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Biomedical subjects

Guy Marchal

Publications and source records attributed to Guy Marchal.

At least 37 records · Page 2Linked to original sources
PubMed2005

Feasibility, safety, and efficacy of percutaneous transhepatic injection of beta-cell grafts.

PURPOSE: To evaluate the safety, feasibility, and clinical efficacy of percutaneous transhepatic injection of beta-cell grafts in patients with type 1 diabetes mellitus. MATERIALS AND METHODS: Between December 2001 and November 2003, 15 patients with C-peptide-negative type 1 diabetes underwent 31 percutaneous injections for intraportal implantation of beta-cell grafts. Grafts consisted of cultured beta-cell preparations as previously described. In 13 cases, the transplant procedure was done under sedation, whereas in 18 cases, general anesthesia was given. In all procedures, percutaneous access to the right portal vein occurred under ultrasound (US) guidance with use of a microbore puncture needle. The subsequent catheterization of the main portal vein was performed under fluoroscopic and angiographic control with use of a microbore delivery catheter and guide wire. Clinical, biochemical, and radiologic evaluation was performed before and after the procedure. RESULTS: In all cases, it was possible to access the portal vein (median number of needle passes, 1; range, 1-6). The volume of cultured beta-cell grafts injected for each transplantation averaged 0.58 mL (range, 0.26-1.60 mL) and the mean recorded procedure time (from puncture to catheter withdrawal) was 19 minutes (range, 10-80 min). Three patients presented with transient abdominal pain immediately after the procedure; postprocedural duplex US of the liver revealed a patent portal vein and end branches in all cases and a minor perihepatic fluid collection in another three patients. From the end of week 1 to week 3, a mean 3.8-fold increase in liver aminotransferase levels was measured in all recipients after the first implantation session. A similar increase was seen in only one patient after a second transplantation session. At 6 months after transplantation, 13 of 15 patients (86%) had a functioning graft with plasma C-peptide levels greater than 0.5 ng/mL. CONCLUSIONS: The combined US, fluoroscopic, and angiographic monitoring of percutaneous transhepatic injection with use of a microbore delivery catheter is a safe and reproducible radiologic procedure for transplantation of beta-cell grafts in diabetic patients. Increased posttransplantation C-peptide levels, which demonstrate acceptable graft function, can be obtained.

Adult↗
PubMed2005

Local recurrence after hepatic radiofrequency coagulation: multivariate meta-analysis and review of contributing factors.

OBJECTIVE: The purpose of this study was to analyze the factors that influence local recurrence after radiofrequency coagulation of liver tumors. SUMMARY BACKGROUND DATA: Local recurrence rate varies widely between 2% and 60%. Apart from tumor size as an important risk factor for local recurrence, little is known about the impact of other factors. METHODS: An exhaustive literature search was carried out for the period from January 1, 1990 to January 1, 2004. Only series with a minimal follow-up of 6 months and/or mean follow-up of 12 months were included. Univariate and multivariate meta-analyses were carried out. RESULTS: Ninety-five independent series were included, allowing the analysis of the local recurrence rate of 5224 treated liver tumors. In a univariate analysis, tumor-dependent factors with significantly less local recurrences were: smaller size, neuroendocrine metastases, nonsubcapsular location, and location away from large vessels. Physician-dependent favorable factors were: surgical (open or laparoscopic) approach, vascular occlusion, general anesthesia, a 1-cm intentional margin, and a greater physician experience. In a multivariate analysis, significantly less local recurrences were observed for small size (P < 0.001) and a surgical (versus percutaneous) approach (P < 0.001). CONCLUSIONS: Radiofrequency coagulation by laparoscopy or laparotomy results in superior local control, independent of tumor size. The percutaneous route should mainly be reserved for patients who cannot tolerate a laparoscopy or laparotomy. The short-term benefits of less invasiveness for the percutaneous route do not outweigh the longer-term higher risk of local recurrence.

Catheter Ablation↗
PubMed2005

Validation of MTF measurement for digital mammography quality control.

