[Ultrasound examination of the posterior ligament complex in thoracolumbar spinal fractures]. / Ultraschall zur beurteilung des posterioren ligamentkomplexes bei thorakolumbalen wirbelsäulenfrakturen.

BACKGROUND: thoracolumbar distraction injuries (AO classification type B) with damage to the posterior ligament complex (PLC) represent an indication for surgery but the use of X-ray and CT imaging often does not identify injuries of the PLC. The aim of this study was to evaluate the accuracy of ultrasound imaging in the assessment of the PLC status in thoracolumbar fractures of the spine. MATERIAL AND METHODS: in a prospective study the findings of the preoperative ultrasound examination were compared to the intraoperative findings. RESULTS: over a period of 2 years a total of 24 patients with 27 thoracolumbar fractures (18 type A, 9 type B) were examined. In 22 cases ultrasound examination was possible and correct ultrasound findings were made in 20 cases (91%). The sensitivity was 83.3%, specificity 93.8%, positive predictive value 83.3% and negative predictive value 93.8%. CONCLUSION: the use of ultrasound examination in thoracolumbar fractures is a suitable diagnostic tool for injuries of the posterior ligament complex in addition to radiological imaging.

Osteochondral defect repair after implantation of biodegradable scaffolds: indirect magnetic resonance arthrography and histopathologic correlation.

BACKGROUND: Biodegradable scaffolds have become an important option in the treatment of osteochondral defects. Therefore, accurate and reproducible monitoring of scaffold repair tissue is crucial. PURPOSE: To assess the feasibility of indirect magnetic resonance (MR) arthrography in determining the quality of osteochondral repair after scaffold implantation using an MR imaging (MRI) scoring and grading system with histology as reference. MATERIAL AND METHODS: Osteochondral defects created at ovine condylar facets were treated with either a commercial poly (DL-lactide-co-glycolide) (PLG) scaffold or a modified softer one (n=6/group; 87% and 55% of the elastic modulus of ovine subchondral bone, respectively). Empty defects at the contralateral condyle served as control group. A 1.5T MRI scan was performed after 6 months with proton density (PD)-weighted (w) fat-saturated (fs) fast spin-echo (FSE), T1-w two-dimensional (2D), and 3D fs gradient echo (GE) sequences 30 min after intravenous Gd-DTPA administration and passive joint movement. Two independent radiologists evaluated the repair tissue. The MR findings were correlated with histological findings. RESULTS: MRI and histological grading correlated well (10/12 cases). The stiff-scaffold group showed significantly superior repair in comparison to the control group (P<0.05). The 3D fs GE sequence proved to be most valuable in evaluating morphologic status. Complete defect filling and integration, intact surface and isointense signal to the adjacent native cartilage, subchondral incorporation with bone marrow edema, and graft plug enhancement were associated with a good histological outcome. Histologically, we found a smooth fibrocartilaginous layer and osseous replacement of the scaffold. Incomplete cartilage repair and irregular subchondral structures on the MRI correlated histologically with fibrocartilage-like repair and subchondral sclerosis, due to substantial degradation of the scaffold. CONCLUSION: Indirect MR arthrography is an accurate, noninvasive monitoring tool in the follow-up of scaffold implants. The MRI scoring and grading system allows reliable assessment of normal and pathological repair, with high correlation to histological findings.

[Diagnostic value of multislice perfusion CT in dementia patients]. / Bedeutung der zerebralen Perfusionsmessung am Mehrzeilenspiral-CT in der Demenzdiagnostik.

BACKGROUND: The diagnostic value of perfusion CT in dementia patients was retrospectively evaluated in comparison to the Mini-Mental State Examination (MMSE). MATERIAL AND METHODS: The perfusion CT database of 55 subjects was investigated. All patients underwent an unenhanced, contrast-enhanced, and perfusion CT of the head. The clinical evaluation of the degree of dementia was performed with the MMSE. In the perfusion CT data, 24 ROI were marked. Then blood volume (BV), blood flow (BF), and mean transit time (MTT) were calculated and compared with the ipsilateral and contralateral regions and with the degree of dementia. RESULTS: With increasing degree of dementia, a significant decrease of the occipital and temporal BV was found. A significant decrease of the BF in the frontal lobe, basal ganglia, and occipital region was found. Concurrently, the MTT increased significantly in the basal ganglia region. The group with Alzheimer's disease showed significant regional hypoperfusion compared with the group of cognitively normal subjects in the frontal, basal ganglia, occipital, and temporal region. CONCLUSIONS: The cerebral perfusion decreased with increasing degree of dementia. The inexpensive and widely available perfusion CT reveals information about regional differences of cerebral perfusion, which may be useful in differentiating severity and types of dementia.

