Assessment of radiation exposure on a dual-source computed tomography-scanner performing coronary computed tomography-angiography

OBJECTIVE

The radiation exposure of a dual-source-64-channel multi-detector-computed-tomography-scanner (Somatom-Defintion, Siemens, Germany) was assessed in a phantom-study performing coronary-CT-angiography (CTCA) in comparison to patients' data randomly selected from routine scanning.

METHODS

240 CT-acquisitions of a computed tomography dose index (CTDI)-phantom (PTW, Freiburg, Germany) were performed using a synthetically generated Electrocardiography (ECG)-signal with variable heart rates (30-180 beats per minute (bpm)). 120 measurements were acquired using continuous tube-output; 120 measurements were performed using ECG-synchronized tube-modulation. The pulsing window was set at minimum duration at 65% of the cardiac cycle between 30 and 75 bpm. From 90-180 bpm the pulsing window was set at 30-70% of the cardiac cycle. Automated pitch adaptation was always used. A comparison between phantom CTDI and two patient groups' CTDI corresponding to the two pulsing groups was performed.

RESULTS

Without ECG-tube-modulation CDTI-values were affected by heart-rate-changes resulting in 85.7 mGray (mGy) at 30 and 45 bpm, 65.5 mGy/60 bpm, 54.7 mGy/75 bpm, 46.5 mGy/90 bpm, 34.2 mGy/120 bpm, 27.0 mGy/150 bpm and 22.1 mGy/180 bpm equal to effective doses between 14.5 mSievert (mSv) at 30/45 bpm and 3.6 mSv at 180 bpm. Using ECG-tube-modulation these CTDI-values resulted: 32.6 mGy/30 bpm, 36.6 mGy/45 bpm, 31.4 mGy/60 bpm, 26.8 mGy/75 bpm, 23.7 mGy/90 bpm, 19.4 mGy/120 bpm, 17.2 mGy/150 bpm and 15.6 mGy/180 bpm equal to effective doses between 5.5 mSv at 30 bpm and 2.6 mSv at 180 bpm. Significant CTDI-differences were found between patients with lower/moderate and higher heart rates in comparison to the phantom CTDI-results.

CONCLUSIONS

Dual source CTCA is particularly dose efficient at high heart rates when automated pitch adaptation, especially in combination with ECG-based tube-modulation is used. However in clinical routine scanning for patients with higher heart rates and corresponding enlarged pulsing window a significant different dose resulted.

Three-dimensional pelvimetry by computed tomography

PURPOSE

This study was undertaken to assess the agreement of computed tomography (CT) pelvimetry with different postprocessing techniques.

MATERIALS AND METHODS

CT data sets of 25 patients were retrospectively analysed. There were no CT examinations performed solely for pelvimetry, and there was no radiation exposure for study purposes. Six pelvimetric measurements were obtained by two independent observers in four data sets of each patient, i.e. on biplanar topograms, multiplanar reconstructions of 1-mm slices, volume-rendered images of the same data and volume-rendered images based on 5-mm-thick images. Interobserver agreement and variability were determined by Bland-Altman analysis. A human skeleton was also scanned and measured with the same techniques and by ruler as reference.

RESULTS

With a correlation coefficient of 0.98, interobserver agreement was best for assessing 3D volume-rendered images reconstructed from 1-mm-thick slices. Interobserver variability was very good for sagittal outlet and midpelvic diameter, transverse inlet diameter and obstetric conjugate (correlation coefficients 0.96-0.99) but limited for intertuberous and interspinous distance. CT and ruler measurements of the skeleton showed excellent agreement.

CONCLUSIONS

Pelvimetry can be obtained with low interobserver variability on 3D volume-rendered CT reconstructions. Thus, CT pelvimetry is suitable to gain exact knowledge of pelvic anatomy to identify relevant parameters for dystocia in retrospective studies.

Buried bumper syndrome causing rectus abdominis necrosis in a man with tetraplegia

STUDY DESIGN

Case report.

OBJECTIVES

To enhance the early recognition of buried bumper syndrome in patients with tetraplegia requiring percutaneous endoscopic gastrostomy (PEG).

SETTING

Inpatient unit, Massachusetts, USA.

METHODS

A 44 year-old man with C2 American Spinal Injury Association grade A tetraplegia with a relatively recent PEG insertion secondary to poor nutritional intake.