The modulation transfer function (MTF) describes the spatial resolution properties of imaging systems. In this work, the accuracy of our implementation of the edge method for calculating the presampled MTF was examined. Synthetic edge images with known MTF were used as gold standards for determining the robustness of the edge method. These images simulated realistic data from clinical digital mammography systems, and contained intrinsic system factors that could affect the MTF accuracy, such as noise, scatter, and flat-field nonuniformities. Our algorithm is not influenced by detector dose variations for MTF accuracy up to 1/2 the sampling frequency. We investigated several methods for noise reduction, including truncating the supersampled line spread function (LSF), windowing the LSF, applying a local exponential fit to the LSF, and applying a monotonic constraint to the supersampled edge spread function. Only the monotonic constraint did not introduce a systematic error; the other methods could result in MTF underestimation. Overall, our edge method consistently computed MTFs which were in good agreement with the true MTF. The edge method was then applied to images from a commercial storage-phosphor based digital mammography system. The calculated MTF was affected by the size (sides of 2.5, 5, or 10 cm) and the composition (lead or tungsten) of the edge device. However, the effects on the MTF were observed only with regard to the low frequency drop (LFD). Scatter nonuniformity was dependent on edge size, and could lead to slight underestimation of LFD. Nevertheless, this negative effect could be minimized by using an edge of 5 cm or larger. An edge composed of lead is susceptible to L-fluorescence, which causes overestimation of the LFD. The results of this work are intended to underline the need for clear guidelines if the MTF is to be given a more crucial role in acceptance tests and routine assessment of digital mammography systems: the MTF algorithm and edge object test tool need to be publicly validated.

Algorithms↗
PubMed2005

Diffusion-weighted MR imaging in monitoring the effect of a vascular targeting agent on rhabdomyosarcoma in rats.

PURPOSE: To evaluate diffusion-weighted magnetic resonance (MR) imaging for monitoring tumor response in rats after administration of combretastatin A4 phosphate. MATERIALS AND METHODS: Study protocol was approved by local ethical committee for animal care and use. Rhabdomyosarcomas implanted subcutaneously in both flanks of 17 rats were evaluated with 1.5-T MR unit by using four-channel wrist coil. Transverse T2-weighted fast spin-echo sequences, T1-weighted spin-echo sequences before and after gadodiamide administration, and transverse echo-planar diffusion-weighted MR examinations were performed before, 1 and 6 hours, and 2 and 9 days after intraperitoneal injection of vascular targeting agent (combretastatin A4 phosphate, 25 mg/kg). Apparent diffusion coefficient (ADC) was automatically calculated from diffusion-weighted MR imaging findings. These findings were compared with histopathologic results at each time point. For statistical analysis, paired Student t tests with Bonferroni correction for multiple testing were used. RESULTS: T1-weighted images before combretastatin administration showed enhancement of solid tumor tissue but not of central necrosis. At 1 and 6 hours after combretastatin injection, enhancement of solid tissue disappeared almost completely, with exception of small peripheral rim. At 2 and 9 days after combretastatin injection, enhancement progressively reappeared in tumor periphery. ADC, however, showed decrease early after combretastatin injection ([1.26 +/- 0.16]x 10(-3) mm2/sec before, [1.18 +/- 0.17]x 10(-3) mm2/sec 1 hour after [P=.0005] and [1.08 +/- 0.14]x 10(-3) mm(2)/sec 6 hours after [P=.0007] combretastatin A4 phosphate injection), histologically corresponding to vessel congestion and vascular shutdown in periphery but no necrosis. An increase of ADC ([1.79 +/- 0.13]x 10(-3) mm2/sec) (P <.0001) 2 days after combretastatin A4 phosphate injection was paralleled by progressive histologic necrosis. A significant (P <.0001) decrease in ADC 9 days after treatment ([1.41 +/- 0.15]x 10(-3) mm2/sec) corresponded to tumor regrowth. CONCLUSION: In addition to basic relaxation-weighted MR imaging and postgadolinium T1-weighted MR imaging to enable prompt detection of vascular shutdown, diffusion-weighted MR imaging was used to discriminate between nonperfused but viable and necrotic tumor tissues for early monitoring of therapeutic effects of vascular targeting agent.

