Medical X-ray Imaging, Current Status and Some Future Challenges

Biomedical x-ray imaging has proven to be an indispensable component of many medical diagnostic and treatment techniques. Major technical advances over the years, culminating in helical scanning, multi slice, x-ray computed tomography, can now provide ∼ 0.5 mm resolution 3D images of the spatial distribution of tissue attenuation coefficients of an entire adult human thorax or abdomen. The utility of the x-ray images is ultimately limited by two opposing factors, one is that increased image spatial and contrast resolution requires an increased number of detected x-ray photons per image resolution unit, and the other is the direct relationship between the number of x-ray photons and the increased risk of tissue damage and ultimate cancer development. This trade-off limits the utility of x-ray imaging in screening of subjects who are likely to be at risk of a disease (e.g., a family history or exposure to an environment that increases the risk of a life-threatening disease) but who have not yet developed the clinical signs or symptoms. Based on increasing experience (especially with synchrotron x-ray-based imaging), x-ray imaging of some consequences of a tissue’s x-ray refractive index, rather than x-ray attenuation, has potential for decreasing the x-ray dose and increasing contrast resolution. This approach, while presenting formidable technological problems for whole-body 3D imaging, could, if achievable in a routine clinical setting, greatly expand the applicability of x-ray imaging for screening and repeated studies of asymptomatic subjects of all ages.