ReIMAGINE: a prostate cancer research consortium with added value through its patient and public involvement and engagement

BACKGROUND

ReIMAGINE aims to improve the current prostate specific antigen (PSA)/biopsy risk stratification for prostate cancer (PCa) and develop a new image-based method (with biomarkers) for diagnosing high/low risk PCa in men. ReIMAGINE's varied patient and public involvement (PPI) and engagement (PE) strategy maximises the impact of its scientific output by informing and shaping the different stages of research.

AIMS

Through including the voice of patients and the public, the ReIMAGINE Consortium aims to translate these different perspectives into the design and implementation process. This will improve the overall quality of the research by: reflecting the needs and priorities of patients and the public, ensuring methods and procedures are feasible and appropriate ensuring information is relevant and accessible to those being recruited to the study identifying dissemination channels relevant to patients/the public and developing outputs that are accessible to a lay audience With support from our patient/user groups, the ReIMAGINE Consortium aims to improve our ability to derive prognostic information and allocate men to the most appropriate and effective therapies, using a novel image-based risk stratification with investigation of non-imaging biomarkers.

FINDINGS

We have been working with patients and the public from initiation of the project to ensure that the research is relevant to men and their families. Our PPI Sub-Committee, led by a PCa patient, has been involved in our dissemination strategy, outreach activities, and study design recommendations. For example, the sub-committee have developed a variety of informative videos relevant and accessible to those being recruited, and organised multiple online research engagement events that are accessible to a lay audience. As quoted by one of the study participants, "the more we present the benefits and opportunities to patients and the public, the more research commitment we obtain, and the sooner critical clinical questions such as PCa diagnostics will be addressed".

Introduction to the National Cancer Imaging Translational Accelerator (NCITA): a UK-wide infrastructure for multicentre clinical translation of cancer imaging biomarkers

The National Cancer Imaging Translational Accelerator (NCITA) is creating a UK national coordinated infrastructure for accelerated translation of imaging biomarkers for clinical use. Through the development of standardised protocols, data integration tools and ongoing training programmes, NCITA provides a unique scalable infrastructure for imaging biomarker qualification using multicentre clinical studies.

Patient deprivation and perceived scan burden negatively impact the quality of whole-body MRI

AIM

To evaluate the association between the image quality of cancer staging whole-body magnetic resonance imaging (WB-MRI) and patient demographics, distress, and perceived scan burden.

MATERIALS AND METHODS

A sample of patients recruited prospectively to multicentre trials comparing WB-MRI with standard scans for staging lung and colorectal cancer were invited to complete two questionnaires. The baseline questionnaire, administered at recruitment, collated data on demographics, distress and co-morbidity. The follow-up questionnaire, completed after staging investigations, measured perceived WB-MRI scan burden (scored 1 low to 7 high). WB-MRI anatomical coverage, and technical quality was graded by a radiographic technician and grading combined to categorise the scan as "optimal", "sub-optimal" or "degraded". A radiologist categorised 30 scans to test interobserver agreement. Data were analysed using the chi-square, Fisher's exact, t-tests, and multinomial regression.

RESULTS

One hundred and fourteen patients were included in the study (53 lung, 61 colorectal; average age 65.3 years, SD=11.8; 66 men [57.9%]). Overall, 45.6% (n=52), scans were classified as "optimal" quality, 39.5% (n=45) "sub-optimal", and 14.9% (n=17) as "degraded". In adjusted analyses, greater deprivation level and higher patient-reported scan burden were both associated with a higher likelihood of having a sub-optimal versus an optimal scan (odds ratio [OR]: 4.465, 95% confidence interval [CI]: 1.454 to 13.709, p=0.009; OR: 1.987, CI: 1.153 to 3.425, p=0.013, respectively). None of the variables predicted the likelihood of having a degraded scan.

CONCLUSIONS

Deprivation and patients' perceived experience of the WB-MRI are related to image quality. Tailored protocols and individualised patient management before and during WB-MRI may improve image quality.

Similarities and differences between Likert and PIRADS v2.1 scores of prostate multiparametric MRI: a pictorial review of histology-validated cases

The UK National Institute for Health and Care Excellence (NICE) 2019 "Prostate cancer: diagnosis and management" guidelines have recommended that all patients suspected of prostate cancer undergo multiparametric magnetic resonance imaging (mpMRI) prior to biopsy. The Likert scoring system is advocated for mpMRI reporting based on multicentre studies that have demonstrated its effectiveness within the National Health Service (NHS). In recent years, there has been considerable drive towards standardised prostate reporting, which led to the development of "Prostate Imaging-Reporting And Data System" (PI-RADS). The PI-RADS system has been adopted by the majority of European countries and within the US. This paper reviews these systems indicating the similarities and specific differences that exist between PI-RADS and Likert assessment through a series of histologically proven clinical cases.

