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Purpose: Application of function-restoring individual implants for the bridging of defects in mandibles with continuity separation requires a stable fixation with special use of the cortical bone stumps., Materials and Methods: Five section planes each of 100 computed tomographies of poly-traumatized patients' jaws were used for measuring the thickness of the cortical layer and the bone density of the mandible. The CT scans of 28 female and 72 male candidates aged between 12 and 86 years with different dentition of the mandible were available., Results: The computed tomographic evaluations of human mandibles regarding the layer thickness of the cortical bone showed that the edge of the mandible in the area of the horizontal branch possesses the biggest layer thickness of the whole of the lower jaws. The highest medians of the cortical bone layer thickness were found in the area of the molars and premolars at the lower edge of the lower jaws in 6-o'clock position, in the area of the molars in the vestibular cranial 10-o'clock position and in the chin region lingual-caudal in the 4-o'clock position. The measurement of the bone density showed the highest values in the 8-o'clock position (vestibular-caudal) in the molar region in both males and females., Conclusion: The average values available of the bone density and the layer thickness of the cortical bone in the various regions of the lower jaw, taking into consideration age, gender and dentition, are an important aid in practice for determining a safe fixation point for implants in the area of the surface layer of the mandible by means of screws or similar fixation elements., (© Georg Thieme Verlag KG Stuttgart · New York.)

Penetrating gunshot injuries to the head and brain are rare in Germany and the rest of Western Europe. Due to the small number of cases over here no consistent diagnostic and therapeutic standards exist in this respect. Thus these kinds of injuries present a great challenge to the attending physicians. Most of these violations are a result of a suicidal attempt or an accident. Beside violations by firearms also penetrating injuries to the head and brain due to captive bolt devices, as used in slaughtery business for the "humane" killing of animals, occur from time to time. The impact on the head differs from that caused by firearms because no projectile is leaving the barrel and the used bolt, as a fix part of the device, does not remain in the affected tissue. That implies characteristic results within the radiological imaging that might be pathbreaking for the further treatment, because the origin of such a head injury is often unknown during primary care. Consequently the knowledge of these specific findings is central to the radiologist to make the appropriate diagnosis. Based on some clinical examples the trauma-related CT-findings are introduced and a short overview of the relevant literature is also given., (© Georg Thieme Verlag KG Stuttgart · New York.)

Purpose: Determination of the influence of tube currents varying during a CT scan on organ doses and on the effective dose as a function of patient constitution. Evaluation of the accuracy of effective dose calculations based on summarizing parameters (effective mAs, dose length product [DLP]) compared to calculations based on slice-specific tube currents., Materials and Methods: Investigation of the CT datasets of 806 patients acquired from the skull base to the proximal thigh with respect to the body mass index (BMI). The effective dose was calculated by means of slice-specific as well as region-specific conversion factors., Results: Dose optimization by means of variable tube current resulted in a reduction of the gonad dose in patients with BMI < or = 20 ... 21 kg/m (2) and of the effective dose in patients with BMI < or = 26 kg/m (2). Effective dose values calculated with the DLP for 90 % of the patients are within an interval of +/- 20 % of the values calculated using slice-specific tube currents., Conclusion: If tube current optimization during the CT scan was applied, for the scan region under investigation, at a BMI already below the German mean value, an increased effective dose was observed. Calculations of the effective dose on the basis of summarizing values such as DLP or effective mAs are of sufficient accuracy.

