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Objective: To compare radiation exposure and image quality of oncological staging multidetector CT (MDCT) examinations of the chest, abdomen and pelvis with and without iterative reconstruction (IR)., Methods: 40 patients with known malignancy underwent staging CT examinations at two time points. Both CT scans were performed on the same scanner (SOMATOM® Definition Flash, Siemens Healthcare, Forchheim, Germany). For the baseline scan, the tube current-time product was set to 250 mAs [image reconstruction: filtered back projection (FBP)] and for the follow-up scan to 150 mAs [reconstruction: iterative reconstruction (IR)]. Effective radiation doses were estimated based on dose-length products for both baseline and follow-up. Noise measurements in defined regions were compared for FBP and IR. Images were also subjectively evaluated for image quality by three radiologists with different levels of experience., Results: Dose reduction was 44.4±8.2% for reduced-dose CT scans with IR compared with baseline with FBP. Image noise was not significantly different between images reconstructed with FBP and IR. The subjective quality of standard-dose FBP images and reduced-dose iteratively reconstructed CT images were identical., Conclusion: Our results show the dose-reducing potential of IR of CT image data in oncological patients., Advances in Knowledge: The algorithm tested in the present scientific study allows a >45% dose reduction at maintained image quality.

Clinical/methodical Issue: Electrocardiogram-gated (ECG) computed tomography (CT) investigations can be accompanied by high amounts of radiation exposure. This is particularly true for the investigation of patients with unclear and acute chest pain., Standard Radiological Methods: The common approach in patients with acute chest pain is standard spiral CT of the chest., Methodical Innovations: The chest pain or triple-rule-out CT protocol is a relatively new ECG-gated protocol of the entire chest. This article reviews and discusses different techniques for the CT investigation of patients with acute chest pain., Performance: By applying the appropriate scan technique, the radiation exposure for an ECG-gated protocol must not necessarily be higher than a standard chest CT scan, Achievements: Aortic pathologies are far better depicted by ECG-gated scan protocols and depending on the heart rate coronary artery disease can also be detected at the same time., Practical Recommendations: The use of ECG-triggered scans will not support the diagnostics of the pulmonary arteries. However, in unspecific chest pain an ECG-triggered scan protocol can provide information on the differential diagnosis.

Objectives: According to an estimated mesh shrinkage following hernia repair of up to 40% a current dogma in hernia surgery requires a mesh overlap of 5 cm around the hernia. However, no valid data addressing this problem of mesh shrinkage are available at present., Patients and Methods: Within the framework of a prospective randomized double-blinded clinical trial, 50 patients were operated on for a ventral abdominal hernia with the open sublay technique using specially prepared radio-opaque polypropylene (PP) meshes. Of the patients 27 received a conventional heavyweight mesh (P group) and 23 a new lightweight mesh construction (NK group). Follow-up for at least 2 years after mesh repair included conventional abdominal x-rays after 7 days, 3 weeks and 4, 12 and 24 months, as well as computed tomography after 7 days and 4 and 12 months. Main criteria were mesh shrinkage, recurrence and complication rates and quality of life comparing groups P and NK., Results: In 46 cases (92%) no mesh shrinkage could be detected and only 4 meshes (8%) showed a moderate shrinkage (1 of 22.2%, 2 of 8% and 1 of 3%) all from the P group. While no hernia recurrences were found, 2 surgical complications occurred with 1 seroma in the P group and 1 hematoma in the NK group. Quality of life showed a linear improvement over time up to the 2 year time point following mesh repair with advantages for the NK group. Pain and mobility scores reached standard values 12 months postoperatively without significant differences between the two groups., Conclusions: In principle PP meshes following an uncomplicated ventral hernia repair do not shrink at all. A moderate shrinkage in isolated cases might occur following heavyweight mesh implantation. Under controlled conditions recurrence as well as complication rates are equal for heavyweight and lightweight PP meshes. Quality of life improves up to 2 years following mesh repair with a trend to a better outcome for lightweight meshes. Pain and mobility scores reached standard values 12 months postoperatively without significant differences between the lightweight and heavyweight meshes.

Report of a 33-year-old woman who had sudden vision problems and homonymous hemianopia on the left. A cranial computed tomography (CCT) was carried out in a radiologic practice. A native homogeneous, smooth-edged hyperdense intracerebral mass of about 5.5 cm diameter on the right parietooccipital region with density values of +50 HU was found. Only a small proportion of about 2 cm diameter was more hyperdense with density values of +65 HU. Following intravenous administration of contrast medium, a patchy increase in density of about 1 cm was seen. The mass had only a thin hypodense rim. The patient was informed that she had a tumor. Three days later, magnetic resonance imaging was to be done for further evaluation. After the patient had returned home, she had headaches, nausea and vomiting in the evening. At night, she was admitted to a hospital as emergency case. With further increase of intracranial pressure, a craniotomy was done and a hemorrhage was removed. Histologically, a bleeding of a cavernous hemangioma was found. The patient appealed to the fact-finding board for medical liability questions because she had not been admitted to a hospital immediately after the CCT. Therefore, surgery was done delayed. The board found that the behavior of the radiologist was wrong. However, it cannot be proven that this medical malpractice is of importance for the existing postoperative complaints.