RESULTS

Several months after PEG placement, patient became febrile, hypotensive and complained of abdominal pain. Plain films showed a dilated bowel suggestive of ileus. Abdominal and pelvic computed tomography with and without contrast revealed PEG tube dislodgement, and a 21 cm x 2.8 cm left anterior abdominal wall collection consisting of air and contrast. Upon surgical intervention, the left rectus abdominis sheath and muscle were found to be necrotic.

CONCLUSION

Buried bumper syndrome is a serious complication related to PEG tubes. For many people with tetraplegia, PEG is a life-saving procedure with minimal risks. However, emergencies do occur, making prompt recognition imperative to prevent a fatal sequela.

Experimental study of the ion critical-gradient length and stiffness level and the impact of rotation in the JET tokamak

Experiments were carried out in the JET tokamak to determine the critical ion temperature inverse gradient length (R/LTi=R|nablaTi|/Ti) for the onset of ion temperature gradient modes and the stiffness of Ti profiles with respect to deviations from the critical value. Threshold and stiffness have been compared with linear and nonlinear predictions of the gyrokinetic code GS2. Plasmas with higher values of toroidal rotation show a significant increase in R/LTi, which is found to be mainly due to a decrease of the stiffness level. This finding has implications on the extrapolation to future machines of present day results on the role of rotation on confinement.

Risk prediction of prevalent diabetes in a Swiss population using a weighted genetic score--the CoLaus Study

AIMS/HYPOTHESIS

Several susceptibility genes for type 2 diabetes have been discovered recently. Individually, these genes increase the disease risk only minimally. The goals of the present study were to determine, at the population level, the risk of diabetes in individuals who carry risk alleles within several susceptibility genes for the disease and the added value of this genetic information over the clinical predictors.

METHODS

We constructed an additive genetic score using the most replicated single-nucleotide polymorphisms (SNPs) within 15 type 2 diabetes-susceptibility genes, weighting each SNP with its reported effect. We tested this score in the extensively phenotyped population-based cross-sectional CoLaus Study in Lausanne, Switzerland (n = 5,360), involving 356 diabetic individuals.

RESULTS

The clinical predictors of prevalent diabetes were age, BMI, family history of diabetes, WHR, and triacylglycerol/HDL-cholesterol ratio. After adjustment for these variables, the risk of diabetes was 2.7 (95% CI 1.8-4.0, p = 0.000006) for individuals with a genetic score within the top quintile, compared with the bottom quintile. Adding the genetic score to the clinical covariates improved the area under the receiver operating characteristic curve slightly (from 0.86 to 0.87), yet significantly (p = 0.002). BMI was similar in these two extreme quintiles.

CONCLUSIONS/INTERPRETATION

In this population, a simple weighted 15 SNP-based genetic score provides additional information over clinical predictors of prevalent diabetes. At this stage, however, the clinical benefit of this genetic information is limited.

The nutritional value of high-protein corn distillers dried grains for broiler chickens and its effect on nutrient excretion

Two experiments were conducted with a co-product of corn endosperm fermentation. The first experiment determined nutrient digestibility of high-protein corn distillers dried grains (HP-DDG; 54% CP) after feeding semipurified diets from 15 to 22 d of age. The AMEn of HP-DDG was 2,526 kcal/kg, whereas standardized ileal Lys, Met, and Thr digestibilities were 73.0, 84.9, and 73.0%, respectively. In a second experiment, an industry control diet (I) regimen was compared with that of either an approximate 25 or 50% replacement for the level of 48% CP soybean meal (SBM) inclusion in the diet utilizing the amino acid digestibility and AMEn determined from the first experiment. From 0 to 14, 14 to 28, and 28 to 42 d of age, the HP-DDG in the 50% SBM replacement diet was added at 25, 23.5, and 21% of the diet, respectively. To meet digestible amino acid needs, the diet containing 50% SBM replacement with HP-DDG contained 3.2, 3.6, and 4.4% units more CP than the I diet regimen from 1 to 14, 14 to 28, and 28 to 42 d of age, respectively. Dietary replacement of up to 50% of SBM inclusion with HP-DDG had no effect on bird performance at 14 or 42 d of age or breast fillet yield at 42 d of age; however, it decreased BW gain and increased feed:gain ratio from 14 to 28 d of age. Birds consuming a diet with 50% replacement of SBM with HP-DDG consumed 17.1% more N compared with those consuming I diets. This additional N and fiber consumed resulted in birds being fed the 50% replacement for SBM diet excreting 21.9 and 31.8% more manure DM and N, respectively. Due in large part to the amino acid profile and digestibility of HP-DDG, use of this feedstuff as a large proportion of the diet is feasible but results in more manure and manure N from broilers.

