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RATIONALE AND OBJECTIVES To compare manganese-DPDP-enhanced and gadolinium-DTPA-enhanced MR imaging in patients suspected of having pancreatic cancer. METHODS Fifteen patients who underwent MR imaging for suspected pancreatic cancer and received gadolinium-DTPA took part in a clinical phase III trial in which the efficacy of manganese-DPDP for detection of pancreatic cancer was evaluated. T1-weighted gradient-echo (GRE) images with and without fat suppression were used. Signal-to-noise ratio and contrast-to-noise ratio were calculated before and after the administration of each contrast agent. Image quality was assessed using a four-step score; delineation of the normal pancreas was assessed by two readers in consensus. RESULTS In terms of pancreatic signal-to-noise ratio, only gadolinium-DTPA-enhanced fat-suppressed and non-fat-suppressed GRE imaging showed a significant (P < 0.001) increase (72% and 61%, respectively). In the patients with a focal pancreatic lesion (n = 14), a significant increase in contrast-to-noise ratio was found only in manganese-DPDP-enhanced GRE imaging without (106%) and with (82%) fat saturation. Qualitative image analysis demonstrated a significant improvement of manganese-DPDP-enhanced fat-suppressed MR images in delineating the pancreatic parenchyma (P < 0.01) as well as pancreatic tumors (P < 0.01). CONCLUSIONS T1-weighted manganese-DPDP-enhanced GRE imaging with fat saturation should be regarded as the most suitable combination for detecting a pancreatic lesion.

The aim of this study was to evaluate the suitability of electron beam tomography (EBT) with fast continuous volume scanning for CT angiography (CTA) in chest and abdomen. An Evolution XP EBT scanner with a new software version (12.34) was used. One hundred forty images per study can be acquired in 17 s using 3-mm collimation and overlapping image reconstruction. Study protocols for five different clinical applications of EBT CTA were established and evaluated. The EBT CTA technique was performed in 155 patients. High- and homogeneous density values were achieved along the whole course of the vessels; the mean density in the aorta was > 240 HU. Coeliac axis, superior and inferior mesenteric artery, renal and lumbar arteries were visualised in all cases. Maximum intensity projection and shaded surface display reconstruction demonstrated the relation between aneurysm and aortic branches very well due to an excellent resolution along the z-axis. In large scan volumes overlapping image reconstruction demonstrated better resolution along the z-axis than is available with helical CT. The EBT CTA technique proved to be very well suited excellent suitability for evaluation of pulmonary vessels. Compared with helical CT, EBT CTA offers a shorter scan time, which allows higher contrast enhancement in pulmonary vessels. The identification of intraluminal emboli and mural thrombi has improved. The EBT CTA technique is a very reliable tool for evaluation of aortic disease and pulmonary vessels.

RATIONALE AND OBJECTIVES: To examine dose and image quality of electron-beam CT (EBCT) with continuous volume scan versus spiral CT. METHODS: An EBCT scanner was compared with a spiral CT (SCT) scanner. Three phantoms were used to measure low-contrast resolution, high-contrast resolution, slice width, and dose. RESULTS: The EBCT scans showed 30% lower high-contrast resolution for most settings. The dose was comparable to that of spiral CT with 3 mm collimation and 76%/106% higher with EBCT for 1.5 mm/6 mm collimation. Low-contrast resolution was comparable to that of spiral CT using 3 mm collimation, slightly worse for 1.5 mm, and bad for 6 mm EBCT collimation (four times higher dose to reach comparable contrast-to-noise ratio). CONCLUSIONS: Significant restrictions were found using EBCT with continuous volume scan. The authors found that 3 mm collimation can yield acceptable high-contrast resolution and good low-contrast resolution compared with spiral CT. The use of 6 mm or 1.5 mm collimation needs to be restricted to selected cases.

