Qiyu Peng

Design and Implementation of a Facility for Discovering New Scintillator Materials

We describe the design and operation of a high-throughput facility for synthesizing thousands of inorganic crystalline samples per year and evaluating them as potential scintillation detector materials. This facility includes a robotic dispenser, arrays of automated furnaces, a dual-beam X-ray generator for diffractometry and luminescence spectroscopy, a pulsed X-ray generator for time response measurements, computer-controlled sample changers, an optical spectrometer, and a network-accessible database management system that captures all synthesis and measurement data.

Mechanisms of Pelvic Floor Muscle Function and the Effect on the Urethra during a Cough

BACKGROUND Current measurement tools have difficulty identifying the automatic physiologic processes maintaining continence, and many questions still remain about pelvic floor muscle (PFM) function during automatic events. OBJECTIVE To perform a feasibility study to characterise the displacement, velocity, and acceleration of the PFM and the urethra during a cough. DESIGN, SETTING, AND PARTICIPANTS A volunteer convenience sample of 23 continent women and 9 women with stress urinary incontinence (SUI) from the general community of San Francisco Bay Area was studied. MEASUREMENTS Methods included perineal ultrasound imaging, motion tracking of the urogenital structures, and digital vaginal examination. Statistical analysis used one-tailed unpaired student t tests, and Welchs correction was applied when variances were unequal. RESULTS AND LIMITATIONS The cough reflex activated the PFM of continent women to compress the urogenital structures towards the pubic symphysis, which was absent in women with SUI. The maximum accelerations that acted on the PFM during a cough were generally more similar than the velocities and displacements. The urethras of women with SUI were exposed to uncontrolled transverse acceleration and were displaced more than twice as far (p=0.0002), with almost twice the velocity (p=0.0015) of the urethras of continent women. Caution regarding the generalisability of this study is warranted due to the small number of women in the SUI group and the significant difference in parity between groups. CONCLUSIONS During a cough, normal PFM function produces timely compression of the pelvic floor and additional external support to the urethra, reducing displacement, velocity, and acceleration. In women with SUI, who have weaker urethral attachments, this shortening contraction does not occur; consequently, the urethras of women with SUI move further and faster for a longer duration.

OpenPET: A flexible electronics system for radiotracer imaging

We present the design for OpenPET, an electronics readout system designed for prototype radiotracer imaging instruments. The critical requirements are that it has sufficient performance, channel count, channel density, and power consumption to service a complete camera, and yet be simple, flexible, and customizable enough to be used with almost any detector or camera design. An important feature of this system is that each analog input is processed independently. Each input can be configured to accept signals of either polarity as well as either differential or ground referenced signals. Each signal is digitized by a continuously sampled ADC, which is processed by an FPGA to extract pulse height information. A leading edge discriminator creates a timing edge that is “time stamped” by a TDC implemented inside the FPGA. This digital information from each channel is sent to an FPGA that services 16 analog channels, and information from multiple channels is processed by this FPGA to perform logic for crystal lookup, DOI calculation, calibration, etc. As all of this processing is controlled by firmware and software, it can be modified/customized easily. The system is open source, meaning that all technical data (specifications, schematics and board layout files, source code, and instructions) will be publicly available.

Influence of Pelvic Floor Muscle Contraction on the Profile of Vaginal Closure Pressure in Continent and Stress Urinary Incontinent Women