Reconstruction of the water table from self-potential data: a bayesian approach

Ground water flow associated with pumping and injection tests generates self-potential signals that can be measured at the ground surface and used to estimate the pattern of ground water flow at depth. We propose an inversion of the self-potential signals that accounts for the heterogeneous nature of the aquifer and a relationship between the electrical resistivity and the streaming current coupling coefficient. We recast the inversion of the self-potential data into a Bayesian framework. Synthetic tests are performed showing the advantage in using self-potential signals in addition to in situ measurements of the potentiometric levels to reconstruct the shape of the water table. This methodology is applied to a new data set from a series of coordinated hydraulic tomography, self-potential, and electrical resistivity tomography experiments performed at the Boise Hydrogeophysical Research Site, Idaho. In particular, we examine one of the dipole hydraulic tests and its reciprocal to show the sensitivity of the self-potential signals to variations of the potentiometric levels under steady-state conditions. However, because of the high pumping rate, the response was also influenced by the Reynolds number, especially near the pumping well for a given test. Ground water flow in the inertial laminar flow regime is responsible for nonlinearity that is not yet accounted for in self-potential tomography. Numerical modeling addresses the sensitivity of the self-potential response to this problem.

Sawtooth-control mechanism using toroidally propagating ion-cyclotron-resonance waves in tokamaks

The sawtooth control mechanism in plasmas employing off-axis toroidally propagating ion cyclotron resonance waves in tokamaks is reinvestigated. The radial drift excursion of energetic passing ions distributed asymmetrically in the velocity parallel to the magnetic field determines stability when the rational q=1 surface resides within a narrow region centered about the shifted fundamental cyclotron resonance.

Neutron emission spectroscopy results for internal transport barrier and mode conversion ion cyclotron resonance heating experiments at JET

The effect of ion cyclotron resonance heating (ICRH) on (3He)D plasmas at JET was studied with the time of flight optimized rate (TOFOR) spectrometer dedicated to 2.5 MeV dd neutron measurements. In internal transport barrier (ITB) plasma experiments with large 3He concentrations (X(3He)>15%) an increase in neutron yield was observed after the ITB disappeared but with the auxiliary neutral beam injection and ICRH power still applied. The analysis of the TOFOR data revealed the formation of a high energy (fast) D population in this regime. The results were compared to other mode conversion experiments with similar X(3He) but slightly different heating conditions. In this study we report on the high energy neutron tails originating from the fast D ions and their correlation with X(3He) and discuss the light it can shed on ICRH-plasma power coupling mechanisms.

Patellofemoral joint forces

In this review of patellofemoral joint forces as they might apply to implant design, methodologies for estimating forces on the patella and estimates of the forces, as reported in the literature, are summarized. Two methodologies exist for studying joint loads; one that measures kinematics in-vivo and uses analysis to estimate the joint loads and another that measures ground reaction forces and uses analysis to estimate the joint loads. In both these analyses many assumptions are required with varying degrees of uncertainty; here, those assumptions are examined with data from the published literature. The topics covered include: relationships between quadriceps forces and patellofemoral forces or patella ligament forces, relationships between knee joint moments and quadriceps forces, knee joint moments in various gaits, relationships between patellofemoral forces and lateral subluxation forces, and relationships between patella forces and inferior-superior forces. In many cases, there is little data on patella forces during normal activities, in other cases, there are some discrepancies in reported patella forces, i.e. during squat.

Acute-phase and 1-year follow-up results of a randomized controlled trial of CBT versus Befriending for first-episode psychosis: the ACE project

BACKGROUND

The ACE project involved 62 participants with a first episode of psychosis randomly assigned to either a cognitive behaviour therapy (CBT) intervention known as Active Cognitive Therapy for Early Psychosis (ACE) or a control condition known as Befriending. The study hypotheses were that: (1) treating participants with ACE in the acute phase would lead to faster reductions in positive and negative symptoms and more rapid improvement in functioning than Befriending; (2) these improvements in symptoms and functioning would be sustained at a 1-year follow-up; and (3) ACE would lead to fewer hospitalizations than Befriending as assessed at the 1-year follow-up.