Radiation risks for the radiologist performing transjugular intrahepatic portosystemic shunt (TIPS).

The aim of this study is to evaluate the radiation dose to the interventional radiologist in transjugular intrahepatic portosystemic shunt (TIPS) concerning the risk of cancer and deterministic radiation effects and the relation to recommended dose limits. In 18 TIPS interventions radiation doses were measured with thermoluminescence dosemeters (TLD) fixed at the eyebrow, thyroid and hand of the radiologist without special lead shielding of these body parts and at the chest, abdomen and testes under the lead apron. The doses of the eye lens, thyroid gland and hand were assumed to be equal to the corresponding surface doses. The dose at the abdomen under the lead apron was used as an estimation of the ovarian dose. Effective dose equivalent was estimated by Webster's method. The estimated effective dose equivalent was 0.087 mSv and the effective dose 0.110 mSv. The risk of fatal cancer was of 10(-6) and the risk of severe genetic defect of 10(-7) for one single intervention. The maximum permissible number of TIPS interventions was 181, otherwise the dose limit for effective dose would be exceeded. When the radiologist performed more than 372 TIPS procedures per year for many years, the dose to the lens of the eye could exceed the threshold for cataract. If the interventionist performs a large number of TIPS procedures in a year, the risk of fatal cancer and developing cataracts becomes relatively high.

[Signal loss in magnetic resonance imaging caused by intraoral anchored dental magnetic materials]. / Signallöschung im MRT-Bild, verursacht durch intraoral verankerte dentale Magnetwerkstoffe.

PURPOSE: To measure the maximum extent of the signal loss areas in the center of the susceptibility artifacts generated by ferromagnetic dental magnet attachments using three different sequences in the 1.5 and 3.0 Tesla MRI. MATERIALS AND METHODS: Five different pieces of standard dental magnet attachments with volumes of 6.5 to 31.4 mm(3) were used: a NdFeB magnet with an open magnetic field, a NdFeB magnet with a closed magnetic field, a SmCo magnet with an open magnetic field, a stainless steel keeper (AUM-20) and a PdCo piece. The attachments were placed between two cylindrical phantoms and examined in 1.5 and 3.0 Tesla MRI using gradient echo and T1- and T2-weighted spin echoes. We measured the maximum extent of the generated signal loss areas parallel and perpendicular to the direction of B (O). RESULTS: In gradient echoes the artifacts were substantially larger and symmetrically adjusted around the object. The areas with total signal loss were mushroom-like with a maximum extent of 7.4 to 9.7 cm parallel to the direction of B (O) and 6.7 to 7.4 cm perpendicular to B (O). In spin echoes the signal loss areas were obviously smaller, but not centered. The maximum values ranged between 4.9 and 7.2 cm (parallel B (O)) and 3.6 and 7.0 cm (perpendicular B (O)). The different ferromagnetic attachments had no clinically relevant influence on the signal loss neither in 1.5 T nor 3.0 T MRI. CONCLUSIONS: Ferromagnetic materials used in dentistry are not intraorally standardized. To ensure, that the area of interest is not affected by the described artifacts, the maximum extent of the signal loss area should be assumed: a radius of up to 7 cm in 1.5 and 3.0 T MRI by T1 and T2 sequences, and a radius of up to 10 cm in T2* sequences. To decide whether magnet attachments have to be removed before MR imaging, physicians should consider both the intact retention of the keepers and the safety distance between the ferromagnetic objects and the area of interest.

[Magnetic resonance analysis of the subscapularis muscle after open anterior shoulder stabilization]. / Magnetresonanztomographische Untersuchung des Musculus subscapularis nach offener vorderer Schulterstabilisierung.