Animals↗
PubMed2005

Diffusion-weighted magnetic resonance imaging allows noninvasive in vivo monitoring of the effects of combretastatin a-4 phosphate after repeated administration.

The noninvasive assessment of anticancer treatment efficacy is very important for the improvement of therapeutic window. The purpose of the present study was to evaluate the antitumoral effects of the vascular targeting agent, combretastatin A-4 phosphate (CA-4-P), at selected time points after repeated intraperitoneal drug administrations (25 mg/kg), using diffusion-weighted magnetic resonance imaging (DW-MRI). The experiments were performed during an overall follow-up period of 3 weeks on WAG/Rij rats with subcutaneously growing rhabdomyosarcomas. Each animal served as its own baseline. The DW-MRI studies were quantified by calculating the apparent diffusion coefficient (ADC) for different low and high b-values to separate the effects on tumor vasculature and cellular integrity. The changes in ADC as well as the extent of necrosis development (proportional to the tumor volume), measured on the MR images, were of comparable magnitude after each treatment. All ADC values showed a significant decrease at 6 hours, followed by a significant increase at 2 days for various CA-4-P administrations. DW-MRI allowed us to monitor both reduction in perfusion and changes in the extent of tumor necrosis after CA-4-P injection. Repeated CA-4-P administration retains efficacy in rat rhabdomyosarcomas, with similar findings after each drug administration.

Animals↗
PubMed2004

Rat cerebral ischemia induced with photochemical occlusion of proximal middle cerebral artery: a stroke model for MR imaging research.

A stroke model in rats with photochemically induced thrombosis (PIT) of proximal cerebral middle artery (MCA) is introduced for magnetic resonance imaging (MRI) study. Thirty-seven rats subjected to surgical and optical procedures for inducing the PIT models were scanned using a 1.5-T scanner with T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), diffusion-weighted imaging (DWI), and contrast-enhanced perfusion-weighted imaging (PWI) at 1 h and 24 h after MCA occlusion. The penumbra evolution and PWI-derived parameters including relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) were monitored; and the relative lesion size (RLS) was compared with the final RLS on the gold standard triphenyl tetrazolium chloride (TTC) staining at 24 h. The results showed that the focal cerebral ischemic lesions were detectable in all rats with different MR approaches. The lesion on PWI at 1 h and on all MR images at 24 h was matched well with that seen on TTC staining; the peri-infarct area decreased from 6.2 +/- 7.2% of the brain volume at 1 h to 0.3 +/- 5.6% at 24 h. Compared to that in the contralateral hemisphere, rCBV in ischemic region was 52.6 +/- 21.4 and 40.0 +/- 15.8% (p > 0.05), and rCBF was 64.6 +/- 11.2 and 47.3 +/- 11.1% (p < 0.05) at 1 h and 24 h respectively. The present PIT model in rats has been successfully adopted for MRI research, which might be feasible for certain stroke studies and should be beneficial for the evaluation on effects of potential diagnostic and therapeutic approaches.

Animals↗
PubMed2004

Visualization of stroke with clinical MR imagers in rats: a feasibility study.