METHOD

Two therapists treated the participants across both conditions. Participants could not receive any more than 20 sessions within 14 weeks. Participants were assessed by independent raters on four primary outcome measures of symptoms and functioning: at pretreatment, the middle of treatment, the end of treatment and at 1-year follow-up. An independent pair of raters assessed treatment integrity.

RESULTS

Both groups improved significantly over time. ACE significantly outperformed Befriending by improving functioning at mid-treatment, but it did not improve positive or negative symptoms. Past the mid-treatment assessment, Befriending caught up with the ACE group and there were no significant differences in any outcome measure and in hospital admissions at follow-up.

CONCLUSIONS

There is some preliminary evidence that ACE promotes better early recovery in functioning and this finding needs to be replicated in other independent research centres with larger samples.

Contrast enhanced ultrasound and Dual Source CT of left atrial myxoma

PURPOSE

Myxomas of the left atrial cavity of the heart are a rare occurrence. Incidental diagnosis is mostly based on transthoracic echocardiography. Contrast enhanced ultrasound (CEUS) seems to be a promising new diagnostic option for diagnosis and preoperative planning of treatment for patients with myxoma. It is an additional examination to baseline ultrasound and CT or MRT.

MATERIALS AND METHODS

We report a case of a 63-year-old woman with myxoma of the left atrial cavity of the heart in which CEUS helped to define the location and its relation to the heart valve.

RESULTS

In contrast enhanced ultrasound (CEUS), the oval mass in the left atrium was scanned in the 4-chamber view. Perfusion of the mass was examined by visualising gradual contrast enhancement. An involvement of the mitral valve could be excluded. The tumour base could be clearly depicted and differentiated from normal surrounding tissue. No thrombotic material was found in the left atrium (LA) or ventricle (LV).

CONCLUSION

CEUS could detect the mass and offer additional information such as vascularity, mobility, attachment to the valve and possible thrombi. Dual Source CT (DSCT) confirmed the findings and provided a very clear morphological characterisation and dynamic evaluation of mobility and valve interference.

Does polymeric formula improve adherence to liquid diet therapy in children with active Crohn's disease?

BACKGROUND

Active Crohn's disease can be treated using liquid diet therapy (LDT), but non-adherence may limit success, necessitating corticosteroid therapy. Whole-protein polymeric formula (PF) seems to be much more palatable than amino acid-based elemental formula (EF) and thus may significantly improve adherence to LDT.

AIM

To compare adherence to LDT using PF versus EF.

METHODS

Success in completing a 6-week course of LDT, need for nasogastric tube administration of formula and use of LDT for relapses were compared between children presenting with active disease and treated with EF (n = 53) and children given PF (n = 45).

RESULTS

Remission rates were similar (EF 64%, 95% CI 51 to 77 vs PF 51%, 95% CI 37 to 66; p>0.15). 72% (95% CI 60 to 84) given EF completed the initial course of LDT compared with 58% (95% CI 44 to 72) given PF (p = 0.15). Of those failing to complete the initial course, 13% on EF and 16% on PF gave up by choice (non-adherence), the remainder stopping due to treatment failure. Nasogastric administration was more frequent with EF (55%, 95% CI 42 to 68) compared to PF (31%, 95% CI 17 to 45) (p = 0.02). Among those treated successfully at first presentation, LDT was used for 28% of relapses in the EF group (95% CI 12 to 44) and 39% in the PF group (95% CI 19 to 59) (p>0.2) over the next year.

CONCLUSION

PF did not effect adherence to LDT but was associated with significantly reduced need for nasogastric tube administration of formula.

[Quantification of coronary artery stenoses: comparison of 64-slice and dual source CT angiography with cardiac catheterization]

BACKGROUND

Until now stenoses of the coronary arteries have been evaluated visually with CT angiography. Therefore, the results were highly dependent on subjective factors inherent in the examiner. New software tools for semiquantitative analysis (CT-QCA, quantitative coronary assessment) might be adequate to improve the diagnostic accuracy und reproducibility.