PURPOSE: Analysis of the magnetic resonance imaging of the subscapularis musculotendinous unit (SSC) after primary and revision open shoulder stabilization and their correlation with the clinical function. MATERIALS AND METHODS: In a retrospective cohort study, 13 patients (mean age of group A: 36.5 years) after primary and 12 (mean age of group B: 34.2 years) after revision open stabilization underwent postoperative MRI of the shoulder. The digital data was analyzed with respect to the vertical und transverse diameters (V[slashed circle], T[slashed circle]) in a defined image slice. A signal intensity analysis was performed (infraspinatus/subscapularis signal-to-noise ratio = ISP/SSC SNR). The clinical examination included the SSC tests and signs and the Constant and Rowe score. Twelve healthy volunteers (group C) served as the control. RESULTS: From group C to group B, the mean V[slashed circle] of the SSC decreased significantly (p < 0.05) as did the mean T[slashed circle] of the cranial part of the SSC muscle (= crSSC) (p < 0.05). The mean T[slashed circle] of the caudal part of the SSC muscle (= caSSC) did not differ significantly between all groups (p > 0.05). The ISP-SSC SNR was significantly lower (p < 0.05) in the crSSC of groups A und B than in group C. In the caSSC, the SNR increased in groups A and B. In 53.8 % of group A and 92.3 % of group B, clinical signs of SSC insufficiency were found. There was no significant difference between the Constant and the Rowe score in both groups (p > 0.05). Complete tendon ruptures were not observed in any case. CONCLUSIONS: MRI enables semi-quantitative analysis of the postoperative changes of the subscapularis muscle. The decrease of the ISP/SSC SNR points to a fatty degeneration in the crSSC. The results provide indications of the causes of the clinical dysfunction of the subscapularis musculotendinous unit after open shoulder stabilization.

Intraoperative Intermittent Blocking of the Common Iliac Arteries in Cases of Placenta Percreta without the Use of Fluoroscopy.

Background: The number of patients with placenta accreta, percreta and increta is increasing. The morbidity and mortality are higher mostly due to hemorrhage. Therefore, new methods to reduce the risk of severe bleeding are necessary. Methods: Three patients were treated in collaboration by obstetricians, urologists, anesthesiologists, and radiologists. An MRI of the pelvis was performed and the diameters and lengths of the iliac arteries were measured to avoid fluoroscopy during the preoperative placement of catheter balloons into the iliac arteries. During the operational procedure the balloons were inflated and deflated depending on the operative site and the occurrence of bleeding. Results: In comparison to the literature, severe bleeding was clearly reduced. No complications of the intervention were observed. Conclusion: The presented method to reduce severe bleeding might represent significant progress in the management of abnormal placenta implantation. Nevertheless, further controlled studies are needed in order to establish evidence-based recommendations. Key Points: • Reduction of perioperative hemorrhage in cases of placenta accreta, percreta, and increta.• A preinterventional MRI of the pelvis allows measurement of the illiac arteries so that the fetus is not exposed to radiation.• The short occlusion time (under the nominal pressure of the balloon) of the common iliac arteries reduced interventional complications. Citation Format: • Heinze S, Filsinger B, Kastenholz G et al. Intraoperative Intermittent Blocking of the Common Iliac Arteries in Cases of Placenta Percreta without the Use of Fluoroscopy. Fortschr Röntgenstr 2016; 188: 1151 - 1155.

[Combination of dynamic MR enteroclysis (Sellink) and MR colonography to diagnose Crohn's disease]. / Kombination von dynamischem MR-Sellink und MR-Kolonographie zur Diagnostik des Morbus Crohn.

