Paediatric cardiac CT examinations: impact of the iterative reconstruction method ASIR on image quality--preliminary findings.

BACKGROUND: Radiation dose exposure is of particular concern in children due to the possible harmful effects of ionizing radiation. The adaptive statistical iterative reconstruction (ASIR) method is a promising new technique that reduces image noise and produces better overall image quality compared with routine-dose contrast-enhanced methods. OBJECTIVE: To assess the benefits of ASIR on the diagnostic image quality in paediatric cardiac CT examinations. MATERIALS AND METHODS: Four paediatric radiologists based at two major hospitals evaluated ten low-dose paediatric cardiac examinations (80 kVp, CTDI(vol) 4.8-7.9 mGy, DLP 37.1-178.9 mGy·cm). The average age of the cohort studied was 2.6 years (range 1 day to 7 years). Acquisitions were performed on a 64-MDCT scanner. All images were reconstructed at various ASIR percentages (0-100%). For each examination, radiologists scored 19 anatomical structures using the relative visual grading analysis method. To estimate the potential for dose reduction, acquisitions were also performed on a Catphan phantom and a paediatric phantom. RESULTS: The best image quality for all clinical images was obtained with 20% and 40% ASIR (p < 0.001) whereas with ASIR above 50%, image quality significantly decreased (p < 0.001). With 100% ASIR, a strong noise-free appearance of the structures reduced image conspicuity. A potential for dose reduction of about 36% is predicted for a 2- to 3-year-old child when using 40% ASIR rather than the standard filtered back-projection method. CONCLUSION: Reconstruction including 20% to 40% ASIR slightly improved the conspicuity of various paediatric cardiac structures in newborns and children with respect to conventional reconstruction (filtered back-projection) alone.

A new approach in the treatment of high flow native AV fistula: the open-pore external scaffolding prosthesis

Objective: The vascular access steal syndrome is a complication occurring in 1-6% after native arterio-venous (AV) fistulas, often due to huge diameter of the vein. This results in very high flow, which could also be responsible for cardiac overload. The aim of this study is to evaluate the efficiency of a new approach in the treatment of this pathology using open-pore external scaffolding prosthesis.Methods: This a retrospective review of all patients presenting symptomatic high flow after native AV fistula between January 2007 and December 2009 in 3 vascular centers. Pre-operative duplex exam confirmed the diagnosis of high flow. The operation consisted in preparation of the whole fistula, measurement of the flow and section on the venous side. The vein was wrapped with this 6 to 8 mm open-pore external scaffolding prosthesis (ProVena, BBraun, Germany) according to its diameter and to the flow and then sutured. Measurement of the flow was repeated. Patients were followed by duplex exam at 1 week and at 1, 3, 6 and 12 months. Procedural success was defined as complete implantation of the prosthesis and reduction of the flow. Primary outcomes were reduction of the flow and recovery of the symptoms and secondary endpoint was patency of the fistula.Results: During the study period, 14 patients, with a mean age of 65・8 years old, have been operated with this technique.There were 2 native forearmfistulas and 12 on the armwith a mean pre-operative flow of 2600 ml/min (1800-3800). The mode of presentation was pain in 6 patients, neurological disorders in 10 and necrosis in 4. Moreover, 3 patients had cardiac insufficiency due to high flow in the fistula. The procedure was technically successful in 100% of cases. Re-intervention was necessary in 2 patients due to hematoma. Recovery of the initial symptoms occurred in 13 patients (93%). The mean flow reduction was 1200 ml/min (600-2000). In 1 patient, a persistent steal syndrome despite flow reduction to 1400 ml/min resulted in fistula closure 2 months later. At a mean follow-up of 22 months (4-35), all remaining patients (13/14) presented a patent fistula without recurrence.Conclusion: This new approach seems to be safe and effective in the treatment of symptomatic high flow native AV fistulas by significantly reducing the flow and avoiding closure of the vascular access. Longer follow-up with more patients are necessary to evaluate the risk of recurrence.

Trabecular bone score: a noninvasive analytical method based upon the DXA image.

The trabecular bone score (TBS) is a gray-level textural metric that can be extracted from the two-dimensional lumbar spine dual-energy X-ray absorptiometry (DXA) image. TBS is related to bone microarchitecture and provides skeletal information that is not captured from the standard bone mineral density (BMD) measurement. Based on experimental variograms of the projected DXA image, TBS has the potential to discern differences between DXA scans that show similar BMD measurements. An elevated TBS value correlates with better skeletal microstructure; a low TBS value correlates with weaker skeletal microstructure. Lumbar spine TBS has been evaluated in cross-sectional and longitudinal studies. The following conclusions are based upon publications reviewed in this article: 1) TBS gives lower values in postmenopausal women and in men with previous fragility fractures than their nonfractured counterparts; 2) TBS is complementary to data available by lumbar spine DXA measurements; 3) TBS results are lower in women who have sustained a fragility fracture but in whom DXA does not indicate osteoporosis or even osteopenia; 4) TBS predicts fracture risk as well as lumbar spine BMD measurements in postmenopausal women; 5) efficacious therapies for osteoporosis differ in the extent to which they influence the TBS; 6) TBS is associated with fracture risk in individuals with conditions related to reduced bone mass or bone quality. Based on these data, lumbar spine TBS holds promise as an emerging technology that could well become a valuable clinical tool in the diagnosis of osteoporosis and in fracture risk assessment.

