By Charles Bankhead

Radiologists have become major consultants and partners in cancer care as advances in technology permit imaging studies to make essential contributions at every level of care.

Taking advantage of advances in imaging technology, radiologists must become "visible and involved partners" in the diagnosis, treatment, and follow-up of cancer, San Francisco radiologist Hedvig Hricak, M.D., Ph.D., urged during the opening plenary session of the RSNA meeting.

Optical technology, three-dimensional volume display, computer-aided design techniques, PET, CT, and MRI all can play key roles in improvement of oncology care. Radiologists can draw from these technologies and others to provide oncologists with multiparameter information that can guide all aspects of cancer management, Hricak said. She is chief of abdominal imaging at the University of California, San Francisco.

"The use of 3-D volume display is essential to oncology," she said, "because tumors grow in three dimensions. The technology can play a role in lesion characterization, treatment planning, including resection and radiation therapy, and treatment follow-up in terms of response to therapy. We can also make large data sets user-friendly."

Hricak cited several key contributions of optical technology to oncology. Optical coherence tomography permits noninvasive biopsy, aids in image-guided biopsy, and permits more accurate assessment of surgical margins.

"With respect to evaluation of surgical margins, optical technology is of tremendous value in the brain, liver, abdomen, and pelvis," she said.

Another aspect of optical technology relates to what she called photoprotein reporters, which are useful in targeting drug delivery and monitoring the response of a tumor to treatment. Optical spectroscopy has added a new dimension to evaluation of tumors by providing the means to perform gene expression imaging.

Optical, nuclear, and MRI technologies all play a role in the emerging field of molecular imaging, Hricak said. Information derived from imaging studies can help pinpoint tumor genotype and tumor phenotype, which can provide invaluable information about tumor behavior to aid in the planning of therapy and follow-up after therapy.

Positron emission tomography also appears to have found a niche in oncology.

"For so long, PET has been looking everywhere for an indication only to find that one of the biggest applications will be in oncology," Hricak said. "In particular, PET is ideal for imaging lung cancer because it allows for much better characterization of tumor biology."

The technology advances have helped make radiologists partners and consultants in clinical oncology care, she said. Radiologists have acquired a good understanding of the nature of clinical problems posed by cancer. In response, they can issue relevant reports to oncologists. Radiologists also serve an important function by consulting and communicating directly with other physicians and with patients.

Increasingly, imaging technology facilitates screening of individuals at high risk for specific cancers. As an example, Hricak cited the use of CT for lung cancer.

"CT can detect lesions that are too small to be seen on a chest radiograph," she said.

Other emerging diagnostic tools include virtual endoscopy for colon cancer and spectroscopy for prostate cancer. The latter imaging study can detect citrate levels, which are decreased in the prostate in the presence of cancer and increased in the colon. A color-coded display can be programmed to reflect specific aspects of an imaging study, such as color enhancement limited to the areas of the prostate that have decreased citrate levels.

MR spectroscopy can provide a variety of information about prostate cancer, including tumor location, size, grade, and aggressiveness, and reveal extracapsular extension or spread into the seminal vesicles.

With respect to follow-up care, imaging technologies can provide surrogates of tumor response, Hricak said. Additionally, imaging studies can permit early prediction of response to treatment and outcome.

Hricak said that imaging technologies increasingly permit the integration of anatomy and function at the molecular level and facilitate the translation of research into clinical practice.