PURPOSE: To investigate whether a combined examination with MRI enteroclysis and MRI colonography is practicable and would provide additional findings in the regions seen with ileo-colonoscopy in the work-up of patients with Crohn's disease. MATERIAL AND METHODS: Twenty-five consecutive patients with Crohn's disease (CD) (age range 19 to 42 years, mean age 29.2 years, gender ratio male:female 8:17) were retrospectively studied. All patients underwent conventional ileo-colonoscopy as a standard of reference followed by a combined examination of MRI enteroclysis and MRI colonography at 1.5T within 15 days. Two blinded radiologists evaluated the MRI examinations and compared them with the colonoscopic results. RESULTS: The MRI examination detected 31 inflamed bowel segments in 25 patients. In comparison to colonoscopy, 5 additional, endoscopically inaccessible lesions were found by MRI and only 2 lesions were missed by MRI. Compared to colonoscopy, MRI found 7 of 10 fistulas detected by colonoscopy, and 3 otherwise indiscernible abscesses. The detection of inflamed bowel segments by means of MRI (endoscopy) revealed a sensitivity of 88.8 % (100 %), specificity of 80 % (100 %) and an overall accuracy of 96 % (100 %). CONCLUSION: This study provides strong evidence that the combination of MRI enteroclysis and MRI colonography is practicable and supplies additional results regarding the regions which are not seen with ileo-colonoscopy in the work-up of patients with Crohn's disease.

[Comparison of radiation dose and image quality of Siremobil-IsoC(3D) with a 16-slice spiral CT for diagnosis and intervention in the human pelvic bone]. / Vergleich von Strahlenexposition und Bildqualität eines Siremobil-IsoC(3D) mit einem 16-Zeilen-Spiral-CT bei Diagnostik und Intervention am humanen Becken.

PURPOSE: To compare the image quality of 16-slice computed tomography with the image quality of Siremobil-IsoC (3D) of the pelvic region and to measure simultaneously the radiation dose before and after implantation of a sacroiliac screw (SI-screw) MATERIALS AND METHODS: The pelvic region of 8 human cadavers was examined in the Siremobil-IsoC (3D) at five different levels. We used a standard protocol for the 16-slice CT of the complete pelvic region before and after insertion of a pelvic screw, followed by stepwise reduction of the tube current to find the tube current that equalizes the image quality of both modalities. We controlled the image quality by judging important structures such as neuroforamen, nerves, sacroiliacal joint space, intervertebral space, osteophytes, iliopsoas muscle, acetabular surface, fovea centralis, hip joint and os pubis. The image quality was judged by three radiologists and three trauma surgeons using a ranking from 1 to 5. The dose was measured with an endorectally placed NOMEX Dosimeter, to obtain the gonadal dose. RESULTS: The medium score for all viewers of the Siremobil-IsoC (3D) examinations was between 3 and 4.3. The medium score for all CT-examinations with a tube current of 250 mA was between 1.3 and 2.2. The reduction of tube current down to 80 mA hardly influenced the marks for the analyzed structures. Under 80 mA, bony structures, even after implantation of a SI-screw, were still marked as good, but soft tissue differentiation was getting worse. For the examination of the pelvis, the average dose-length product for the IsoC (3D) was 41.2 mGy x cm. The medium dose-length product for CT was 389 mGy x cm for 250 mA, 125 mGy x cm for 80 mA and 82 mGy x cm for 60 mA. CONCLUSION: The Siremobil-IsoC (3D) is sufficient for therapeutic intraoperative purpose, but the image quality is not sufficient for diagnostic purpose. The higher dose-length product of a CT examination is justifiable because of a better overview, shorter examination time and qualitative superiority. An advantage of the Siremobil-IsoC (3D) is the intraoperative availability with acceptable 3D image quality compared to conventional fluoroscopy.

[Detection of airways stenoses: comparison of virtual and flexible bronchoscopy]. / Detektion von Atemwegsstenosen: Vergleich der virtuellen mit der flexiblen Bronchoskopie.