Measurement of liver and spleen interstitial volume in patients with systemic amyloid light-chain amyloidosis using equilibrium contrast CT

OBJECTIVES

To investigate equilibrium contrast-enhanced CT (EQ-CT) measurement of extracellular volume fraction (ECV) in patients with systemic amyloid light-chain (AL) amyloidosis, testing the hypothesis that ECV becomes elevated in the liver and spleen and ECV correlates with other estimates of organ amyloid burden.

METHODS

26 patients with AL amyloidosis underwent EQ-CT, and ECV was measured in the liver and spleen. Patients also underwent serum amyloid P (SAP) component scintigraphy with grading of liver and spleen involvement. Mann-Whitney U test was used to test for a difference between patients with amyloid deposition (SAP grade 1-3) and those without (SAP grade 0). Variation in ECV across SAP grades was assessed using the Kruskal-Wallis test and association between ECV and SAP grades with Spearman correlation.

RESULTS

Mean ECV in the spleen and liver was significantly greater (p < 0.0005) in amyloidotic organs (SAP grade 1-3) [spleen, liver: 0.430, 0.375] compared with healthy tissues [spleen, liver: 0.304, 0.269]. ECV increased with increasing amyloid burden, showing positive correlation with SAP grade in both the liver (r = 0.758) and spleen (r = 0.867).

CONCLUSION

In patients with systemic AL amyloidosis, EQ-CT can demonstrate increased spleen and liver ECV, which is associated with amyloid disease burden.

Intratumoural evolutionary landscape of high-risk prostate cancer: the PROGENY study of genomic and immune parameters

BACKGROUND

Intratumoural heterogeneity (ITH) is well recognised in prostate cancer (PC), but its role in high-risk disease is uncertain. A prospective, single-arm, translational study using targeted multiregion prostate biopsies was carried out to study genomic and T-cell ITH in clinically high-risk PC aiming to identify drivers and potential therapeutic strategies.

PATIENTS AND METHODS

Forty-nine men with elevated prostate-specific antigen and multiparametric-magnetic resonance imaging detected PC underwent image-guided multiregion transperineal biopsy. Seventy-nine tumour regions from 25 patients with PC underwent sequencing, analysis of mutations, copy number and neoepitopes combined with tumour infiltrating T-cell subset quantification.

RESULTS

We demonstrated extensive somatic nucleotide variation and somatic copy number alteration heterogeneity in high-risk PC. Overall, the mutational burden was low (0.93/Megabase), but two patients had hypermutation, with loss of mismatch repair (MMR) proteins, MSH2 and MSH6. Somatic copy number alteration burden was higher in patients with metastatic hormone-naive PC (mHNPC) than in those with high-risk localised PC (hrlPC), independent of Gleason grade. Mutations were rarely ubiquitous and mutational frequencies were similar for mHNPC and hrlPC patients. Enrichment of focal 3q26.2 and 3q21.3, regions containing putative metastasis drivers, was seen in mHNPC patients. We found evidence of parallel evolution with three separate clones containing activating mutations of β-catenin in a single patient. We demonstrated extensive intratumoural and intertumoural T-cell heterogeneity and high inflammatory infiltrate in the MMR-deficient (MMRD) patients and the patient with parallel evolution of β-catenin. Analysis of all patients with activating Wnt/β-catenin mutations demonstrated a low CD8+/FOXP3+ ratio, a potential surrogate marker of immune evasion.

CONCLUSIONS

The PROGENY (PROstate cancer GENomic heterogeneitY) study provides a diagnostic platform suitable for studying tumour ITH. Genetic aberrations in clinically high-risk PC are associated with altered patterns of immune infiltrate in tumours. Activating mutations of Wnt/β-catenin signalling pathway or MMRD could be considered as potential biomarkers for immunomodulation therapies.

CLINICAL TRIALS.GOV IDENTIFIER

NCT02022371.

Magnetic resonance imaging targeted transperineal prostate biopsy: a local anaesthetic approach

BACKGROUND

Despite high rates of disease misclassification and sepsis, the use of transrectal biopsy remains commonplace. Transperineal mapping biopsies mitigate these problems but carry increased cost and patient burden. Local anaesthetic, multiparametric magnetic resonance imaging (MRI)-targeted transperineal biopsy may offer an alternative. Here, we aim to determine the feasibility, tolerability and detection rates of clinically significant prostate cancer using a local anaesthetic, transperineal, MRI-targeted biopsy technique.