So far C-arm CT images were predominantly used for a precise guidance of an endovascular or intra-arterial therapy. A novel combined 3D-navigation C-arm system now also allows cross-sectional and fluoroscopy controlled interventions. Studies have reported about successful CT-image guided navigation with C-arm systems in vertebroplasty. Insertion of the radiofrequency ablation probe is also conceivable for lung and liver tumors that had been labelled with lipiodol. In the future C-arm CT based navigation systems will probably allow simplified and safer complex interventions and simultaneously reduce radiation exposure.

Objective: This study examined the explanatory power of 3-dimensional visualization of middle ear prostheses and to introduce this method as a supplementary diagnostic tool., Methods: Various prostheses were examined in vitro. Surface rendering and perspective volume-rendering techniques were compared with axial, curviplanar, and maximum intensity projection images. One hundred three patients with hearing difficulty underwent high-resolution computed tomography scanning. The 3-dimensional images of 41 patients after nonspecific middle ear surgery were compared with the tympanoscopic findings., Results: The PVR technique allowed the depiction of the smallest individual substructures of the prostheses. The evaluation of the prostheses' localization using PVR was significantly better than using maximum intensity projection (P < 0.001). Surface rendering showed no advantages over 2-dimensional imaging. Diagnostic findings of high-resolution computed tomography were comparable to tympanoscopy (specificity 100%, sensitivity 95.1%)., Conclusion: The 3D depiction facilitates the evaluation of middle ear prostheses fitting.

Objectives: To assess the feasibility of flat-panel detector based volumetric CT (fpVCT) scanning of the whole human skull base and maxillofacial region, which has thus far only been demonstrated on small, excised specimens. Flat-panel detectors offer more favourable imaging properties than image intensifiers. It is therefore likely that they will replace them in cone-beam CT scanners that are currently used to scan parts of the skull base and maxillofacial region. Furthermore, the resolution of current CT imaging limits diagnosis, surgical planning and intraoperative navigation within these regions. fpVCT might overcome these limitations because it offers higher resolution of high contrast structures than current CT., Methods: Three embalmed cadaver heads were scanned in two scanners: an experimental fpVCT that offers a scan field large enough for a whole human head, and in a current multislice CT (MSCT). 28 structures were compared., Results: Both scanners produced bone images of diagnostic quality. Small high contrast structures such as parts of the ossicular chain and thin bony laminas were better delineated in fpVCT than in MSCT. fpVCT of maxillofacial region and skull base was rated superior to MSCT (P=0.002) as found in this limited, experimental study., Conclusions: High spatial resolution fpVCT scanning of both regions in a whole human head is feasible and might be slightly superior to MSCT. fpVCT could improve diagnostic accuracy in selected cases, as well as surgical planning and intraoperative navigation accuracy.

Hypothesis: High-resolution imaging, as provided by flat-panel-based volume computed tomography (fpVCT), could increase navigation accuracy and could therefore improve image-guided procedures or make novel navigated surgery concepts possible., Background: Intraoperative navigation is an accepted tool in head and neck surgery. However, its use is limited in the lateral cranial base because of its low surgical accuracy. Surgical accuracy is substantially influenced by the resolution of the underlying data set. The fpVCT offers a resolution of nearly two times higher than multislice computed tomography (MSCT). Target registration error (TRE), as a measurement for surgical navigation accuracy, should decrease when navigation is based on fpVCT data sets., Methods: An acrylic glass phantom with 37 fiducial points was scanned in a current MSCT and in an experimental fpVCT. Both data sets were imported in an optical navigation system. Five fiducial points were used for registration, and seven points were used for measuring TRE. The distance between the indicated pointer tip and the corresponding fiducial point in data set was measured as TRE. Registration and TRE measurement were repeated five times for each computed tomographic data set. Average TREs were calculated, and results were compared using t-test., Results: The average TRE using MSCT (0.82 mm [standard deviation, 0.35 mm]) was significantly higher than that using fpVCT (0.46 mm [standard deviation, 0.22 mm]) (p < 0.01)., Conclusion: Submillimeter surgical navigation accuracy is possible using high-resolution fpVCT. This could be highly beneficial in cranial base surgery navigation.

Twelve patients with ICA stenosis underwent dynamic perfusion computed tomography (CT) and positron emission tomography (PET) studies at rest and after acetazolamide challenge. Cerebral blood flow (CBF) maps on perfusion CT resulted from a deconvolution of parenchymal time-concentration curves by an arterial input function (AIF) in the anterior cerebral artery as well as in both anterior choroidal arteries. CBF was measured by [(15)O]H(2)O PET using multilinear least-squares minimization procedure based on the one-compartment model. In corresponding transaxial PET scans, CBF values were extracted using standardized ROIs. The baseline perfusion CT-CBF values were lower in perfusion CT than in PET (P>0.05). CBF values obtained by perfusion CT were significantly correlated with those measured by PET before (P<0.05) and after (P<0.01) acetazolamide challenge. Nevertheless, the cerebrovascular reserve capacity was overestimated (P=0.05) using perfusion CT measurements. The AIF selection relative to the side of carotid stenosis did not significantly affect calculated perfusion CT-CBF values. In conclusion, the perfusion CT-CBF measurements correlate significantly with the PET-CBF measurements in chronic carotid stenotic disease and contribute useful information to the evaluation of the altered cerebral hemodynamics.

