In-vivo measurements of coronary blood flow using 16-slice multidetector spiral computed tomography (MDCT) in a porcine model.

PURPOSE: To determine whether CTCA supplemented with CT flow measurements can be used to demonstrate and semiquantitatively evaluate poststenotic coronary blood flow in a porcine model. MATERIALS AND METHODS: In 10 thoracotomized pigs, transit time flow meter probes were attached to the aorta and left anterior descending artery (LAD) for real-time blood flow volumetry. A vascular silicone occluder was deployed around the LAD proximal to the probe to create medium-grade (MGS) and high-grade stenoses (HGS). The blood flow was measured by CT without vessel occlusion and distal to the stenoses. Time-density curves were generated from CT data. The curves were evaluated by calculating and cross-plotting the variables "slope of the density increase", "peak density" and "slope of the post-peak density decrease" from the LAD and aortic CT data. RESULTS: The flow in the LAD dropped to 41 % +/- 9 % (mean +/- SD) for MGS and 12 % +/- 6 % for HGS of the baseline. Coronary time-density curves plateaued proportional to luminal narrowing. Unimpaired flow could be differentiated statistically significant from poststenotic flow adjacent to MGS and HGS (p < 0.000 and p < 0.002, respectively). Flow adjacent to MGS and HGS was successfully differentiated for "slope of the density increase" and "slope of the post-peak density decrease" (p < 0.003 and p < 0.030, respectively). CONCLUSION: CT measurements allow semiquantitative evaluation of poststenotic coronary blood flow.

Detection of porcine bone lesions and fissures: comparing digital selenium, digital luminescence, and analog film-screen radiography.

OBJECTIVE: The purpose of our study was to compare the diagnostic performance of a digital selenium detector (Thoravision) with that of analog film-screen systems and digital luminescence radiography in skeletal radiography for the detection of fissures and lesions in porcine bones. MATERIALS AND METHODS: One hundred bones taken from domestic pigs (50 ribs and 50 femurs) were divided into two equal groups. Fissures and bone lesions were created in 50 bones and 50 served as controls. The bones were examined using film-screen systems, digital luminescence radiography, and digital selenium radiography at various doses. Digital selenium radiography exposure values were adapted to the image geometry differing from the reference methods with a detector focus distance of 2.15 m. Four radiologists independently evaluated image quality and detectability of fissures and lesions on a five-point scale of confidence. Statistical evaluation was based on receiver operating characteristic curve analysis. RESULTS: Fissures and bone lesions were detected most reliably using the mammography film-screen system, but the difference in the results of the analog and digital reference images did not achieve statistical significance. CONCLUSION: Compared with analog film-screen systems, the lower spatial resolution of the digital selenium and digital luminescence radiography systems does not affect detectability of fissures and bone lesions in porcine bone. Selenium is effective in skeletal radiography for detecting fissures and bone lesions. With digital selenium and digital luminescence radiography, the surface dose can be cut to half that required for 200-speed film-screen systems without losing any diagnostically relevant information.

Functional magnetic resonance imaging of human pontine auditory pathway.

The purpose of this study is to visualize brainstem auditory pathways by functional magnetic resonance imaging (fMRI). Eighteen healthy volunteers (age 28 to 42 years) with normal hearing function underwent fMRI examination on a 1.5 Tesla imaging system (Philips, Best, The Netherlands) with periodic click stimulation. Blood oxygen level dependent images were obtained using a three-dimensional EPI sequence with shifted echo technique (principles of echo shifting with a train of observations). Control scans without click stimulation were obtained in the identical setting. Cross correlation activation maps were calculated using a postprocessing tool (Philips). They were matched with anatomic slices of identical orientation and thickness. Five of 18 subjects were excluded because of motion artifacts. In 4/13 significant activation was observed at the root entry zone of the ipsilateral acoustic nerve corresponding to the cochlear nuclei. In 11/13 subjects, significant activation was found in the same slice contralaterally close to the floor of the 4th ventricle, corresponding to the expected region of the superior olivary nucleus. Activation of the rostral parts of the auditory pathway (inferior colliculus, medial geniculate body) was not found. In the absence of the stimulus no activation occurred in these structures. It was concluded that activation of the brainstem auditory pathways by click stimuli can be visualized by fMRI.

Non-invasive determination of metabolite concentrations in human transplanted kidney in vivo by 31P MR spectroscopy.