METHODS

Tertiary referral centre in which 181 consecutive men underwent local anaesthetic, transperineal MRI-targeted prostate biopsy (September 2014 to January 2016). A standardized local anaesthetic technique was used to obtain targeted biopsies using visual estimation with the number of targeted cores determined by each of a number of users. We assessed adverse events, patient visual analogue pain scores and detection rates of clinically significant cancer (defined by University College London (UCL) definitions one and two and separately by the presence of dominant and non-dominant Gleason pattern 4). We secondarily assessed detection of any cancer, rates of detection by MRI (Likert) score and by presenting PSA. Differences were assessed using Chi-squared tests (P<0.05).

RESULTS

One hundred eighty-one men with 243 lesions were included. There were no episodes of sepsis or re-admissions and one procedure was abandoned owing to patient discomfort. Twenty-three out of 25 (92%) men would recommend the procedure to another. Median visual analogue pain score was 1.0 (interquartile range: 0.0-2.4). A total 104/181 (57%) had UCL definition 1 disease (Gleason ⩾4+3 and/or maximum cancer length ⩾6 mm) and 129/181 (71%) had UCL definition 2 cancer (Gleason ⩾3+4 and/or maximum cancer length ⩾4 mm). Fifty-four out of 181 (30%) and 124/181 (69%) had dominant and non-dominant pattern 4 disease or greater (irrespective of cancer length). Any cancer was detected in 142/181 (78%). Significant disease was more likely in higher MRI-scoring lesions and in men with PSAs ⩾10 ng ml-1.

CONCLUSIONS

This approach to prostate biopsy is feasible, tolerable and can be performed in ambulatory settings.

Evolution of multi-parametric MRI quantitative parameters following transrectal ultrasound-guided biopsy of the prostate

BACKGROUND

To determine the evolution of prostatic multi-parametric magnetic resonance imaging (mp-MRI) signal following transrectal ultrasound (TRUS)-guided biopsy.

METHODS

Local ethical permission and informed written consent was obtained from all the participants (n=14, aged 43-69, mean 64 years). Patients with a clinical suspicion of prostate cancer (PSA range 2.2-11.7, mean 6.2) and a negative (PIRAD 1-2/5) pre-biopsy mp-MRI (pre-contrast T1, T2, diffusion-weighted and dynamic-contrast-enhanced MRI) who underwent 10-core TRUS-guided biopsy were recruited for additional mp-MRI examinations performed at 1, 2 and 6 months post biopsy. We quantified mp-MRI peripheral zone (PZ) and transition zone (TZ) normalized T2 signal intensity (nT2-SI); T1 relaxation time (T10); diffusion-weighted MRI, apparent diffusion coefficient (ADC); dynamic contrast-enhanced MRI, maximum enhancement (ME); slope of enhancement (SoE) and area-under-the-contrast-enhancement-curve at 120 s (AUC120). Significant changes in mp-MRI parameters were identified by analysis of variance with Dunnett's post testing.

RESULTS

Diffuse signal changes were observed post-biopsy throughout the PZ. No significant signal change occurred following biopsy within the TZ. Left and right PZ mean nT2-SI (left PZ: 5.73, 5.16, 4.90 and 5.12; right PZ: 5.80, 5.10, 4.84 and 5.05 at pre-biopsy, 1, 2 and 6 months post biopsy, respectively) and mean T10 (left PZ: 1.02, 0.67, 0.78, 0.85; right PZ: 1.29, 0.64, 0.78, 0.87 at pre-biopsy, 1, 2 and 6 months post biopsy, respectively) were reduced significantly (P<0.05) from pre-biopsy values for up to 6 months post biopsy. Significant changes (P<0.05) of PZ-ME and AUC120 were observed at 1 month but resolved by 2 months post biopsy. PZ ADC did not change significantly following biopsy (P=0.23-1.0). There was no significant change of any TZ mp-MRI parameter at any time point following biopsy (P=0.1-1.0).

CONCLUSIONS

Significant PZ (but not TZ) T2 signal changes persist up to 6 months post biopsy, whereas PZ and TZ ADC is not significantly altered as early as 1 month post biopsy. Caution must be exercised when interpreting T1- and T2-weighted imaging early post biopsy, whereas ADC images are more likely to maintain clinical efficacy.

The FORECAST study - Focal recurrent assessment and salvage treatment for radiorecurrent prostate cancer

BACKGROUND

One-third of men may experience biochemical failure by 8years following radical radiotherapy for localised prostate cancer. Over 90% of men are started on androgen deprivation therapy (ADT) which is non-curative and confers systemic side-effects. Focal salvage therapy (FST) limits collateral tissue damage and may improve therapeutic ratios. In order to deliver FST, distant disease must be ruled-out and intra-prostatic disease must be accurately detected, localised and characterised.

