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The evolution of medical imaging has greatly improved the rate and accuracy of diagnosis of disease in patients, this in turn has led to more timely treatment, and ultimately better prognosis for patients. Imaging during clinical trials is critical in the staging of disease for subjects at enrolment, following the progress of disease, and being able to accurately assess treatment effects.
Basic imaging techniques such as x-ray and ultrasound are implemented early in disease diagnosis as they are cheap and readily available. However, these low-resolution modalities have severe limitations in the accuracy of diagnosis and identification of early stage disease. Computer tomography (CT) provides higher resolution images, but harbors motion-related artifacts, requires sophisticated image reconstruction algorithms, and has low reproducibility over time and across operators. The evolution of magnetic resonance imaging (MRI) has lead to high quality, high contrast images, which allow clear delineation of anatomical features. Optical coherence tomography (OCT) has superior resolution to CT and MRI scanning, does not require ionizing radiation, and is less susceptible to motion artifacts; however, it requires a blood free environment and has poor penetration so only superficial structures can be visualized.
Positron emission tomography (PET) scanning has lead to the ability to clearly differentiate metabolic activity in tissues, important in the diagnosis and staging of cancer. When coupled with CT scanning PET/CT enables clear identification of tumor structure, robust staging of disease, and can clearly differentiate between viable and nonviable tumor parts providing an indication of the amount of tumor necrosis, treatment effect, and ultimately more accurate prognosis.
With the multiple imaging techniques available to accurately follow diseases important decisions have to be made when selecting and implementing the appropriate modality for clinical studies and can be essential to the success of the trial. Imaging can be limited by the technical parameters of the imaging modality itself: the scanner, agreement on the best methods and algorithms to use to analyze the data, operator variability. In order to conduct trials across multiple sites the measurements performed on images need to be validated and reproducible across sites over time. Questions that should be asked when deciding on the appropriate imaging modality include: can the modality detect subtle but clinically relevant changes in disease progression? Can it be used to detect therapeutic responsiveness to the clinical trial material? What are the costs/logistics of implementing these modalities?
This is a post by Catherine Sheppard, Ph.D. Catherine is a Senior Clinical Scientist in Cato Research’s Montreal, Canada office.
Related articles:
- Novel Approaches to Clinical Trial Recruitment (ask-cato.com)
- Adaptive Designs and Clinical Supplies (ask-cato.com)
