Pulmonary nodules: experimental and clinical studies at low-dose CT.

PURPOSE: To compare the number of pulmonary nodules detected at helical low- and standard-dose computed tomography (CT) and to investigate the diagnostic value of low-dose CT with a radiation exposure equivalent to that used at chest radiography. MATERIALS AND METHODS: Two radiologists recorded pulmonary nodules at standard-dose (250 or 100 mA, pitch of 1; 200 mA, pitch of 2) or low-dose CT (50 or 25 mA, pitch of 1 or 2) in five postmortem specimens and 75 patients. Nodules were assessed by size (5 mm or smaller, 6-10 mm, or larger than 10 mm) and by diagnostic confidence ("definite nodule," "definite lesion, not classic nodule," or "questionable lesion, possibly representing a vessel") with the Wilcoxon signed rank test. Artifacts depicted at low-dose CT were recorded. RESULTS: There were no statistically significant differences in the number of nodules detected at standard- or low-dose CT except in nodules 5 mm or smaller that were assessed as definite nodules at standard- or low-dose CT (25 mA, pitch of 2) (472 vs 397, P < .05). Artifacts that possibly interfered with nodule detection were observed exclusively at CT with 25 mA and a pitch of 2. CONCLUSION: Pulmonary nodules were detected reliably at CT with 50 mA and pitch of 2 or with 25 mA and a pitch of 1. However, further reduction of the dose to that used at chest radiography was associated with a significant decrease in the number of nodules 5 mm or smaller that were detected, possibly due to artifacts.

Is image selection a useful strategy to decrease the transmission time in teleradiology? A study using 100 emergency cranial CTs.

This study examines the suitability of working with a selection of images in a teleradiology consulting system in neurological or neurosurgical emergency situations. The teleradiology system was based on IBM-compatible personal computers, video digitization for data acquisition, and data transmission by Integrated System Digital Network. Forty normal and 60 abnormal emergency cranial computed tomograms were shown to a radiologist on call who presented all cases he regarded as pathologic to a neuroradiologic expert by teleradiology. To reduce transmission time, only a selection of images from the CT study was presented (up to four images per case). For each case the on-call radiologist's diagnosis (D(on-call)), the expert's diagnosis on the teleradiology screen (D(monitor)), and the expert's diagnosis on the original film (D(original)) was documented, together with an estimation of the agreement between those diagnoses. There was clinically relevant disagreement between the on-call radiologist's diagnosis and the neuroradiologist's diagnosis based on the image selection on the teleradiology monitor in 23% of cases. A clinically important discrepancy between the neuroradiologist's diagnosis based on the image selection and his diagnosis using the original films was found in 30% of cases. This was due to the presence of clinically relevant information on images not transferred by the on-call radiologist. Image quality of the transferred images was sufficient in all cases. Drastic selection of images from a complete CT study leads to a high rate of incorrect diagnoses and is not appropriate to reduce transmission time in teleradiology.

Morphological findings in the brain after experimental gunshots using radiology, pathology and histology.

The tissue disruption inside the brain after experimental gunshots to the head was investigated with special reference to secondary bone missiles and intracranial pressure effects such as cortical contusion and deep intracerebral haemorrhages. The evidential value of various examination methods is compared. 9 mm Parabellum ammunition was fired to the temporal region of calves (n = 10) from a distance of 0-10 cm. Plain film radiography, CT, MRI, visual inspection and histology were performed on every brain. The tissue disruption of the permanent tract is delineated best by artefact-free MRI. Cortical contusions and deep intracerebral haemorrhages were detected infrequently by visual inspection and imaging techniques although they were present in every brain as verified by histology. These injuries remote from the tract increase cerebral wounding compared to non-confined tissue. In particular, the brain stem and central areas were frequent sites of haemorrhages, which can be expected to have serious and immediate consequences. Ectopic bone fragments were found in all brains using CT scans. Bone fragments were located inside clearly enlarged permanent tracts or were driven into brain tissue. In the latter cases, secondary shot channels up to 4 cm in length could be verified by histology. Cortical contusions and intracerebral haemorrhages can only be detected reliably by histology. The localization of bone fragments requires CT scans. Therefore, a detailed examination is accomplished best by a combination of the methods applied in this study.