AIM

FORECAST - Focal Recurrent Assessment and Salvage Treatment - is a study designed to evaluate a novel imaging-based diagnostic and therapeutic complex intervention pathway for men who fail radiotherapy.

METHODS

Men with biochemical failure following radical prostate radiotherapy, prior to salvage therapy will be recruited. They will undergo whole-body multi-parametric MRI (WB-MRI), choline PET/CT, bone-scan and pelvic-mpMRI and then MRI transperineal-targeted biopsies (MRI-TB) and Transperineal Template Prostate Mapping Biopsy (TPM). Those suitable for FST will undergo either high intensity focused ultrasound (HIFU) or cryotherapy.

RESULTS

Primary outcome measures: a) the accuracy of WB-MRI to detect distant metastatic disease; b) accuracy of prostate mpMRI in local detection of radiorecurrent prostate cancer; c) detection accuracy of MRI-TB; and d) rate of urinary incontinence following FST.

CONCLUSION

Focal salvage therapy may confer lower rates of morbidity whilst retaining disease control. In order to deliver FST, intra- and extra-prostatic disease must be detected early and localised accurately. Novel diagnostic techniques including WB-MRI and MRI-TB may improve the detection of distant and local disease whilst reducing healthcare burdens compared with current imaging and biopsy strategies.

Multiparametric MRI for detection of radiorecurrent prostate cancer: added value of apparent diffusion coefficient maps and dynamic contrast-enhanced images

BACKGROUND

Multiparametric magnetic resonance imaging (mp-MRI) is increasingly advocated for prostate cancer detection. There are limited reports of its use in the setting of radiorecurrent disease. Our aim was to assess mp-MRI for detection of radiorecurrent prostate cancer and examine the added value of its functional sequences.

METHODS

Thirty-seven men with mean age of 69.7 (interquartile range, 66-74) with biochemical failure after external beam radiotherapy underwent mp-MRI (T2-weighted, high b-value, multi-b-value apparent diffusion coefficient (ADC) and dynamic contrast-enhanced (DCE) imaging); then transperineal systematic template prostate mapping (TPM) biopsy. Using a locked sequential read paradigm (with the sequence order above), two experienced radiologists independently reported mp-MRI studies using score 1-5. Radiologist scores were matched with TPM histopathology at the hemigland level (n=74). Accuracy statistics were derived for each reader. Interobserver agreement was evaluated using kappa statistics.

RESULTS

Receiver-operator characteristic area under curve (AUC) for readers 1 and 2 increased from 0.67 (95% confidence interval (CI), 0.55-0.80) to 0.80 (95% CI, 0.69-0.91) and from 0.67 (95% CI, 0.55-0.80) to 0.84 (95% CI, 0.76-0.93), respectively, between T2-weighted imaging alone and full mp-MRI reads. Addition of ADC maps and DCE imaging to the examination did not significantly improve AUC for either reader (P=0.08 and 0.47 after adding ADC, P=0.90 and 0.27 after adding DCE imaging) compared with T2+high b-value review. Inter-reader agreement increased from k=0.39 to k=0.65 between T2 and full mp-MRI review.

CONCLUSIONS

mp-MRI can detect radiorecurrent prostate cancer. The optimal examination included T2-weighted imaging and high b-value DWI; adding ADC maps and DCE imaging did not significantly improve the diagnostic accuracy.

The use of molecular imaging combined with genomic techniques to understand the heterogeneity in cancer metastasis

Tumour heterogeneity has, in recent times, come to play a vital role in how we understand and treat cancers; however, the clinical translation of this has lagged behind advances in research. Although significant advancements in oncological management have been made, personalized care remains an elusive goal. Inter- and intratumour heterogeneity, particularly in the clinical setting, has been difficult to quantify and therefore to treat. The histological quantification of heterogeneity of tumours can be a logistical and clinical challenge. The ability to examine not just the whole tumour but also all the molecular variations of metastatic disease in a patient is obviously difficult with current histological techniques. Advances in imaging techniques and novel applications, alongside our understanding of tumour heterogeneity, have opened up a plethora of non-invasive biomarker potential to examine tumours, their heterogeneity and the clinical translation. This review will focus on how various imaging methods that allow for quantification of metastatic tumour heterogeneity, along with the potential of developing imaging, integrated with other in vitro diagnostic approaches such as genomics and exosome analyses, have the potential role as a non-invasive biomarker for guiding the treatment algorithm.

Small bowel strictures in Crohn's disease: a quantitative investigation of intestinal motility using MR enterography

BACKGROUND

Intestinal stricturing and aberrant small bowel motility are common complications in patients with Crohn's disease (CD) leading to significant morbidity. A retrospective study was performed quantifying small bowel motility within and upstream of strictures in CD patients using magnetic resonance enterography (MRE).