PURPOSE: To compare virtual with flexible bronchoscopy for the detection of bronchial stenoses. MATERIALS AND METHODS: In a retrospective study, we compared the results of 26 patients, who had clinical suspected pathologies of the tracheobronchial airways and underwent both flexible bronchoscopy and multislice CT with 3D surface rendering of the airways. Flexible bronchoscopy and virtual bronchoscopy were compared as to the rate of detecting bronchial stenoses. For statistical analysis, we divided the tracheobronchial tree in the following sections: trachea, 2 main bronchi, 6 lobar bronchi, 18 segmental bronchi and 36 subsegmental bronchi, corresponding to 63 bronchial sections for each patient (on average) and a total of 1638 bronchial sections for all 26 patients. We graded the bronchial stenosis as less than 50 %, as 50 to 95 % and as complete obstruction. RESULTS: Virtual bronchoscopy detected 25 bronchial stenoses, while flexible bronchoscopy only revealed 17 stenoses. Stenoses with a diameter less than 50 % were found with virtual bronchoscopy 14 times and with flexible bronchoscopy 10 times. Stenoses with a diameter between 50 and 95 % were detected 7 and 4 times, respectively, and complete obstructions 4 and 3 times, respectively. Tracheobronchial stenoses were well recognized with virtual bronchoscopy. Moreover, the virtual method enabled the visualization of high-grade stenoses and post-stenotic areas that could not be passed by the fiberoptic bronchoscope. Virtual bronchoscopy detected stenoses at a higher rate but the difference was not statistically significant (stenoses < 50 %: p = 0.352, 50 - 95 %: p = 0.339, complete obstruction: p = 0.696). CONCLUSION: Virtual bronchoscopy is a useful non-invasive method for the diagnostic evaluation of the tracheobronchial tree. In comparison with flexible bronchoscopy, virtual bronchoscopy is superior in revealing high-grade stenoses and visualizing post-stenotic areas.

[Diagnostic value of MR analysis of cartilaginous lesions compared with intraoperative arthroscopy in calcaneal fractures]. / Diagnostische Wertigkeit der MR-tomographischen Knorpelläsionsdarstellung im Vergleich mit der intraoperativen Arthroskopie bei Calcaneusfrakturen.

PURPOSE: To determine the diagnostic value of MRI in preoperative analysis and classification of cartilaginous lesions - especially of the posterior facet - in traumatic calcaneal fractures compared with intraoperative arthroscopy. MATERIALS AND METHODS: Twenty-four consecutive patients with traumatic calcaneal fractures underwent prospective MRI of the subtalar joint surface using T1- and T2-weighted spin echo sequences and fat suppressed 3D gradient echo sequences in semicoronal slice orientation (1.5 T MRI). After randomization, the images were analyzed by two blinded and independent readers experienced in MRI. The results were compared with the intraoperative arthroscopic findings as to location and depth of the defects using the Outerbridge classification. RESULTS: We examined 12 calcaneal fractures of type 2, 8 of type 3 and 4 of type 4 according to the Sanders classification. With respect to principal detection and exact classification, 67 of 96 (69.8 %) of all arthroscopic verified cartilaginous defects were diagnosed correctly by MRI. Disregarding the degree of the defects, 38 of 44 (86.4 %) chondral lesions were detected (sensitivity: 86.4 %, specificity: 86.5 %, diagnostic accuracy: 86.5 %). Considering the chondral lesions of degrees 3 and 4 together, the sensitivity was 86.0 %, the specificity 86.8 %, and the diagnostic accuracy 86.5 % . Assessing these degrees separately, the sensitivity was only 33.3 % for degree 3 and 58.1 % for degree 4, whereas the specificity was definitely higher with 82.1 % for degree 3 and 89.2 % for degree 4. CONCLUSION: The MR detection of cartilaginous defects in calcaneal fractures has a sufficient diagnostic accuracy for planning the surgical intervention and assessing the long-term postsurgical prognosis.

[The effect of the field strength on standardized MRI of the brain to demonstrate cranial nerves and vessels: a comparison of 1.5 and 3.0 Tesla]. / Auswirkung der Feldstärke bei der standardisierten Kernspintomographie des Gehirns am Beispiel der Darstellung von Hirnnerven und Gefässen in den basalen Zisternen: Vergleich zwischen 1.5 und 3.0 Tesla.