MATERIAL AND METHODS

CTAs of 20 patients were analyzed. Ten patients each were evaluated using 64-slice CT (64SCT) and dual source CT (DSCT) (Somatom Sensation 64 and Somatom Definition, Siemens Medical Solutions, Forchheim), respectively. Two radiologists independently evaluated the data visually and with the help of a software tool (Syngo Circulation, Siemens Medical Solutions, Forchheim). The results of the quantitative assessment of the invasive heart catheterization served as the reference standard. Sensitivity and specificity as well as the correlation coefficient, the systematic error, and the interobserver agreement (kappa) were determined.

RESULTS

In each of both patient groups 12 stenoses were detected. For the detection of stenoses >75%, sensitivity and specificity for the visual evaluation using the 64SCT were 100% and 90%, and with the CT-QCA both were 100%. For the DSCT sensitivity and specificity were 100% for both the visual and semiautomated evaluation. The Bland-Altman plot of the results of the 64SCT showed an overestimation of 3.3% (+/-62.7%/56.2%) compared to the heart catheterization. The results of the DSCT exhibited an overestimation of 6.2% (+/-33.1%/19.8%). The interobserver agreement of the CT-QCA and the visual evaluation showed a kappa value of 0.75 and for DSCT of 1.0.

CONCLUSION

The results showed a good correlation of grading stenosis between the software-assisted evaluation and the results of the coronary catheter angiography. The promising results of the DSCT are due to a superior temporal resolution compared to the 64SCT. Confirmation of these data by trials in larger patient collectives is warranted.

Commissioning and performance of the variable line spacing plane grating monochromator beamline at the Canadian Light Source

The variable line spacing plane grating monochromator beamline at the Canadian Light Source (CLS) employs three grazing incidence variable line spacing gratings to cover a photon energy range of 5-250 eV. It uses a 185 mm period length planar permanent magnet insertion device as the photon source, sharing a straight section with another soft x-ray beamline at the CLS. The commissioning and performance of the beamline is reported. The high resolution photoabsorption spectra of Ar and PF(5) gases are reported. A resolving power of over 40,000 for photons in the low energy region and >10,000 for a wider energy range (8-200 eV) can be achieved. A photon flux of up to 2 x 10(12) photons/s per 100 mA with slit settings of 50 microm has been measured.

Einsatz der Dual-source-Computertomographie in der prä- und postoperativen kardiochirurgischen Diagnostik

PURPOSE

The aim of this study was to evaluate the clinical potential of dual-source computed tomography (DSCT) in pre- and postsurgical diagnostics in the field of cardiac surgery.

MATERIAL AND METHODS

A total of 20 patients underwent DSCT of the heart. This CT system with two rotating X-ray tubes (Somatom Definition, Siemens Medical Solutions, Forchheim, Germany) achieves a temporal resolution of 83 ms and a spatial resolution of 0.4 x 0.4 x 0.4 mm. The patient cohort consisted of two subgroups. In a group of ten patients with known coronary artery disease (CAD), scheduled for bypass surgery (i.e., high pretest likelihood for having significant CAD), the results of DSCT coronary angiography (CTA) and invasive quantitative catheter angiography (QCA) were compared to assess the diagnostic accuracy of DSCT in the detection of significant coronary artery stenoses (>50%). In a second group of ten patients with previous aortic valve replacement (homografts), the valve opening area of the transplanted aortic valve graft was measured by DSCT and compared with echocardiography as a standard of reference to exclude postsurgical restenosis of the valve.

RESULTS

Of 150 coronary artery segments depicted by CT, 144 (96%) were classified as "assessable." A significant CAD was known in all patients, and altogether 43 significant stenoses were present according to the results of QCA. Blinded to these results, DSCTA reached a sensitivity and specificity of 95% (41/43) and 93% (103/111), yielding a positive and negative predictive value (PPV, NPV) of 79% (31/39) and 98% (103/105), respectively. In patients with aortic valve homografts, all DSCT datasets were considered as being of diagnostic image quality concerning valve depiction. The planimetric evaluation of the CT data as compared to results of echocardiography showed a significant correlation of the results (r=0.64, p=0.0467). A high-grade valve stenosis (opening area <1.0 cm(2)) could be correctly excluded by DSCT in all patients.

CONCLUSIONS

Dual-source CT shows great diagnostic potential in patients before or after cardiac surgery. DSCT provides a high diagnostic accuracy for detection of coronary artery stenosis before bypass surgery. DSCT also proved to be accurate in the assessment of patients who received aortic valve replacement.