METHODS

A total of 91 subjects with stricturing CD (mean age 36 range 18-88) and undergoing MRE with dynamic motility imaging were identified. Of this cohort, 84 subjects were scanned at 1.5 T field strength with the remainder at 3 T. Linear regions of interest (ROI) were placed at the stricture, immediately upstream of the stricture, and in a proximal normal segment of bowel. Maximum bowel calibre (mm) and motility (Arbitrary units) at each ROI were calculated using previously validated software. Diameters and motility were compared using repeat measures anova and diameter correlated with motility score. In 21 subjects with follow-up MRE, ROIs were duplicated and percentage diameter and motility change across the two time points correlated.

KEY RESULTS

Mean diameter within the normal, prestricture and strictured bowel was 20, 30, and 15 mm (p < 0.001) with motility score 0.43, 0.28, and 0.15 AU, respectively (p < 0.001). There was a negative correlation between prestricture bowel diameter and motility (Pearson's R = -0.47, p < 0.001). For patients with follow-up MRE, there was a negative correlation between percentage change in prestricture diameter and motility, Spearman's Rho -0.6 p = 0.007.

CONCLUSIONS & INFERENCES

Quantified small bowel motility during MRE differs significantly between normal, prestricture, and strictured bowel. As prestricture bowel dilates, motility decreases, although this appears reversible in some.

Clinical and research applications of simultaneous positron emission tomography and MRI

Evaluation of the molecular processes responsible for disease pathogenesis and progression represents the new frontier of clinical radiology. Multimodality imaging lies at the cutting edge, combining the power of MRI for tissue characterization, microstructural appraisal and functional assessment together with new positron emission tomography (PET) tracers designed to target specific metabolic processes. The recent commercial availability of an integrated clinical whole-body PET-MRI provides a hybrid platform for exploring and exploiting the synergies of multimodal imaging. First experiences on the clinical and research application of hybrid PET-MRI are emerging. This article reviews the rapidly evolving field and speculates on the potential future direction.

Prostate MRI: who, when, and how? Report from a UK consensus meeting

The current pathway for men suspected of having prostate cancer [transrectal biopsy, followed in some cases by magnetic resonance imaging (MRI) for staging] results in over-diagnosis of insignificant tumours, and systematically misses disease in the anterior prostate. Multiparametric MRI has the potential to change this pathway, and if performed before biopsy, might enable the exclusion of significant disease in some men without biopsy, targeted biopsy in others, and improvements in the performance of active surveillance. For the potential benefits to be realized, the setting of standards is vital. This article summarizes the outcome of a meeting of UK radiologists, at which a consensus was achieved on (1) the indications for MRI, (2) the conduct of the scan, (3) a method and template for reporting, and (4) minimum standards for radiologists.

Quantitative MRI of colonic mural enhancement: segmental differences exist in endoscopically proven normal colon

OBJECTIVES

Abnormal contrast enhancement on MRI is advocated as a biomarker for inflammation in colitis, although the enhancement kinetics of normal colon are poorly described. Our purpose was to quantitatively assess mural enhancement in normal colon and test for intersegmental differences.

METHODS

Eight patients without prior history of inflammatory bowel disease underwent standard MRI colonography followed by normal same-day colonoscopy. Acquired sequences included a volumetric interpolated breath-hold examination (VIBE) to encompass the whole colonic volume, performed at 5°, 10° and 35° flip angles for T(1) quantitation and then at a fixed 35° flip angle three times prior to and every 30 s following intravenous gadoterate meglumine for 220 s. Ascending colon, descending colon and rectal R(1) (1/T(1)) was plotted against time. Mean pre-contrast R(1), initial change of R(1) (ΔR(1)), early and late "plateau phase" enhancement and the area under the R(1)-time (AUC-R(1)) curve were compared between segments using the Student's paired t-test.

RESULTS

There was no significant difference of pre-contrast R(1) between segments (p=0.49 to 0.62). ΔR(1) was higher for ascending colon compared with descending colon (0.0023±0.0012 ms(-1) vs 0.0010±0.0011 ms(-1), p=0.03). There was no significant difference for early or late plateau phase R(1) between colonic segments (p=0.08 to 1.00). AUC-R(1) was greater for ascending than descending colon (0.54±0.19 vs 0.30±0.14, p=0.03).

CONCLUSIONS

Intersegmental differences in colonic enhancement are present and should be considered when interpreting differential segmental enhancement.

