CT-Kolonographie mit dem 16-Zeilen-Detektor zur Diagnostik kolorektaler Neoplasien und entzündlicher Kolonerkrankungen

PURPOSE

Comparison of the performance of virtual and conventional colonoscopy for the detection of colorectal polyps and inflammatory colon diseases using a 16-slice spiral CT scanner. Furthermore, presentation of the first experiences with a new three-dimensional reconstruction mode ("colon-dissection") that dissects the colonic wall like a pathologic-anatomic preparation to increase the sensitivity.

MATERIALS AND METHODS

Forty patients were studied using a 16-slice spiral CT (Lightspeed 16, General Electric Medical Systems, Milwaukee, Wisconsin 53201, USA). The examination was performed after standard oral preparation for colonoscopy. The colonic distension was achieved with room air and intravenous butylscopolamine. Images were obtained in supine and prone position using a detector configuration of 16 x 0.625 mm, pitch 1.7, rotation time 0.5 s, 160 mAs and 120 kV. Axial reconstruction with a slice thickness of 0.625 mm. The CT data were assessed by two radiologists on an Advantage Workstation (Volume Analysis 2, USA) using a software with the capabilities of axial, multiplanar and volume rendering, virtual endoscopy, and colon dissection. Conventional colonoscopy was used to determine the sensitivity.

RESULTS

A total of 30 polyps were found in 8 patients and a carcinoma was detected in two patients. Colonography identified 4 polyps with a diameter of 10 mm or more, 6 polyps with a diameter of 5 mm to 9.9 mm, 11 polyps with a diameter of 3 to 4.9 mm and 9 polyps with a diameter of 3.0 mm or less. There were two false negative findings (one polyp of 3 mm and one of 4 mm had been overseen) and two false positive findings for polyps (polyps of 4 mm and 6 mm). The sensitivity and specificity for the detection of colonic polyps were 93% and 94% with the "colonic-dissection" mode, 87 % and 94 % with the "virtual-endoscopy" mode and 63 % and 97 % with multi-planar reconstruction, respectively. Depending on the diameter of the colonic polyps, the "colon-dissection" mode ("virtual-coloscopy") had a sensitivity and specificity of 100 % and 100 % for polyps with a diameter over 5.0 mm, 91 % and 82 % for polyps with a diameter from 3.0 to 4.9 mm and 89 % and 78 % for polyps with a diameter under 3.0 mm, respectively. Inflammatory colon diseases presented as thickening of the colon wall over 5 mm.

CONCLUSIONS

Virtual colonoscopy with 16-slice spiral CT allows accurate detection of colonic polyps, including small polyps below a diameter of 3 mm. In comparison with the 2D- and 3D-"virtual-endoscopic" reconstruction, the 3D-reconstruction software "colon-dissection" achieves the highest sensitivity for the detection of colonic masses. Therefore, the combination of a 16-slice spiral CT and the "colon-dissection" reconstruction software provides a high resolution in the z-axis for detecting colonic masses and polyps down to a diameter of less than 2 mm, with a sensitivity of about 90 %. This sensitivity is much higher than the sensitivity achievable with 4-slice spiral CT and without "colon-dissection" mode. A thickened colon wall over 5 mm indicates inflammatory colon disease.

[Accuracy of routine MRI in lesions of the supraspinatus tendon--comparison with surgical findings]

PURPOSE

To determine the correlation of the extent of lesions of the supraspinatus tendon in MRI's of the shoulder with surgical or arthroscopic findings using the classification of Snyders and Batemann, respectively.

MATERIALS AND METHODS

The preoperative MRI's of 80 patients (age: 16 - 76/47.4 +/- 14.0 years) which were performed due to various complaints of the shoulder were analyzed retrospectively by two experienced and blinded radiologists. We evaluated the incidence and the extent of partial or complete ruptures of the supraspinatus tendon. After MRI, an arthroscopic or open surgical intervention was performed (= gold standard). Various MR-scanners were used with a field strength of 1.0 T (17 cases), or 1.5 T (63 cases) and flexible or inflexible arthro coils. Additionally to plain MRI, 38 of 80 patients underwent contrast enhanced MRI. The MR and the surgical or arthroscopic findings were compared and statistically analyzed.

