The Use of Phantoms for Cross-Calibration in Clinical Trials

The advent of oncology and other disease treatments that require the collective use of different imaging modalities means that several different types of scanners might be used within one treatment plan, protocol or multi-center trial.

Reducing variability as much as possible between these different imaging modalities is key to ensuring that the data acquired for a clinical trial is accurate. This makes cross-calibration of different types of scanners a key component of routine maintenance.

This blog post will define phantoms and explain how they can be used in clinical trials.

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What Are Imaging Phantoms?

Phantoms are specially designed physical objects that are scanned or imaged to evaluate, analyze, and optimize the performance of various imaging modalities. They act as a stand-in for the human body. A phantom needs to respond in a way that is similar to how human tissues and organs would act in that specific imaging modality.

Phantoms are generally made from hard, soft and digital materials that mimic the responses of human tissues under specified conditions. Materials are chosen based on their similarity to human tissues, and properties such as density, stretching, strength and hardness. The material’s availability, cost and toxicity level are also considered.

The materials themselves can include plastics, salt solutions, silicone, epoxy, polyurethane foams, carbon powder, water, disposable diapers and radioactive substances. The particular application will determine such substances.


Why and How Are Phantoms Used?

Using phantoms means that patients do not need to be repeatedly exposed to radiation in order to calibrate equipment.  

Phantoms increase the reliability and accuracy of data obtained from medical imaging. Additionally, they assess the reproducibility of measurements across platforms and time, making phantoms highly useful in multi-center trials.

Measurements taken using phantoms can be directly traceable, or linked, to national or international technical standards. Phantoms provide confidence that imaging results taken on different scanners or on the same scanner at different times are directly comparable, meaning that data is more accurate.


Imaging Modalities and Therapeutic Areas

Various imaging modalities that have been calibrated using a phantom can be compared and are used across the spectrum of therapeutic areas. In the field of oncology, CT, MRI, and PET/CT scans are widely used. MRIs are utilized primarily in the musculoskeletal field. Ultrasounds will be chosen for diseases of the liver and have been prevalent in obstetrics research and trials.

Imaging contributes to the generation of primary, secondary and exploratory study end points. Various imaging modalities — such as CT, MRI, and PET/CT — provide evidence of drug effects and treatment efficacy by delivering response biomarkers.

The broad range of imaging modalities used in clinical trials means that several different types of phantoms are needed. For example, phantoms designed for PET scans are made of a uniform cylindrical shape. These phantoms are routinely used for staging and treatment monitoring.


Why Calibration Is Important for Imaging Scanners Used in Clinical Trials

In early and later stages of clinical development, imaging forms the foundation of strong response and progression criteria in order to interrogate a drug in many clinical trial subjects.

Calibration is important in multi-center studies to provide confidence that quantitative imaging parameters that are frequently used as imaging biomarker endpoints (such as standardized uptake values) are comparable among patients and sites, see Keosys, Cross Calibrating Pet Scanners in Clinical Trials: Why and How.



Ensuring optimum data quality for a clinical trial when multiple imaging modalities are part of the protocol is complex. Phantoms are key to reducing data variability and quality between different image modalities in image acquisition in clinical trials. Leveraging a partner with operational expertise is imperative.

Keosys is a leading team at the forefront of managing all imaging aspects in clinical trials. If you’d like to speak with one of our experts on the topic, we encourage you to reach out via this page.


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