What the Diagnostic Radiologist Needs to Know about Radiation Oncology

Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins School of Medicine, Baltimore MD 21231, USA.
Radiology (Impact Factor: 6.87). 10/2011; 261(1):30-44. DOI: 10.1148/radiol.11101688
Source: PubMed


Substantial technologic advances in radiation treatment planning and delivery have made possible exquisite tailoring of three-dimensional radiation dose distributions that conform to the tumor treatment volume while avoiding adjacent normal tissues. Although such highly precise treatment can increase the therapeutic ratio, it also introduces the potential that tumor extension outside the target is missed because it is unrecognized at the time of radiation treatment planning. As a result, accurate targeting of the tumor with radiation is of utmost importance to the radiation oncologist. Communication between diagnostic radiologists and radiation oncologists is essential, particularly given the subtleties that accompany image interpretation, to optimize the care of the cancer patient.

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    ABSTRACT: Accurate interpretation of posttherapeutic images obtained in radiation oncology patients requires familiarity with modern radiation therapy techniques and their expected effects on normal tissues. Three-dimensional conformal external-beam radiation therapy techniques (eg, intensity-modulated radiation therapy, stereotactic body radiation therapy), although they are designed to reduce the amount of normal tissue exposed to high-dose radiation, inevitably increase the amount of normal tissue that is exposed to low-dose radiation, with the potential for resultant changes that may evolve over time. Currently available internal radiation therapy techniques (eg, arterial radioembolization for hepatic malignancies, brachytherapy for prostate cancer and gynecologic cancers) also carry risks of possible injury to adjacent nontargeted tissues. The sensitivity of tissues to radiation exposure varies according to the tissue type but is generally proportional to the rate of cellular division, with rapidly regenerating tissues such as intestinal mucosa being the most radiosensitive. The characteristic response to radiation-induced injury likewise varies according to tissue type, with atrophy predominating in epithelial tissue whereas fibrosis predominates in stromal tissue. Moreover, changes in irradiated tissues evolve over time: In the liver, decreased attenuation at computed tomography and increased signal intensity at T2-weighted magnetic resonance imaging reflect hyperemia and edema in the early posttherapeutic period; later, veno-occlusive changes alter the hepatic enhancement pattern; and finally, fibrosis develops in some patients. In the small bowel, wall thickening and mucosal hyperenhancement predominate initially, whereas luminal narrowing is the most prominent feature of chronic enteropathy. Correlation of posttherapeutic images with images used for treatment planning may be helpful when interpreting complex cases. © RSNA, 2013.
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    ABSTRACT: Radiation injuries often occur during or after radiation therapy in the abdomen or pelvis. Although any organ in the abdomen or pelvis may be exposed to and injured by radiation therapy directed to a nearby organ, this article focuses on more frequently encountered imaging findings of inadvertent radiation damage. It is important for the radiologist to be familiar with the imaging appearances of inadvertent radiation damage to abdominopelvic viscera in order to sustain clinical relevance and not mistake radiation injuries for other entities.
    No preview · Article · Sep 2014 · Radiologic Clinics of North America
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