The purpose of this study was to evaluate the potential of superparamagnetic iron oxide particles (SPIO) as tissue specific contrast agent in magnetic resonance (MR) imaging in detection and characterization of focal hepatic lesions. We investigated 45 patients with focal hepatic lesions. T 1 -weighted SE (TR 650/TE 15 ms) and T 2 -weighted SE (TR 2015–2030/TE 45 and 90 ms) unenhanced images were obtained. After SPIO application we performed T 1 -weighted images with and T 2 -weighted images with and without fat suppression using the same image parameters. Liver signal intensity decreased by 74% (min 47%, max 83%) on T 2 -weighted images after application of the contrast agent. Benign lesions (FNH, adenoma) showed an average signal drop of 40% (min 20%, max 47%) whereas malignant lesions showed no significant change of signal intensity on post-contrast images. The mean tumor-to-liver contrast-to-noise ratio (C/N) was improved in all post-contrast sequences irrespective of the lesion type. An additional increase of tumor-to-liver contrast by use of fat suppression technique could be established in the slightly T 2 -weighted sequence (TE 45 ms). In metastases, divided in different size groups, we could determine a significant size relation of tumor-to-liver C/N. After SPIO application the number of detected lesions increased distinctly, especially small foci are more easily demonstrated. SPIO particles are a efficacious contrast agent for MR examinations of the liver. For tumor characterization T 1 - and T 2 -weighted pre- and post-contrast images are necessary. The T 1 -weighted sequences are helpful to differentiate benign lesions such as cysts and hemangiomas from malignant lesions. Detection and differential diagnoses of hepatic lesions are improved by use of the SPIO-particles.

The authors report their experience with three different metallic stents for the treatment of biliary obstructions during a 6.5-year period (between February 1989 and June 1995).In an uncontrolled, nonrandomized, and prospective study, 168 patients with obstructive jaundice underwent transhepatic placement of metallic stents. Patients were excluded if they were deemed too ill for intervention or had incorrectable coagulopathy. Those patients undergoing external and/or intraluminal radiation therapy, and patients in whom an internal-external catheter was kept in place after insertion of a stent were not included. Inoperable malignant disease was diagnosed in 157 patients (93.5%). Eleven patients presented with a benign biliary stricture that could not be managed by means of angioplasty. One hundred fifty-five Wallstents were placed in 122 patients, 65 tantalum Strecker stents were placed in 30 patients, and 18 Memotherm stents were placed in 16 patients. The patients were followed until September 1996 or until death.Regarding malignant obstruction, the 30-day mortality rate was 10.7% without any procedure-related death, and overall survival rates after 100 and 200 days were 63% and 22%, respectively. Regarding benign stricture, eight of 11 patients were alive after a median follow-up of 50.6 months without any 30-day mortality. Major complications occurred in 16 patients (10.2%) who had malignancy, and in two patients (18.2%) with benign biliary disease. The cumulative patency rate in malignant obstructions was significantly higher for the Wallstent than for the Memotherm stent (P.05) and nonsignificantly higher for the Wallstent than for the tantalum Strecker stent (P.05). Reintervention due to recurrent obstructive jaundice was necessary in 28 patients (17.8%) with malignancy, and in six patients (54.5%) with benign stricture.The Wallstent is the most effective in achieving long-term palliation in patients with malignant obstructive jaundice. The treatment of benign biliary strictures with metallic stents is associated with a low long-term patency rate.

Lyme disease is a cause of illness involving multiple organ systems, including, in 10-15 % of cases, the nervous system. Peripheral radiculoneuritis, cranial neuritis, encephalitis and myelitis are among the neurological manifestations found in the second and third stages. We present the MRI findings in isolated oculomotor nerve involvement by Lyme disease and discuss the differential diagnosis.

To evaluate prospectively our experience with transjugular intrahepatic portosystemic shunt (TIPS) using four different metallic stents.Between November 1991 and April 1995, 57 patients (41 men and 16 women; age 35-72 years, mean 54 years) underwent the TIPS procedure. Techniques for portal vein localization before and during TIPS were fluoroscopy, computed tomography (CT) studies, wedged hepatic venography, arterial portography, and ultrasound. After predilation we deployed balloon-expandable (n = 48) and self-expanding (n = 45) metallic stents. Fifteen patients underwent variceal embolization. Initial follow-up angiograms (mean 6.9 months, range 3-24 months) were obtained in 39 of these patients.Fifty-three patients (93%) had successful TIPS placement. The mean decrease in portal pressure was 42.7%. Besides fluoroscopy, the most helpful techniques for portal vein localization were venography and CT. Residual stenosis (n = 1) and late shortening (n = 4) of Wallstents resulted in shunt dysfunction. The technical problems encountered with the Palmaz stent resulted from its lack of flexibility. We combined balloon-expandable and self-expanding stents in 12 patients. The 30-day and late follow-up (mean 11.9 months) percutaneous reintervention rates were 11.3% and 64.2%, respectively. There were no clinically significant complications related to the TIPS insertions.An ideal stent does not exist for TIPS, and the authors recommend combining a Palmaz stent with a flexible self-expanding stent.