PURPOSE: Comparison of MR images acquired as routine examinations at a field strength of 3.0 T and 1.5 T to determine whether and to which degree the image quality improves at the higher field strength of 3.0 T. MATERIALS AND METHODS: Routine MR images of 200 patients were examined retrospectively, with 100 images obtained at 1.5 T and 100 obtained at 3.0 T. The examinations were performed with a quadrature head coil and focused on the basal cisterns because of the abundance of small distinct structures in this region. We selected the T2-weighted 2D-FSE sequence in transverse direction for comparison. At both field strengths, the same section thickness of 5 mm and a matrix of 512 x 388 (FOV: 220 mm) were used. The quality of the images was evaluated with regard to depicting the cranial nerves N. III, V - X, the AICA and PICA. For comparison, image quality was rated with a score from 1 (well defined) to 5 (not depicted). RESULTS: A score of 1 was obtained in 46 % of the anatomic structures examined at 3.0 T and in only 9.2 % at 1.5 T. A score of 2 was given in 27.6 % of the anatomic structures at 3.0 T vs. 23.5 % at 1.5 T, a score of 3 in 17.2 % vs. 28.1 %, a score of 4 in 8.6 % vs. 28.7 %, and a score of 5 in 0.4 % vs. 10.3 %, respectively. The Mann-Whitney U test showed significance at p < 0.001 for the comparison of images at 1.5 and 3.0 Tesla. CONCLUSION: Routine magnetic resonance imaging using the same quadrature coil technique and similar acquisition times at 3.0 T and 1.5 T shows an improvement for T2-weighted images at the higher field strength.

Portal vein thrombosis: etiology, diagnostic strategy, therapy and management.

Myeloproliferative disorder, liver cirrhosis with portal hypertension, deficiency of natural anticoagulant proteins, gene mutation and hepatocellular carcinoma are the most frequent causes of portal vein thrombosis (PVT). Higher accuracy of the diagnostic methods is the reason why today the cause of PVT can be found more frequently. With imaging methods, PVT with or without cavernous transformation can be diagnosed. Fresh thrombus can be undetected in sonography due to the low echogenity but can be recognized in color Doppler sonography, especially with contrast-enhancing agent. Contrast-enhanced 3D MR angiography allows a comparable accuracy in the detection of PVT as digital subtraction angiography. Therapeutical options of PVT consist of mechanical recanalization of the portal vein, local fibrinolysis with or without placement of transjugular intrahepatic portosystemic stent shunt (TIPS), combination of mechanical recanalization and local fibrinolysis, systemic thrombolytic therapy, anticoagulation alone and surgical thrombectomy. Once PVT is found in sonography, Doppler sonography may be performed in order to distinguish benign from malignant thrombus. If further information is needed, MR angiography or contrast enhanced CT is the next step. If these tests are unsatisfactory, digital subtraction angiography should be performed. Until the early nineties, shunt surgery was recommended in patients with PVT who bled despite endoscopic treatment. Today, in symptomatic noncavernomatous PVT, recanalization with local methods is recommended. Additional implantation of TIPS should be performed when the patient is cirrhotic. In recent PVT in non-cirrhotic patients anticoagulation alone is recommended. It is expected that in old PVT anticoagulation can prevent further extension of the thrombus.

MRI and CT in the differential diagnosis of pleural disease.

STUDY OBJECTIVE: To explore the role of MRI in the differential diagnosis of pleural disease. PATIENTS: Forty-two patients with pleural disease were included. METHOD: Retrospective study. All patients were examined with both CT and MRI. The morphologic features of pleural lesions and magnetic resonance signal intensity on T1-weighted, T2-weighted, and contrast-enhanced T1-weighted images were evaluated. RESULTS: Mediastinal pleural involvement, circumferential pleural thickening, nodularity, irregularity of pleural contour, and infiltration of the chest wall and/or diaphragm were most suggestive of a malignant cause both on CT and MRI. Pleural calcification on CT was suggestive of a benign cause. Contrary to what has been previously reported in the literature, neither on CT nor on MRI, pleural thickness >1 cm revealed significant difference between malignant and benign pleural disease (p>0.05, chi(2) test). High signal intensity in relation to intercostal muscles on T2-weighted and/or contrast-enhanced T1-weighted images was significantly suggestive for a malignant disease. Using morphologic features in combination with the signal intensity features, MRI had a sensitivity of 100% and a specificity of 93% in the detection of pleural malignancy. CONCLUSION: When signal intensity and morphologic features are assessed, MRI is more useful and therefore superior to CT in differentiation of malignant from benign pleural disease.

