Paul F. G. M. van Waes

Computer-aided diagnosis in high resolution CT of the lungs

A computer-aided diagnosis (CAD) system is presented to automatically distinguish normal from abnormal tissue in high-resolution CT chest scans acquired during daily clinical practice. From high-resolution computed tomography scans of 116 patients, 657 regions of interest are extracted that are to be classified as displaying either normal or abnormal lung tissue. A principled texture analysis approach is used, extracting features to describe local image structure by means of a multi-scale filter bank. The use of various classifiers and feature subsets is compared and results are evaluated with ROC analysis. Performance of the system is shown to approach that of two expert radiologists in diagnosing the local regions of interest, with an area under the ROC curve of 0.862 for the CAD scheme versus 0.877 and 0.893 for the radiologists.

Preoperative staging of rectal cancer with computerized tomography. Accuracy, efficacy, and effect on patient management

Twenty‐three consecutive patients with rectal cancer were evaluated by pelvic computerized tomography (CT). The study was designed to assess the accuracy of preoperative CT staging. The results showed that the CT and surgical and/or pathologic staging agreed in 18 patients. In two patients, the pelvic extent was correctly assessed, but small liver implants were not recognized. In three patients, CT over‐estimated the extent of disease. The authors also studied whether or not CT yielded significant new information, which was not obtainable by other diagnostic methods. In most patients this was the case. Finally, the authors wanted to know the extent to which this knowledge influenced the decision about how to treat the patient. Computerized tomography findings influenced the treatment in less than 50% of the patients. It is concluded that the accuracy in staging, and the addition of new and unique information justified the routine use of CT prior to surgical intervention in all patients with known invasive rectal cancer.

Computed tomography in complicated acute appendicitis

Due to the position and length of the appendix, intraabdominal abscesses after perforation in complicated acute appendicitis may occur in several different and sometimes unsuspected anatomical locations. Five patients are described with proven complicated acute appendicitis and inflammatory processes in multiple sites: anterior pararenal space, general retroperitoneum, subcutaneous fat space, intraperitoneal cavity, and small bowel mesentery. A confusing case of ileocecal carcinoid with mesenteric involvement is also presented.In all cases complicated acute appendicitis was diagnosed on CT prior to surgery, except in 1 case in which a pelvic abscess developed after intramural cecal bleeding in a patient with hemophilia B.

New post-imaging software provides fast and accurate volume data from CTA surveillance after endovascular aneurysm repair.

Purpose: To quantify intra- and interobserver variabilities when measuring total aneurysm volume after endovascular aneurysm repair using the Vitrea 2 System and to compare it in terms of accuracy and processing time with the gold standard methods using the Easy Vision workstation. Methods: Total aneurysm volumes from 30 postendograft CTA datasets were randomly selected from a database consisting of ∼400 CTA datasets recorded in 89 patients. The intra- and interobserver variabilities were measured on the Vitrea workstation by 2 investigators. The intermodality variability was calculated for the same measurements using the Easy Vision workstation. The differences of each pair of measurements were plotted against their mean, and the repeatability coefficient (RC) was calculated. The mean differences were also expressed as a percentage of the first measurements. Results: The intraobserver mean difference was 1.6 mL (1.4%) with an RC of 10.8 mL (10.1%) and the interobserver mean difference was −1.4 mL (–1.4%) with an RC of 11.7 mL (10.2%). The intermodality mean difference was 1.8 mL (2.0%) with an RC of 15.8 mL (11.1%). The Vitrea workstation required a median of 8 minutes (interquartile range 7–10) for 1 observer and 6 minutes (interquartile range 5–8) for the other to perform a complete volume segmentation of each patient dataset compared to an estimated average of 30 minutes using the Easy Vision workstation. Conclusions: The Vitrea workstation provides fast and accurate volume data from spiral CTA follow-up of endovascular aneurysm repair. This software may enhance the acceptability of volume surveillance in daily practice.

Role of CT in diagnosis and management of complications of diverticular disease.

The clinical complications of diverticular disease may be unclear. Seven patients with complicated diverticulitis of the transverse, descending, and sigmoid colon were examined with computed tomography. Exact knowledge of the anatomical relationships of the transverse, descending, and sigmoid colon and neighboring structures are a prerequisite for understanding and interpreting the extensions of peridiverticular disease. Computed tomography proved to be useful in evaluating the presence and extent of sequelae of perforations, and, as a consequence, influenced the planning and timing of treatment.

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 (<

Pancreatic lesions and transfascial perirenal spread: computed tomographic demonstration

10000) allow this to be a reality. It is now possible to manipulate 3D images of 2563 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.

Xanthogranulomatous pyelonephritis: Comparison of extent using computed tomography and magnetic resonance imaging in one case

Computed tomographic (CT) findings in 105 cases of pancreatitis and 107 cases of pancreatic carcinoma were analyzed retrospectively to determine the occurrence and roentgenologic signs of penetration of the anterior renal fascial planes in relation to clinical symptoms. In pancreatitis, the perirenal fat was infiltrated in 7% to variable extents by extrapancreatic fluid collections, either as asymptomatic fluid lying alongside renal fascial planes and perirenal septa (5 cases) or as well-circumscribed fluid collections causing clinical symptoms (2 cases). In pancreatic carcinoma the occurrence of retropancreatic extension to a perirenal space was rarer (3%). Distinction on CT between perirenal involvement from the pancreas and primary adrenal or renal lesions with anterior spread can prevent unnecessary surgery.

Direct multiplanar computed tomography of the petrous bone

In a case of diffuse xanthogranulomatous pyelonephritis, computed tomography (CT) and magnetic resonance (MR) were used. The MR proved to be more precise in the preoperative evaluation of inflammatory extension to the spleen and into the abdominal wall. The CT was more accurate in excluding spread to the colon.