Prostatic cancer surveillance following whole-gland high-intensity focused ultrasound: comparison of MRI and prostate-specific antigen for detection of residual or recurrent disease

OBJECTIVE

This retrospective study compares dynamic contrast-enhanced (DCE) MRI with the serial prostate-specific antigen (PSA) measurement for detection of residual disease following whole-gland high-intensity focused ultrasound (HIFU) therapy of prostate cancer.

METHODS

Patients in whom post-HIFU DCE-MRI was followed within 3 months by ultrasound-guided transrectal biopsy were selected from a local database. 26 patients met the study inclusion criteria. Serial PSA levels following HIFU and post-HIFU follow-up MRI were retrieved for each patient. Three radiologists unaware of other investigative results independently assessed post-HIFU MRI studies for the presence of cancer, scoring on a four-point scale (1, no disease; 2, probably no disease; 3, probably residual disease; and 4, residual disease). Sensitivity, specificity and receiver operating characteristic (ROC) analysis were performed for each reader, post-HIFU PSA nadir and pre-biopsy PSA level thresholds of >0.2 and >0.5 ng ml(-1).

RESULTS

The sensitivity of DCE-MRI for detection of residual disease for the three readers ranged between 73% and 87%, and the specificity between 73% and 82%. There was good agreement between readers (κ = 0.69-0.77). The sensitivity and specificity of PSA thresholds was 60-87% and 73-100%, respectively. The area under the ROC curve was greatest for pre-biopsy PSA (0.95).

CONCLUSION

DCE-MRI performed following whole-gland HIFU has similar sensitivity and specificity and ROC performance to serial PSA measurements for detection of residual or recurrent disease.

Diagnostic and therapeutic impact of MR enterography in Crohn's disease

AIM

To assess the impact of magnetic resonance enterography (MRE) on clinician diagnostic confidence and therapeutic strategy in patients under investigation for small bowel Crohn's disease.

MATERIAL AND METHODS

Gastroenterologists completed a proforma before and following MRE in 51 patients (mean age 35 years, 26 female) under investigation for small bowel Crohn's disease, indicating percentage confidence for presence/absence of small bowel involvement. In suspected disease, diagnostic confidence (using a scoring system from 1=no to 6=yes) was scored for subcategories: extent >30 cm (DE), terminal ileum (lTI), jejunal (JD), colonic disease (CoD), strictures (ST), activity (AD), extraluminal complications (EL), and surgical need (NS). Therapeutic strategy was recorded. Patients were divided into three groups: 1=suspected disease, MRE normal (n=15); 2=suspected disease, MRE abnormal (n=30); 3=no suspected disease, MRE normal (n=6). Binomial exact and paired t-tests were use to compare confidence pre and post-MRE.

RESULTS

Mean percentage confidence for the presence/absence of small bowel disease increased from 62 to 84% (p=0.003), 87 to 98% (p=0.0001), and 83 to 98% (p=0.005) after MRE for groups 1, 2, and 3, respectively. In suspected disease, confidence changed significantly for all of the subcategories (p<0.001) except EL in group 1. The percentage of patients with a confidence change ranged from 40% (CoD) to 87% (lTI; group 1) and from 7% (EL) to 93% (DE; group 2). Therapeutic strategy changed in 31/51 (61%, 95% CI 47-74%), 14 with a reduction in planned therapy and 17 with an increase.

CONCLUSION

MRE had a positive diagnostic impact in patients under investigation for small bowel Crohn's disease and this influenced therapeutic strategy in 61% of the patients.

CT colonography: computer-assisted detection of colorectal cancer

OBJECTIVES

Computer-aided detection (CAD) for CT colonography (CTC) has been developed to detect benign polyps in asymptomatic patients. We aimed to determine whether such a CAD system can also detect cancer in symptomatic patients.

METHODS

CTC data from 137 symptomatic patients subsequently proven to have colorectal cancer were analysed by a CAD system at 4 different sphericity settings: 0, 50, 75 and 100. CAD prompts were classified by an observer as either true-positive if overlapping a cancer or false-positive if elsewhere. Colonoscopic data were used to aid matching.

RESULTS

Of 137 cancers, CAD identified 124 (90.5%), 122 (89.1%), 119 (86.9%) and 102 (74.5%) at a sphericity of 0, 50, 75 and 100, respectively. A substantial proportion of cancers were detected on either the prone or supine acquisition alone. Of 125 patients with prone and supine acquisitions, 39.3%, 38.3%, 43.2% and 50.5% of cancers were detected on a single acquisition at a sphericity of 0, 50, 75 and 100, respectively. CAD detected three cancers missed by radiologists at the original clinical interpretation. False-positive prompts decreased with increasing sphericity value (median 65, 57, 45, 24 per patient at values of 0, 50, 75, 100, respectively) but many patients were poorly prepared.