The recent improvements in magnetic resonance (MR) imaging using the new ultrafast echo-planar technique for diagnosis of hepatobiliary lesions are outstanding. Besides the detection and preoperative evaluation of benign and malignant hepatobiliary tumors, angiography and cholangiography can be simultaneously performed using the techniques of MR angiography or MR cholangiography Looking ahead, further advantages such as three-dimensional image reconstruction, no X-ray exposure, and short examination time, this MR technique will become the preferred diagnostic procedure for evaluating hepatobiliary lesions.

To quantitatively assess cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease.In 21 symptomatic patients with occlusive cerebrovascular disease, magnetic resonance (MR) imaging was performed with a 1.5-T system. Before, during, and after a brief bolus injection of gadopentetate dimeglumine into the antecubital vain, a series of 32 rapid T2*-weighted gradient-echo images of two different sections were acquired simultaneously to measure the concentration-time-curves in the brain tissue and in the brain-feeding arteries. Principles of indicator dilution analysis were applied to compute regional cerebral blood flow (rCBF) and volume. Each patient underwent two examinations, the first before and the second after acetazolamide stimulation.In the asymptomatic hemisphere, a mean increase in rCBF value of 47.1% was observed after acetazolamide stimulation. In the affected areas of the symptomatic hemisphere, a statistically significantly reduced response to acetazolamide stimulation was found, indicating a severely compromised cerebrovascular reserve capacity.MR imaging with the described techniques provides quantitative information about the cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease.

Cephalopelvic disproportion between pelvic and fetal diameters has been evaluated by pelvimetry. The study consisted of 257 women with pelvimetry by digital-image-intensifier radiography and fetometry by US. Information about the management of labour and the mode of delivery has been obtained from the obsterician. Differences between five pelvimetric diameters and the fetal biparietal diameter (BIP) have been correlated to the mode of delivery. Kruskal-Wallis and Mann-Whitney U-tests show high significance for small or negative differences between interspinous as well as intertuberous distance and BIP in the group of Caesarean sections. According to empirical determination cephalopelvic disproportion can be supposed for differences ≤ 0.0 cm and borderline conditions for 0.0–1.0 cm. The investigated sagittal pelvic diameters did not show a correlation to the mode of delivery. For the detection of cephalopelvic disproportion “interspinous distance-BIP” is suited best. In conclusion, the plane of the mid-pelvis has been found to be the most important parameter.

Objective Dynamic susceptibility contrast (DSC) enhanced MRI was used to study relative cerebral blood volume (rCBV). Materials and Methods We examined 15 healthy subjects and 47 patients with vascular stenosis or occlusion, with brain infarctions, and with cerebral neoplasms. During bolus injection of Gd-diethylenetriamine pentaacetic acid, a series of rapid T2*-weighted fast low angle shot two-dimensional images were recorded from the same slice. From these images, changes in signal intensity during bolus passage were computed pixel-by-pixel and converted into contrast agent concentration curves. Applying the principles of indicator dilution theory, images of rCBV were calculated. Results and Conclusion Regions of infarctions show almost zero rCBV. In patients with high-grade vascular stenosis or occlusion a bolus delay in comparison to the unaffected side and an increased mean transit time can be observed. Some of the affected areas show an increased rCBV, which is a well-known physiological mechanism that takes place to compensate for the reduced cerebral blood pressure. In brain tumors, rCBV imaging reveals focal or homogeneous areas of increased blood volume. This can even be observed in low-grade astrocytomas with unaffected blood-brain barrier. In CBV imaging, the effects of radiotherapy on tumor tissue can be monitored as a significant decrease of rCBV in tumor tissue after therapy.