This experiment was conducted in compliance with the guidelines of the International Committee on Thrombosis and Hemostasis and the current institutional regulations for use and care of laboratory animals. The purpose of the present study was to report the feasibility of using clinical magnetic resonance (MR) imaging devices for depiction of stroke in a rat model. Twenty-four rats with photochemically induced thrombosis of the middle cerebral artery were examined at superacute (1 hour, n = 24), acute (12 hours, n = 12), and subacute (24 hours, n = 12) phases with 1.5-T MR imaging weighted for T1, T2, diffusion, and gadopentetate dimeglumine-enhanced perfusion. With reasonable signal-to-noise ratio and imaging times, ischemic lesions were well distinguished on MR images as validated qualitatively and quantitatively with postmortem standard-of-reference techniques, including volume-rendered computed tomography, microangiography, and histochemistry. In the superacute phase, the perfusion defect at perfusion-weighted MR imaging was well matched with microangiographic and pathologic findings (P > .05). There was no difference in lesion size at perfusion-weighted MR imaging between superacute and subacute phases (P > .05). Performance of certain stroke-related research in rats is feasible with clinical MR imagers.

Animals↗
PubMed2004

Microplasmin reduces ischemic brain damage and improves neurological function in a rat stroke model monitored with MRI.

BACKGROUND AND PURPOSE: Microplasmin (microPli), a derivative of plasmin lacking the 5 "kringle" domains, was studied in a rat thrombotic stroke model with MRI monitoring. METHODS: Brain ischemia was induced by middle cerebral artery (MCA) occlusion with photochemically induced thrombosis. Brain tissue damage was assessed at 1 hour and 24 hours after MCA occlusion by MRI and 2,3,5-triphenyl tetrazolium chloride (TTC) staining. Neurological symptoms were scored at 24 hours. Animals with insufficient evidence of significant jeopardized brain tissue on perfusion-weighted imaging (PWI) at 1 hour were excluded before randomization. Included animals were randomized (blinded) to controls (solvent), 7.5 or 10 mg/kg microPli, administered as an intravenous bolus 90 minutes after MCA occlusion (n=8 per dose group). RESULTS: microPli treatment reduced cerebral damage measured by TTC staining at 24 hours, from 250+/-69 mm3 (mean+/-SD) in controls to 150+/-30 and 170+/-62 mm3 with 7.5 and 10 mg/kg microPli, respectively; it reduced the expansion of the PWI positive area between 1 and 24 hours, and it reduced neurological deficits from a Bederson score of 7 (6 to 9) in controls to 4.5 (3 to 8) and 4 (3 to 6), with 7.5 and 10 mg/kg microPli, respectively (median and rangeP<0.05 for each dose versus controls for all parameters). CONCLUSIONS: Bolus intravenous microPli given 90 minutes after thrombotic MCA occlusion in rats reduces cerebral ischemic damage and improves neurological dysfunction, suggesting that microPli could be beneficial in ischemic stroke patients.

Animals↗
PubMed2004

Quantification of Al-equivalent thickness of just visible microcalcifications in full field digital mammograms.

Characterization of digital mammography systems is often performed by means of contrast-detail curves using a homogeneous phantom with inserts of different sizes and thicknesses. In this article, a more direct measure of the threshold contrast-detail characteristics of microcalcifications in clinical mammograms is proposed, which also takes into account routine processing and display. The proposed method scores the detectability of simulated microcalcifications with known size and aluminum-equivalent thickness. Thickness estimates, based on x-ray transmission coefficients, were first validated for Al particles. The same approach was then applied to associate Al-equivalent thickness with simulated microcalcifications. Thirty-five mammograms of patients were acquired using a full field digital mammography (FFDM) system operating under standard exposure conditions. Different microcalcifications were simulated using templates of real microcalcifications as described in Med. Phys. 30, 2234-2240 (2003). These templates were first modified such that they simulated a template of the same microcalcification for an ideally sharp detector. They were then adjusted for the imaging characteristics of the FFDM, beam quality, and breast thickness. Microcalcification sizes in the image plane ranged from 200 to 800 microm. Their peak Al-equivalent thickness varied between 70 and 1000 microm. Software phantoms were created. They consisted of 0-10 simulated microcalcifications randomly distributed in 2 cm by 2 cm frames embedded within digital mammograms. Routine processing and printing followed. Three experienced radiologists recorded the locations of the microcalcifications, and confidence ratings were given. Free response receiver operating characteristics (FROC) analysis was performed. Using a binary score, the fractions of detected microcalcifications were plotted as a function of equivalent diameter for the different Al-equivalent thicknesses. Pair-wise agreement of the detected microcalcifications was calculated for the different Al-equivalent thickness groups. The FROC curves of each radiologist indicated similar true positive fractions for a given number of false positives per image. One radiologist applied a more conservative scoring. Detected fractions for the different sizes of the microcalcifications showed the same trend for all observers. In addition, the observer with the least FP also detected less microcalcifications. The pair-wise agreement of the detected microcalcifications was good. The average detected fractions were >0.5 for microcalcifications with equivalent diameter >400 microm and Al-equivalent thickness >400 microm. An average detected fraction >0.5 was also seen for microcalcifications with equivalent diameter <400 microm and equivalent thickness >800 microm. The detected fractions of smaller microcalcifications were <0.5. The results obtained with this method indicate that it may be possible to quantify the performance of a digital mammography detector including processing and viewing for the detection of microcalcifications. We hypothesize that the FROC curves and detected fractions of simulated microcalcifications of different sizes reflect the clinical reality.