Hypothesis: Flat-panel based volume computed tomography could improve cochlear implant electrode evaluation in comparison with multislice computed tomography., Background: Flat-panel based volume computed tomography offers higher spatial resolution and less metal artifacts than multislice computed tomography. Both characteristics could improve the evaluation of challenging but important questions in cochlear implantation assessment, such as an exact imaging of cochlea, osseous spiral lamina, electrode array position, and single electrode contacts. These questions are not currently fully answered by multislice computed tomography., Methods: Four isolated temporal bone specimens were scanned in a current multislice computed tomography scanner and in two experimental flat-panel based volume computed tomography scanners before and after cochlea implantation. To compare flat-panel based volume computed tomography and multislice computed tomography, four features were rated according to the following criteria: 1) visibility of the cochlea; 2) visibility of the osseous spiral lamina; 3) discernibility of individual electrode contacts; and 4) the ability to determine the electrode array position relative to scala tympani and scala vestibuli. Layer-by-layer microgrinding pictures were used as the ground truth for verification of imaging findings., Results: Flat-panel based volume computed tomography was superior to multislice computed tomography in all four features rated. The cochlea and facial nerve canal were much better delineated in flat-panel based volume computed tomography. The osseous spiral lamina and single electrode contacts were only visible in flat-panel based volume computed tomography. Assessment of implant position with regard to the cochlear spaces was considerably improved by flat-panel based volume computed tomography., Conclusion: Cochlear implantation assessment could be improved by flat-panel based volume computed tomography and, therefore, would be highly beneficial for cochlea implantation research and for clinical evaluation. However, these first results were shown by scanning isolated temporal bone specimens; scanning whole human skull bases might be more challenging.

Objective: To present and evaluate a registration method to fuse complementary information of CT and MRI of the temporal bone., Methods: CT and MRI of the temporal bone of 26 patients were independently registered 4 times. A manual, iterative, intrinsic, rigid, and retrospective registration method was used. Mean CREm (consistency registration error) was calculated as a reproducibility measurement., Results: CREm was 0.6 mm (95% CI = 0.52-0.68 mm). T-test revealed no difference between pathologic and normal cases (t[102] = -1.71; P = 0.09). Time needed: 13 minutes. In the registered and fused datasets, important bony surgical landmarks (eg, facial nerve canal, inner ear) could be assessed in 3 dimensions relatively to tumor tissue (eg, acoustic schwannoma). Fluid distribution within partially obliterated cochleae could be assigned to either scalae., Conclusion: An accurate, reproducible registration and fusion method that improves tumor surgery and cochlea implantation planning with only minor changes to the clinical workflow was presented and described. We suggest this method in selected cases.

The purpose of this four-part series is to show the high-resolution axial and coronal anatomy of the temporal bone from a flat-panel detector-based volume CT (parts 1 and 2); these imaging planes are then used to outline the effect of different surgical procedures commonly applied to the temporal bone (parts 3 and 4). The structures that are removed or altered in 11 different surgical procedures are color-coded and inscribed in axial and coronal sections. Clinically important imaging features and complications following these surgeries will also be discussed. In these high-resolution images, many structures that are below the resolution limit of conventional CT can be seen and localized. It is hoped that one would be able to picture these structures and surgeries, in the mind's eye, even when they fall below the resolution limit using a conventional CT scanner. This article (part 1) focuses on the preoperative axial anatomy.

Objective: In this study, perfusion CT and diffusion-weighted magnetic resonance imaging (DWI) were compared as means of assessing the ischemic brain in hyperacute stroke., Methods: Twenty patients with ischemic stroke underwent perfusion computed tomography (CT) and magnetic resonance imaging (MRI) studies <3 hours after stroke onset. Cerebral blood flow thresholds were used to delineate the ischemic lesion, penumbra, and infarct. Correlations between the volume of the hypoperfused areas, the abnormality volume in admission DWI and follow-up CT/MRI studies, and the clinical National Institutes of Health Stroke Scale (NIHSS) scores were performed., Results: The volume of the ischemic (core and penumbra) lesion on admission perfusion CT was correlated with the volume of admission DWI abnormalities (r=0.89, P=0.001). The infarcted core tissue volume (on admission CT) correlated more strongly (r=0.77, P=0.0001) than the admission DWI abnormality volume (r=0.69, P=0.002) with the follow-up infarct volume on fluid-attenuated inversion recovery images. A correlation was demonstrated between infarct volume in perfusion CT and follow-up DWI abnormality volume (r=0.89, r=0.77, P=0.002). Significant correlations were found between ischemic and infarct region volumes in perfusion CT and NIHSS admission and follow-up scores (P < or = 0.01)., Conclusions: Both imaging modalities provide a sufficient assessment of the hyperacute brain infarct, with significant correlation between them and the clinical condition at admission. Perfusion CT allows differentiation of the penumbra and infarct core region with significant predictive value of follow-up infarct volume and clinical outcome.

Background and Purpose: A CT scanner employing a digital flat-panel detector is capable of very high spatial resolution as compared with a multi-section CT (MSCT) scanner. Our purpose was to determine how well a prototypical volume CT (VCT) scanner with a flat-panel detector system defines fine structures in temporal bone., Methods: Four partially manipulated temporal-bone specimens were imaged by use of a prototypical cone-beam VCT scanner with a flat-panel detector system at an isometric resolution of 150 microm at the isocenter. These specimens were also depicted by state-of-the-art multisection CT (MSCT). Forty-two structures imaged by both scanners were qualitatively assessed and rated, and scores assigned to VCT findings were compared with those of MSCT., Results: Qualitative assessment of anatomic structures, lesions, cochlear implants, and middle-ear hearing aids indicated that image quality was significantly better with VCT (P < .001). Structures near the spatial-resolution limit of MSCT (e.g., bony covering of the tympanic segment of the facial canal, the incudo-stapedial joint, the proximal vestibular aqueduct, the interscalar septum, and the modiolus) had higher contrast and less partial-volume effect with VCT., Conclusion: The flat-panel prototype provides better definition of fine osseous structures of temporal bone than that of currently available MSCT scanners. This study provides impetus for further research in increasing spatial resolution beyond that offered by the current state-of-the-art scanners.

