MRI assessment of cerebral perfusion in clinical trials

Neurodegenerative mechanisms affect the brain through a variety of processes that are reflected as changes in brain structure and physiology. Although some biomarkers for these changes are well established, others are at different stages of development for use in clinical trials. One of the most challenging biomarkers to harmonize for clinical trials is cerebral blood flow (CBF). There are several magnetic resonance imaging (MRI) methods for quantifying CBF without the use of contrast agents, in particular arterial spin labeling (ASL) perfusion MRI, which has been increasingly applied in clinical trials. In this review, we present ASL MRI techniques, including strategies for implementation across multiple imaging centers, levels of confidence in assessing disease progression and treatment effects, and details of image analysis.

A Path to Qualification of PET/MR Scanners for Multicenter Brain Imaging Studies: Evaluation of MR-based Attenuation Correction Methods Using a Patient Phantom

PET/MRI scanners cannot be qualified in the manner adopted for hybrid PET/CT devices. The main hurdle with qualification in PET/MRI is that attenuation correction (AC) cannot be adequately measured in conventional PET phantoms because of the difficulty in converting the MR images of the physical structures (e.g., plastic) into electron density maps. Over the last decade, a plethora of novel MRI-based algorithms has been developed to more accurately derive the attenuation properties of the human head, including the skull. Although promising, none of these techniques has yet emerged as an optimal and universally adopted strategy for AC in PET/MRI. In this work, we propose a path for PET/MRI qualification for multicenter brain imaging studies. Specifically, our solution is to separate the head AC from the other factors that affect PET data quantification and use a patient as a phantom to assess the former. The emission data collected on the integrated PET/MRI scanner to be qualified should be reconstructed using both MRI- and CT-based AC methods, and whole-brain qualitative and quantitative (both voxelwise and regional) analyses should be performed. The MRI-based approach will be considered satisfactory if the PET quantification bias is within the acceptance criteria specified here. We have implemented this approach successfully across 2 PET/MRI scanner manufacturers at 2 sites.

Quality Control Procedures and Baseline Values for Electroretinography, Perimetry, Color Vision, and Visual Acuity in an International Multicenter Study: Observations from a Safety Trial in Chronic Stable Angina Pectoris

Purpose

To describe quality control procedures and baseline values of electroretinography (ERG), kinetic and static perimetry, color discrimination, and best-corrected visual acuity from a multicenter ocular safety study.

Methods

A multicenter prospective longitudinal randomized placebo-controlled study was conducted at 11 ophthalmic centers that had received certification following training, instruction, and monitoring. ERGs were obtained with the Espion E2 Ganzfeld console, perimetry with the Octopus 101 perimeter, color discrimination with the Lanthony desaturated D15 test, and best-corrected visual acuity with the Early Treatment Diabetic Retinopathy Study chart. Ophthalmic eligibility required satisfactory outcomes for ERG and perimetry by the second or third pre-inclusion attempts, respectively. Quality control for the ERG was undertaken by two central readers.

Results

The mean (SD) age of the 97 individuals was 63.5 (7.9) range, 44–83 years. The overall coefficients of variation (CVs) for the ERG peak times were less than those of the only comparable single-center study. The CV for the mean defect of standard automated perimetry was approximately one-third that of the Ocular Hypertension Treatment Study. With increasing age, ERG peak times and color discrimination Total Error Score increased while ERG amplitudes and isopter area all decreased.

Conclusions

The data illustrate the benefit of identical equipment, stringent on-site instruction and training, quality control, certification, and validation methods. The latter are recommended for planning and conducting multicenter trials using ERG and perimetry to monitor safety and/or efficacy of treatment intervention.

Translational Relevance

Stringent quality control procedures and reliable reference values are indispensable prerequisites for informative clinical trials.

Demonstration of nonlinearity bias in the measurement of the apparent diffusion coefficient in multicenter trials

PURPOSE

Characterize system-specific bias across common magnetic resonance imaging (MRI) platforms for quantitative diffusion measurements in multicenter trials.

METHODS

Diffusion weighted imaging (DWI) was performed on an ice-water phantom along the superior-inferior (SI) and right-left (RL) orientations spanning ± 150 mm. The same scanning protocol was implemented on 14 MRI systems at seven imaging centers. The bias was estimated as a deviation of measured from known apparent diffusion coefficient (ADC) along individual DWI directions. The relative contributions of gradient nonlinearity, shim errors, imaging gradients, and eddy currents were assessed independently. The observed bias errors were compared with numerical models.

RESULTS

The measured systematic ADC errors scaled quadratically with offset from isocenter, and ranged between -55% (SI) and 25% (RL). Nonlinearity bias was dependent on system design and diffusion gradient direction. Consistent with numerical models, minor ADC errors (± 5%) due to shim, imaging and eddy currents were mitigated by double echo DWI and image coregistration of individual gradient directions.

CONCLUSION

The analysis confirms gradient nonlinearity as a major source of spatial DW bias and variability in off-center ADC measurements across MRI platforms, with minor contributions from shim, imaging gradients and eddy currents. The developed protocol enables empiric description of systematic bias in multicenter quantitative DWI studies.

