Pediatric Oncology: Radiation Free Imaging Test as Alternative to PET/CT Scans

Dr Heike Daldrup-Link Associate Professor of Radiology Stanford University School of Medicine, Palo Interview with:
Dr Heike Daldrup-Link
Associate Professor of Radiology
Stanford University School of Medicine, Palo Alto What are the main findings of the study?

Answer: We use magnetic resonance imaging, a technology based on magnetic fields rather than radiotracers or x-rays. The underlying technology is not new – it has been used for tumor staging for many years. This is an advantage as MR scanners are available in nearly every major Children’s Hospital where children with cancer are treated. What is new about our approach is that we combined anatomical and functional images, similar to current approaches that use radiotracers and CT (PET/CT):  We first acquired scans that showed the anatomy of the patient very well and we then acquired scans that depict tumors as bright spots with little or no background information. We did that by using an iron supplement as a contrast agent: The iron supplement can be detected by the MRI magnet and improved tumor detection and vessel delineation MR scans. We then fused the anatomical scans with the tumor scans.

One could compare this to highlighting roads and points of interests (the tumors) simultaneously on a geographic map. Previous MR imaging approaches have either shown the point of interest very well or the anatomical map, but not both. By fusing MR scans that highlight the tumor with MR scans that provide a very detailed anatomical map of the body, we created radiation-free images that shows us very clearly, where tumors are in relation to anatomical landmarks.

Our radiation free WB-DW MR imaging technique detected 158 of 174 malignant tumors and FDG-PET/CT detected 163 of 174 malignant tumors. The resultant sensitivities, specificities, and diagnostic accuracies were all excellent, with values above 90%, and were not significantly different between the two imaging modalities. Tumour staging results also showed very good agreement between both imaging modalities with a κ of 0.93. At the same time, the associated radiation exposure could be reduced from about 12.5 mSv for the PET scans to zero for the WB-DW scans. Both exams required roughly the same time between tracer injection and end of scan and the estimated exam costs were comparable. What should clinicians and patients take away from your report?

Answer:  Accurate staging of malignant tumors in children and adolescents is critical, as the presence and location of tumor manifestations throughout the body determines therapy management and prognosis.  However, several human population studies have shown that exposure to ionizing radiation above doses of about 50-100 mSv increases the risk for development of secondary cancers later in life. This is especially concerning for young patients because they are more susceptible to the effects of radiation than older patients and they live long enough to encounter secondary cancers later in live.

We demonstrate that it is possible to provide sensitive tumor staging of children with malignant tumors by using a completely radiation free imaging test as an alternative to PET/CT scans. Maybe, one could compare this to replacing conventional light bulbs with LED lights, which eliminate unwanted heat production. Just as we want light only for our lamps, we want tumor detection only without associated side effects from radiation. Current imaging techniques do not meet our high standards of patient care without side effects. Creating a potential risk of inducing new cancers with our diagnostic imaging tests is not acceptable. Our new radiation-free imaging test provides a solution for this problem. The next step will be to prove our findings in larger patient populations, beyond our single center. We are currently planning a multi-institutional initiative of six major Children’s hospital in the US, who want to compare the value of whole body MRI and PET/CT for staging of Hodgkins lymphoma. And we were recently also contacted by centers in Europe who want to join in. This could potentially evolve into a truly global initiative that could make this imaging test widely available. Our ultimate goal is to provide global access to tumor staging tests with substantially reduced or eliminated radiation exposure. What recommendations do you have for future research as a result of this study?

Answer: We evaluated the value of our new imaging test for the initial diagnosis of tumors in pediatric patients. Further studies have to show if this imaging test is also useful for evaluation of a response of the detected tumors to treatment. Such studies are also under way. There are new technological developments that combine radiotracer based imaging studies with our MRI technique. Those imaging tests still have a substantially reduced radiation exposure compared to classical PET/CT scans, but may provide additional information compared to our radiation free scan. Future studies will have to show, which patients will benefit most from a completely radiation-free whole body imaging test, as described in our article, versus new ULD (ultra low dose) PET/MR imaging tests. This is a major focus of our future multi-institutional research efforts.


Published online February 19, 2014

Christopher Klenk, Rakhee Gawande, Lebriz Uslu, Aman Khurana, Deqiang Qiu, Andrew Quon, Jessica Donig, Jarrett Rosenberg,
Sandra Luna-Fineman, Michael Moseley, Heike E Daldrup-Link. Ionising radiation-free whole-body MRI versus ¹⁸F-fluorodeoxyglucose PET/CT scans for children and young adults with cancer: a prospective, non-randomised, single-centre study
Lancet (2014)

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