Study of normal and cancerous urine using photoacoustic spectroscopy

Feasibility of photoacoustic-guided teleoperated hysterectomies

Hysterectomies (i.e., surgical removal of the uterus) are the prevailing solution to treat medical conditions such as uterine cancer, endometriosis, and uterine prolapse. One complication of hysterectomies is accidental injury to the ureters located within millimeters of the uterine arteries that are severed and cauterized to hinder blood flow and enable full uterus removal. This work explores the feasibility of using photoacoustic imaging to visualize the uterine arteries (and potentially the ureter) when this imaging method is uniquely combined with a da Vinci^® surgical robot that enables teleoperated hysterectomies. We developed a specialized light delivery system to surround a da Vinci^® curved scissor tool, and an ultrasound probe was placed externally, representing a transvaginal approach, to receive the acoustic signals. Photoacoustic images were acquired while sweeping the tool across our custom 3-D uterine vessel model covered in ex vivo bovine tissue that was placed between the 3-D model and the fiber, as well as between the ultrasound probe and the 3-D model. Four tool orientations were explored, and the robot kinematics were used to provide tool position and orientation information simultaneously with each photoacoustic image acquisition. The optimal tool orientation produced images with contrast >10  dB and background signal-to-noise ratios (SNRs) >1.7, indicating minimal acoustic clutter from the tool tip. We achieved similar contrast and SNR measurements with four unique wrist orientations explored with the scissor tool in open and closed configurations. Results indicate that photoacoustic imaging is a promising approach to enable visualization of the uterine arteries to guide hysterectomies (and other gynecological surgeries). These results are additionally applicable to other da Vinci^® surgeries and other surgical instruments with similar tip geometry.

Effective normalization method for sample-position-dependence effect in photoacoustic spectrometry

Sample position dependence effect in photoacoustic (PA) spectrometry has been reported by several scientists. This effect must be taken into account in a PA application that requires a quantitative theoretical treatment. In this work, we experimentally investigated PA signal magnitude varying with sample-to-window distance in an MTEC Model 300 Photoacoustic Detector, which has a fixed empty (gas) volume in addition to the sample-to-window-distance-dependent gas volume. An operative method was introduced to obtain the coefficient, which considered the sample-to-window distance and the additional gas volume. With this coefficient, the one-dimensional PA model, developed by Aamodt, Murphy, and Parker, can be employed to quantitatively process PA experimental data, no matter what the sample-to-window distance is. Quantitative measurements of thermal effusivities of two samples were performed to prove this effective normalization method.

Photoacoustic study of iron-deficiency anaemia

A photoacoustic spectrum of a smear of whole blood clearly shows all of the details of the haem absorption in an optical spectrum and good optical absorption data without a data extraction procedure. There are three peaks; gamma (420 nm), beta (550 nm), and alpha (585 nm) in the band 350-700 nm. For iron-deficiency anaemia the peak/peak ratios, ratios of the value of peak gamma to that of the peak beta and peak alpha, and the integral/integral ratios, ratios of the value of the integral under the peak gamma to that under the peak beta, peak alpha, peak beta and peak alpha are closely related to the variation of haemoglobin concentration. Linear relationships among the ratios and the Hb concentration are found. These ratios could be a good index of haem synthesis disturbance.