Introduction: Neoadjuvant radiochemotherapy (neoRT/CT) in locally advanced rectal cancer requires an exact initial determination of the depth of the cancerous infiltration (T-status) and of locoregional lymph node metastasis (N-status). For staging and restaging, contrast-enhanced computed tomography (CT) is usually used. In specialised centers, the endorectal ultrasound (rES) may be preferred., Methods: Between January 1998 and May 2001, the T- and N-status of 102 patients with adenocarcinoma of the rectum (> or =T3 or N+) was determined prospectively by rES and CT (group I: n=61 without neo-RT/CT, examined once; group II: n=41 examined before and after neoRT/CT). All diagnostic findings were compared using the (y)pTNM-classification., Results: In the patients from group I, the depth of infiltration (uT) was predicted correctly by rES in 75% and by CT in 48% of cases; the carcinomas were understaged in 10% and 41% of cases and overstaged in 15% and 11%, respectively. According to the histopathological findings, the N-status was determined correctly by rES and CT in 75% and 57% of cases, understaging occurred in 8% and 30% and overstaging in 17% and 13%, respectively. In cases in which both methods resulted in identical T- (uT+ctT) or N-staging (uN+ctN), the accuracy increased to 82% and 80%, respectively. In patients from group II, after neoRT/CT rES and CT allowed the exact prediction of the yuT-stage in 66% and 51%, respectively. Only 2% were understaged by rES (understaging by CT: 22%). Overstaging occurred in 32% and 27% by rES and CT, respectively. The N-status determined by rES and CT was in accordance with the histopathological findings in 68% and 76%of cases, respectively. Understaging occurred in 20% and 17%,overstaging in 12% and 7%, respectively. Again identical staging results in both rES and CT increased the accuracy of the T- (yuT+yctT) or N- (yuN+yctN) classification to 90% and 83%, respectively. In group II, downsizing of the tumor by more than one T-stage was correctly assessed by rES results in 15/20 cases (75%). A complete remission of initial uT3-carcinoma was diagnosed correctly in only two of eight ypT0-cases. In contrast, CT demonstrated a remission of disease in all cases but was unable to predict the extent of tumour reduction. A remission of lymph node metastasis was accurately shown by rES in 17/19 cases (90%) and by CT in 10/12 cases (83%)., Conclusion: The staging of pretherapeutic, locoregional T- and N-status by rES is superior to that by CT (T-status: P=0.0164, N-status: P=0.0035). At restaging, rES offers higher accuracy in the detection of residual tumour infiltration (but not significantly to CT, yT-status: P=0.0833, yN-status: P=0.7962) and assessment of local remission. Therefore rES should be the method of choice in staging to avoid overtreatment in neoadjuvant settings.After neoRT/CT, the predictive efficacy of the rES for the downsizing/-staging of rectal cancer must be evaluated on greater numbers of patients receiving standardised diagnostic procedures and therapy.

The 3D imaging of the middle ear facilitates better understanding of the patient's anatomy. Cross-sectional slices, however, often allow a more accurate evaluation of anatomical structures, as some detail may be lost through post-processing. In order to demonstrate the advantages of combining both approaches, we performed computed tomography (CT) imaging in two normal and 15 different pathological cases, and the 3D models were correlated to the cross-sectional CT slices. Reconstructed CT datasets were acquired by multi-slice CT. Post-processing was performed using the in-house software "3D Slicer", applying thresholding and manual segmentation. 3D models of the individual anatomical structures were generated and displayed in different colours. The display of relevant anatomical and pathological structures was evaluated in the greyscale 2D slices, 3D images, and the 2D slices showing the segmented 2D anatomy in different colours for each structure. Correlating 2D slices to the 3D models and virtual endoscopy helps to combine the advantages of each method. As generating 3D models can be extremely time-consuming, this approach can be a clinically applicable way of gaining a 3D understanding of the patient's anatomy by using models as a reference. Furthermore, it can help radiologists and otolaryngologists evaluating the 2D slices by adding the correct 3D information that would otherwise have to be mentally integrated. The method can be applied to radiological diagnosis, surgical planning, and especially, to teaching.

Virtual endoscopy (VE) enables non-invasive 3D endoluminal imaging of the middle ear by post-processing of CT data. To optimise the clinical application a standardised approach was evaluated in normal and pathologic cases. Data acquisition was performed using multi-slice helical CT in 20 normal patients and 15 patients with malformation or trauma. Virtual endoscopy of the tympanic cavity and 3D images of the ossicles were generated using surface and volume rendering. Qualitative assessment of the representation of anatomical structures was performed in normal patients. In 15 pathological cases the diagnostic benefit was evaluated by comparing the 3D images to the 2D images and intra-operative findings. In all 35 cases 3D imaging was possible using the standardised approach. The ossicular chain as well as the bony and soft tissue structures of the tympanic cavity were visualised in 20 normal patients. In 7 of 8 patients with malformation and 1 of 7 patients with trauma the original diagnosis was changed by 3D imaging. Standardisation and evaluation of the method in normal patients is essential as it enhances the diagnostic reliability. Virtual endoscopy facilitates understanding of the complex anatomy of the middle ear. In cases of suspected malformation and confirmed trauma it is helpful for diagnosis and surgical planning.