Algorithms↗
PubMed2003

Evolution of regional performance after an acute anterior myocardial infarction in humans using magnetic resonance tagging.

Regional remodelling after a left ventricular myocardial infarction is the first step in a cascade that may lead to heart failure and death. To understand better the mechanisms underlying this process, it is important to study not only the evolution in local deformation parameters but also the corresponding loading conditions. Using magnetic resonance (MR) myocardial tagging, we measured the regional contribution to ejection (regional ejection fraction) and loading (systolic blood pressure x radius of curvature (mean of short and long axes)/wall thickness) in 32 regions throughout the left ventricle (LV) in patients 1 week (1W) and 3 months (3M) after a first anterior infarction. Using positron emission tomography (PET), the LV was divided into infarct, adjacent and remote regions. In the remote regions the average deformation decreased between 1W and 3M (from 59.3 +/- 5.6 to 57.9 +/- 6.7 %, P < 0.05) due to an increase in loading conditions only (from 730 +/- 290 to 837 +/- 299 mmHg, P < 0.05). In the adjacent myocardium, no change in function was observed (49.0 +/- 10.8 to 49.0 +/- 6.5 %, P = n.s.), although loading increased (806 +/- 297 to 978 +/- 287 mmHg, P < 0.05). In the infarct region only, an increase in deformation was seen (30.7 +/- 14.2 to 37 +/- 6.9 %, P < 0.05), together with a higher loading level (1229 +/- 422 to 1466 +/- 284 mmHg, P < 0.05), which indicates a true improvement in function. The fact that MR tagging can identify both regional deformation and loading permits us to differentiate between changes due to alterations in regional loading conditions and true changes in function. After an acute myocardial infarction (MI), an improvement can be observed in the deformation-loading relation in the adjacent and infarct regions, but the improvement is mainly in the infarct region. Using this technique, types of intervention leading to even more functional gain could be evaluated.

Adult↗
PubMed2003

Gadobenate dimeglumine-enhanced magnetic resonance angiography of the pelvic arteries.

RATIONALE AND OBJECTIVES: To evaluate 4 doses of gadobenate dimeglumine (Gd-BOPTA) for contrast-enhanced magnetic resonance angiography (CE-MRA) of the pelvic arteries and to compare CE-MRA with unenhanced time-of-flight MRA (2D-TOF-MRA). METHODS: A multicenter Phase II dose-finding study was performed in 136 patients with Gd-BOPTA doses of 0.025, 0.05, 0.1, and 0.2 mmol/kg bodyweight. Evaluation of CE-MRA images and comparison with 2D-TOF-MRA images was performed onsite and by 2 blinded offsite reviewers in terms of subjective image quality, number of lesions detected, and confidence in lesion characterization. RESULTS: Significant (P < 0.05) improvements over unenhanced findings were observed for CE-MRA at all dose levels. For reviewer 1 and the onsite investigators, the overall image quality increased up to a dose of 0.1 mmol/kg and then plateaued. For reviewer 2, increased image quality was noted up to a dose of 0.2 mmol/kg. Significant (P < 0.005) increases in diagnostic confidence on CE-MRA versus unenhanced MRA was observed for all dose groups by reviewer 1 and the onsite investigators and for the 0.1 and 0.2 mmol/kg dose groups by reviewer 2. No serious adverse events were recorded that were attributable to the study drug and no trends in laboratory parameters, vital signs, or electrocardiogram recordings were observed. CONCLUSIONS: Gadobenate dimeglumine-enhanced MRA is safe and significantly more effective than unenhanced 2D-TOF-MRA for imaging the pelvic arteries. A dose of 0.1 mmol/kg appears the most appropriate dose for subsequent Phase III clinical evaluation.