Klinik und Laborbefunde sind nur bei etwa 3/4 A aller Patienten mit Ikterus in der Lage, zwischen einer parenchymatosen und einer mechanischen Ursache zu unterscheiden [10]. Fur den Nachweis und die weitere Differenzierung des Verschlusikterus steht eine Vielzahl bildgebender Verfahren zur Verfugung. Im Interesse der Schonung des untersuchten Patienten und der heute viel diskutierten Kostenreduktion ist es notwendig, sie moglichst zweckmasig einzusetzen. Ziel dieses Beitrags ist es, hierbei die nichtinvasiven Untersuchungsmethoden einer kritischen Wertung zu unterziehen.

The use of digital image intensifier radiography (DIIR) for examinations in projection radiography is becoming more common. Fluoroscopic controlled contrast studies (barium- or iodine-based), particularly of the gastrointestinal tract, can be performed quickly and easily with a considerable decrease in radiation exposure. A wide dynamic range permits a constant high image quality with fewer incorrect exposure. The limited spatial resolution of large image intensifier input screens is the major drawback of DIIR. Digital image acquisition enables post-processing, digital storage and transfer of images, thus allowing an integration into PACS-systems. Imaging capabilities and clinical applications are described here.

In recent years new analogue and digital techniques have become available for chest imaging. This study compares conventional film/screen, asymmetric film/screen (InSight), equalization (Amber), storage phosphor and digital image intensifier techniques by phantom exposures and patient examinations. The quality of chest images of 43 patients was classified by seven observers in four different hospitals. According to the results of phantom measurements and a previous study, digital image intensifier radiography was excluded from the patient examinations because of its low image quality. The Amber system had the best image quality. Images of the storage phosphor system were of good quality in both mediastinal and peripheral fields of the chest. Compared to conventional film/screen, the asymmetric film/screen (InSight) was graded higher in the mediastinal field, but lower in the peripheral field.

Due to a wide dynamic range it is possible to vary the dose (signal-to-noise ratio) of DIIR according to the required image quality for each type of examination. The image intensifier entrance dose (IIED) has to be fixed, therefore, as an additional acquisition parameter. In order to define the possible decrease of dose compared to film-screen radiography (speed 200) the dependence of spatial resolution and contrast detectability upon dose was evaluated. We used a Polytron 1000, which was connected to a Siregraph D and an Optilux 57 (Siemens). Acquisition parameters were fixed for different types of examination and tested by imaging anthropomorphic phantoms as well as patients (gastro-intestinal N=62, skeleton N=25, chest N=30, hysterosalpingography N=30, pelvimetry N=60).

In den vergangenen 15 Jahren hat die interventionelle Radiologie beim Pankreaskarzinom zunehmend an Bedeutung gewonnen. Grundlage dieser Entwicklung war die Ubertragung angiographischer Techniken zur Entlastung des gestauten Gallengangsystems und die Einfuhrung moderner Schnittbildverfahren. So konnte mit der Computertomographie das normale und pathologisch veranderte Pankreas direkt dargestellt werden, was zuvor-meist inkomplett-nur mit Angiographie moglich war. Obwohl die Computertomographie ihre Grenzen hat, ist sie in der Lage, bei nachweisbaren Raumforderungen des Pankreas eine gezielte Nadelbiopsie zu gewahrleisten. Ebenso kann mit ihrer Hilfe auch die gezielte perkutane Neurolyse des Plexus coeliacus vorgenommen werden. Die heute bewahrten interventionell-radiologischen Verfahren beim Pankreaskarzinom sind in Tabelle 1 aufgefuhrt.

Sadick M, Diehl SJ, Lehmann KJ, Gaa J, Mockel R, Georgi M. Evaluation of breath-hold contrast-enhanced 3D magnetic resonance angiography technique for imaging visceral abdominal arteries and veins. Invest Radiol 2000;35:111–117. To evaluate the diagnostic value of breath-hold contrast-enhanced 3D magnetic resonance angiography (MRA) for assessment of the visceral abdominal arteries and veins in patients with suspected abdominal neoplasms. Twenty-one patients underwent MR imaging on a 1.5 T unit using a body phased-array coil. MRA was performed with a 3D-FLASH sequence (TR 3.8 ms, TE 1.3 ms, flip angle 25°, acquisition time 20 seconds), 8 to 12 seconds after an intravenous bolus injection of Gd-DTPA. The acquisition delay between the arterial and the portal venous phase was 12 seconds. The image quality and the degree of vascular involvement were evaluated using coronal source images and maximum intensity projection reconstructions. Diagnosis was confirmed by surgery/histology. Image quality was optimal in more than 85% of the patients (19/21 arterial phase and 17/21 portal venous phase). MRA correctly predicted vascular status in 20 of 21 patients (95%), with complete concordance between MRA results and surgical findings. In one patient with chronic pancreatitis, MRA demonstrated a false-positive finding that could not be confirmed surgically. Breath-hold contrast-enhanced 3D-MRA is a valuable technique for assessing visceral abdominal arteries and veins.

