The Research of Sarah Patch
Algorithm development for direct image reconstruction is Dr. Patch's area of training, although she collects experimental data. Her current research focus is thermoacoustic tomography (TCT), a hybrid imaging technique. Her long-term goal is to quantify the robustness of TCT across different sizes, depths, and types of cancer. Ideally, TCT deposits electromagnetic (EM) energy impulsively in time and uniformly throughout the imaging object, causing thermal expansion. Rapid thermal expansion generates thermoacoustic signals which are detected by ultrasound receivers placed outside of the object. Different types of tissue absorb different amounts of EM energy, which leads to variable heating and thermal expansion throughout the object. By "listening" for the emitted TA pulses from different locations around the object, we collect a TCT dataset (sinogram) similar to those collected by xray CT scanners. Dr. Patch has developed an inversion formula for idealized TCT data and now works to account for physical and experimental effects upon TCT data.
The Patch Lab utilizes very high frequency EM energy, to enable whole organ imaging. Choice of EM frequency impacts the contrast mechanism and imaging depth. For instance, optical energy is preferentially absorbed by hemoglobin in blood and has a penetration depth of less than 2 cm in soft tissue. Microwaves heat pure (deionized) water and can develop standing waves in tissue creating "hotspots" and also "coldspots" from which no thermoacoustic information is available. (Recall uneven heating in microwave ovens without rotary tables.) Very high frequency (VHF) energy is absorbed by ions which are present in electrically conductive blood and other fluids. VHF energy is used to excite MRI signals and can easily penetrate the abdomen of a large adult, enabling whole organ imaging.
Acronyms: PCa~prostate cancer, INFL~inflammation, HGPin~high-grade prostatic intraepithelial neoplasia, ECE~extracapsular extension of cancer outside the prostate
If results of a larger study also support the hypothesis that VHF-induced thermoacoustic imaging is sensitive to prostate cancer then development of a clinical prototype for in vivo imaging will be warranted.