PEATGAS pilot plant operating results

The Institute of Gas Technology has been developing the PEATGAS process for the conversion of peat to synthetic fuels. A program has recently been completed for the pilot-plant-scale testing of the process. In this scheme, peat is gasified in a two-stage reactor system, which operates at temperatures up to 1750/sup 0/F and pressures up to 500 psig. The process can be controlled to maximize the production of either substitute natural gas (SNG) or liquid hydrocarbons. The technical feasibility of the process was demonstrated in a series of five gasification tests. Highlights of this operating program are presented in this paper

Estimation of contrast agent bolus arrival delays for improved reproducibility of liver DCE MRI

Delays between contrast agent (CA) arrival at the site of vascular input function (VIF) sampling and the tissue of interest affect dynamic contrast enhanced (DCE) MRI pharmacokinetic modelling. We investigate effects of altering VIF CA bolus arrival delays on liver DCE MRI perfusion parameters, propose an alternative approach to estimating delays and evaluate reproducibility. Thirteen healthy volunteers (28.7  ±  1.9 years, seven males) underwent liver DCE MRI using dual-input single compartment modelling, with reproducibility (n  =  9) measured at 7 days. Effects of VIF CA bolus arrival delays were assessed for arterial and portal venous input functions. Delays were pre-estimated using linear regression, with restricted free modelling around the pre-estimated delay. Perfusion parameters and 7 days reproducibility were compared using this method, freely modelled delays and no delays using one-way ANOVA. Reproducibility was assessed using Bland–Altman analysis of agreement. Maximum percent change relative to parameters obtained using zero delays, were  −31% for portal venous (PV) perfusion, +43% for total liver blood flow (TLBF), +3247% for hepatic arterial (HA) fraction, +150% for mean transit time and  −10% for distribution volume. Differences were demonstrated between the 3 methods for PV perfusion (p  =  0.0085) and HA fraction (p  <  0.0001), but not other parameters. Improved mean differences and Bland–Altman 95% Limits-of-Agreement for reproducibility of PV perfusion (9.3 ml/min/100 g, ±506.1 ml/min/100 g) and TLBF (43.8 ml/min/100 g, ±586.7 ml/min/100 g) were demonstrated using pre-estimated delays with constrained free modelling. CA bolus arrival delays cause profound differences in liver DCE MRI quantification. Pre-estimation of delays with constrained free modelling improved 7 days reproducibility of perfusion parameters in volunteers

A diffusion-based quantification technique for assessment of sacroiliitis in adolescents with enthesitis-related arthritis

OBJECTIVE: To investigate the use of a quantitative diffusion-weighted imaging (DWI) tool for measuring inflammation of the sacroiliac joints (SIJs) in enthesitis-related arthritis (ERA). METHODS: A retrospective study was performed with institutional review board approval. Subjects were adolescents who had undergone MRI of the SIJs since January 2010. 10 patients with a clinical diagnosis of ERA and 10 controls with a clinical diagnosis of mechanical back pain were assessed. Axial T1 weighted, short tau inversion recovery (STIR) and DWI (b-values 0, 50, 100, 300 and 600 mm(2) s(-1)) images were acquired. Apparent diffusion coefficient (ADC) maps were generated using a monoexponential fit. On each of four slices, two to three linear regions-of-interest were placed on each joint. Normalized ADC (nADC) values were defined as joint ADC divided by a reference ADC derived from normal sacral bone. STIR images were scored using a modification of an established technique. The correlation between nADC values and STIR scores was evaluated using Spearman's rank correlation. RESULTS: Mean nADC values were significantly higher in cases than in controls (p = 0.0015). There was a strong correlation between STIR scores and nADC values (R = 0.85). CONCLUSION: ADC values are significantly increased in inflamed SIJs compared with controls. There is a good correlation between this diffusion-based method and STIR scores of inflammation. ADVANCES IN KNOWLEDGE: We have described and provisionally validated a method for quantifying the severity of inflammation in the SIJs in ERA using ADC measurements. This method is quick, is reproducible and could potentially be automated

Improved hepatic arterial fraction estimation using cardiac output correction of arterial input functions for liver DCE MRI