RESULTS

Neglecting the localization and the extent of discontinuity of the supraspinatus tendon, the sensitivity of the 80 MRI's was 0.93, the specificity 0.69, and the accuracy 0.85. The sensitivity increased to 0.96 with constant specificity and an accuracy of 0.83 excluding the lesions with an extent below 1 cm. Compared with non-enhanced examinations, the contrast enhanced MRI revealed higher sensitivity (+ 7 %, 0.89 vs. 0.96), higher specificity (+ 11 %, 0.64 vs. 0.75), and higher accuracy (+ 8 %, 0.81 vs. 0.89) in depicting lesions of the supraspinatus tendon at all. On T 1 -weighted images, the detection of lesions at all and the differentiation between partial and complete ruptures were improved significantly by contrast enhancement, especially in lesions with an extent below 1 cm. Diagnostic failures were seen in examinations without intravenous contrast application, artifacts, extent of the lesion below 1 cm, differentiating between degeneration and partial rupture of the tendon, differentiating between severely degenerated tendons with partial rupture and complete rupture, and covered ruptures.

CONCLUSIONS

The performance and consecutively the analysis of the widely used MRI of the shoulder is often not sufficiently reliable in its present routine form. To be able to compete with other imaging modalities such as sonography, standardized MR protocol, contrast enhancement as needed, avoiding the described source of failure, and an exact analysis should be applied.

PET imaging with yttrium-86: comparison of phantom measurements acquired with different PET scanners before and after applying background subtraction

Quantitative imaging with the positron emitter (86)Y is the method of choice to determine the uptake and dosimetry of (90)Y-labelled radiopharmaceuticals. To examine the quantitative accuracy of positron emission tomography findings with (86)Y, this non-pure positron emitter was evaluated in a cylindrical phantom with rods of Teflon, water and air and measured with three different scanners: ECAT EXACT (2D/3D), ECAT HR+ (2D/3D) and PC4096+ (2D). After standard reconstruction, (86)Y radioactivity measured with the ECAT EXACT and related to the true radioactivity varied between 0.84 and 0.99 in 2D and between 0.93 and 1.20 in 3D from the first to the last acquisition (eight half-life times later). The water and Teflon rods exhibited considerable amounts of reconstructed radioactivity-21% in 2D and 67% in 3D for water and 65% and 147%, respectively, for Teflon-compared with the actual (86)Y radioactivity of the phantom. For the ECAT HR+ similar results were obtained in 3D, but there were even greater overestimations in 2D. Measurements with the PC4096+ showed rather small errors, with 10% for water and 20% for Teflon. To correct for the background of gamma-coincidences, sinograms were analysed and an experimental percentage of the background was subtracted from the sinograms. In order to minimise the errors in reconstructed radioactivity, the subtraction value had to be different for the individual scanners and modes. Our results demonstrate that (90)Y/(86)Y-based dosimetry for bone and red marrow must be regarded with caution if it is derived from regions of interest over the bone, the density of which is similar to that of Teflon. To obtain more reliable estimates, an appropriate background correction must be applied and tailored individually with respect to the scanner and acquisition mode.