Purpose: Evaluation of ultrasound-guided percutaneous marking of breast cancer using an "O-Twist Marker" (BARD GmbH, Karlsruhe, Germany) in patients undergoing neoadjuvant chemotherapy. In the event of complete remission, the lesion of interest can be missed after completion of therapy. In these cases marking of the tumor site is essential., Materials and Methods: We monitored patients with breast cancer proven by biopsy who were undergoing neoadjuvant chemotherapy with ultrasound. In cases in which the follow-up ultrasound examination after the second chemotherapy cycle showed a significant tumor mass reduction (> 30 %), we pinpointed the lesion with an ultrasound-guided "O-Twist Marker". The position of the marker was documented by ultrasound and mammography. Between January and November 2006, we marked 7 patients., Results: The visibility of the marker was excellent on mammography, but only moderate on ultrasound. The marker did not cause any imaging interference. The instrument was easy to operate. We did not detect any migration of the marker. In 3/7 patients it would have been possible to locate the remaining tumor tissue after the completion of neoadjuvant chemotherapy without the marking. In 4/7 cases the clip was very useful or even essential for preoperative site determination., Conclusion: The use of "O-Twist Marker" is a reliable and effective technique for locating breast cancer sites in remission during neoadjuvant chemotherapy. The visibility of the marker on ultrasound should be improved. In 57 % of the cases tumor marking was advantageous for surgical procedures.

Purpose: The individual jaw position is determined by the masticatory muscle among other factors. Before surgical treatment of malocclusions, thorough evaluation of the muscles is required to estimate the relapse risk., Materials and Methods: By means of computer tomography, lateral radiographs of the skull and denture models, the relationships between morphological parameters of the masticatory muscles and the jaw bone were analyzed. Furthermore, possible causes for the extent of the malocclusion are described., Results: A patient group with deep overbite was found to have significantly higher muscle densities (measured in Hounsfield units [HU]) in the medial pterygoideus muscle (59.89 +/- 3.91 HU to 48.94 +/- 4.14 HU, p < 0.01), masseter muscle, and genioglossus muscle (p < 0.05) in comparison to open bite patients. Significant differences of the muscle cross-section were measured in the masseter muscle between patients with retroclined maxillary incisors and with an open bite (5.4 +/- 0.7 cm (2) to 3.8 +/- 0.4 cm (2), p < 0.05)., Conclusion: The results show a correlation between different jaw positions and masticatory muscles. They also suggest that the function of each muscle may be different. Additional examinations of the muscle structures are required for verification of the influence of the masticatory muscles on facial morphology.

Aim: In MR perfusion measurements of contrast uptaking lesions, time intensity curves are hampered by T 1 shortening as well as by the change of T 2 * due to interstitial contrast material (CM). Using double echo sequences, the influence of T 1 can be mathematically eliminated. For correction of the T 2 * influence an empirical algorithm using time-intensity-curves exclusively measured in the suspected lesion is proposed., Methods: The interstitial CM concentration is assumed to be proportional to the change of the intensity for T E = 0 or to the change of the relaxation rate DeltaR 1 respectively. The intravascular CM concentration is estimated from DeltaR 2 *. It is adjusted to zero for a time point sufficiently late after the bolus injection by subtraction of the interstitial concentration. This method was applied to double echo FLASH measurements on 15 pharyngeal tumors., Results: The proposed correction transforms the time dependence of the estimated intravascular CM concentration into a plausible course., Conclusion: Double echo perfusion measurements can be corrected for the interstitial CM induced T 2 * shortening without additional measurements with proneness to errors. This does not necessarily improve the diagnostic value, since possibly "implied multivariate aspects" of uncorrected parameters (here: contrast uptake of the lesion is related to tumor neoangiogenesis as well) are eliminated.

Purpose: To analyse the diagnostic accuracy of computed tomography (CT) in ventilator-associated pneumonia (VAP)., Materials and Methods: 23 patients on mechanical ventilation with a new pulmonary abnormality on chest X-ray were examined with both spiral-CT and high-resolution CT. The diagnosis VAP was made according to prospectively defined criteria. Bronchoscopic specimen asservation with protected specimen brushing (PSB) served as gold standard., Results: With PSB, 11 of 23 patients were found to have VAP. CT showed a sensitivity and specificity of 53% and 63%, respectively. Ground glass infiltrates appeared to have a 100% specificity but were found in only 5/11 patients., Conclusions: CT is not the method of choice for diagnosing VAP. Ground glass infiltrates seeming to be highly specific are only inconstantly found.