PURPOSE: To investigate concentrations of phosphorus-containing metabolites in human transplanted kidney in vivo by quantitative 31P MR spectroscopy (MRS) using surface coils and to compare the obtained values with previous data. MATERIAL AND METHODS: In 5 patients with well-functioning transplanted kidneys, 31P spectra were obtained with the three-dimensional localization image-selected in vivo spectroscopy technique applying a protocol for quantitative spectroscopy using surface coils. Relaxation corrected signal intensities determined by time domain fitting were used to derive absolute molar concentrations for phosphate-containing metabolites. RESULTS: Little or no phosphocreatine in all spectra verified the absence of muscle contamination, confirming proper volume localization. The mean concentrations in the transplanted kidneys were as follows: ATP 1.60 +/- 0.26 mmol/ 1, PDE 2.14 +/- 0.91 mmol/l, Pi 0.66 +/- 0.25 mmol/l, PME 2.32+ /- 0.50 mmol/l. These values are consistent with previously reported values determined by other techniques. CONCLUSION: The non-invasive determination of absolute metabolite concentrations in human kidney using MRS supplements the use of signal intensity ratios to detect pathologic changes in the energy metabolism of transplanted kidneys.

MR imaging of the chest: mediastinum and chest wall.

This review presents the options and limitations of MRI in non-vascular diseases of the mediastinum and the chest wall. In numerous thoracic pathologies, MRI is a useful supplement to spiral CT. This imaging procedure also allows a contrast-media-free differentiation of solid tumors and vascular lesions (e. g., aortic aneurysms). The advantages of MRI over CT are particularly useful when multiplanar tumor imaging is required prior to surgery to establish the exact spatial relationship between tumor and the other mediastinal structures. Primary indications for MRI in diseases of the mediastinum and chest wall are therefore: (a) tumors of the posterior mediastinum for determining their position in relation to the neural foramina and the spinal canal; (b) chest wall tumors; (c) preoperative multiplanar imaging of primary mediastinal tumors; and (d) contraindications against CT exams with iodine contrast media.

[Digital selenium radiography: a comparison of the picture quality of thoracic images in normal and reduced image formats based on the structural anatomical details]. / Digitale Selenradiographie: Vergleich der Bildqualität von Thoraxaufnahmen in normalem und verkleinertem Bildformat anhand anatomischer Detailstrukturen.

PURPOSE: Is there a loss of information when using selenium radiographic images displayed with reduced image format compared to full format? METHOD: Digital selenium radiographic chest images in two planes were obtained in 35 patients for medical reasons. The digital data sets of each patient were separately displayed in full format on two different films and were printed in reduced format on one film. The format was reduced to 61% of the full format using an acquisition matrix of 2166 x 2488 pixels, an image display matrix of 4000 x 5000 pixels and a film format of 43 x 49 cm. All images were anonymously evaluated by four independent readers using a questionnaire concerning anatomic structures. RESULTS: Format reduction did not result in a loss of information in diagnostically relevant anatomic details. CONCLUSIONS: Displaying digital selenium radiographic data sets of thoracic view in two planes on one film presumably does not lead to a loss of diagnostic information. This procedure may help to reduce film costs.

[Direct-current treatment of chemically induced mammary carcinoma in an animal model: MR volumetric assessment of the effect of the therapy]. / Gleichstrombehandlung des chemisch induzierten Mammakarzinoms im Tiermodell: MR-volumetrische Erfassung des Therapieeinflusses.

PURPOSE: To investigate the effect of direct current treatment (DCT) on the growth of mammary carcinomas in rats by MR-volumetry. METHODS: Chemically induced mammary adenocarcinomas in a control group (n = 17) were compared with treated tumours (18 C/cm3 in group A: n = 7 or 36 C/cm3 in group B: n = 12). 31 untreated tumours were situated near a treated tumour (group C). Experiments were carried out using one positive electrode in the tumour centre and three negative electrodes in the periphery. The tumour volume was measured by MRI before, and 1, 3, 6, 9 and 12 weeks after treatment. RESULTS: 12 weeks after DCT, the mean tumour volume in group A (164% +/- 158%, p < 0.05) and group B (13% +/- 24%, p < 0.001) was significantly reduced compared to the control group (434% +/- 230, Mann-Whitney U-Test). Complete tumour regression occurred in 42% of tumours in group B and was not achieved in group A, C and control group. Tumour growth in group C was decreased compared to the control group. CONCLUSIONS: The effectiveness of DCT was found to depend on the applied dosage -36 C/cm3 was more effective than 18 C/cm3. The effect of DCT is not limited to the area between the electrodes.