Introduction: Fifty-eight patients (mean age 27 years, range 17-44) with primary spontaneous pneumothorax (PSP) underwent resection of apical bullae and partial apical pleurectomy via mini-thoracotomy or thoracoscopy, in 12 cases bilaterally, between 1982 and 1999., Method: After a mean follow-up period of 111 (16-212) months, 26 patients with 31 operated lungs were reassessed by high-resolution CT (HRCT) to demonstrate postoperative morphological changes., Results: Neither relevant clinical symptoms nor recurrence of a pneumothorax were found. However, HRCT revealed new apical bleb formations in 22 (71%) of 31 lungs. Neither the surgical approach, the technique of resection nor giving up smoking could be correlated to the tissue alterations. Surgical excision of the apex of the lung does not stop bleb formation., Conclusion: This study confirms earlier results from a different institution, when blebs recurred in 50% of the cases. The presence of these new apical formations neither influenced the clinical outcome nor predisposed to recurrence of PSP. Parietal (partial) pleurectomy seems mandatory to prevent PSP in the long-term.

Purpose: To show that CT of the petrous bone can be realized using a low-dose technique., Material: and methods: A high-contrast phantom was scanned with 1.5 mm slice thickness and 60-510 mAs using the reconstruction algorithms standard, bone and edge. In 50 patients, the petrous bone was examined using the standard protocol at 510 mAS. Additionally, selected slices were made at 120 or 210 mAs. The resolution of relevant structures was compared. Phantom studies were repeated on a second CT-device; images of patients scanned with 80 mAs were analyzed in regard to resolution of osseous details., Results: With the first CT-device structures of the phantom up to 0. 5 mm were depicted using 510 mAs and the edge kernel. With 120 mAs and the bone kernel structures of 0.6 mm could be distinguished. Although the same resolution was achieved with 60 mAs and the edge kernel, patient examinations showed a profound image noise. The results achieved with 120 mAs and the bone algorithm, however, were equal to that of 510 mAs. With the second device the same image quality was realized with only 80 mAs., Conclusion: CT-examinations of the petrous bone can be effected without loss of diagnostic information using only 15% of the radiation dose used for a standard brain examination.

Purpose: To quantify the contribution of a computed tomography (CT) scan to navigation accuracy in computer-assisted surgery., Methods: Eighty-eight patients undergoing computer-assisted facial or skull-base surgery were fitted preoperatively with 4 to 12 markers, either attached to the skin (n = 20) or fixed in the osseous skull (micro-screws; n = 68). Low-dose high-resolution spiral CT was achieved with 25-cm field of view (FoV), 1-mm slice thickness, 2-mm table increment, 1-mm reconstruction interval, 140 kV, 40 mA, bony reconstruction algorithm, and 180 degrees reconstruction profile (effective slice thickness = 1.8 mm). During surgery, navigation accuracy was evaluated using two navigation systems., Results: Mean error was 0.66 mm for osseous markers and 1.58 mm for cutaneous markers. Both values are markedly smaller than the effective slice thickness of the scan protocol used. Radiation exposure of the patient for the entire examination never exceeded that necessary for one single 10-mm slice in a standard brain examination. Despite the reduced dose, landmarks and fiducials were precisely identified in all cases., Conclusions: The CT-induced positioning error in the Z-axis is considerably reduced by overlapping raw data reconstruction. For 1-mm slices and a 25-cm FoV, the average scan-induced positioning error is about 0.3 mm. Spatial resolution is not affected by the low dose applied. For MRI-based navigation, a 1 mm3 voxel size is the best compromise between signal-to-noise ratio, spatial resolution and scan time.

Purpose: To establish the relationship between window width and dose to be applied in low-dose high-resolution (HR) computed tomography (CT)., Material and Methods: Low-dose HR CT-scans of the petrous bone displayed with different window values were analyzed for identification of osseous details. For two homogeneous phantoms, standard deviation of CT-numbers were measured in order to calculate the fraction of pixels not displayed within the correct grey level., Results: The broadest window used (4000 HU) allowed the best distinction of osseous structures. Standard deviation of CT-numbers in the phantoms varied between 28.5 and 43.2 (mean = 33.6) HU. Thus, only 26.6% of all pixels are displayed in the correct grey level for a 1000 HU-window, but 82.3% for a 4000 HU-window., Conclusion: When using low doses and HR-reconstruction algorithms, large window widths allow for an optimal assessment of high-contrast structures. Under these conditions, even high standard deviations of the CT-numbers will not compromise image evaluation. Due to the restricted number of grey-levels that can be distinguished by the human eye, image noise is compressed into a smaller number of discernable grey-levels. Because of the inverse square root function between dose to be applied and window width used (derived in the article), an even minor enlargement of window permits considerable reductions of patient exposure while the discernable image noise remains constant.