Wrist and Radius Injury Surgical Trial (WRIST) Study Group. Reflections 1 year into the 21-Center National Institutes of Health--funded WRIST study: a primer on conducting a multicenter clinical trial

The Wrist and Radius Injury Surgery Trial (WRIST) study group is a collaboration of 21 hand surgery centers in the United States, Canada, and Singapore, to showcase the interest and capability of hand surgeons to conduct a multicenter clinical trial. The WRIST study group was formed in response to the seminal systematic review by Margaliot et al and the Cochrane report that indicated marked deficiency in the quality of evidence in the distal radius fracture literature. Since the initial description of this fracture by Colles in 1814, over 2,000 studies have been published on this subject; yet, high-level studies based on the principles of evidence-based medicine are lacking. As we continue to embrace evidence-based medicine to raise the quality of research, the lessons learned during the organization and conduct of WRIST can serve as a template for others contemplating similar efforts. This article traces the course of WRIST by sharing the triumphs and, more important, the struggles faced in the first year of this study.

Advancing the evidence base in cancer: psychosocial multicenter trials

BACKGROUND

The diagnosis and treatment of cancer is associated with significant distress and psychosocial morbidity. Although psychosocial interventions have been developed in an attempt to improve psychosocial outcomes in cancer patients and survivors, there is continued debate about whether there is adequate high-level evidence to establish the effectiveness of these interventions. The evidence base is limited as a result of numerous challenges faced by those attempting to conduct psychosocial intervention trials within the health system. Barriers include insufficient participant recruitment, difficulty generalizing from single-trial studies, difficulty in building and managing research teams with multidisciplinary expertise, lack of research design expertise and a lack of incentives for researchers conducting intervention research. To strengthen the evidence base, more intervention studies employing methodologically rigorous research designs are necessary.

METHODS

In order to advance the evidence base of interventions designed to improve psychosocial outcomes for cancer patients and survivors, we propose the formation of a collaborative trials group that conducts multicenter trials to test the effectiveness of such interventions.

RESULTS

Establishment of such a group would improve the quality of the evidence base in psychosocial research in cancer patients, by increasing support for conducting intervention research and providing intervention research training opportunities. A multidisciplinary collaborative group conducting multicenter trials would have the capacity to overcome many of the barriers that currently exist.

CONCLUSIONS

A stronger evidence base is necessary to identify effective psychosocial interventions for cancer patients. The proposed formation of a psycho-oncology collaborative trials group that conducts multicenter trials to test the effectiveness of psychosocial interventions would assist in achieving this outcome.

Informative value of Patient Reported Outcomes (PRO) in Health Technology Assessment (HTA)

Background

“Patient-Reported Outcome” (PRO) is used as an umbrella term for different concepts for measuring subjectively perceived health status e. g. as treatment effects. Their common characteristic is, that the appraisal of the health status is reported by the patient himself. In order to describe the informative value of PRO in Health Technology Assessment (HTA) first an overview of concepts, classifications and methods of measurement is given. The overview is complemented by an empirical analysis of clinical trials and HTA-reports on rheumatoid arthritis and breast cancer in order to report on type, frequency and consequences of PRO used in these documents.

Methods

For both issues systematic reviews of the literature have been performed. The search for methodological literature covers the publication period from 1990 to 2009, the search for clinical trials of rheumatoid arthritis and breast cancer covers the period 2005 to 2009. Both searches were performed in the medical databases of the German Institute of Medical Documentation and Information (DIMDI). The search for HTA-reports and methodological papers of HTA-agencies was performed in the CRD-Databases (CRD = Centre for Reviews and Dissemination) and by handsearching the websites of INAHTA member agencies (INAHTA = International Network of Agencies for Health Technology Assessment). For all issues specific inclusion and exclusion criteria were defined. The methodological quality of randomized controlled trials (RCT) was assessed by a modified version of the Cochrane Risk of Bias Tool. For the methodological part information extraction from the literature is structured by the report’s chapters, for the empirical part data extraction sheets were constructed. All information is summarized in a qualitative manner.

Results

Concerning the methodological issues the literature search retrieved 158 documents (87 documents related to definition or classification, 125 documents related to operationalisation of PRO). For the empirical analyses 225 RCT (rheumatoid arthritis: 77; breast cancer: 148) and 40 HTA-reports and method papers were found.

The analysis of the methodological literature confirms the role of PRO as an umbrella term for a variety of different concepts. The newest classification system facilitates the description of PRO measures by construct, target population and the method of measurement. Steps of operationalisation involve defining a conceptual framework, instrument development, exploration of measurement properties or, possibly, the modification of existing instruments.

Seven out of 59 RCT analysing the effects of antibody therapy for rheumatoid arthritis define PRO as the primary endpoint, 38 trials utilize composite measures (ACR, DAS) and ten trials report clinical or radiological parameters as the primary endpoint. Six out of 123 chemotherapy trials for breast cancer define PRO as the primary endpoint, while 98 trials report clinical endpoints (survival, tumour response, progression) in their primary analyses. Discrepancies in the number of trials result from inaccurate specifications of endpoints in the publications. This distribution is reflected in the HTA-reports: while almost all reports on rheumatoid arthritis refer to PRO, this is only the case in about half of the reports on breast cancer.

Conclusions

As definition and classification of PRO are concerned, coherent concepts are found in the literature. Their operationalisation and implementation must be guided by scientific principles. The type and frequency of PRO used in clinical trials largely depend on the disease analysed. The HTA-community seems to pursue the utilization of PRO proactively – in case of missing data the need for further research is stated.

Solving the challenges of large multicenter trials in anesthesia

This paper describes many of the challenges encountered when establishing a large multicentre trial in cardiac anesthesia. We address funding, authorship, multisite ethics review, patient recruitment, data quality management, communication with individual sites, and strategies to enhance cooperation and patient recruitment.