Adolescent↗
PubMed2003

Magnetic resonance imaging of the effects of infliximab on perianal fistulizing Crohn's disease.

OBJECTIVES: Although the clinical efficacy of infliximab as measured by closure of fistulas in Crohn's disease has been demonstrated, its influence on the inflammatory changes in the fistula tracks is less clear. The aim of the present study was to assess the behavior of perianal fistulas before and after infliximab treatment. METHODS: Magnetic resonance imaging (MRI) and clinical evaluation were performed in a total of 18 patients before and after treatment with infliximab. An MRI-based score of perianal Crohn's disease severity was developed using both criteria of local extension of fistulas (complexity, supralavetoric extension, relation to the sphincters and of active inflammation (T2 hyperintensity, presence of cavities/abscesses, and rectal wall involvement). RESULTS: The MRI score was reliable in assessing the fistula tracks, with a good interobserver concordance (p < 0.001). Fistula tracks with signs of active inflammation were found in all 18 patients at baseline and collections in seven. After short-term infliximab treatment, active tracks persisted in eight of 11 patients who had clinically responded to infliximab. After long-term (46 wk) infliximab therapy, MRI signs of active track inflammation had resolved in three of six patients. CONCLUSIONS: We have developed an MRI-based score of perianal Crohn's disease severity to assess the anatomical evolution of Crohn's fistulas. Our study demonstrates that despite closure of draining external orifices after infliximab therapy, fistula tracks persist with varying degrees of residual inflammation, which may cause recurrent fistulas and pelvic abscesses. Whether complete fistula fibrosis occurs over time with repeated infliximab infusions needs further study.

Adult↗
PubMed2003

Development and validation of a simulation procedure to study the visibility of micro calcifications in digital mammograms.

The visibility of micro calcifications is a determining factor for digital mammography. To address the problem of quantification, we developed a procedure to simulate micro calcifications into real mammograms. First, the shapes, sizes and x-ray transmission coefficients of real micro calcifications were derived from the appearance of biopsy specimens in the raw data of magnified, digital images acquired at 27 kVp and Mo/Mo anode-filter combination. This allowed us to create "ideal templates" of micro calcifications. The x-ray transmissions of the real micro calcifications values were expressed in Al-equivalent thickness. This made it possible to recalculate the x-ray transmission characteristics of a particular ideal template for other x-ray beam qualities. Extra corrections for differences in spatial resolution were based on the presampled two-dimensional modulation transfer functions and on the difference in pixel size. Three radiologists compared the appearance of real and simulated micro calcifications in a two-alternative forced choice (2AFC) evaluation. They perceived no differences between real and simulated lesions. Preliminary results show that it is possible to simulate micro calcifications with well defined characteristics that are indistinguishable from real ones. It should be noted, however, that the full potential of the approach has not been proven. In future work, these templates may be useful to evaluate particular aspects of digital mammograms, such as the effects of processing and of viewing conditions on the visibility of micro calcifications.

Breast↗
PubMed2003

Spiral CT in gastric carcinoma: comparison with barium study, fiberoptic gastroscopy and histopathology.