[Determination of blood circulation time for optimizing contrast medium administration in CT angiography]. / Kreislaufzeitbestimmung zur Optimierung der Kontrastmittelapplikation bei der CT-Angiographie.

INTENTION: CT angiography of intracranial vascular lesions requires a constant and high intra-arterial concentration of the contrast medium over the period of data acquisition. The volume of the injected contrast medium can be minimized by exact timing of the bolus injection. Non-predictable interindividual variance of veno-arterial circulation time, e.g., in patients with impaired cerebral hemodynamics after subarachnoidal hemorrhage, requires determination of the appropriate prescan delay. METHODS: We used the CT scanner (Philips SR 7000) with a low-dose scan parameter to determine the veno-arterial circulation time with a bolus injection of 20 ml contrast medium IV and compared these values with the results of an algorithm (t = n x 60 x f-1) based on the duration of n = 12 heart actions. On CT seven scans (1-s scan time) without table feed were applied at the level of the circle of Willis 4 s after the beginning of contrast medium bolus injection (5 ml/s). An interscan delay of 4 s was used. A region of interest was placed exactly on the most evident part of one of the cerebral base arteries contralateral to pathology. RESULTS: In 35 patients we measured circulation times between 10 and 25 s, all of which were confirmed by CT angiography, which followed. There was no correlation with systolic or diastolic blood pressure, heart rate or body length, body weight or body surface. Differences of up to 18 s were seen between the measured and calculated circulation times. CONCLUSION: Transit time to peak concentration in cerebral vessels following antecubital bolus injection of contrast medium cannot be calculated on the basis of hemodynamic parameters or body measurement, even in patients without cardiopulmonary or occlusive vessel disease. The quick method presented for measurement of the veno-arterial circulation time with a test bolus of contrast medium using the CT scanner and scan parameters with low-radiation exposure provided an exact time setting and saved on the amount of contrast medium needed in CT angiography.

[Low dose computerized tomography of the thorax. Experimental and clinical studies]. / Niedrigdosiscomputertomographie des Thorax. Experimentelle und Klinische Untersuchungen.

INTRODUCTION: Computed tomography is a significant source of medical radiation exposure for populations in Europe. Reduced radiation exposure may be possible with modern CT scanners with an image quality that while less good than before remains acceptable for clinical purposes. The lung appears particularly well suited to investigation with low-dose CT owing to the high contrast between normal and diseased pulmonary parenchyma. METHODS: We analysed the diagnostic accuracy of different low-dose CT protocols for the detection of pulmonary nodules using inflation-fixed isolated postmortem lung specimens in a chest phantom. In a comparative patient study diagnostic accuracies of standard-dose CT (120 kV, 250 mAs; slice thickness 10 mm, pitch 1) and low-dose CT (120 or 140 kV, 50 mAs; slice thickness 5 or 10 mm, pitch 1 or 2) were assessed. RESULTS: Preliminary results suggest that low-dose CT protocols with radiation exposure of 10-20% of that with standard-dose CT an reliably depict soft tissue density pulmonary nodules with a diameter of more than 5 mm and can also demonstrate smaller nodules equally well is many cases. CONCLUSIONS: Low-dose CT may frequently be an adequate imaging procedure in a given clinical setting, particularly in young patients with benign disease.

Reduced GABAA receptor density contralateral to a potentially epileptogenic MRI abnormality in a patient with complex partial seizures.