CONCLUSION

CAD can detect symptomatic colorectal cancer but must be applied to both prone and supine acquisitions for best performance.

Non-invasive quantification of pancreatic exocrine function using secretin-stimulated MRCP

Our objective was to quantify water volume using magnetic resonance cholangiopancreatography (MRCP) sequences and apply this to secretin-stimulated studies with the aim of quantifying pancreatic exocrine function. A commercially available single-shot MRCP sequence was used in conjunction with a body phased-array coil and a 1.5-T MR system. Signal intensity was measured in samples of water, pancreatic, duodenal juice, and secretin-stimulated pancreatic juice. A water phantom was made and MR calculated volumes compared with known water volumes within the phantom. Changes in small intestinal volume in response to secretin were measured in a group of 11 patients with no evidence of pancreatic disease. Changes in water volume were plotted over time. The pancreatic duct diameter before and after secretin was noted and filling defects were sought. All patients also underwent an axial breath-hold T1-weighted gradient-echo sequence and the pancreatic parenchyma was evaluated for size and signal intensity. There was no difference in the signal intensity of the different juice samples. There was excellent correlation between known and calculated MRCP volumes (chi(2)=0.99). All patients demonstrated normal duct morphology on MRCP and normal pancreatic parenchyma on T1-weighted imaging. The mean flow rate in the patient population was 8.1+/-2.5 ml/s over a median of 7 min (range 5-9 min). The MRCP sequence can be used to measure water volume. Sequential MRCP measurements following secretin permitted calculation of volume change and flow rate. This should prove useful as an indicator of pancreatic exocrine function.

Use of mitochondrial inhibitors to demonstrate that cytochrome oxidase near-infrared spectroscopy can measure mitochondrial dysfunction noninvasively in the brain

The use of near-infrared spectroscopy to measure noninvasively changes in the redox state of cerebral cytochrome oxidase in vivo is controversial. We therefore tested these measurements using a multiwavelength detector in the neonatal pig brain. Exchange transfusion with perfluorocarbons revealed that the spectrum of cytochrome oxidase in the near-infrared was identical in the neonatal pig, the adult rat, and in the purified enzyme. Under normoxic conditions, the neonatal pig brain contained 15 micromol/L deoxyhemoglobin, 29 micromol/L oxyhemoglobin, and 1.2 micromol/L oxidized cytochrome oxidase. The mitochondrial inhibitor cyanide was used to determine whether redox changes in cytochrome oxidase could be detected in the presence of the larger cerebral hemoglobin concentration. Addition of cyanide induced full reduction of cytochrome oxidase in both blooded and bloodless animals. In the blooded animals, subsequent anoxia caused large changes in hemoglobin oxygenation and concentration but did not affect the cytochrome oxidase near-infrared signal. Simultaneous blood oxygenation level-dependent magnetic resonance imaging measurements showed a good correlation with near-infrared measurements of deoxyhemoglobin concentration. Possible interference in the near-infrared measurements from light scattering changes was discounted by simultaneous measurements of the optical pathlength using the cerebral water absorbance as a standard chromophore. We conclude that, under these conditions, near-infrared spectroscopy can accurately measure changes in the cerebral cytochrome oxidase redox state.

MRI measurements of cerebral deoxyhaemoglobin concentration [dHb]--correlation with near infrared spectroscopy (NIRS)

Changes in physiological parameters such as cerebral blood flow, cerebral blood volume, oxygen extraction, and the size and distribution of cerebral blood vessels, result in changes in the local concentration of deoxyhaemoglobin ([dHb]). The purpose of this study was to quantitatively investigate the dependence of the R2* relaxation rate upon the [dHb] per voxel. Five neonatal piglets were studied in a 7 T/20 cm bore magnet. MRI was conducted using a 2.5 cm diameter surface coil placed over the parietal lobes. Four progressively T2*-weighted images were acquired, allowing the absolute quantitation of R2*. Simultaneous near infrared spectroscopy (NIRS) measurements were made from an area encompassing the MR imaging slice, and allowed the absolute quantitation of [dHb]. The arterial oxygen saturation (SaO2) of the piglet was lowered stepwise by decreasing the fractional inspired oxygen concentration (FiO2), which precipitated a change in [dHb]. NIRS and MRI measurements were made at each FiO2 step. The results demonstrate an extremely strong, linear relationship between R2* as determined by MRI and [dHb], as measured by NIRS. Whereas NIRS can only give us a global measure of [dHb], the results suggest the future use of MRI in producing high resolution relaxation rate maps related to the [dHb] distribution of the brain.