Liver dynamic contrast enhanced (DCE) MRI pharmacokinetic modelling could be useful in the assessment of diffuse liver disease and focal liver lesions, but is compromised by errors in arterial input function (AIF) sampling. In this study, we apply cardiac output correction to arterial input functions (AIFs) for liver dynamic contrast enhanced (DCE) MRI and investigate the effect on dual-input single compartment hepatic perfusion parameter estimation and reproducibility. Thirteen healthy volunteers (28.7±1.94 years, seven males) underwent liver DCE MRI and cardiac output measurement using aortic root phase contrast MRI (PCMRI), with reproducibility (n=9) measured at seven days. Cardiac output AIF correction was undertaken by constraining the first pass AIF enhancement curve using the indicator-dilution principle. Hepatic perfusion parameters with and without cardiac output AIF correction were compared and seven-day reproducibility assessed. Differences between cardiac output corrected and uncorrected liver DCE MRI portal venous (PV) perfusion (p=0.066), total liver blood flow (TLBF)(p=0.101), hepatic arterial (HA) fraction (p=0.895), mean transit time (MTT)(p=0.646), distribution volume (DV)(p=0.890) were not significantly different. Seven-day corrected HA fraction reproducibility was improved (mean difference 0.3%, Bland-Altman 95% Limits-of-Agreement (BA95%LoA) ±27.9%, Coefficient of Variation (CoV) 61.4% vs 9.3%, ±35.5%, 81.7% respectively without correction). Seven-day uncorrected PV perfusion was also improved (mean difference 9.3 ml/min/100g, BA95%LoA ±506.1 ml/min/100g, CoV 64.1% vs 0.9 ml/min/100g, ±562.8 ml/min/100g, 65.1% respectively with correction) as was uncorrected TLBF(mean difference 43.8 ml/min/100g, BA95%LoA ±586.7 ml/min/100g, CoV 58.3% vs 13.3 ml/min/100g, ±661.5 ml/min/100g, 60.9% respectively with correction). Reproducibility of uncorrected MTT was similar (uncorrected mean difference 2.4s, BA95%LoA ±26.7s, CoV 60.8% uncorrected vs 3.7s, ±27.8s, 62.0% respectively with correction), as was and DV (uncorrected mean difference 14.1%, BA95%LoA ±48.2%, CoV 24.7% vs 10.3%, ±46.0%, 23.9% respectively with correction). Cardiac output AIF correction does not significantly affect the estimation of hepatic perfusion parameters but demonstrates improvements in normal volunteer seven-day HA fraction reproducibility, but deterioration in PV perfusion and TLBF reproducibility. Improved HA fraction reproducibility maybe important as arterialisation of liver perfusion is increased in chronic liver disease and within malignant liver lesions

Sequential prostate MRI reporting in men on active surveillance: initial experience of a dedicated PRECISE software program

BACKGROUND AND OBJECTIVES: There is interest in using sequential multiparametric magnetic resonance imaging (mpMRI) to assess men on active surveillance (AS) for prostate cancer. The Prostate Cancer Radiological Estimation of Change in Sequential Evaluation (PRECISE) recommendations propose standardised reporting mpMRI data for these men. This includes accurate size measurements of lesions over time, but such approach is time consuming for the radiologist and there is a strong need of dedicated tools to report serial scans in a systematic manner. We present the results from an initial validation cohort using dedicated PRECISE reporting software to allow automated comparison between sequential scans on AS. MATERIALS AND METHODS: We retrospectively analysed baseline and follow-up scans of 20 men randomised to 6 months of daily dutasteride (n = 10) or placebo (n = 10) from the MAPPED trial. Men underwent 3T mpMRI at baseline and after 6 months, and a dedicated radiologist reported the scans using both a widespread commercially-available platform (Osirix®) and a semi-automated dedicated PRECISE reporting tool (MIM®). Tumour volume by planimetry in all sequences and conspicuity on diffusion-weighted imaging were assessed. Reporting time was recorded, and we used the Wilcoxon test for statistical analysis. RESULTS: Median tumour volumes and conspicuity were similar using both approaches. The reporting time of the follow-up scan was quicker using the PRECISE reporting workflow both in the whole population (12'33″ vs 10'52″; p = 0.005) and in the dutasteride arm (15'50″ vs 12'59″; p = 0.01). A structured report including clinical and imaging data was generated according to the PRECISE recommendations and a comparison table between lesion characteristics at baseline and follow-up scans was also included. CONCLUSION: We conclude that a dedicated PRECISE reporting tool for sequential scans in men on AS results in a significant reduction in the reporting time and allows the radiologist to easily compare scans over time. This tool will help with our understanding of the natural history of mpMRI changes during AS