[Can digital selenium-based radiography in thoracic diagnosis replace the analog x-ray imaging technic?]. / Kann die digitale Selenradiographie in der Thoraxdiagnostik die analoge Röntgenaufnahmetechnik ersetzen?

PURPOSE: To find out the diagnostic value of digital selenium radiography, we compared the image quality of chest x-ray images from 50 patients who had been examined via conventional chest x-ray and digital selenium radiography of the chest. METHOD: 50 patients with a malignant melanoma underwent chest x-ray within 3 months in conventional technique and with digital selenium radiography (Thoravision: Philips Medical Systems, Hamburg, Germany). In this period none of the patients showed a difference in respect of clinical status or radiological diagnosis. Simultaneous examinations on the same day were not performed to avoid unnecessary exposure to x-rays. The digital and conventional images were compared by 4 radiologists with regard to image quality by the detection of defined anatomic structures. RESULTS: Image quality of digital selenium radiography was considered superior to that of conventional chest x-rays in the mediastinum, the retrocardiac and retrodiaphragmatic areas, the superior and inferior lobes of the lung especially near the parietal pleura, and the chest wall. CONCLUSIONS: Compared to analogous techniques there is no loss of image information when employing digital selenium radiography in chest x-rays. On the contrary, new assessment criteria may be gained. We conclude that digital selenium radiography offers diagnostic advantages in chest x-ray examination.

[Diagnostic value of digital projection radiography in comparison with conventional roentgen technique]. / Diagnostischer Stellenwert der digitalen Projektionsradiographie im Vergleich zur konventionellen Röntgentechnik.

Digital projection radiography provides digital data in x-ray examinations, which used to be carried out by examinations screen-film system combinations. The technological basis and clinical performances of digital luminescent radiography (DLR) and digital radiography are reviewed. Digital projection radiography does not allow to reduce selenium exposure significantly, compared to screen-film system combinations. Digital luminescent radiography can be used for the entire spectrum of analogous projection radiography the only exception being extremely subtile structural changes. The clinical experiences with digital selenium radiography achieved so far in chest x-rays are promising and the technique is expected to be increasing used in other anatomic regions as well.

31P magnetic resonance spectroscopy in dilated cardiomyopathy and coronary artery disease. Altered cardiac high-energy phosphate metabolism in heart failure.

BACKGROUND: The purpose of this work was to further define the value of cardiac 31P magnetic resonance (MR) spectroscopy for patients with coronary artery disease and dilated cardiomyopathy. METHODS AND RESULTS: Blood-corrected and T1-corrected 31P MR spectra of anteroseptal myocardium were obtained at rest using image-selected in vivo spectroscopy localization, a selected volume of 85 +/- 12 cm3, and a field strength of 1.5 T. Nineteen volunteers had a creatine phosphate (CP)/ATP ratio of 1.95 +/- 0.45 (mean +/- SD) and a PDE/ATP ratio of 1.06 +/- 0.53; in four patients with left anterior descending coronary artery (LAD) stenosis, six patients with chronic anterior wall infarction, and four patients with chronic posterior wall infarction, CP/ATP and phosphodiester (PDE)/ATP ratios did not differ from those in volunteers. Twenty-five measurements of 19 patients with dilated cardiomyopathy yielded a CP/ATP of 1.78 +/- 0.51 and a PDE/ATP of 0.98 +/- 0.56 (p = NS versus volunteers). When these patients were grouped according to the severity of heart failure, however, CP/ATP was 1.94 +/- 0.43 in mild (p = NS versus volunteers) and 1.44 +/- 0.52 in severe DCM (p < 0.05), respectively. No correlation was found between CP/ATP and left ventricular ejection fraction or fractional shortening, but correlation of CP/ATP with the New York Heart Association (NYHA) class was significant (r = 0.60, p < 0.005). Six patients with dilated cardiomyopathy were studied repeatedly before and after 12 +/- 6 weeks of drug treatment leading to clinical recompensation with improvement of the NYHA status by 0.8 +/- 0.3 classes. Concomitantly, CP/ATP increased from 1.51 +/- 0.32 to 2.15 +/- 0.27 (p < 0.01), whereas PDE/ATP did not change significantly. CONCLUSIONS: Cardiac high-energy phosphate metabolism at rest is normal in LAD stenosis and chronic myocardial infarction in the absence of heart failure. The CP/ATP ratio has low specificity for the diagnosis of dilated cardiomyopathy. However, CP/ATP correlated with the clinical severity of heart failure and may improve during clinical recompensation.