The paramagnetic extracellular Gd contrast media (Gd-CM) Magnevist, Dotarem, Omniscan, and ProHance are on the market, whereas Gadovist, Optimark, and MultiHance (also used as a hepatobiliary CM) are undergoing clinical trials (phase III). Among other indications, Gd-CM are applied in tumours, inflammation, vascular pathologies, and MR-angiography. The paramagnetic hepatobiliary CM Teslascan, Eovist and MultiHance are in clinical trials (phase II and III). They improve tumour detection and characterisation. The Mn-CM Teslascan is also suited for pancreatic imaging, the Gd-CM MultiHance for imaging of myocardial infarction and the brain, and the Gd-CM Eovist has been used in liver CT. The superparamagnetic reticuloendothelial CM Endorem is on the market whereas Resovist is undergoing phase-III trials. Both agents have the same indications as the hepatobiliary CM. Sinerem is another superparamagnetic CM. However, it acts as a blood pool agent and accumulates in lymph nodes (MR lymphography). Gastrointestinal CM are divided into paramagnetic, superparamagnetic and diamagnetic agents acting either as positive or negative CM. Some are on the market, but their clinical value is limited.

Purpose: Evaluation of an echo contrast medium (Echovist) for color-coded duplex sonography of deep venous thrombosis of the thigh., Material and Methods: In 19 patients with deep vein thrombosis of the thigh, diagnosed by contrast phlebography, 22 color-coded duplex sonography studies were performed for flow analysis at the top of the thrombus. During the studies 8.5 ml echo contrast medium were injected in an ipsilateral vein at the back of the foot. The flow signals of the non-enhanced color coded duplex sonography were compared with those of the echo enhanced study for differentiation between floating thrombi from those adherent to the vein wall., Results: The echo-enhanced color-coded duplex sonography showed a significant increase in detection of perfusion at the top of the thrombus in comparison with non-enhanced color-coded duplex sonography (p < 0.01). 9 thrombi were regarded as wall adherent after the native study, 7 of these could be identified as floating thrombi by echo-enhanced color-coded duplex sonography., Conclusion: Echo-enhanced color-coded duplex sonography yields a significant increase of diagnostic information in certain findings of the non-enhanced color-coded duplex sonography differentiating between floating thrombi and wall adherent thrombi in the deep venous system of the thigh.

Following oral administration of a buffered gadopentetate-dimeglumine solution (Magnevist enteral, 1 mmol/l, 6-17 ml/kg) T1-, proton-density- and T2-weighted spin-echo images of abdominal and retroperitoneal lesions were acquired (0.5 T). Gadopentetate is a signal-enhancing, positive MR contrast agent, intraluminal air served as a model of a signal-free, negative agent. In 21 patients contrast/noise ratios of gadopentetate and air versus lesions and fat were compared quantitatively (t-test). In T1- and T2-weighted images contrast/noise ratios of gadopentetate versus lesions were significantly higher than those of air. In proton-density images there was no significant difference. In T1- and proton-density images contrast/noise ratios of air versus abdominal fat were significantly higher than those of gadopentetate, in T2-weighted images gadopentetate had a significantly higher contrast/noise ratio than air. Signal-enhancing positive contrast agents seem advantageous over signal-free negative enteral MR contrast agents.

Superparamagnetic iron oxide particles (AMI-25) were evaluated as a liver contrast agent in high-field MR imaging (1.5 T). 16 patients with up to 5 presumed focal liver lesions (liver metastases n = 8, HCC n = 5, Klatskin tumours n = 2, FNH n = 1) received 15 mumol Fe/kg BW intravenously and were examined via standard T1- and T2-weighted spin-echo sequences. Quantitative image analysis showed a post-contrast increase of the contrast-to-noise ratio (C/N) from 1.6 to 7.4 on SE 2,500/15 images (p < .05). However, C/N was in the same range on plain SE 2,500/90 scans. Blind evaluation by two independent readers revealed that AMI-25-enhanced images did not provide a significantly increased number of lesions. Two patients reported minor, self-limited side-effects (flush, back pain). We conclude that in contrast to reports at mid-field MR imagers, the use of AMI-25 at 1.5 T does not significantly improve the detection of focal liver lesions on conventional SE images.