AIM: To evaluate spiral computed tomography (CT) including virtual gastroscopy for diagnosis of gastric carcinoma in comparison with upper gastrointestinal series (UGI), fiberoptic gastroscopy (FG) and histopathology. METHODS: Sixty patients with histologically proven gastric carcinoma (54 advanced and 6 early) were included in this study. The results of spiral CT were compared with those of UGI and FG. Two observers blindly evaluated images of spiral CT and UGI and video recording of FG with consensus in terms of diagnostic confidence with a five-point scale. Sensitivities of lesion detection, Borrmann's classification of spiral CT, UGI and FG, as well as the accuracy of TNM staging of spiral CT were determined by comparing them to surgical and histological findings. RESULTS: The lesion detection rate was 98 % (59/60), 95 % (57/60) and 98 % (59/60) for spiral CT, UGI and FG, respectively. There were no statistical differences in the detection sensitivity among the three techniques (P>0.05). For the sensitivity in Borrmann's classification, spiral CT was higher than that of UGI (P=0.025) and similar to that of FG (P>0.05). The accuracy of spiral CT in staging the gastric carcinoma was 76.7 %. Six cases of early gastric carcinoma were all detected by spiral CT as well as FG. CONCLUSION: Spiral CT is equivalent to UGI and FG in the detection of gastric carcinoma, and superior to UGI but similar to FG in the Borrmann's classification of advanced gastric carcinoma. Spiral CT is more valuable than FG in the staging of gastric carcinoma.

Adult↗
PubMed2002

Dry preparation for virtual CT colonography with fecal tagging using water-soluble contrast medium: initial results.

The purpose of this study was to evaluate the feasibility of a dry bowel preparation, i.e. without laxative fluids, for virtual CT colonography (VCTC), and its impact on patient acceptance compared with conventional colonoscopy (CC). A randomly chosen patient population scheduled for CC ( n=11) was first submitted to VCTC after a dry preparation, consisting of low-residue meals combined with a small amount of a iodinated water-soluble contrast medium during each meal 3 days before VCTC. In different colon segments and between different persons, the degree of tagging in VCTC was evaluated and graded. Patient acceptance and future preference were assessed for both preparations as well as for both investigations. The mixing of the contrast with the intestinal content results in contrast impregnated stool, the tagged feces. The degree of fecal tagging was good in the majority of the patients and the colonic segments, especially in the descending colon and sigmoid. Furthermore, patient acceptance and preference were clearly in favour of VCTC compared with CC merely because of the non-invasiveness of the dry preparation. Dry bowel preparation and VCTC is a promising approach towards a patient-friendly colon cancer-screening setup.

Adult↗
PubMed2002

The use of ECG and respiratory triggering to improve the sensitivity of oxygen-enhanced proton MRI of lung ventilation.

Changes in lung signal between normal breathing and breathing pure oxygen is the basis for oxygen-enhanced ventilation MRI. An optimal technique guarantees a significant response to pure oxygen in well-ventilated lung tissue. To improve the sensitivity, we investigated the effect of ECG and respiratory triggering. Centric reordered single-shot rapid acquisition relaxation enhancement sequences (TE 4.2 ms, echo spacing 4.2 ms, bandwidth 650 Hz/pixel), with an inversion recovery preparation pulse (TI 700 ms), were used. Series of 20 measurements were performed with and without ECG and respiratory triggering in five young volunteers. Subsequently, series of 100 images were acquired during breathing normal air and pure oxygen (as "stimulus"). Ventilation maps showed by means of the z-score how far the response deviates from the signal intensities during the normal air condition. The standard deviation of the lung signal intensities was lowest for the cardiac-triggered series. In the ventilation maps, on the other hand, signal changes were statistically more significant in the respiratory than in the cardiac-triggered series. The average z-scores in the right (left) cranial part of the lung were 12.4 (13.0) and 9.2 (9.7) for respiratory and ECG-triggered acquisitions. We propose to use respiratory triggering as a means to improve the sensitivity of MR ventilation studies.

Adult↗