A total of 208 multiple trauma patients with head injury (HI) were investigated who had been treated in the period from 1990 to 1995. The average age was 35.2 +/- 17.7 years; the injury severity according to ISS was 30.2 +/- 8.6 points; 20.5% died as a result of the HI; the mortality of all patients was 26.5%. The Glasgow Coma Scale (GCS) was determined at an average of 22 min after trauma (8.0 +/- 4.3 points) at the scene of accident. The patients were classified according to GCS into minor HI (group 1: 14-15 points), moderate HI (group 2: 9-13 points) and severe HI (group 3: 3-8 points). Patient outcome was assessed by the Glasgow Outcome Scale (GOS) and was classified as good (GOS 4 and 5) and poor (GOS 1, 2 and 3) outcome. At the latest, 2 h after trauma, a CT scan of the head (CCT) was done. The HI groups are compared regarding frequency of types of injury. In all HI groups the fractures of the bony face occurred at the same frequency (36.0-38.9%). The frequency of calotte fractures (Kal-Fx) increased from group 1 (8.0%) to 2 (19.2%) and 3 (25.6%); fractures of the skull base significantly differed between group 1 (16.0%), 2 (7.8%) and 3 (33.4%). Epidural hemorrhage (EDB) appeared only in group 2 (7.8%) and 3 (6.7); subdural hemorrhage was found in group 1 (2.7%), 2 (7.8%) and 3 (10.0%). Subarachnoid hemorrhage (SAB) was significantly more frequently seen, dependent on HI severity, in group 3 (26.7%) compared to group 2 (11.7%) and 1 (8.0%). Intracerebral contusion (ICK) significantly increased from group 1 (12.0%) to 2 (27.3) and 3 (45.6%). Brain swelling (BS) also significantly increased from group 1 (8.0%) to 2 (19.5%) and 3 (49.0%) and lesions of ventricles (VL) from group 1 (2.7%) to 2 (11.7%) and 3 (20.0%). Midline shift (13.4%) and signs of herniation (4.5%) only occurred in group 3. The analysis of correlation/regression and receiver operating characteristics was able to predict 79% of patients' outcome accurately using GCS (r 0.54; P < 0.0001) alone, using CCT (r 0.65; P < 0.0001) 87% were correctly predicted with significant variables Cal-Fx, EDB, SAB and BS. CCT with GCS (r 0.74; P < 0.0001) were able to predict 88% accurately with significant variables Cal-Fx, EDB, BS and GCS. The combination of CCT with GCS, age and ISS (r 0.78; P < 0.0001) was able to predict only 87% correctly, although the r value was the highest; significant variable were Kal-Fx, EDB, BS, VL, GCS, age and ISS.

Purpose: The purpose of this study was to determine the value of CT angiography in the detection of intracranial aneurysms and to discuss its qualities compared with DSA., Methods: 26 patients with subarachnoid bleeding confirmed by unenhanced CT or lumbar puncture were examined with CT angiography. In 23 of these patients results of DSA were available., Results: In 21 cases 30 aneurysms were found with DSA, whereas in two cases there were no aneurysms. The size of the aneurysms was between 3 and 36 mm. With CT angiography two small 3 mm aneurysms were not detected. In three patients with vasospasms the diagnosis was primarily confirmed by CT angiography. The sizes measured by CTA and DSA were approximately the same., Conclusion: Because of the limited spatial resolution small aneurysms (< 5 mm) could not be diagnosed in CTA. Definitive exclusion of aneurysms is therefore not possible. Aneurysms larger than 5 mm are reliably diagnosed. CTA is indicated if identification of the bleeding aneurysm is sufficient for further patient management.

In this investigation the following anatomical measurements of the petrous bone preceding cochlear implant were evaluated using computed tomography (CT): the width of the basal coil of the cochlea, the thickness of the promontory, the distance between the sigmoid sinus and the posterior wall of the external auditory canal and the thickness of the squamous part of the temporal bone in the area of operation. Initially it was necessary to ascertain how accurately CT represents the anatomical structures of the petrous bone. The procedure of CT investigation in adult patients was simulated using the base of a skull. The CT plane in which the above mentioned measurements preceding cochlear implant can be made was represented and measurements were taken. Subsequently the same plane in CT was represented macroscopically with a specially developed method. The results show that anatomical structures measured in CT are magnified by 5% in contrast to the original. This magnification is presumably attributable to the computing of connective tissue which is adjacent to bone and the incapacity of CT to image structures of different density in the same voxel. In the second part of this investigation we evaluated 66 preoperative CT's of patients who were given a cochlear implant. The results must be adjusted by 5% to allow for this error in magnification. In conclusion a preoperative radiologic evaluation of the anatomical structures relevant to cochlear implant is without doubt tenable. Also the negligible difference between CT and the anatomical original requires no operative consequences. Because cochleostomy is carried out with a diamond burr of 1 mm diameter, a tenth of a millimeter is negligible according to our experience.

Three-dimensional (3D) computed tomographic (CT) reconstructions were studied retrospectively in 14 patients with skull base fractures. Our aim was to assess the clarity of visualisation and pattern of these fractures. The reformations were obtained from 3 mm thick two-dimensional (2D) CT images. The 2D data stored on optical discs were retrieved and reformatted using the scanner's software. The 3D technique could demonstrate the presence of fractures as well as 2D images. It was of special value in defining the depth and extent of fractures in the floor of the cranial fossae. Undisplaced and displaced fractures could both be demonstrated. Fractures in the anterior fossa run diagonally towards the midline and then cross the cribriform plate of the ethmoid bone. Fractures of the middle fossa run obliquely anteroposterior. Fractures in the lamina papyracea and cribriform plate were difficult to reconstruct due to the thinness of these bones and threshold definitions. The volume of the 3D block determines the angles suitable for viewing the fractures. In spite of present technical difficulties, the 3D images are of greater anatomical and diagnostic value, particularly in anterior fossa fractures. There is no additional radiation risk to the patient, since reconstructions are made from routine 2D images.