In order to establish diagnostic criteria, colour-coded duplex sonography was performed on 40 patients who had a total of 43 operatively confirmed thyroid lesions which were scintigraphically "cold" (28 adenomas, 8 carcinomas, 4 cases of thyroiditis and 3 cysts). 32 of these patients also had MRT with T2- and T1-weighted images before and after injection of Gd-DTPA (0.1 mmol/kg). Adenomatous nodules and adenomas showed a peripheral vascular halo on colour-coded duplex sonography with a sensitivity of 96% and a specificity of 93%. Malignant lesions showed marked central vascularisation and on B-images irregular marginal structures. Adenomas and adenomatous nodules showed hyperintense areas on T1-weighted unenhanced MR images and/or homogeneous uptake in the lesion (sensitivity 100%, specificity 77%). Malignant lesions typically showed an irregular margin with increased contrast uptake on MRT. If sonography and colour-coded duplex sonography is unable to classify a lesion with any degree of assurance then MRT with Gd-DTPA enhancement should be performed.

The method of localised 1H MR spectroscopy was used in 19 examinations in 9 patients with primary bone tumours in order to obtain spectral signals and to determine whether these are specific for tumour classification. The spectra were obtained by a double spin echo method and the tumour tissue showed very high water content and only minor lipid and proton signals which showed J-coupling characteristics. The latter are not found in normal bone marrow and are probably due to products of tumour metabolism. The resolution of the spectra within a 13 mm or 20 mm tissue cube depends largely on the structural homogeneity of the tumour. The signal patterns in the spectra were not specific to histological tumour types.

The value of selective imaging of fat and water compared with proton density, T1- and T2- weighted MR sequences was studied in the course of 32 examinations on 22 primary bone tumours in various parts of the body. Fat selective images showed practically signal free areas for osteogenic tumours which could be distinguished from surrounding fat containing soft tissues. Water selective images improved definition of the tumour margin from oedema in the bone marrow. Chemical shift artefacts are avoided by these methods and therefore fat and water selective images provide better spatial resolution for identical pixel sizes.

Twenty patients with focal liver lesions (18 metastases, 1 hepatocellular carcinoma, 1 cholangiocarcinoma) were given manganese DPDP as part of a multicentric phase II study of paramagnetic hepatobiliary MR contrast media. 5 mumol/kg manganese DPDP were injected into 10 patients in a concentration of 50 mumol/ml or 10 mumol/ml (3 ml/min). Blood pressure, pulse rate, ECG, respiratory rate, body temperature, blood and serum parameters and the patients' subjective feelings were recorded. MRI was performed with 1.5 T using T1- and T2-weighted sequences. 6 patients reported 8 side effects (flushing, feeling of warmth, metallic taste); 7 of these were produced by the 50 mumol concentration. Two hours after injection there was a significant reduction in alkaline phosphatase which was no longer present after 24 hours. On T1-weighted images manganese DPDP resulted in marked improvement in the contrast difference between the lesions and the liver parenchyma which resulted in a marked increase in the signal to noise ratio. Comparing the two concentrations, better results were obtained by the lower concentration. Extrahepatic uptake was found in the gallbladder, duodenum, pancreas, kidneys, gastric mucosa and myocardium. Manganese DPDP in a concentration of 10 mumol/ml and a dose of 5 mumol/kg is a well tolerated contrast medium which improves the demonstration of focal liver lesions in view of its distribution and uptake. The mechanisms for the transitory side effects require further studies.

Safety and efficacy of gadopentetate-dimeglumine (Gd-DTPA) as a MR bowel contrast agent were determined in 133 patients with CT-proved abdominal and retroperitoneal mass lesions using a buffered formulation (1 mmol/l Gd-DTPA, 15 g/l mannitol, 25 mmol/l sodium-citrate, 6-17 ml/kg). Short-lived gastrointestinal side effects were noted in 32% of patients. Gd-DTPA provided uniform, hyperintense bowel labelling and contrast enhancement in the region of interest in 81% of patients. Among 78 patients with pre- and postcontrast images lesion delineation was improved in 62%. In 55 studies with postcontrast images only, Gd-DTPA proved useful in 65%. In 105 of 109 cases IV injection of scopolamine or glucagon eliminated image artifacts arising from peristalsis of opacified bowel. The authors conclude that Gd-DTPA is a safe and effective MR bowel contrast agent.