[The (11C) acetate positron emission tomography in prostatic carcinoma. New prospects in metabolic imaging]

The exact staging of prostate cancer is mandatory to allow selection of the appropriate primary therapy. In addition, if the PSA level rises again it is extremely important to find the site(s) of local recurrence or metastatic spread as soon as possible. However, with the morphological and metabolic imaging techniques currently available it is often not possible to answer these questions with adequate sensitivity and specificity, since small metastases < or = 1 cm in diameter are likely to remain undetected by them. In the last few years new radioactive labelled tracers have been introduced for use in positron emission tomography (PET), and it is hoped that the shortcomings in the diagnostic procedures used for prostate carcinoma might be compensated by their use. Besides 11C- or 18F-labelled choline, [11C]Acetate is also attracting attention as a promising PET tracer. In this paper we review the various PET tracers available and evaluate the advantages and the drawbacks of [11C]Acetate in three case studies by comparing [11C]Acetate-PET with histology and with other imaging techniques. The use of [11C]Acetate appears to be feasible and helpful in the diagnosis of prostate carcinoma. However, its final value relative to other imaging techniques needs further investigation, with special reference to initial lymph node involvement, early localisation of recurrence and possible noninvasive differentiation between prostate cancer, prostatis and benign hyperplasia of the prostate.

Novel neuropeptide Y1 and Y5 receptor gene variants: associations with serum triglyceride and high-density lipoprotein cholesterol levels

Neuropeptide Y (NPY) appears to play a critical role in the integration of appetite and energy expenditure through NPY Y1 and Y5 receptor subtypes. Moreover, the NPY Y1 receptor is highly expressed on human adipocytes, where it inhibits lipolysis. The genes encoding these receptors are transcribed co-ordinately in opposite directions from a common promoter in a region of chromosome 4 that has been previously linked to triglyceride and small low-density lipoprotein (LDL) particle concentration. Therefore, the purpose of this investigation was to examine the relationship between polymorphisms in the genes encoding NPY Y1 and Y5 and the development of obesity and dyslipidemia. We screened the promoter and coding regions and identified four polymorphic variants. One of these, a cytosine to thymine (C-->T) substitution in the untranslated region between the genes for NPY Y1 and Y5 (allele frequency 0.11), was significantly associated with both lower fasting triglyceride level (152 vs 125 mg/dl), and higher high-density lipoprotein (HDL) concentrations (49 vs 45 mg/dl) (p < 0.01) in 306 obese subjects. Given the stimulatory effect of NPY on adipocyte lipoprotein lipase (LPL) activity, and the lack of association of other polymorphisms with serum lipid levels, we hypothesize that this is a gain-in-function polymorphism.

Expression of the neuropeptide Y Y1 receptor in the CNS of rat and of wild-type and Y1 receptor knock-out mice. Focus on immunohistochemical localization

The distribution of neuropeptide Y (NPY) Y1 receptor-like immunoreactivity (Y1R-LI) has been studied in detail in the CNS of rat using a rabbit polyclonal antibody against the C-terminal 13 amino acids of the rat receptor protein. The indirect immunofluorescence technique with tyramide signal amplification has been employed. For specificity and comparative reasons Y1 knock-out mice and wild-type controls were analyzed. The distribution of Y1R mRNA was also studied using in situ hybridization. A limited comparison between Y1R-LI and NPY-LI was carried out.A widespread and abundant distribution of Y1R-LI, predominantly in processes but also in cell bodies, was observed. In fact, Y1R-LI was found in most regions of the CNS with a similar distribution pattern between rat and wild-type mouse. This staining was specific in the sense that it was absent in adjacent sections following preadsorption of the antibody with 10(-5) M of the antigenic peptide, and that it could not be observed in sections of the Y1 KO mouse. In contrast, the staining obtained with an N-terminally directed Y1R antiserum did not disappear, strongly suggesting unspecificity. In brief, very high levels of Y1R-LI were seen in the islands of Calleja, the anterior olfactory nucleus, the molecular layer of the dentate gyrus, parts of the habenula, the interpeduncular nucleus, the mammillary body, the spinal nucleus of the trigeminal, caudal part, the paratrigeminal nucleus, and superficial layers of the dorsal horn. High levels were found in most cortical areas, many thalamic nuclei, some subnuclei of the amygdaloid complex, the hypothalamus and the nucleus of the stria terminalis, the nucleus of the solitary tract, the parabrachial nucleus, and the inferior olive. Moderate levels of Y1R-LI were detected in the cornu Ammonis and the subicular complex, many septal, some thalamic and many brainstem regions. Y1R staining of processes, often fiber and/or dot-like, and occasional cell bodies was also seen in tracts, such as the lateral lemniscus, the rubrospinal tract and the spinal tract of the trigeminal. There was in general a good overlap between Y1R-LI and NPY-LI, but some exceptions were found. Thus, some areas had NPY innervation but apparently lacked Y1Rs, whereas in other regions Y1R-LI, but no or only few NPY-positive nerve endings could be detected. Our results demonstrate that NPY signalling through the Y1R is common in the rat (and mouse) CNS. Mostly the Y1R is postsynaptic but there are also presynaptic Y1Rs. Mostly there is a good match between NPY-releasing nerve endings and Y1Rs, but 'volume transmission' may be 'needed' in some regions. Finally, the importance of using proper control experiments for immunohistochemical studies on seven-transmembrane receptors is stressed.