Radiation exposure in spiral computed tomography. Dose distribution and dose reduction.

RATIONALE AND OBJECTIVES: The authors investigate the dose distribution of spiral and conventional computed tomography (CT) with film densitometry and to present a new method of evaluating the possibility of dose savings with spiral CT. METHODS: Films were exposed in a cuboid polymethyl-methacrylate phantom in conventional and spiral scan technique. Axial density profiles were obtained by digitizing the films using a fluorescent light scanner. The ratio of the number of rotations in spiral CT to the number of slices in conventional CT was calculated. RESULTS: In spiral CT with a pitch of 2, the densities in all points were lower than those in corresponding points in spiral CT with a pitch of 1 and in conventional CT with slice distance equal to slice thickness. A pitch of 1.5 in spiral CT led to a dose reduction of 14% to 30% compared with conventional CT. CONCLUSIONS: Increasing the pitch in spiral CT leads to a reduction of both integral dose and absorbed doses within the examined body region. The reduction of the integral dose can be significant, especially in cases where slice overlapping is diagnostically advantageous.

Relationships between physical dose quantities and patient dose in CT.

Patient dose in CT is usually expressed in terms of organ dose and effective dose. The latter is used as a measure of the stochastic risk. Determination of these doses by measurements or calculations can be time-consuming. We investigated the efficacy of physical dose quantities to describe the organ dose and effective dose. For various CT examinations of the head, neck and trunk, organ doses and effective doses were determined using conversion factors. Dose free-in-air on the axis of rotation (Dair) and weighted computed tomography dose index (CTDIw) were compared with the absorbed doses of organs which are located totally within the body region examined. Dose-length product (DLP) was compared with the effective dose. The ratio of the organ dose to CTDIw was 1.37 (0.87-1.79) mSv mGy-1. DLP showed a significant correlation with the effective dose (p < 0.005). The average ratio of effective dose to DLP was 0.28 x 10(-2) mSv (mGy cm)-1 for CT of the head, 0.62 x 10(-2) mSv (mGy cm)-1 for CT of the neck and 1.90 x 10(-2) mSv (mGy cm)-1 for CT of the trunk. CTDIw and DLP can be used for estimating the organ dose and effective dose associated with CT examinations of the head, neck and trunk.

[The digital reprocessing of underexposed x-rays. Studies with a fluorescent light scanner]. / Digitale Nachbearbeitung von unterbelichteten Röntgenaufnahmen. Untersuchungen mit einem Fluoreszenzlichtscanner.

Incorrect exposure of conventional radiographs frequently leads to repetition of the examination and thereby to increased radiation exposure for the patient. Underexposed films of an Alderson-Rando phantom, an ankle joint and a patella were digitised by means of an inexpensive fluorescent light scanner, and subsequent image manipulation improved quality so as to make the image diagnostically adequate. For the demonstration of markedly underexposed structures digitalisation with subsequent contrast enhancement was used. Well exposed structures are best evaluated in contrast enhanced transmitted light. Our results suggest it should be possible to reduce the number of repeat exposures and thereby to limit radiation exposure.

[The efficacy of lead shielding in patient dosage reduction in computed tomography]. / Effektivität der Bleiabdeckung zur Dosisreduktion beim Patienten in der Computertomographie.

PURPOSE: Investigation of the efficacy of lead apron, testis capsule and thyroid collar for dose reduction in uterus, ovaries, testes and thyroid gland in computed tomography examinations. METHODS: At an Alderson-Rando phantom dose of uterus, ovaries, testes and thyroid gland was measured with thermoluminescent dose meters. CT of the upper abdomen, the whole abdomen and the skull were simulated without and with lead shielding. As lead shielding, a lead apron was attached around the pelvis of the phantom in case of CT of the upper abdomen, a testis capsule was used in CT of the whole abdomen and a thyroid collar in CT of the skull. RESULTS: In CT of the upper abdomen the lead apron did not lead to any recognisable dose reduction in uterus and ovaries. In CT of the whole abdomen the testis capsule led to a dose reduction in testes of 95% (1.39 mSv) and in CT of the skull the thyroid collar to a dose reduction in thyroid gland of 23% (0.19 mSv). CONCLUSIONS: In abdominal CT examinations the testis capsule is an important instrument to reduce the dose of the testes whereas the lead apron is not appropriate for a dose reduction in the uterus and ovaries. In CT of the skull the thyroid collar can remarkably reduce the scattered radiation exposure of the thyroid gland and should be recommended.