A new method for constructing exact tests without making any assumptions

We present a new method for constructing exact distribution-free tests (and confidence intervals) for variables that can generate more than two possible outcomes.This method separates the search for an exact test from the goal to create a non-randomized test. Randomization is used to extend any exact test relating to meansof variables with finitely many outcomes to variables with outcomes belonging to agiven bounded set. Tests in terms of variance and covariance are reduced to testsrelating to means. Randomness is then eliminated in a separate step.This method is used to create confidence intervals for the difference between twomeans (or variances) and tests of stochastic inequality and correlation.

A randomized concave programming method for choice network revenue management

Models incorporating more realistic models of customer behavior, as customers choosing froman offer set, have recently become popular in assortment optimization and revenue management.The dynamic program for these models is intractable and approximated by a deterministiclinear program called the CDLP which has an exponential number of columns. However, whenthe segment consideration sets overlap, the CDLP is difficult to solve. Column generationhas been proposed but finding an entering column has been shown to be NP-hard. In thispaper we propose a new approach called SDCP to solving CDLP based on segments and theirconsideration sets. SDCP is a relaxation of CDLP and hence forms a looser upper bound onthe dynamic program but coincides with CDLP for the case of non-overlapping segments. Ifthe number of elements in a consideration set for a segment is not very large (SDCP) can beapplied to any discrete-choice model of consumer behavior. We tighten the SDCP bound by(i) simulations, called the randomized concave programming (RCP) method, and (ii) by addingcuts to a recent compact formulation of the problem for a latent multinomial-choice model ofdemand (SBLP+). This latter approach turns out to be very effective, essentially obtainingCDLP value, and excellent revenue performance in simulations, even for overlapping segments.By formulating the problem as a separation problem, we give insight into why CDLP is easyfor the MNL with non-overlapping considerations sets and why generalizations of MNL posedifficulties. We perform numerical simulations to determine the revenue performance of all themethods on reference data sets in the literature.

Biological markers of alcohol consumption in alcoholised drivers: Comparison of capillary electrophoresis (CZE CDT) and a direct immunoassay (N Latex CDT) with the traditional method of anion-exchange chromatography-immunoturbidimetry (%CDT TIA).

Objectives: The aim of this study was to compare specificity and sensitivity of different biological markers that can be used in a forensic field to identify potentially dangerous drivers because of their alcohol habits. Methods: We studied 280 Swiss drivers after driving while under the alcohol influence. 33 were excluded for not having CDT N results, 247 were included (218 men (88%) and 29 women (12%). Mean age was 42,4 (SD:12, min: 20 max: 76). The evaluation of the alcohol consumption concerned the month before the CDT test and was considered as such after the interview: Heavy drinkers (>3 drinks per day): 60 (32.7%), < 3 drinks per day and moderate: 127 (51.4%) 114 (46.5%), abstinent: 60 (24.3%) 51 (21%). Alcohol intake was monitored by structured interviews, self-reported drinking habits and the C-Audit questionnaire as well as information provided by their family and general practitioner. Consumption was quantified in terms of standard drinks, which contain approximately 10 grams of pure alcohol (Ref. WHO). Results: comparison between moderate (less or equal to 3 drinks per day) and excessive drinkers (more than 3 drinks) Marker ROC area 95% CI cut-off sensitivity specificity CDT TIA 0.852 0.786-0917 2.6* 0.93 LR+1.43 0.35 LR-0.192 CDT N latex 0.875 0.821-0.930 2.5* 0.66 LR+ 6.93 0.90 LR- 0.369 Asialo+disialo-tf 0.881 0.826-0.936 1.2* 0.78 LR+4.07 0.80 LR-0.268 1.7° 0.66 LR+8.9 0.93 LR-0.360 GGT 0.659 0.580-0.737 85* 0.37 LR+2.14 0.83 LR-0.764 * cut-off point suggested by the manufacturer ° cut-off point suggested by our laboratory Conclusion: With the cut-off point established by the manufacturer, CDT TIA performed poorly in term of specificity. N latex CDT and CZE CDT were better, especially if a 1.7 cut-off is used with CZE

Is the person trade-off a valid method for allocating health care resources? Some caveats

