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P F Van Waes

Publications and source records attributed to P F Van Waes.

9 recordsLinked to original sources
PubMed1998

Advances in three-dimensional diagnostic radiology.

The maturity of current 3D rendering software in combination with recent developments in computer vision techniques enable an exciting range of applications for the visualisation, measurement and interactive manipulation of volumetric data, relevant both for diagnostic imaging and for anatomy. This paper reviews recent work in this area from the Image Sciences Institute at Utrecht University. The processes that yield a useful visual presentation are sequential. After acquisition and before any visualisation, an essential step is to prepare the data properly: this field is known as 'image processing' or 'computer vision' in analogy with the processing in human vision. Examples will be discussed of modern image enhancement and denoising techniques, and the complex process of automatically finding the objects or regions of interest, i.e. segmentation. One of the newer and promising methodologies for image analysis is based on a mathematical analysis of the human (cortical) visual processing: multiscale image analysis. After preprocessing the 3D rendering can be acquired by simulating the 'ray casting' in the computer. New possibilities are presented, such as the integrated visualisation in one image of (accurately registered) datasets of the same patient acquired in different modality scanners. Other examples include colour coding of functional data such as SPECT brain perfusion or functional magnetic resonance (MR) data and even metric data such as skull thickness on the rendered 3D anatomy from MR or computed tomography (CT). Optimal use and perception of 3D visualisation in radiology requires fast display and truly interactive manipulation facilities. Modern and increasingly cheaper workstations ( < $10000) allow this to be a reality. It is now possible to manipulate 3D images of 256 at 15 frames per second interactively, placing virtual reality within reach. The possibilities of modern workstations become increasingly more sophisticated and versatile. Examples presented include the automatic detection of the optimal viewing angle of the neck of aneurysms and the simulation of the design and placement procedure of intra-abdominal aortic stents. Such developments, together with the availability of high-resolution datasets of modern scanners and data such as from the NIH Visible Human project, have a dramatic impact on interactive 3D anatomical atlases.

Humans↗
PubMed1996

Value of sinus radiographs in the diagnosis of maxillary sinus disease: interobserver agreement on sinus radiographs by otolaryngologists and radiologists.

Variability between observers and specificity of sinus radiographic findings are subject to discussion. The aim of this study was to assess interobserver variability, between four physicians, two otolaryngologists and two radiologists, in the evaluation of 100 maxillary sinus radiographs. Equal agreement was found within the specialties when rating radiographs as normal or abnormal (80%). Kappa values for interobserver agreement were 0.45 for otolaryngologists and 0.58 for radiologists, both representing fair to good agreement. Otolaryngologists reported more abnormalities (67 vs, 57). Agreement on specific findings (complete opacity, fluid level and mucosal swelling) was fair to good (kappa values between 0.38 and 0.83). Agreement between the four physicians was lower on all outcomes. It is concluded that interobserver variability is within acceptable limits and justifies the continued use of conventional sinus radiographs for confirmation of maxillary sinus disease.

Adult↗
PubMed1996

Clinical safety and efficacy of iobitridol in urography.

PURPOSE: Evaluation of imaging quality and safety of iobitridol 300 compared to iohexol 300 in urography. MATERIALS AND METHODS: 180 patients were included in an urography multicenter study (3 centers, 60 patients in each). RESULTS: There was no significant difference in either the imaging quality or the clinical safety between the 2 contrast media groups. CONCLUSION: Iobitridol is a safe and efficient contrast agent in urography.

Contrast Media↗
PubMed1994

Dynamic rectal examination (defecography).

Dynamic rectal examination (DRE), first described in 1952, is becoming more widely used in the dynamic evaluation of pelvic floor and anorectal motility disorders. It is a minimally invasive investigation which is well tolerated by patients and provides information about the anosphincteric, puborectal and levator muscle in addition to insight in rectal function and structure. DRE is the only investigation of anorectal function that can give detailed anatomical information such as the presence of a rectocele, an enterocele and an intussusception. DRE should be performed in a quiet environment with a minimum number of investigators present. Any technique which attempts to study the defecatory mechanism must be a compromise since the patient is aware of being studied. In order to defecate on command the radiologist must make the patient comfortable before starting the investigative procedures to avoid any possible psychological inhibition. We have not encountered any failures in this regard. The relative value of the radiological findings with respect to symptoms and complaints is insufficiently known. This has been the main incentive to design carefully and carry out a large prospective critical evaluation of various aspects of DRE in particular the correlation with objective findings and symptoms. Moreover an assessment has been made of its overall clinical utility (Wiersma, 1994). It is very likely that DRE is both investigator- and technique-dependent. To ensure that the study is as physiological as possible the contrast medium used to fill the rectum needs to be semi-solid and malleable equivalent in consistency to a normal faecal bolus. For proper anatomical studies in females vaginal opacification is mandatory. The acceptance of vaginal contrast was good. Only 4% of the female patients preferred not to have the vaginal application of contrast. The technique of DRE when performed with small bowel and vaginal opacification provides a sensitive and objective method of detecting enteroceles. A substantial number of female patients related the onset of their complaints to hysterectomy. In female patients with constipation there was a significantly higher incidence of enteroceles in patients with a hysterectomy compared to the group of females without hysterectomy. Because of these findings a series of pre- and postoperative DREs in hysterectomy patients are on their way in our institute. Unlike a rectocele which is usually most obvious during defecation, enteroceles are sometimes appreciated only with repeated straining after evacuation.(ABSTRACT TRUNCATED AT 400 WORDS)

Anal Canal↗
PubMed1981

Bilateral occurrence of pheochromocytoma in patients with the multiple endocrine neoplasia syndrome type 2A (Sipple's syndrome).

Two kindreds with the multiple endocrine neoplasia type 2A syndrome were studied. Of one of these we examined 150 members, 20 of whom were treated with thyroidectomy for medullary carcinoma and nine with bilateral adrenalectomy for pheochromocytoma. Of the second kindred 50 members were examined, seven of whom were thyroidectomized and seven treated with bilateral adrenalectomy. Pheochromocytomas were invariably found on both sides, even in four cases in which the adrenals on one side appeared to be completely normal, not only at preoperative roentgenologic examination but also on inspection during the operation. The microscopic finding of micronodules and a cluster of abnormal medullary cells identical with those found in pheochromocytomas in one of the apparently normal adrenals represents a first stage in the development of diffuse medullary hyperplasia as well as nodular hyperplasia. This is in accordance with the fact that in the MEN type 2A syndrome pheochromocytomas are always multicentric and multiple in origin. On the basis of these findings we conclude that all patients with the MEN 2A syndrome who show symptoms and signs of active pheochromocytoma should be subjected to bilateral adrenalectomy, even when one or both of the adrenals appear to be normal at roentgenologic investigation.

Adrenal Gland Neoplasms↗