[Determination of monitor radiation scattering contribution in photon radiation of clinical electron linear accelerators]. / Bestimmung des Monitorrückstreubeitrags im Photonenbetrieb klinischer Elektronenlinearbeschleuniger.

BACKGROUND: Modern linear accelerators permit the use of irregular fields due to their flexible collimator systems with separately movable jaws or multileaf collimators. When using such irregular fields in the clinical practice output factors have to be corrected for enhanced backscatter to the dose monitor as compared with the conventional block shieldings. METHODS: A method is presented to detect the monitor backscatter contributions to the output factor for irregular field settings. RESULTS: The monitor backscatter factors have been measured using a telescopic device for 2 different treatment head geometries (Varian Clinac 2100C/D, General Electric Saturne 15) and for 3 photon radiation qualities (nominal energies X6, X18, X12). A method is introduced to calculate the monitor backscatter for arbitrary irregular treatment fields from the experimental data for square or rectangular fields. CONCLUSIONS: Besides the corrections for changes in phantom scatter and changes in the aperture, corrections for monitor backscatter have to be taken into account in many clinical cases. They can contribute up to more than 10% compared with the monitor values for free regular fields.

[Sonographic diagnosis of liver tumors. Results of comparative studies of ultrasound, computerized tomography, laparoscopy, biopsy and scintigraphy in 413 patients]. / Sonographische Diagnostik von Lebertumoren. Ergebnisse vergeichender Untersuchungen von Ultraschall, Computertomographie, Laparoskopie, Biopsie und Szintigraphie bei 413 Patienten.

Based on a retrospective study of 413 patients, the accuracy of sonography compared to CT, laparoscopy, biopsy and scintigraphy in the primary diagnosis of liver masses is shown. False positive sonographic reports are analysed in retrospect. 190 of 338 solid space-occupying growths of the liver have sonographically been called definite growths and 148 have been considered suspicious of being such growths. 49 of the cystic lesions were considered definitely cystic and 26 suspicious. Sonography made correct positive diagnoses in 91.8% of the cysts and in 88.9% of the solid growths. The diagnostic accuracy of solid growths (without further specification) was 90%. Among the sonographically suspicious ones the specific diagnosis was correct in 80.8% of the cystic lesions and in 44.5% of the solid lesions and a correct diagnosis without further specification was made in 55.4%. The majority of false positive diagnoses corresponded to normal findings in other methods. The number of false positive diagnoses in sonography in contrast to CT depends to a high degree on the experience of the physician. Before the use of other more invasive methods the sonographically suspicious findings should therefore be double-checked by an experienced colleague with several years of sonographic experience.

[Sonographic diagnosis of kidney calculi--comparative study of ultrasound, excretory urography and computer tomography in 310 patients]. / Sonographische Nierensteindiagnostik--Vergleichende Untersuchung von Ultraschall, Ausscheidungsurogramm und Computertomographie bei 310 Patienten.

The authors compared the value of sonography with I.V. urography and CT in the diagnosis of nephrolithiasis, employing a retrospective study conducted on 310 patients. False positive and false negative sonographic findings were analysed in retrospect and the differential diagnosis discussed. Sonography proved of equal value to I.V. urography. 90% correct diagnoses were made via sonography; its sensitivity was 89%, its specificity 91%. 29% of the sonographically correctly diagnosed kidney stones had been detected by chance. The smallest sonographically identified stone was 3 mm, whereas the biggest stone that had been missed out was 7 mm. Sonography is definitely superior to I.V. urography in the detection of nephrocalcinosis and of roentgen-negative stones. Sonographically questionable parenchymal calcifications without shadowing should be investigated further by CT in case of clinical significance, even if the plain film is negative. The number of false positive findings in sonography can thus be reduced. Sonographic differentiation between central parenchymal calcification and stone formation is difficult in rare cases only. If required, additional information can be obtained via I.V. urography. The authors recommend sonography as the method of choice for suspected nephrolithiasis before I.V. urography is performed.

[2-dimensional echoencephalography or cranial CT in premature or newborn infants with suspected intracranial hemorrhages]. / Zweidimensionale Echoenzephalographie oder kraniale CT bei Früh- oder Neugeborenen mit Verdacht auf intrakranielle Blutungen.

65 newborns or low-birthweight infants with suspicion of intracranial hemorrhage were examined with B-mode small part scanners. In 12 cases the diagnosis made by ultrasound could be compared with CT. There was a similar accuracy of both methods in case of intraventricular (IVH) and subependymal (SEH) hemorrhage. SEH seems to be easier detected by US. On the other hand there are problems in diagnosing subdural (SDH) and intracerebral (IHC) hemorrhages by US. These problems are caused by the adjacent skull, but does not exist for CT. B-mode-Echoencephalography is the method of choice for examination of high risk infants and for the follow up, because US is a cribside method and of high diagnostic accuracy. CT-studies should be done in case of hemorrhage adjacent to the skull and if the US-diagnosis seems not to be reliable.

[Computerized tomography of the liver. Accuracy of the method in biopsy proven diagnoses (author's transl)]. / Computertomographie der Leber. Treffsicherheit der Methode bei bioptisch gesicherten Diagnosen.

To evaluate the diagnostic accuracy of computerized tomography (CT) in detecting liver disease, CT-findings of 320 patients examined with a slow CT-scanner (2.5 min scanning time/slice) could be compared to the results of bioptic procedures. Sensitivity was 81% for circumscript liver disease, specificity was 85%. In 69% of the cases, a type-specific diagnosis of circumscript liver diseases was possible, this percentage increased by 5% if patients with a true-positive differential diagnosis were included. 73% of the patients with liver metastases were correctly identified to have metastatic liver disease. Obstructive jaundice was correctly identified in 77% and correctly excluded in all patients with medical jaundice. For a large variety of hepatocellular disease, ratio of true positive diagnoses was 16% only. The value of CT in hepatocellular disease concerns exclusion of presumed space-occupying lesions. In a control group of 310 patients with only "clinically" and not bioptically confirmed diagnoses, specificity was 96% and sensitivity concerning focal liver disease was 82%. Our results prove CT to be a valuable non-invasive tool in the evaluation of circumscript liver disease.

Computed tomography in hydatid disease of the liver: a report on 13 cases.

Computed tomography (CT) findings in hydatid disease (echinococciasis) of the liver are described. Disease was caused by Echinococcus granulosus (n = 8) or E. alveolaris (n = 5), respectively. The CT appearance of these two types of echinococciasis is quite different; in disease caused by E. granulosus the CT appearance is pathognomonic when cysts and daughter cysts surrounded by a capsula and peripheral calcification are discernible. In addition, the extent of organ involvement can be determined prior to surgical intervention. The CT appearance of E. alveolaris lesions may be indiscernible from malignant tumors.