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There has been a definite increase in the incidence of Crohn's disease in recent years. A particular feature of this disease is the high incidence of recurrence after surgical removal of affected portions of the gut. This may be due to a resection carried out through a diseased segment and this stresses the importance of recognising early changes. This is not possible by conventional radiology (small bowel examination, barium enema) and is therefore an indication for pre-operative visceral angiography. The results obtained in ten patients, who subsequently came to surgery, were compared with the findings on conventional radiology and endoscopy. Angiography proved the best method for the early demonstration of inflammatory changes. This was confirmed by histological examination of the resected specimen.

Thirty-five patients with fractures of the anterior pelvis, in whom there was clinical suspicion of trauma to the posterior part of the pelvis, were examined by conventional radiology, bone scintigraphy and computed tomography, and the results were compared. CT provided the most information and made it possible to evaluate the soft tissues and organs of the pelvis. Bone scintigraphy produced the same number of abnormal findings as CT (sensitivity 100%), but was unable to differentiate between lesions of the sacro-iliac joints, fractures of the sacrum, combined injuries or degenerative processes. A positive bone scintigram is a reliable finding, with a high predictive value. A negative result excludes a fracture or other lesions of the dorsal portion of the pelvis completely. Conventional radiographs provided a correct diagnosis in only 37.1% as compared with CT.

Diagnosis of ligament ruptures via the possibilities of conventional radiology is often insufficient. To verify CT efficiency, postmortem specimens were scanned in axial, coronal and sagittal planes and compared with anatomical findings of sections in identical planes. After the preliminary examinations we conducted a study on 32 patients. The examinations of the anterior talofibular ligament showed a correlation between CT and operative findings in 30 of 32 cases.

Thirty-six patients with bacterial spondylitis and eight patients with hemispherical spondylosclerosis (Dihlmann 1981) were examined by conventional x-ray techniques, computed tomography, 99mTc-MDP scintigraphy and 67Gallium scintigraphy. Conventional radiology is adequate for making the diagnosis. Where there is doubt, however, and for observing the progress of the disease, CT and scintigraphy may be used. Hemispherical spondylosclerosis can be identified by means of these additional methods.

Four patients with retroperitoneal fibrosis (Ormond's disease) were examined by computer tomography; the appearances are described and the differential diagnosis discussed. Computer tomography clearly defines the proliferative-inflammatory process and together with conventional radiology, angiography and lymphangiography it permits a presumptive diagnosis of retroperitoneal fibrosis. The non-invasive nature of computer tomography makes it the method of choice for follow-up of this disease.

CT of the foot often helps clarification of difficult problems where conventional radiology has proved inadequate. Sections in the coronary and transverse plane may demonstrate fractures, joint involvement and displacement of bone fragments. Ill-defined degenerative changes in the talo-calcaneal joint can be demonstrated. The extent and localisation of rare tumours of the foot can be shown and additional information may be obtained by densitometric studies.

After breathing pure oxygen, total atelectasis of one lung was produced in ten dogs; its development and regression was followed by CT and by conventional radiology. 30 seconds after cessation of ventilation, it was possible to show a rise in CT density of the atelectatic lung from -764 +/- 32 HU to -739 +/- 49 HU. The average time from the cessation of ventilation to total atelectasis averaged 5.5 +/- 1.1 minutes. The earliest sign on conventional radiographs was often seen after 30 seconds and usually after 60 seconds and consisted of mediastinal displacement. Extensive atelectasis regressed in only one out of six animals within one hour after resuming ventilation. The experimental methods and results and the significance of the physiological findings in a clinical context are discussed.

Xeroradiograms and conventional radiographs of the hands of 50 patients with chronic polyarthritis were performed. These were compared with regard to the features which are found in chronic polyarthritis. There were no significant differences between xeroradiography and conventional radiology. Xeroradiography was a little better for demonstrating changes in the soft tissues and erosions, but conventional radiographs were superior in showing osteoporosis, cysts and the absorption of subchondral lamellae. In general, xeroradiography and conventional procedures were of equal value in the diagnosis of chronic polyarthritis. For practical purposes, conventional radiography is to be preferred and xeroradiography may be regarded as an additional procedure, particularly for the investigation of soft tissue changes.