PURPOSE We characterized the vaginal pressure profile as a representation of closure forces along the length and circumference of the vaginal wall. Vaginal pressure profile data were used to test the hypothesis that the strength of pelvic floor muscle contractions differs significantly between continent women and women with stress urinary incontinence. MATERIALS AND METHODS Vaginal pressure profile recordings were made in 23 continent subjects and in 10 patients with stress urinary incontinence. The recordings characterized closure forces along the entire length of the vagina and identified differences among the anterior, posterior, left and right sides of the vaginal wall. Using a novel, directionally sensitive vaginal probe we made vaginal pressure profile measurements with the women at rest and during pelvic floor muscle contraction while supine. RESULTS The nature of the vaginal pressure profile was characterized in terms of force distribution in the anterior and posterior vaginal walls, which was significantly greater than that on the left and right sides. The continent group had significant greater maximum pressure than the stress urinary incontinence group on the posterior side at rest (mean +/- SE 3.4 +/- 0.3 vs 2.01 +/- 0.36 N/cm(2)) and during pelvic floor muscle contraction (4.18 +/- 0.26 vs 2.25 +/- 0.41 N/cm(2)). The activity pressure difference between the posterior and anterior vaginal walls in the continent group was significantly increased when the pelvic floor muscles contracted vs that at rest (3.29 +/- 0.21 vs 2.45 +/- 0.26 N/cm(2)). However, the change observed in the stress urinary incontinence group was not significant (1.85 +/- 0.38 vs 1.35 +/- 0.27 N/cm(2)). CONCLUSIONS The results demonstrate that the voluntary pelvic floor muscles impose significant closure forces along the vaginal wall of continent women but not in women with stress urinary incontinence. The implication of these findings is that extrinsic urethral closure pressure is insufficiently augmented by pelvic floor muscle contraction in women with stress urinary incontinence.

ZigBee-based Wireless Intra-oral Control System for Quadriplegic Patients

A human-to-computer system that includes a wireless intra-oral module, a wireless coordinator and distributed wireless controllers, is presented. The state-of-the-art ZigBee protocol is employed to achieve reliable, low- power and cost-efficient wireless communication between the tongue, computer and controllers. By manipulating five buttons on the wireless intra-oral module using the tongue, the subject can control cursors, computer menus, wheelchair, lights, TV, phone and robotic devices. The system is designed to improve the life quality of patients with stroke and patients with spinal cord injury.

Spatial distribution of vaginal closure pressures of continent and stress urinary incontinent women.

Clinically the strength of the contraction of the female pelvic floor is qualitatively evaluated by vaginal tactile palpation. We therefore developed a probe to enable the quantitative evaluation of the closure pressures along the vagina. Four force sensors mounted on the four orthogonal directions of an intra-vaginal probe were used to measure the vaginal pressure profile (VPP) along the vaginal wall. Clinical experiments on 23 controls and 10 patients with stress urinary incontinence (SUI) were performed using the probe to test the hypothesis that the strength of pelvic floor muscle (PFM) contractions, imposed by voluntary contraction, is related to urinary continence. The results show that VPPs, characterized in terms of pressure distribution on the anterior and posterior vaginal walls, are significantly greater than those in the left and right vaginal walls. When the PFM contracted, the positions of the maximum posterior pressures in continent females and SUI patients were 0.63+/-0.15 cm and 1.19+/-0.2 cm proximal from their peak points of anterior pressure, which are 1.52+/-0.09 cm and 1.69+/-0.13 cm proximal from the introitus of vagina, respectively. The statistical analysis shows that the maximum posterior vaginal pressures of the controls were significantly greater than those of the SUI patients both at rest (continent: 3.4+/-0.3 N cm(-2), SUI: 2.01+/-0.36 N cm(-2), p<0.05) and during PFM contraction (continent: 4.18+/-0.26 N cm(-2), SUI: 2.25+/-0.41 N cm(-2), p<0.01). In addition, the difference between the posterior and anterior vaginal walls is significantly increased when the controls contract the PFM. By contrast, there are no significant differences in the SUI group. The results show that the VPP measured by the prototype probe can be used to quantitatively evaluate the strength of the PFM, which is a clinical index for the diagnosis or assessment of female SUI.

Multi-modality phantom development

Multi-modality imaging has an increasing role in the diagnosis and treatment of a large number of diseases, particularly if both functional and anatomical information are acquired and accurately co-registered. Although PET-CT has recently revolutionized the role of imaging for many kinds of cancer, ultrasound is the preferred imaging technology for many diseases such as prostate cancer. Transrectal ultrasound (TRUS) is an integral part of diagnosis and treatment for prostate cancer, so we are developing a dual imaging system that will acquire PET and TRUS data during the same patient imaging session and accurately co-register the images. In order to validate our methods prior to patient imaging, we will use a novel custom PET-TRUS prostate phantom. We present our initial PET- ultrasound phantom development, including PET and ultrasound images of a simple phantom, as well as discuss of our future phantom construction plans. We will use agar-gelatin tissue mimicking materials mixed with radioactive water solutions. Although we are currently focused on prostate imaging, this phantom development is applicable to all PET-ultrasound imaging applications. In addition, we discuss how to make a PET-ultrasound phantom also MRI and/or CT compatible.