PET quantitation and imaging of the non-pure positron-emitting iodine isotope 124I

A series of PET studies using phantoms is presented to characterize the imaging and quantitative performance of the positron-emitting iodine isotope 124I. Measurements were performed on the 2D-PET scanner GE 4096+ as well as on the Siemens PET scanner HRR+ operated in both 2D and 3D modes. No specific correction was applied for the gamma-rays emitted together with the positrons. As compared to 18F, in studies with 124I there is a small loss of image resolution and contrast, and an increase in background. The quantitative results varied between different scanners and various acquisition as well as reconstruction modes, with an average relative difference of -6 +/- 13% (mean+/-SD) in respect of the phantom radioactivity as measured with gamma-ray spectroscopy. We conclude that quantitation of a radiopharmaceutical labelled with 124I is feasible and may be improved by the development of specific corrections.

Brain systems engaged in encoding and retrieval of word-pair associates independent of their imagery content or presentation modalities

In this study, we aimed to characterize commonalities and differences of activation patterns during verbal episodic memory processes across different presentation modalities (visual or auditory) and different imagery content (low or high) of the presented verbal memory items. Twelve right-handed normal male volunteers took part in the study. Each subject underwent six O-15-butanol positron emission tomography scans. In six of the subjects the verbal material was presented visually, and in six subjects auditorily. The subjects had to encode and retrieve two sets of 12 word-pair associates of high (set 1) or low (set 2) imagery content (not semantically related). The presentation of nonsense words served as reference condition. Images were analyzed with statistical parametric mapping. Conjunction analysis was used to identify commonalities, and cognitive subtraction analysis was used to identify differences. The use of conjunction analyses enabled us to identify commonly activated regions involved in episodic encoding and retrieval of verbal material irrespective of the presentation modality or the imagery content. Our results add further evidence to recent findings that bilateral prefrontal activations are important for episodic retrieval and thus the role of the left prefrontal cortex has been underestimated during episodic retrieval. Furthermore, our results support the idea of functionally segregated areas in the prefrontal cortex. Finally, our results provide strong evidence that mesial parietal cortex (precuneus) involvement is not restricted to processes involving imagery.

Conscious and subconscious sensorimotor synchronization--prefrontal cortex and the influence of awareness

One of the most compelling challenges for modern neuroscience is the influence of awareness on behavior. We studied prefrontal correlates of conscious and subconscious motor adjustments to changing auditory rhythms using regional cerebral blood flow measurements. At a subconscious level, movement adjustments were performed employing bilateral ventral mediofrontal cortex. Awareness of change without explicit knowledge of the nature of change led to additional ventral prefrontal and premotor but not dorsolateral prefrontal activations. Only fully conscious motor adaptations to a changing rhythmic pattern showed prominent involvement of anterior cingulate and dorsolateral prefrontal cortex. These results demonstrate that while ventral prefrontal areas may be engaged in motor adaptations performed subconsciously, only fully conscious motor control which includes motor planning will involve dorsolateral prefrontal cortex.