Twenty-three patients with intra cranial meningiomas were examined by means of magnetic resonance tomography (MRT). In 13 patients the paramagnetic contrast medium gadolinium DTPA was used. Meningiomas show only slight changes in signal intensity compared with brain in the spin-echo mode, the greatest contrast being found on photon density images (TR 1600 ms, TE 35 ms). In T1 images, more than 50% patients showed a low signal margin between tumour and brain, Hyperostosis of the calvarium is easily recognised, but MRT is unreliable for showing tumour calcification. After intravenous injection of gadolinium DTPA, there was marked homogeneous uptake in the meningiomas. These signs are useful for the diagnosis of a meningioma by MRT.

A multislice gradient echo sequence (FLASH) was compared with a conventional spin-echo (SE) technique with regard to its value for contrast enhanced MR diagnosis. In 28 patients with cerebral tumours, SE images (SE 400/30; four images/3.4 minutes) and FLASH images (FLASH 315/14; 15 images/1.4 minutes) were obtained before and after gadolinium DTPA. After gadolinium-DTPA results were comparable for both techniques with respect to contrast enhancement, tumor contrast and delineation. Because of the higher efficiency of the FLASH 315/14 technique, this sequence is the method of choice for contrast enhanced cerebral MR imaging.

Beagle dogs were investigated by MRI (Siemens Magnetom, 0.35 T) after oral administration of aqueous solutions of Gd-DTPA (n = 4), ferric ammonium citrate (n = 1), and magnetite dextran (n = 2). High signal intensity of the GI-tract versus adjacent structures was obtained with Gd-DTPA and ferric ammonium citrate. Magnetite showed negative contrast versus adjacent structures. However, magnetite displayed lower contrast relative to liver, muscle and gut wall compared to Gd-DTPA and ferric ammonium citrate. In relatively T2-weighted sequences labeling of poorly filled bowel loops was significantly better with Gd-DTPA and ferric ammonium citrate. For GI-tract contrast enhancement we conclude that positive contrast media are of higher diagnostic value compared to negative contrast agents.

Nuclear magnetic resonance tomography was performed on 38 patients with intracranial tumours, before and after the administration of contrast, using a 0.35 T Magnetom. The MR examinations included various plain spin-echo sequences (SE 400/35, 800/35, 1600/35, 1600/70, 1600/105, 1600/120) as well as examinations after the iv-administration of gadolinium-DTPA (SE 800/35). On all occasions, the abnormalities were visible without contrast. Differentiation of tumour and its surroundings was possible in 19 out of 38 cases without contrast. Delineation of expansively growing tumours (eg. meningiomas) was possible in twelve out of 14 cases, but in only seven out of 24 cases with infiltrating tumours (eg. glioblastomas). On the other hand, clear differentiation between tumour and adjacent edema and normal brain, respectively, was possible in 35 out of 38 cases after Gadolinium-DTPA.

In an initial clinical trial we examined the tolerance and the influence exercised on signals in nuclear magnetic resonance tomography by gadolinium-DTPA. In an open study, 4 dosages between 0.005 and 0.25 mmol Gd-DTPA/kg body-weight were tested on 5 healthy volunteers each. To ensure renal elimination of Gd-DTPA, NMR images were produced (0.35 T Magnetom) visualising the kidneys and urinary bladder before and more than 60 minutes after application of the contrast medium. The article shows in what manner the image is influenced by the dosage of the contrast medium and also by the time interval elapsing between injection of the contrast medium and production of the NMR tomogram. - Finally, first clinical results of NMR tomography contrast medium application are demonstrated in the case of 5 patients with cerebral tumours.

Contrast media can significantly improve the diagnostic value of MR tomography. The basis of using contrast material for MR depends on totally different physical principles from those employed in conventional radiological diagnosis. The physical factors underlying the use of these contrast media are described, various suitable substances are discussed, and experience so far gained with some contrast agents is outlined.