According to the principle of the dynamic computed tomography, stable xenon computed tomography allows measurement of the increase in density caused by xenon in the brain tissue. During a period of about 4 min a patient inhales a mixture of xenon (33%) and oxygen. By means of a special software, this method can be used to calculate flowmaps and to determine the local cerebral blood flow in a 1 cm x 1 cm areal. Stable xenon computed tomography is used mainly for cerebral blood flow measurements in patients with cerebrovascular diseases and also allows calculation of cerebral reserve capacity following stimulation of blood flow by the carboanhydrase inhibitor acetazolamide (Diamox).

Three-dimensional imaging in computer tomography (3-D CT) has been rendered feasible by the development of special software programs. On the basis of the data from 50 spinal CTs, 3-D reformations are made. The method has proved effective especially in complicated vertebral fractures. There are regular correlations between the plane of the fracture and the choice of the axis of rotation as well as the nature of the reformations. A 3-D reformation is frequently more appropriate than a coronary or a sagittal 2-D reformation. In destructions of vertebrae due to tumors, the extent of bone destruction and the altered position of the vertebrae in relation to each other can be imaged. 3-D computer tomograms do not provide fundamentally new diagnostic information, but the understanding of pathological topography is improved.

Three-dimensional (3D) computed tomography of the middle ear and adjacent structures has been carried out in two cadaveric heads from axial and coronal high-resolution images. The structures shown on the images of the walls of the tympanic cavity are illustrated. The usefulness and limitations of the technique, in this region, are discussed: use of grey level volumes at the surface of the slices and the inclusion of structural landmarks is emphasized. The 3D representations show the anatomical spacial relationships of the small structures in and around the middle ear to advantage. The information may be of use in surgical orientation.

Objectives: Do CAT-scans provide useful information in terms of preoperative localization of insulinomas after a biochemical diagnosis is established or may CAT-scan imaging be safely abandoned?, Patients and Methods: CAT-scan results from 30 consecutive patients between 1980-1990 with established insulinomas were retrospectively evaluated with regard to actual tumour size (volume) and identification and localization as verified during surgery., Results: In all patients, the tumours were easily detected by manual palpation during surgery, although the size of 67% of the tumours (n = 20) was less than 2.5 cm3. In only 7 patients (23%) the tumour had been correctly localized by computer tomography. Detected tumours were significantly larger than undetected tumours (median size 5.3 vs 1.3 cm3; p < 0.005)., Conclusion: Despite the low sensitivity of computer tomography as documented in this study, all patients with an insulinoma were definitely cured after surgical intervention. Thus, CAT-scans are neither necessary nor helpful for preoperative localization of insulinomas.

As a cause of an occlusive hydrocephalus, sometimes by CT a cystic malformation of the third ventricle is falsely assumed. This misinterpretation is based on the enlargement of the ventricular system, which leads to an unusual visualization of the interthalamic adhesion and the epithalamic (posterior) commissure. We show these structures to be the reason for the misleading diagnosis by comparing anatomical sections, ventriculography and magnetic resonance imaging (MR) with each other. Finally we discuss the clinical significance by presenting cases, in which an operative treatment of the so called "cyst" already had been planned. For the definite diagnosis we favor MR.

In addition to showing the structures of the brain, it is possible with computed tomography to demonstrate the bone of the skull. For this the window width has to be increased, or one has to use additive photographic manipulation (integral photography). The clinical value of views of the skull base is illustrated. The advantages of computed tomography compared with conventional radiographic technique are stressed.

In 90% of all cases an ovarian tumor about 2 to 3 cm in size can be visualized computertomographically using a contrast medium. Determination of the dignity can be achieved in about 81% of all cases. Malignant tumors which are impressive as smooth-walled cysts are only recognized as such in 50% of all cases. Correct staging also occurs in 50% of all cases. An accuracy of about 90% can be expected in aftercare.

CT investigations of 783 cases of brain tumors, which were covered by histology, were checked with regard to frequency and configurations of calcifications. As expected the calcifications were detected more frequently by CT than by conventional radiology because of higher resolution. Most frequently calcifications were detected in craniopharyngeomas (72%) and in oligodendrogliomas (51%). The calcifications shown by CT can be changed by variation of technical parameters. Certain patterns of calcifications can be differentiated, if constant and best technical conditions are used. One single pattern cannot be specific. A homogeneous calcification of the tumor as a whole has been observed in meningeomas only. For other brain tumors calcifications are useful for the diagnosis, if localisation, density, and reaction of the surrounding tissue after injection of contrast medium and clinical data are known.

Computed tomography (CT) and ultrasonography are based on entirely different physical principles. In the abdomen the two techniques have similar diagnostic applications. Whereas CT is in many instances more informative, it is also a more time-consuming and much more costly procedure. For clinicians who practise in areas where these techniques are available, this article may be useful as a quick guide to the choice of procedure.

In accident diagnosis, the computed tomogram (CT) is nowadays decisive for the determination of craniocerebral traumas. This is true for children as well as for adult patients. Besides the rapid handling and the non-invasiveness, the exact diagnosis with direct imaging of the traumatic cranial lesions is a special advantage of computed tomography. The authors present the characteristic CT modifications of the epidural hematoma, the subdural hematoma and traumatic subdural hygroma, the brain contusion, traumatic subarachnoidal hemorrhage and ventricular hemorrhage. Furthermore the injuries to the osseous skull which can be represented by CT and the late consequences of the accident are mentioned. The special aspects of craniocerebral traumas in children are taken into consideration.