The Person Trade-Off (PTO) is a methodology aimed at measuring thesocial value of health states. The rest of methodologies would measure individualutility and would be less appropriate for taking resource allocation decisions.However few studies have been conducted to test the validity of the method.We present a pilot study with this objective. The study is based on theresult of interviews to 30 undergraduate students in Economics. We judgethe validity of PTO answers by their adequacy to three hypothesis of rationality.First, we show that, given certain rationality assumptions, PTO answersshould be predicted from answers to Standard Gamble questions. This firsthypothesis is not verified. The second hypothesis is that PTO answersshould not vary with different frames of equivalent PTO questions. Thissecond hypothesis is also not verified. Our third hypothesis is that PTOvalues should predict social preferences for allocating resources betweenpatients. This hypothesis is verified. The evidence on the validity of themethod is then conflicting.

Improving the sensitivity of the sequence profile method.

The sequence profile method (Gribskov M, McLachlan AD, Eisenberg D, 1987, Proc Natl Acad Sci USA 84:4355-4358) is a powerful tool to detect distant relationships between amino acid sequences. A profile is a table of position-specific scores and gap penalties, providing a generalized description of a protein motif, which can be used for sequence alignments and database searches instead of an individual sequence. A sequence profile is derived from a multiple sequence alignment. We have found 2 ways to improve the sensitivity of sequence profiles: (1) Sequence weights: Usage of individual weights for each sequence avoids bias toward closely related sequences. These weights are automatically assigned based on the distance of the sequences using a published procedure (Sibbald PR, Argos P, 1990, J Mol Biol 216:813-818). (2) Amino acid substitution table: In addition to the alignment, the construction of a profile also needs an amino acid substitution table. We have found that in some cases a new table, the BLOSUM45 table (Henikoff S, Henikoff JG, 1992, Proc Natl Acad Sci USA 89:10915-10919), is more sensitive than the original Dayhoff table or the modified Dayhoff table used in the current implementation. Profiles derived by the improved method are more sensitive and selective in a number of cases where previous methods have failed to completely separate true members from false positives.

Off-resonance angiography: a new method to depict vessels--phantom and rabbit studies.

PURPOSE: To evaluate the utility of inversion recovery with on-resonant water suppression (IRON) in combination with injection of the long-circulating monocrystalline iron oxide nanoparticle (MION)-47 for contrast material-enhanced magnetic resonance (MR) angiography. MATERIALS AND METhods: Experiments were approved by the institutional animal care committee. Eleven rabbits were imaged at baseline before injection of a contrast agent and then serially 5-30 minutes, 2 hours, 1 day, and 3 days after a single intravenous bolus injection of 80 micromol of MION-47 per kilogram of body weight (n = 6) or 250 micromol/kg MION-47 (n = 5). Conventional T1-weighted MR angiography and IRON MR angiography were performed on a clinical 3.0-T imager. Signal-to-noise and contrast-to-noise ratios were measured in the aorta of rabbits in vivo. Venous blood was obtained from the rabbits before and after MION-47 injection for use in phantom studies. RESULTS: In vitro blood that contained MION-47 appeared signal attenuated on T1-weighted angiograms, while characteristic signal-enhanced dipolar fields were observed on IRON angiograms. In vivo, the vessel lumen was signal attenuated on T1-weighted MR angiograms after MION-47 injection, while IRON supported high intravascular contrast by simultaneously providing positive signal within the vessels and suppressing background tissue (mean contrast-to-noise ratio, 61.9 +/- 12.4 [standard deviation] after injection vs 1.1 +/- 0.4 at baseline, P < .001). Contrast-to-noise ratio was higher on IRON MR angiograms than on conventional T1-weighted MR angiograms (9.0 +/- 2.5, P < .001 vs IRON MR angiography) and persisted up to 24 hours after MION-47 injection (76.2 +/- 15.9, P < .001 vs baseline). CONCLUSION: IRON MR angiography in conjunction with superparamagnetic nanoparticle administration provides high intravascular contrast over a long time and without the need for image subtraction.

Percutaneous central venous catheterization in premature infants: a method for facilitating insertion of silastic catheters via peripheral veins.

Peripheral venous cannulation is the preferred method of inserting central venous silastic catheters in premature infants. The standard techniques are placement of the catheter using a breakaway introducer needle or introduction of the catheter through a cannula. In extremely low birth weight infants (<1000 g) successful cannulation is impeded by the small size of the vessels. After repeated attempts, both procedures can be time-consuming and stressful to the infant. We present a modified insertion technique of the standard 2-French silastic catheter with an increased success rate, thus reducing insertion time, stress to the infant, and costs. The method uses the tip of a 20-gauge cannula as dilator/introducer for the 2-French catheter. This tip is inserted into the vessel with a standard 24-gauge cannula. After successful insertion of the dilator/introducer cannula, the standard 2-French catheter can then be advanced easily.