In 60 patients with intracerebral lesions, examined by MRI, a new gradient-echo sequence was employed. This imaging technique uses excitation pulse angles smaller than 90 degrees and echoes are produced by an inversion of the read gradient. Since no 180 degrees pulse between successive excitations is necessary, very short repetition times can be used. Depending on matrix-size and signal averaging, MR imaging time can be reduced to approximately 5 to 40 seconds for single slice scan. For comparison, conventional T1- and T2-weighted spin-echo images were performed. Diagnostic results of the T1-weighted fast gradient-echo images corresponded with T1-weighted spin-echo images in 30% of cases. Diagnostic information was lower in 40% of cases. In the remainder of cases (30%) lesions were not detected with the gradient-echo technique. This especially applied to multiple sclerosis, infarctions and low-grade gliomas. Due to image artefacts and low contrast, visualization of small pathologic lesions was limited. Significant improvement of tumor visualization on gradient-echo scans was observed after injection of Gd-DTPA (0.1 mmol/kg).

The principles underlying contrast media for MR tomography are totally different from those for conventional contrast media. Substances suitable for MR tomography are paramagnetic complexes which alter the relaxation times of the tissues. Signal intensity on the MR images are influenced correspondingly. The mode of action of MR contrast media is explained. Gadolinium-DTPA, the first MR contrast medium in clinical use by means of intravenous injection, is described. Its tolerance has been investigated by animal experiments and its effectiveness as an contrast agent has been studied in normal individuals. In the second part of the paper, early results from the use of gadolinium DTPA are given. The additional information which can be obtained by using MR contrast media is discussed.

Aggressive fibromatoses (desmoid tumours) tend to grow in an infiltrative and destructive manner without metastases. Computed tomography of aggressive fibromatoses yields no uniform attenuation pattern. The tumours are typically isodense when no contrast medium is used and enhance clearly to hyperdense during infusion of contrast medium. In magnetic resonance tomography (MRT) a high signal (long T2) on T2-weighted pulse sequences as well as an accumulation of i.v. Gd-DTPA seems to be the characteristic appearance of aggressive fibromatoses, although different signal intensities can be seen. The MRT histopathologic correlation shows increasing signal intensities on T2-weighted sequences dependent on an increment in cellular content of the tumours. Only histopathological methods can provide a definite diagnosis.

The early results of the use of the MR specific contrast medium gadolinium-DTPA in 40 patients with intracranial tumours are reported. Optimal pulse sequences, contrast dose and timing are discussed. The relationship between the blood-brain barrier and contrast distribution within tumour tissue is elaborated. The clinical significance of the application of contrast agents in the diagnosis of brain tumours is evaluated.

32 patients with abdominal tumours or inflammatory abdominal diseases were examined by MRI (0.5 T) prior to and after oral administration of gadolinium-DTPA (Gd-DTPA). T1- and T2-weighted sequences were employed. 10 ml/kg body weight of a Gd-DTPA formulation were administered (1.0 mmol/l, 15 g mannitol/l). Gd-DTPA provided markedly hyperintensive opacification of the gastrointestinal tract. In 19 of 32 studies Gd-DTPA-enhanced scans showed improved delineation of abdominal pathologies. In most cases Gd-DTPA-enhanced T1-weighted multislice gradient echo images provided the most useful diagnostic result. Meteorism and diarrhea were recorded in 13 patients.

20 male volunteers were examined by MRI to determine safety and efficacy of Gd-DTPA formulations for gastrointestinal (GI)-tract contrast enhancement. Prior to and after administration of contrast spin-echo images were obtained. Volunteers were studied after administration of 10 ml contrast medium/kg (1.0 mmol Gd-DTPA/l vs. 0.5 mmol Gd-DTPA/l, no mannitol vs. 15 g mannitol/l vs. 30 g mannitol/l). Gd-DTPA provided high signal intensity in the GI tract. Contrast medium in gastric lumen and duodenum permitted improved delineation of pancreatic head and ventral outline in 16 of 20 subjects. No clinically relevant side effects were seen.