Stiffness mapping prostate biopsy samples using a tactile sensor

Previous studies have demonstrated that the stiffness of cancerous cells reflects their pathological stage and progression rates, with increased cancerous cell stiffness associated with increased aggressiveness. Therefore, the elasticity of the cancerous cells has the potential to be used as an indicator of the cancers aggressiveness. However, the sensitivity and resolution of current palpation and imaging techniques are not sufficient to detect small cancerous tissues. In previous studies, we developed a tactile-based device to map with high resolution the stiffness of a tissue section. The purpose of this study is to evaluate this device using different tissues (BPH, Cancer and PZ) collected from human prostates. The preliminary results show that the tactile device is sensitive enough to tell the differences of the stiffness of different tissues. The results also disclosed the factors (humidity, temperature and tissue degradation) which could dramatically affect the results of stiffness mapping. The tactile technology described in this paper has the potential to help disclose the underlying mechanical mechanisms that lead to increased stiffness in prostate tumors.

Development of a PET-Transrectal Ultrasound Prostate Imaging System

Multimodality imaging has an increasing role in the management of a large number of diseases, particularly if both functional and structural information are acquired and accurately registered. Transrectal ultrasound (TRUS) imaging is currently an integral part of prostate cancer diagnosis and treatment procedures, providing high-resolution anatomical detail of the prostate region. Positron Emission Tomography (PET) imaging with 11C-choline is a sensitive functional imaging technique that can identify biochemical states associated with prostate cancer. We believe that merging these prostate imaging technologies will help identify the location and aggressiveness of prostate cancer. We envision using dual PET-TRUS prostate imaging to guide biopsy, guide treatment procedures, and detect local recurrence earlier than is currently possible. Hence, we have developed a dual PET-TRUS prostate imaging system and protocol designed to allow accurate 3-D image registration. We have evaluated this PET-TRUS system by performing dual PET-TRUS imaging of custom phantoms. We describe here our dual-modality imaging system, custom phantoms and phantom study results. We also discuss our investigation of the PET-TRUS registration accuracy. We measure an average PET-TRUS registration error for our phantom studies of 2.1 ±1.7&nbsp;mm in the x direction, 1.9 ±1.6&nbsp;mm in the y direction, and 0.6 ±0.2&nbsp;mm in the z direction. This registration accuracy is sufficient for some clinical applications such as biopsy guidance and early detection of recurrence.

Preliminary performance characterization of DbPET2.1, a PET scanner dedicated to the imaging of the breast and extremities

The combined effort of several laboratories at our institution resulted in the building of the first high resolution PET/CT prototype dedicated to imaging the body extremities. Ongoing clinical trials for breast cancer diagnosis and assessment of response to treatment underlined the need for a second generation prototype with improved electronics and spatial resolution. A preliminary version has been assembled and fully characterized. In this work we present further improvements in the detector performance as well as the readout electronics for the PET component. The detector consists of a 16×16 array of 1.27×1.27×20mm3 LYSO crystals, the smallest crystal size for completed breast PET prototypes to date, directly coupled to a position-sensitive photomultiplier tube (PSPMT). The scintillator crystals are polished on all 6 faces and separated by ~70 μm ESR reflector. The readout electronics were redesigned to reduce their footprint and improve timing resolution. We report a detector energy and timing resolution of 12% and 1.0 ns, respectively, and an average intrinsic spatial resolution of 1.29 mm (central row in one detector array). The new PET/CT has been fully assembled and initial system characterization is being perfomed. We report a system energy resolution of 15.7%, a timing resolution of 1.5 ns and an FBP image spatial resolution in the center of the FOV of 1.6 mm.