This application relates generally to tissue characterization. More specifically, this application relates to methods and systems for using electromagnetic radiation to characterize tissue.
It is well known that cancer continues to be a highly destructive disease, resulting in large numbers of deaths every year. For example, approximately 30,000 new case of oral squamous cell carcinoma are diagnosed every year, resulting in an annual death rate of this type of cancer itself of about 8000. Current treatments of cancer, whether they be surgical, chemical, or radiological, have a number of complications that can greatly diminish quality of life of patients by themselves. A recognized way to avoid these complications centers around early detection of malignant cells, or of cell properties that are precursors to malignancy. Treatment options are far less invasive and damaging when these conditions are detected early.
In the case of oral cancer, for example, oral carcinoma is commonly preceded by dysplasia. Dysplastic and cancerous cells differ in their biochemical and morphological properties when compared with healthy cells, and this may, in principle, be used as a mechanism for diagnosis. Currently, such precancerous molecular or chromosomal abnormalities are largely undetectable. In addition, geographic misses frequently occur, leading to false-negative biopsies. Cancers are often multifocal—a positive biopsy at one site may not give a full picture of the extent of the disease if the cancer is multifocal or has extended to “skip areas.” Furthermore, there is currently no standard technique for determining genetically abnormal tissue at resection margins in operating rooms. Such abnormalities are clinically undetectable and may lead to recurrence despite complete resection as determined by frozen section.
Prostate cancer is another example of a multifocal disease characterized by a high prevalence and marked heterogeneity of its morphology and clinical behavior. Prostate cancer remains the most common visceral cancer and the second most common cause of male cancer deaths in the United States. Nearly 1 million men are screened for prostate cancer annually in the United States. In 2006, it is estimated that 234,460 of these men will be diagnosed with prostate cancer and 27,350 will die from this disease.
Transrectal ultrasound (TRUS) guided needle biopsy is the current standard to diagnose prostate cancer. However, the clinical prostate cancer detection rate of TRUS-guided needle biopsies is only 25-30%, while more than 50% of cancers that require definitive treatment remain undetected during initial biopsies. Such undetected cancers are at high risk of spreading beyond the prostate gland and metastasizing to distant sites. Since prostate biopsies are taken randomly without any knowledge of tissue morphology, they often fail to provide an accurate pathologic/clinical stage of the disease.
Opportunities to intervene may be enhanced if accurate detection of the predisease/disease state can be achieved at the biochemical, structural, or pathological/physiological level. Presently, there are no real-time diagnostic tools available to assist the urologist in the in vivo detection of tissue abnormalities associated with prostate cancer. While TRUS images can identify prostate borders, the procedure cannot discriminate between benign and malignant prostatic tissue.
All of these factors contribute to a general need for methods and systems that permit accurate and simple in vivo characterization of tissue.