Temporal and anatomical variations of brain water apparent diffusion coefficient in perinatal cerebral hypoxic-ischemic injury: relationships to cerebral energy metabolism

Cerebral apparent diffusion coefficients (ADCs) were determined in nine newborn piglets before and for 48 h after transient hypoxia-ischemia. Phosphorus MRS revealed severely reduced cerebral energy metabolism during the insult and an apparently complete recovery 2 h after resuscitation commenced. At this time, mean ADC over the imaging slice (ADCglobal) was 0.88 (0.04) x 10(-9) m2 x s(-1) (mean (SD)), which was close to the baseline value of 0.92 (0.4) x 10(-9) m2 x s(-1). In seven of the animals, a "secondary" failure of energy metabolism then evolved, accompanied by a decline in ADCglobal to 0.64 (0.17) x 10(-9) m2 x s(-1) at 46 h postresuscitation (P < 0.001 versus baseline). For these seven animals, ADCglobal correlated linearly with the concentration ratio [phosphocreatine (PCr)]/[inorganic phosphate (Pi)] (0.94 < r < 0.99; P < 0.001). A nonlinear relationship was demonstrated between ADCglobal and the concentration ratio [nucleotide triphosphate (NTP)]/[Pi + PCr + 3 NTP]. The ADC reduction commenced in the parasagittal cortex before spreading in a characteristic pattern throughout the brain. ADC seems to be closely related to cerebral energy status and shows considerable potential for the assessment of hypoxic-ischemic injury in the newborn brain.

Magnesium sulfate after transient hypoxia-ischemia fails to prevent delayed cerebral energy failure in the newborn piglet

Severely birth-asphyxiated human infants develop delayed ("secondary") cerebral energy failure, which carries a poor prognosis, during the first few days of life. This study tested the hypothesis that i.v. magnesium sulfate (MgSO4) after severe transient cerebral hypoxia-ischemia decreases the severity of delayed energy failure in the newborn piglet. Twelve piglets underwent temporary occlusion of the common carotid arteries and hypoxemia. Resuscitation was started when cerebral [phosphocreatine (PCr)]/[inorganic phosphate (Pi)], as determined by phosphorus magnetic resonance spectroscopy, had fallen virtually to zero, and nucleotide triphosphate (NTP) had fallen below a third of baseline. The piglets were randomized to receive, blind, either: 1) three i.v. infusions of 12.5% MgSO4 heptahydrate solution: 400 mg.kg-1 MgSO4.7H2O starting 1 h after resuscitation, and 200 mg.kg-1 12 and 24 h later (n = 6); or 2) three infusions of placebo, 0.9% NaCl (n = 6). Phosphorus and proton spectroscopy were continued until 48 h after resuscitation, and values were compared between the two groups. Mean plasma magnesium levels, 1 h after each of the three doses of MgSO4, were 2.1, 2.0, and 1.9 mmol.L-1, respectively. The severity of the primary insult, determined by the time-integral of depletion of cerebral [NTP]/[exchangeable phosphate pool (EPP)], was similar in the MgSO4-treated and placebo groups. After resuscitation, there was no difference in the progression or severity of delayed energy failure between the two groups, as judged by cerebral [PCr]/[Pi], [NTP]/[EPP], or lactate/creatine and N-acetylaspartate/creatine peak-area ratios. We conclude that MgSO4 did not decrease the severity of delayed cerebral energy failure.

Anisotropic water diffusion in white and gray matter of the neonatal piglet brain before and after transient hypoxia-ischaemia

Measurements of tissue water apparent diffusion coefficient (ADC) performed with diffusion sensitization applied separately along the x, y, and z axes revealed significant diffusion anisotropy in both cerebral white and gray matter in six newborn (< 24 h old) piglets. Mean baseline white matter ADC for a particular region of interest was 125.8% (SD 32.0%; p < .001) greater when the diffusion gradients were applied along the y axis as compared to along the x. For the cortical gray matter region considered, the situation was reversed, the mean ADC value measured along x exceeding that along y by 15.2% (SD 6.1%; p < .01). Forty-three hours subsequent to a transient cerebral hypoxic-ischaemic insult, phosphorous MRS measurements indicated that the animals had suffered severe secondary cerebral energy failure. This was accompanied by a significant (p < .01) decrease in the white matter anisotropy, such that the mean y direction ADC now exceeded that along the x by only 70.9% (SD 29.4%; p < .03). There was no change in the gray matter anisotropy. The average of the ADC values measured in the x, y, and z directions had decreased by 35.3% (SD 18.5%; p < .01) in white matter and 31.4% (SD 21.9%; p < .05) in cortical gray matter. Diffusion anisotropy measurements may provide additional information useful in the characterisation of hypoxic-ischaemic injury in the neonatal brain, and must be considered if tissue water ADC values are to be unambiguously interpreted in this context.