[The direct measurement of the spin-grid-relaxation times of phosphorus metabolites in the human myocardium]. / Direkte Messung der Spin-Gitter-Relaxationszeiten von Phosphormetaboliten im menschlichen Myokard.

The T1 relaxation times of the phosphorus metabolites in human heart muscle measurable by 31P-MR spectra were determined in 12 individuals using a 1.5 Tesla system. Several spectra were recorded consecutively with a pulse repetition time of 1.6 s to 24 s. The T1 times of creatine phosphate (CP), of gamma-, alpha-, beta-adenosintriphosphate (ATP), 2,3-diphosphoglycerate (2,3-DPG) together with anorganic phosphate) and phosphodiester (PDE) showed mean measurements of 6.1 +/- 0.5, 5.4 +/- 0.5, 5.0 +/- 0.5, 5.8 +/- 1.0, 7.6 +/- 1.0, and 5.0 +/- 1.0 s (M +/- SE). The accuracy of the ISIS technique was tested with a special phantom. T1 times were also measured in standard solutions (20 mM CP, 10 mM ATP); CP was 8.7 +/- 0.2 s and gamma-ATP was 9.9 +/- 0.7 s. Corrections for partially saturated 31P-MR spectra--at least for CP/ATP ratios--are relatively small.

Direct measurement of spin-lattice relaxation times of phosphorus metabolites in human myocardium.

T1 values of phosphorus metabolites visible in human cardiac 31P-MR spectra were determined in 12 volunteers at 1.5 T. Consecutive spectra were acquired with varying pulse repetition time (TR) from 1.6 to 24 s; volume selection was achieved with ISIS. T1's of creatine phosphate (CP), [gamma-P], [alpha-P], and [beta-P]ATP, 2-3 diphosphoglycerate, and phosphodiesters were 6.1 +/- 0.5, 5.4 +/- 0.5, 5.5 +/- 0.5, 5.8 +/- 1.0, 7.6 +/- 1.0, and 5.0 +/- 1.0 s, respectively. CP/ATP ratios showed little change with varying TR; linear regression of CP/ATP vs TR was of borderline significance (r = 0.28, P = 0.06). T1's for CP and ATP were also determined in standard solution (20 mM CP, 10 mM ATP) yielding T1CP of 8.7 +/- 0.2 and T1[gamma-P]-ATP of 9.9 +/- 0.7 s. Thus, T1's for CP and ATP were similar at 1.5 T in both human heart and standard solution. In human cardiac 31P-MR spectra, CP/ATP ratios may need little correction for partial saturation.

[Adverse reactions following high-dose intravenous injection of urographic contrast media]. / Nebenwirkungen nach hochdosierter intravenöser Injektion nierengängiger Kontrastmittel.

The frequency and type of side effects from high-dose renographic contrast media correspond with those quoted in the literature for injections of small doses of contrast. In addition to the usual contra-indications against injection of renographic contrast, one should also consider the effect of short-lived increase in circulating volume in patients with left heart insufficiency.

[Percutaneous puncture of renal cysts for diagnostic and therapeutic purposes (author's transl)]. / Perkutane Punktion zystischer Raumforderungen der Niere zur Diagnostik und Therapie.

Percutaneous needle puncture of space-occupying lesions is an innocuous procedure in the differential diagnosis of renal masses. In conjunction with intravenous urography, ultrasonography and CT-scan it is a method of considerable diagnostic value, which will lead to a nearly complete accurate diagnosis. In this study we will report our experiences with diagnostic and therapeutic puncture of renal cysts. The instillation of Lipiodol has been given up, since a follow-up study became impossible due to radiological problems. The diagnostic procedure to differentiate expanding lesions of the kidney and the technique of percutaneous needle puncture are described as well as indications for surgical exploration.