Imaging cerebral GABAA receptor density (GRD) with single-photon emission tomography (SPET) and iodine-123 iomazenil is highly accurate in lateralizing epileptogenic foci in patients with complex partial seizures of temporal origin. Limited knowledge exists on how iomazenil SPET compares with magnetic resonance imaging (MRI) in this regard. We present a patient with complex partial seizures in whom MRI had identified an arachnoid cyst anterior to the tip of the left temporal lobe. Contralaterally to this structural abnormality, interictal electroencephalography (EEG) performed after sleep deprivation disclosed an intermittent frontotemporal dysrhythmic focus with slow and sharp waves. On iomazenil SPET images GRD was significantly reduced in the right temporal lobe and thus contralaterally to the MRI abnormality, but ipsilaterally to the pathological EEG findings. These data suggest that iomazenil SPET may significantly contribute to the presurgical evaluation of epileptic patients even when MRI identifies potentially epileptogenic structural lesions.

Increased intracranial pressure and cardiac arrest after heart transplantation. What about the Cushing response in a denervated heart? Case report.

A 13-year-old boy suffered cerebrovascular complications after heart transplantation (ischemic mass effect in the posterior cranial fossa). He had to be resuscitated from cardiac arrest with coma. After a modified cerebellar hemispherectomy the course was favorable.--The most conclusive explanation for the acute event is that a Cushing response was preserved even in the presumably denervated heart.

[Postmortem high-resolution computed tomography of the lung. Radiologic-morphologic correlations]. / Postmortale hochauflösende Computertomographie der Lunge. Radiologisch-morphologische Korrelationen.

To establish precise correlations between high-resolution computed tomography (CT) and normal pulmonary anatomy and pulmonary pathology, 49 lungs affected by different diseases were analysed. Post-mortem high-resolution CT scans were compared with the corresponding macroscopic and microscopic pathological findings. For scanning, lungs were inflated and fixed, which avoided any decrease in the structural resolution of pulmonary parenchyma and allowed a topographically exact correlation between CT appearances and morphological changes. After demonstration of the structural details relevant for CT in normal pulmonary parenchyma, an attempt is made to establish the morphological basis of the following CT phenomena: thickening of interlobular septae, increase in pulmonary translucency, consolidation of the non-nodular alveolar and of the nodular type, and changes in the pleural region. Although CT findings in pulmonary lesions are mainly non-specific, knowledge of the corresponding morphological basis is helpful in diagnostic evaluation.

Subdural hematoma due to dural metastasis: case report and review of the literature.

A case of chronic subdural hematoma associated with dural metastasis from gastric cancer is reported. It is compatible with the concept that subdural bleeding may result from obstruction of dural vessels by neoplastic cells. Other possible pathogenetic mechanisms of this rare complication are discussed and a literature review is given. For proper diagnosis of this condition histologic investigation of the subdural membrane is mandatory.

Blood transit and recirculation kinetics of lymphocyte subsets in normal rats.

Thoracic duct lymphocytes (TDL) were labelled with fluorescein isothiocyanate (FITC) and injected into normal, unanaesthetized rats with either a central venous catheter or a thoracic duct cannula. The blood transit time and the appearance in the lymph was calculated and then the percentages of B, T, T helper, and T suppressor lymphocytes were determined with monoclonal antibodies (Ox12, Ox19, W3/25, and Ox8, respectively). The blood transit time of all subsets was about 30 min. However, the percentage of B lymphocytes from 5 min after injection onwards is reduced (14.5 +/- 1.9%) compared to the injected TDL (32.7 +/- 1.7%). These cells are not in the lung vascular pool. The recovery of FITC-labelled TDL in the thoracic duct within 48 h is much higher (56.8 +/- 5.3% of the injected lymphocytes) than in previous studies using radioactive markers. B lymphocytes appear later and in a reduced number in the thoracic duct. The mean transit time is 26 h and the recovery 31.5 +/- 4.2% in contrast to T lymphocytes (18 h and 66.3 +/- 6.5%, respectively). The technique of combining FITC in vitro labelling with surface staining after completion of migration does not interfere with lymphocyte migration. It can therefore be used to study the migration of lymphocyte subsets in normal, untreated animals.