Two-dimensional NMR studies of size fractionated Suwannee River fulvic and humic acid reference

Two-dimensional phase sensitive 13C,1H correlation spectra were applied to the investigation of substructures in size fractions obtained by tangential flow multistage ultrafiltration (MST-UF) of humic substances (HS) Suwannee River Fulvic Acid Reference (HS SR FA) and Suwannee River Humic Acid Reference (HS SR HA), purchased from the International Humic Substances Society (IHSS). After size fractionation with MST-UF the HS samples give well resolved two-dimensional 13C,1H-correlated NMR spectra which offer a great potential for substructure elucidation and even quantification. It is shown that low molecular size lignin moieties undergo demethylation of the methoxy groups, accompanied by removal of the phenylpropane side chains and subsequent reaggregation of the aromatic rings. These findings provide insight into the processes of lignin degradation. Only the fraction >100 kDa contains macromolecules that have spin-spin relaxation times too short for investigations employing NMR multipulse sequences.

Cerebral glucose transport implies individualized glial cell function

Previous positron emission tomography (PET) measurements of cerebral glucose transport using [11C]-3-O-methylglucose (CMG) suggested an interindividual variation in the values of the rate constant of tracer outflow (k2) larger than that for the clearance rate of inflow (K1). These two parameters were examined in healthy cerebral cortex by dynamic PET in 4 men and 2 women (aged 24 to 73 years) without neurologic disease, and in 1 man (42 years) with a recent left hemispheric cerebral infarction under normoglycemia (average blood plasma d-glucose concentration, 5.44 +/- 1.94 micromol/mL) and again under hyperglycemia (average, 10.24 +/- 1.44 micromol/mL). Time-radioactivity curves were obtained from healthy cortex (grey matter) and plasma and analyzed for the values of K1 and k2 by two graphical approaches and two fitting procedures. Both K1 and k2 significantly declined with increasing plasma glucose levels. A highly significant interindividual but not intraindividual variability for k2 was found at normoglycemia and hyperglycemia. The interindividual variability of K1, although borderline significant, was less than that of k2. Accordingly variable were the distribution volumes K1/k2. These data suggest individualized glial cell function and may be relevant to pathogenesis of neuropsychiatric disease.

Syntactic processing in left prefrontal cortex is independent of lexical meaning

In language comprehension a syntactic representation is built up even when the input is semantically uninterpretable. We report data on brain activation during syntactic processing, from an experiment on the detection of grammatical errors in meaningless sentences. The experimental paradigm was such that the syntactic processing was distinguished from other cognitive and linguistic functions. The data reveal that in syntactic error detection an area of the left dorsolateral prefrontal cortex, adjacent to Broca's area, is specifically involved in the syntactic processing aspects, whereas other prefrontal areas subserve general error detection processes.

The peptide YY-preferring receptor mediating inhibition of small intestinal secretion is a peripheral Y(2) receptor: pharmacological evidence and molecular cloning

A peptide YY (PYY)-preferring receptor [PYY > neuropeptide Y (NPY)] was previously characterized in rat small intestinal crypt cells, where it mediates inhibition of fluid secretion. Here, we investigated the possible status of this receptor as a peripheral Y(2) receptor in rats. Typical Y(2) agonists (PYY(3-36), NPY(3-36), NPY(13-36), C2-NPY) and very short PYY analogs (N-alpha-Ac-PYY(22-36) and N-alpha-Ac-PYY(25-36)) acting at the intestinal PYY receptor were tested for their ability to inhibit the binding of (125)I-PYY to membranes of rat intestinal crypt cells and of CHO cells stably transfected with the rat hippocampal Y(2) receptor cDNA. Similar PYY preference was observed and all analogs exhibited comparable high affinity in both binding assays. The same held true for the specific Y(2) antagonist BIIE0246 with a K(i) value of 6.5 and 9.0 nM, respectively. BIIE0246 completely abolished the inhibition of cAMP production by PYY in crypt cells and transfected CHO cells. Moreover, the antagonist 1) considerably reversed the PYY-induced reduction of short-circuit current in rat jejunum mucosa in Ussing chamber and 2) completely abolished the antisecretory action of PYY on vasoactive intestinal peptide (VIP)-induced fluid secretion in rat jejunum in vivo. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) experiments showed that Y(2) receptor transcripts were present in intestinal crypt cells (3 x 10(2) molecules/100 ng RNA(T)) with no expression in villus cells, in complete agreement with the exclusive binding of PYY in crypt cells. Finally, a full-length Y(2) receptor was cloned by RT-PCR from rat intestinal crypt cells and also from human small intestine. We conclude that the so-called PYY-preferring receptor mediating inhibition of intestinal secretion is a peripheral Y(2) receptor.

