04A new probe has been developed by researchers at Stanford University that combines two imaging techniques to reveal anatomical, functional, and molecular details of the prostate. The probe simultaneously performs both ultrasound and photoacoustic scans of the prostate to help doctors diagnose prostate cancer earlier and with greater reliability.
Currently, patients are sent for a Transrectal Ultrasound (TRUS) scan when a doctor feels a lump in the prostate during a digital rectal exam, if prostate-specific antigen (PSA) levels are high, or if symptoms of prostate cancer are experienced. TRUS sends ultrasound waves through the prostate and surrounding tissues and the echoes are detected and converted to an image which is viewed on screen. However, TRUS does not always reveal the presence of cancerous cells.
Positron emission tomography (PET) scans can produce images that capture molecular detail, but the equipment is not widely available, and scans are expensive. Radiation is also used, which carries a risk to patients.
The researchers combined TRUS technology with photoacoustic imaging techniques in what they call a Transrectal Ultrasound and photoacoustic (TRUSPA) probe. Photoacoustic imaging involves sending non-ionizing laser pulses through the prostate and surrounding tissues to reveal functional and molecular information.
The researchers used a dye that is actively taken up by cancerous tissue, which makes it easier for tumors to be detected by the probe. This also allows doctors to see exactly where in the prostate the tumor is located. Since the dye is already approved for use in patients by the FDA, this allowed the researchers to use their new probe in a pilot study on patients with prostate cancer to test the effectiveness of the probe.
The greater level of detail provided by the new imaging technique could allow prostate cancer to be detected earlier, at a time when treatment is likely to be most effective. Typically, anatomical changes in the prostate that are picked up by the TRUS scan are only detectable in more advanced stages of the disease when the tumor is large or has spread beyond the prostate to the lymph nodes.
In a pilot study on 20 patients who had been previously diagnosed with prostate cancer, the researchers were even able to differentiate between malignant and non-malignant cancerous tissue.
The researchers are now looking for a dye that is only taken up by prostate cancer cells to further improve the accuracy of the imaging technique. They are also exploring the use of the hybrid probe for detecting ovarian cancer, skin cancer, and thyroid cancer.
The study is detailed in the paper – Simultaneous transrectal ultrasound and photoacoustic human prostate imaging– which was recently published in the journal Science Translational Medicine. DOI: 10.1126/scitranslmed.aav2169