Aneurysms of the pancreatic arteries are a rare complication of pancreatitis. Most usually they are observed with pancreatic pseudocysts or pancreatic abscesses. In view of the danger of haemorrhage, the diagnosis and treatment of these aneurysms is of considerable clinical significance. Angiography plays a dominant role, since it can demonstrate the source of bleeding and, at the same time, provides effective treatment by means of vascular embolisation. This is illustrated by three examples.

3342 patients were examined by means of a 57 cm image intensifier during one year. The installation permits examination with the patient standing or lying. The resolution was measured with a lead grid under conditions resembling actual practice and were found to be similar to those obtained with angiographic equipment. Using a medium format technique for examining the gut and vascular system resulted in radiographic quality which was not significantly different from the use of a large format technique. For examination of the skeleton, radiographic quality, using the intensifier, was markedly poorer than that resulting from Bucky examinations. There was no diagnostic difference when carrying out lymphograms. The large intensifier window of 53 cm was particularly advantageous for DSA of the pelvic and lower limb vessels when compared with smaller intensifiers. Possible savings of film and contrast medium costs are discussed.

Renal ischemia and cooling may be achieved by intraluminal balloon occlusion and intermittent hypothermic perfusion using a double lumen, balloon-tipped catheter introduced into the renal artery percutaneously. This technique was used successfully in 26 of 31 extensive nephrolithotomies, eliminating the need for dissection and clamping of the renal artery and intricate surface cooling. Intrarenal operations could be performed as effectively as with clamp occlusion. Despite a mean ischemia time of 54 minutes the individual 131I-hippuran clearance of the operated kidneys was only reduced to a mean 78.4 per cent of the preoperative value 2 to 3 weeks postoperatively and increased to 92.2 per cent after 3 to 6 months, with a tendency toward further improvement.

The quality of hardcopies produced by a video- or laser imager was compared. Laser printing could be performed after analogue or digital data transmission, whereas the video imager allowed only analogue data transfer. Evaluation of CT-, MR-, DSA- and radiographic images showed no difference in diagnostic information between video and laser-produced hardcopies. For large formats (35 X 35 cm.), laser images produced by digital transmission were considerably superior to video signals and analogue transmission. There were advantages and disadvantages of both types of imaging, depending on the size of the matrix, the type of image produced, ease of use and capital cost.

The diagnosis of phaeochromocytomas is based on the clinical features and on the hormone findings in the peripheral blood. Localisation, however, depends on radiological methods. Pneumoperitoneum was abandoned, because of its low accuracy, in favour of arteriography; lately, suprarenal phlebography has been available for the localisation of phaeochromocytomas. Our experience in nine patients with operatively confirmed phaeochromocytomas is described. Together with venous sampling from the caval system and the suprarenal veins for catecholamine estimations, it was possible to localise all tumours correctly. One tumour lying in the sympathetic chain in the thorax was correctly localised by hormone estimation. Our experience suggests that suprarenal phlebography represents a reliable method for localising phaeochromocytomas which carries a low risk and is to be preferred to arteriography.

Cystic diseases of the adrenal glands, which were thought to be rare, are being found more frequently nowadays by means of sonography and computer tomography. Our experience of fifteen cases is reported; of these, ten were confirmed at operation. Contrary to expectations based on the relevant literature, only one of the operated cases proved to be an endothelial cyst of lymphangiomatous origin. All other patients had pseudo-cysts of the adrenals. These are due to bleeding into a normal or tumour-containing gland. About one quarter of the pseudo cysts showed circular calcification on the plain films, although the incidence of this is given as 8-15% in the literature. The cystic nature of these lesions can be readily demonstrated by ultrasound or CT. The latter also provided information concerning the wall of the cyst and of the remaining adrenal tissue. An aspiration biopsy of the cyst can be carried out under ultrasound or CT control; cytological examination will confirm the benign nature of the lesion. A benign lesion without symptoms requires no further diagnostic or therapeutic measures. If there is hypertension, as may occur with a cystic phaeochromocytoma or lymphangioma, angiography is still indicated. Hormone assays are possible following catheterisation of the vena cava combined with adrenal phlebography. The origin and extent of a malignant pseudo-cyst can be demonstrated by arteriography, if this information is lacking following CT.