Integrating electrophysiology and neuroimaging of spatial selective attention to simple isolated visual stimuli

Visual-spatial attention involves modulations of activity in human visual cortex as indexed by electrophysiological and functional neuroimaging measures. Prior studies investigating the time course and functional anatomy of spatial attention mechanisms in visual cortex have used higher-order discrimination tasks with complex stimuli (e.g. symbol matching in bilateral stimulus arrays, or letter discrimination), or simple detection tasks but in the presence of complex distracting information (e.g. luminance detection with superimposed symbols as distractors). Here we tested the hypothesis that short-latency modulations of incoming sensory signals in extrastriate visual cortex reflect an early spatially specific attentional mechanism. We sought evidence of attentional modulations of sensory input processing for simple, isolated stimuli requiring only an elementary discrimination (i.e. size discrimination). As in prior studies using complex symbols, we observed attention-related changes in regional cerebral blood flow in extrastriate visual cortex that were associated with changes in event-related potentials at a specific latency range. These findings support the idea that early in cortical processing, spatially-specific attentional selection mechanisms can modulate incoming sensory signals based on their spatial location and perhaps independently of higher-order stimulus form.

A new two-dimensional pulse sequence for T(2)* measurements of protons in (13)C isotopomers

A new two-dimensional pulse sequence for T(2)* measurement of protons directly coupled to (13)C spins is proposed. The sequence measures the tranverse relaxation time of heteronuclear proton single-quantum coherence under conditions of free precession and is therefore well suited to evaluate relaxation losses of proton magnetization during preparation delays of heteronuclear pulse experiments in analytical NMR. The relevant part of the pulse sequence can be inserted as a "building block" into any direct or inverse detecting H,C correlation pulse sequence if proton spin-spin relaxation is to be investigated. In this contribution, the building block is inserted into a HETCOR as well as into a HMQC pulse sequence. Experimental results for the HETCOR-based sequence are given.

Interdependence of regional and global cerebral blood flow during visual stimulation: an O-15-butanol positron emission tomography study

The authors investigated the influence of variations in global cerebral blood flow (gCBF) on regional flow changes during visual stimulation. Global flow was varied using different end-expiratory CO2 values (PETCO2) between 20 and 70 mm Hg. Visual stimulation was performed with a red LED-array flashing at 8 Hz. Blood flow was measured with 0-15-butanol, continuous arterial blood sampling, and positron emission tomography (PET). Global flow changes surpassed the published values of O-15-H2O studies, better fitting the results of the inert gas technique (gCBF at 20, 40, and 70 mm Hg PETCO2 +/- SD was 31 +/- 4, 48 +/- 13, and 160 +/- 50 mL 100 g(-1) min(-1), respectively). The relation between PETCO2 and CBF in the current study was best described by an exponential rather than a linear function. At low PETCO2, the activation-induced flow changes are moderately damped, whereas at high PETCO2, they are nearly lost (deltaCBF (+/-SD): 52% +/- 25%, 68% +/- 22%, 16% +/- 25% at PETCO2 = 20, 40, 70 mm Hg, respectively).