220 hospitalized psychiatric patients were examined by computerized tomography (CT) mostly to exclude organic brain dammage. A third of the material proved to be within the normal range, when also slight cortical and subcortical atrophies are considered to be abnormal. Pronounced cerebral atrophy was found in 26.8% of the cases, 5% revealed other significant lesions. CT is a very promissing help in distinguishing vascular from purely degenerative processes. Chronic alcoholism showed an amount of 67% cortical atrophies of all degrees. Endogenic psychoses on the other side failed to demonstrate characteristic results. Many of possible unspecific pathogenetic factors seem to play an important role in this and other disease processes. CT as an almost non-invasive method may be repeated in dubious cases.

Sixty adult patients with chronic alcoholism were examined by CT. Psychiatric and neurologic syndromes were given equal consideration. Pronounced brain atrophy was found in 75% of the cases. Cortical, as opposed to subcortical, atrophy was apparent in 64%; it was found especially in the frontotemporal region and cerebellum. Cases of Wernicke's encephalopathy as well as epileptic manifestations revealed global signs of atrophy, not restricted to the brain stem. Further correlations to problems of mental deficiency in alcoholism are discussed together with earlier results.

Magnetic resonance (MR) is a new digital imaging method which is of particular interest in the radiological diagnosis of the central nervous system. It provides a new form for demonstrating the brain and the spinal cord. To evaluate the scope of the method, it was compared with CT. The results in patients with epilepsy of unknown origin, cerebral infarcts, sellar space-occupying lesions and spinal angiomas are described. MR provides information concerning tumours causing epilepsy and also fresh infarcts at an earlier stage than CT. MR has not, so far, provided any new insights in the diagnosis of sellar tumours or spinal angiomas. In these cases, MR can, nevertheless, compete with CT and with conventional radiological methods. Present experience, particularly with problem cases, indicates that MR is becoming an important method of examination in neuroradiology.

The diagnostic information obtained from 35 examinations of the skull base by computed tomography (CT) was compared with the findings furnished by conventional or blurring tomography (BT). Computed tomography yielded diagnostically valuable information not only on the soft tissues but also on the bony structures. Compared with BT, CT was superior in 40%, equivalent in 40%, and inferior in 20% of the cases in assessing pathological findings involving the bony structures of the skull base. Obviously, CT's additional capability of accurate display of soft tissue changes represents a fundamental diagnostic advantage.

Nine chordomas of the skull base and their CT appearances are described. Destruction of the clivus and of the parasellar portions of the middle fossa are characteristic, as is calcification which may be spotty, coarse or ill-defined. The tumour is characterised by marked enhancement following contrast but, on the unenhanced CT, contrary to statements in the literature, it is hypodense or isodense with respect to cerebral tissue. The tendency to recurrence and an altogether poor prognosis is confirmed.

Patients must be thoroughly tested for their suitability for a cochlear implant. Promontory testing and electrocochleography are of fundamental importance. It is possible to distinguish sensory deafness from other forms by combining the results of both tests. The implantation of intracochlear electrodes requires exact information of the anatomy of the cochlea, the tympanic wall of the cochlea and the endocochlear space. This can be assessed by axial high resolution computed tomographic scans. 8 of 70 patients were inoperable because of cochlea lesions (fractures or malformations). The advantage of computer tomography compared to conventional tomography is the fact that radiation exposure is less while the resolution is nearly the same. If computer tomography and conventional tomography do not reveal any fractures an exploratory tympanotomy should precede the cochlear implant operation in patients with a history of cranio-cerebral trauma.

A clinical study comparing the relative sensitivities of computed tomography, skull radiography, and radionuclide scanning in the detection of skull metastases indicated that CT was the least sensitive of these three modalities. CT could however detect a majority of lesions if scans were viewed at appropriate window settings. Phantom studies showed that the limitations of CT can be related to limited spatial resolution, the density of the lesions, partial volume averaging, and plane of section.

Several investigators have described CT-negative low flow areas in TIA and stroke patients in the chronic phase. The emission tomographic SPECT image they employed has, in contrast to the xenon CT method, no direct relation to the x-ray transmission CT scan. The aim of our study was to study the phenomenon of CT-negative low flow areas using the xenon CT method, a method especially well suited for such cases. 57 xenon CT examinations were performed in 40 TIA patients. Flow data from brain tissue which appeared to be anatomically intact in a slice 5 cm above the canthomeatal plane were analyzed. In the TIA group, the flow in the gray matter was found to be significantly lower on the clinically affected side: symptomatic side, 61.8 +/- 14.7 ml/100 g/min; asymptomatic side, 66.4 +/- 15.8 ml/100 g/min (p less than 0.001). In the stroke group, the flow in the white matter was also affected; symptomatic side, 31.2 +/- 9.8 ml/100, g/min; asymptomatic side, 35.3 +/- 11.1 ml/100 g/min (p less than 0.01). Gray matter: symptomatic side, 56.1 +/- 11.4 ml/100 g/min; asymptomatic side, 66.0 +/- 11.0 ml/100 g/min (p less than 0.001). The findings indicate that the appearance of CT-negative low flow areas in TIA and stroke patients during the chronic phase is the rule rather than the exception. Flow adaptation to anatomic changes not discernible by CT can be differentiated from clinically relevant flow impairment only by testing the cerebrovascular reserve.