100 consecutive intraarterial DSA's of the lower extremities obtained with a 57 cm image intensifier were evaluated retrospectively by 2 radiologists and 3 surgeons. The studies were considered diagnostic in 95% of the cases. The results, advantages and possible disadvantages are presented and compared to those associated with conventional film angiography and with i.v. DSA.

In 64 patients suspected of having had pulmonary emboli due to thrombo-embolic disease, radionuclide venography (RNV) and contrast phlebography were carried out (84 examinations of extremities, 64 examinations of extremities and pelvis). Phleboscintigraphy proved informative in the thigh and in the pelvis. Around the knee, RNV was sufficiently accurate as a screening method. In the calf, RNV was of diagnostic value only in the presence of positive findings on scintigraphy.

Between 1979 and 1982, 47 patients with pathological process of the adrenals were surgically treated after preceding thorough non-evasive angiographic diagnosis (6 phaeochromocytomas, 20 adrenal adenomas, 8 adrenal hyperplasias, 5 adrenal carcinomas, 5 adrenal cysts and 3 adrenal metastases). The most consistently accurate results were obtained via adrenal phlebography with an accuracy of 94%. This was followed by non-evasive computed tomography (87%). Compared with the data given in literature, hormone determination in the adrenal venous blood was less favourable (79%). Selective adrenal arteriography, which was used less often, yielded correct results in 83% of the cases, whereas the number of accurate diagnoses achieved via sonography was lowest with 54%.

Since January 1988, digital image intensifier radiography has been used in the Clinic in Mannheim for DSA examinations and also in place of conventional screen/film examinations. Measurements have shown that compared with 100 mm and film/screen formats, digital radiography has poorer spatial resolution, but improved contrast resolution. The most common use of digital radiography was for examinations of the gastrointestinal tract. Using the demonstration of the mucosal fine relief pattern as a criterion of image quality, digital image intensifier radiography was able to achieve this satisfactorily. Comparison with film/screen examinations showed no loss of diagnostic information. Advantages of image intensifier radiography are reduced radiation dose, the possibility of postprocessing and economy. On the basis of 399 examinations, digital image intensifier radiography is now firmly established as part of the daily routine of the Mannheim Clinic.

Obstetric pelvimetry can be performed by digital image intensifier radiography using very low exposure doses. Comparative measurements show a reduction of the entrance dose to 5% of conventional respectively 15% of high speed film-screen radiography. Phantom measurements have shown an accuracy of +/- 5 mm. In 30 patients the transverse diameter of the pelvic entrance, of the interspinous and of the intertuberous level as well as the sagittal diameter of the pelvic entrance and outlet were measured. Pelvimetry is indicated for the early recognition of certain risks if anamnestic (previous Caesarean section), clinical (eg. external pelvimetry) or fetometric features indicate the evidence of disproportion. As a radiological method the image intensifier radiography appears particularly recommendable in respect of its low exposure dose and the possibility of interactive measurements with subsequent documentation of the diameters and values.

Urinary catecholamines and urinary excretion of vanillylmandelic acid confirmed the diagnosis of phaeochromocytoma in ten patients. In two of seven a modified glucagon test significantly aided confirmation of the diagnosis. In all patients the tumour was localised both by catecholamine determination in blood from the vein draining into the inferior vena cava (IVC) and by adrenal phlebography. Site of the adrenal tumour was definitively determined by the high catecholamine level in the adrenal veins and by phlebography. Three extra-adrenal tumours, a thoracic and two abdominal ones, were localised by high catecholamine levels in blood from other veins draining into the IVC. Vanillylmandelic acid determinaion was unreliable in the diagnosis of small phaeochromocytomas.

A stereotactic apparatus for percutaneous needle biopsy under computed tomographic (CT) control is described. A program was developed that allows the transfer of CT data to the stereotactic apparatus. No artifacts of the CT images are caused by the stereotactic apparatus. Preliminary results in 36 patients (34 biopsies and two nerve blocks) are reported.