the routine evaluation of cardiac data sets. Common imaging techniques available to the radiologist at standard workstations are multiplanar reformation (MPR), oblique MPR, curved MPR, maximum-intensity projection (MIP), shaded-surface display, and direct volume rendering. Each of these techniques has its advantages and disadvantages for the visualization of the coronary artery tree. Several additions to the basic techniques have been developed to overcome some of their shortcomings. Different clinical examinations, such as stent evaluation, stenosis evaluation, and bypass evaluation, require different visualization techniques. The choice of preferred technique for each clinical study depends on the advantages and disadvantages of the various techniques as described in the literature. Because of the large number of possible settings and projection angles, it is important for users to interactively manipulate the images and review the whole vessel volume rather than just looking at static reformatted images. Errors such as findings of false stenoses can be avoided by means of accurate and appropriate use of software features. This requires training of users both with regard to the capabilities of the software and the background of the different techniques and their possible pitfalls. The authors believe that volume rendering of the whole heart is useful for anatomic evaluation of the coronary arteries. For more detailed observation of specific lesions, slab imaging with volume rendering or MIP is required.

Coronary Angiography↗
PubMed2003

Noninvasive coronary imaging: CT versus MR.

Conventional coronary angiography is the undisputed gold standard in coronary lumenography. The small but serious risk involved in the procedure, the cost, and the necessary radiation dose have triggered the development of noninvasive alternatives such as electron-beam computed tomography, multi-slice computed tomography, and magnetic resonance coronary angiography. This paper will discuss the background, benefits and drawbacks of these imaging modalities with respect to the coronary arteries. Evolution in techniques and increase in sensitivity and specificity are clearly seen in all imaging modalities, thus increasing the clinical relevance and the ability to replace conventional coronary angiography.

Coronary Angiography↗
PubMed2002

Comparison of contrast-enhanced magnetic resonance angiography and conventional pulmonary angiography for the diagnosis of pulmonary embolism: a prospective study.

BACKGROUND: Diagnostic strategies for pulmonary embolism are complex and consist of non-invasive diagnostic tests done to avoid conventional pulmonary angiography as much as possible. We aimed to assess the diagnostic accuracy of magnetic resonance angiography (MRA) for the diagnosis of pulmonary embolism, using conventional pulmonary angiography as a reference method. METHODS: In a prospective study, we enrolled 141 patients with suspected pulmonary embolism and an abnormal perfusion scan. Patients underwent MRA before conventional pulmonary angiography. Two reviewers, masked with respect to the results of conventional pulmonary angiography, assessed MRA images independently. Statistical analyses used chi(2) and 95% CI. FINDINGS: MRA was contraindicated in 13 patients (9%), and images were not interpretable in eight (6%). MRA was done in two patients in whom conventional pulmonary angiography was contraindicated. Thus, MRA and conventional pulmonary angiography results were available in 118 patients (84%). Prevalence of pulmonary embolism was 30%. Images were read independently in 115 patients, and agreement obtained in 105 (91%), kappa=0.75. MRA identified 27 of 35 patients with proven pulmonary embolism (sensitivity 77%, 95% CI 61-90). Sensitivity of MRA for isolated subsegmental, segmental, and central or lobar pulmonary embolism was 40%, 84%, and 100%, respectively (p<0.01 for isolated subsegmental vs segmental or larger pulmonary embolism). However, subgroups contained small numbers. MRA identified pulmonary embolism in two patients with normal angiogram (98%, 92-100). INTERPRETATION: MRA is sensitive and specific for segmental or larger pulmonary embolism. Results are similar to those obtained with helical computed tomography, but MRA has safer contrast agents and does not involve ionising radiation. MRA could become part of the diagnostic strategy for pulmonary embolism.

Adolescent↗
PubMedDate not supplied

Initial results on visualization of coronary artery stents at multiple heart rates on a moving heart phantom using 64-MDCT.

OBJECTIVE: Evaluation of the image quality of coronary artery stents at various heart rates using Multi Detector Computed Tomography (MDCT). METHODS: Nine different coronary stents were attached to a moving heart phantom and scanned using a 64-MDCT with a rotation time of 330 milliseconds (ms). The heart rate of the phantom was varied between 0 and 115 beats per minute (bpm). Two independent methods were used to investigate image quality. After reconstruction the average Houndsfield Unit (HU) value in the stent lumen was measured in the longitudinal and the cross-sectional plane. The stent images were then presented to two radiologists. The radiologists were asked to rank the images from good to bad based on lumen visibility and overall image quality. A second ranking was obtained using the CT density values. Finally two rankings were compared. RESULTS: Compared to the value for air, the HU-values measured in the lumen increased by 50 to 700 HU. Average slope value in the longitudinal plane was 1.7 +/- 0.6 HU/bpm, and the average slope value in the cross-sectional plane was 1.7 +/- 0.8 HU/bpm. This shows increased attenuation with increasing heart rate and thus a negative correlation between image quality and heart rate in both planes for all stents. The ranking acquired from the radiologists resembled the measured results as they also showed a negative correlation between the two variables. Using the results of the CT density measurements an analysis was done on multi-segment reconstruction (MSR). CONCLUSION: A negative correlation between the heart rate and image quality of coronary stents was found by two independent methods. MSR showed no benefit for image quality in this study.

Air↗