[Calculated organ doses and effective dosage for computerized tomography examination of the thorax and abdomen: are these doses realistic?]. / Berechnete Organdosen und effektive Dosis für die computertomographische Untersuchung des Thorax und des Abdomens: Sind diese Dosen realistisch?.

PURPOSE: To analyse how far dose calculations for the CT examination of the thorax and abdomen can lead to faulty estimations of organ doses and effective dose due to differences in the topographic anatomy between mathematical phantom and man. METHODS: For the CT examination of the thorax, upper abdomen, pancreas, pelvis and the entire abdomen, organ doses were calculated with conversion factors, first with regard to the topographic relation within the phantom, then with additional regard to the real anatomy of the man. RESULTS: In the phantom, the abdomen lies outside the scan volume in case of CT-examination of the thorax and the whole intestine outside the scan volume in case of CT-examination of the upper abdomen and the pancreas, whereas the entire intestine is directly exposed in case of CT-examination of the pelvis. Dependent on whether dose calculations take real anatomy into account, doses of special organs can differ by a factor greater than 15. The calculated effective doses differ by a factor less than 1.5. CONCLUSIONS: Calculations of organ doses for the CT examination of the thorax and abdomen can lead to considerable errors due to different topographic relations between phantom and man. In contrast the calculated effective dose is realistic. Hence, dose calculations with the help of mathematical phantom is an efficient method to estimate the total radiogenic risk.

[Value of contrast-enhanced ultrasound vs. CT and MRI in palpable enlarged lymph nodes of the head and neck]. / Wertigkeit der kontrastmittelverstärkten Sonographie von Lymphknotenvergrösserungen im Kopf-Hals-Bereich versus Computertomographie und Magnetresonanztomographie.

PURPOSE: To compare the value of B-mode-, plain and contrast enhanced color Doppler ultrasound, CT and MRI with respect to their diagnostic accuracy in palpable enlarged cervical lymph nodes. MATERIAL AND METHODS: Thirty patients (18 - 90 years old) with palpable enlarged lymph nodes of the head and neck underwent B-mode-ultrasound, plain and contrast enhanced color Doppler, CT and MRI (gold standard: histologic analysis in 22 and clinical follow up for at least six months in eight patients). The criteria of malignancy were maximal and minimal lymph node diameter, M/Q-ratio, various morphologic criteria (necrosis, hilus line, internal structure, contour, contrast enhancement), spectral Doppler indices, and vascular architecture in color Doppler. RESULTS: The highest sensitivity (= 1.00, specificity = 0.07 - 0.15) was obtained measuring the lymph node diameter independent on the used imaging modality (ultrasound, CT, MRI), the highest specificity (= 1.00, sensitivity = 0.71) analyzing the vascularity of the lymph node by plain color Doppler. The highest diagnostic (= 0.93) accuracy was delivered by contrast enhanced color Doppler analysis of the vascularity. Sensitivity (= 0.94) and specificity (= 0.92) of this imaging modality were only slightly inferior to the top values. Fisher's exact test revealed significant values in differentiating malignant from benign lymph nodes for B-mode- and MR-analysis of the M/Q-ratio (p < 0001/p < 0.05), B-mode morphology (p < 0.00005), plain and contrast enhanced color Doppler analysis of the vascularity (p < 0.0001/p < 0.000005), MR-morphology (p < 0.0001), and CT-morphology (p < 0.005). CONCLUSION: CT is inferior to MRI, B-mode-ultrasound and contrast-enhanced color Doppler in the differential diagnosis of selectively analyzed, palpably enlarged cervical lymph nodes using the criteria of our study. The analysis of the MR-morphology revealed a slightly inferior diagnostic accuracy to B-mode morphology and color Doppler analysis of the vascularity.