Neural network prediction of prostate tissue composition based on magnetic resonance imaging analysis. A pilot study.

OBJECTIVE: To develop a neural network model that estimates prostate histology using magnetic resonance imaging (MRI). STUDY DESIGN: Fifty-three men with lower urinary tract symptoms (average age = 63.8 +/- 8.9 years) underwent a prostate MRI (T2) and sextant biopsy of the prostate. Masson Trichome and immunohistochemical prostate-specific antigen staining of the biopsy material were used to calculate the amount of stroma and epithelium in the inner gland (central plus transition zone). MRIs were normalized to the mean intensity of the obturator internus muscle for comparative analyses. Gray scale and texture features were extracted from the inner gland in the midsection transverse MRI slice. Clinical and image variables were used in two neural networks predicting a high amount of stroma and a high amount of epithelium, respectively. RESULTS: The positive and negative predictive values of the stroma and epithelium neural networks were 95%, 69% and 65%, 92%, respectively. CONCLUSION: These data suggest that the combined use of these neural networks may predict patient response to medical therapy targeting prostatic stroma or epithelium.

Prostatic growth rate determined from MRI data: age-related longitudinal changes.

Men with prostatic enlargement are at highest risk of developing symptomatic lower urinary tract symptoms (LUTS) and related outcomes, such as acute urinary retention. The study of prostatic growth rate can identify the age range at which prostate growth peaks. Evaluation of the natural course of prostate growth requires repeated intraindividual volume measurements at time intervals sufficient to document growth. Our objective was to examine age-stratified prostate growth rates from men taking part in a longitudinal study of aging using magnetic resonance imaging (MRI) of the prostate. Sixty-four men (ages 30-71 years) enrolled in the Baltimore Longitudinal Study of Aging (BLSA) who had T2 pelvic MRIs taken approximately every 2 years were studied. Men were age stratified into four groups: <45, 45-55, 56-65, and >65 years old. Whole prostate and central gland (anatomically referred to as the transition zone) volumes were determined from the MRI images by a semi-automated image analysis program. Peripheral gland volumes were calculated as the difference between whole prostate and central gland volumes. Growth rates (cc per year) were calculated as change in volume divided by the time interval. On the basis of measurements from the T2 images (n = 128), we observed a linear trend between prostate volume and age. The overall prostate growth rate was 2.36 +/- 3.52 cc per year. Age-stratified growth rates revealed that prostate growth increased with age, peaked at 4.15 +/- 4.98 cc/year for the 56-65-year-old age group and then declined rapidly for the older-aged men. The central gland growth rates followed a trend similar to total prostate volume. These data suggest that there is an age-related increase in prostate growth rate that peaks in men ages 56-65 and then declines. Identification of this trend in prostate growth may aid physicians in targeting men for early diagnosis of LUTS and for possible early intervention. Future studies with a larger sample size are necessary to substantiate these findings.

Fiberoptic delivery of laser energy to remove occlusions from ventricular shunts: technical report.

OBJECTIVES: Shunts frequently require surgical replacement because occlusions block the ventricular tubing. We have examined the hypothesis that a surgical laser coupled to an optical fiber can deliver sufficient energy to disrupt the occlusion in situ and thus afford a less invasive method of repair. METHODS: Choroid plexus tissue found in shunts explanted from patients, model tissues such as polyacrylamide gel, and animal tissues inserted into shunts were examined. Occlusions were fragmented by pulsed laser energy of 2.09-microm wavelength and 300-microsecond duration delivered via a flexible optical fiber several meters in length. The methods and conditions were similar to those likely to be used for preclinical in vivo studies. RESULTS: Short-lived vapor bubbles generated at the fiber tip disrupted occlusions within the shunt and expelled tissue blocking the inflow holes. Energy requirements to disrupt and remove occlusions in vitro were determined. Laser pulse energies and exposure thresholds that cause intentional damage to shunts also were determined. CONCLUSION: Laser energies needed to disrupt occlusions were below the energy needed to damage the shunt components. Our results show that a strategy using surgical lasers and optical fibers is feasible and suggest that the procedure could be used to repair blocked shunts without requiring surgical replacement.

Automated image analysis system for detecting boundaries of live prostate cancer cells.

Image analysis provides a powerful tool for quantifying cell motility and has been used to correlate motility with metastatic potential in an animal model of prostate cancer. However, widespread use of this image analysis method has been limited because earlier methods of quantitative analysis required time-intensive and subjective manual tracing of cell contours. In this report, we describe a fully automated image segmentation algorithm for detection and morphometric description of prostatic cells. The segmentation system was tested on prostate cell images generated from Hoffman modulation contrast microscopy (47 cells at 64 time points = 3,008 images) and differential interference contrast microscopy (29 cells at 64 times points plus 1 cell at 62 time points = 1,918 images). Morphometric measurements were derived from computer-determined cell boundaries and compared with the same measurements derived from manually traced cell boundaries. Final correlation coefficients for area and perimeter measurements for Hoffman and differential interference contrast microscopy were (0.76, 0.62) and (0.93, 0.93), respectively. Results with our differential interference contrast images demonstrate that our segmentation algorithm reliably and efficiently replaces the need for manually traced cell boundaries in addition to eliminating intraobserver variation. Our automated segmentation process will have immediate utility in our motility analysis system that relates cell motility with metastatic potential of prostate cancer.

Spatial mapping of polarized light transmission in the central rabbit cornea.

In this paper polarized light transmission measurements are made under conditions that closely approximate the physiological state in order to probe lamellar structure in the central cornea of New Zealand white rabbits. The results are interpreted with the aid of a newly developed theory (published elsewhere) in which the cornea is modeled as stacked birefringent layers corresponding to the lamellae. The theory enables predictions of the statistical properties of lamellar ordering based on characteristics of the transmission of polarized light. The experimental results are consistent with a structure in which a number of lamellae have a fixed azimuthal orientation (i.e. about an axis normal to the corneal surface), whereas the remainder are essentially randomly oriented. Comparisons with the theoretical predictions are consistent with a model in which the preferred direction in the apical region of the cornea does not vary significantly among rabbits; and the preferred lamellar orientation direction determined for the population measured here is very close to that suggested in previous experiments on a smaller number of rabbits. Mapping experiments using a new goniometric holder showed that the preferential order at the apical region is closely preserved throughout the central approximately 4 mm diameter optical zone in individual corneas.

Raman spectroscopy of supercoiled and nicked ColE1 plasmid.

Native supercoiled and nicked ColE1 DNA were examined using laser Raman spectroscopy. ColE1 contains 6646 base pairs (bp) and, when supercoiled, approximately 47 negative supercoils. An analytical buoyant density gradient centrifugation technique developed by Burke and Bauer was scaled to preparative quantities, and used to isolate the supercoiled plasmid fraction from its nicked counterpart. This procedure allowed enriched fractions of the supercoiled plasmid to be extracted without the use of the optical contaminant ethidium bromide. The intensities of several Raman bands were altered between the spectra of the two topological forms. Notably absent were any changes in bands arising from cytosine and guanine vibrations. The observed changes are interpreted in terms of the polymorphic structures which have been observed in many DNA structural studies. The results of this study suggest that accommodation of supercoiling takes place chiefly in A-T base pairs and backbone moieties, without substantial modification of G-C base-pair structure. Premelting effects may account for the observed changes, including a slight shift to lower frequency of a band known to be responsive to base-pair disruption. Heteronomous ribose sugar pucker is evident in both supercoiled and nicked plasmid species. No gross conformational transitions were detected for native supercoiled DNA, and consequently, subtle rearrangements appear sufficient to absorb the supercoiling deformations.