Laparoscopic image analysis for robotic arm guidance.

Some of the most important problems arising during a laparoscopic surgery relate to the limited perception of depth and field of view (fov). In this paper we explore the possibilities of dealing with these problems using appropriate re-modeling of the laparoscopic equipment and image processing algorithms, as to increase the perception ability of the surgeon within the operation space. We demonstrate that by using two camera units and appropriate estimation of the epipolar geometry between the camera views, we can acquire an accurate 3D map of the scene, as well as increased field of view. The benefits for the surgeon include the enhancement of the visible operating space and the increased perception of this space, with the ability of accurately estimating distances of sensitive abdomen regions and organs from the end of the laparoscope tip. Several simulation and real-world experiments are presented as to validate the potential of the proposed scheme.

Prostate-specific antigen in hemodialysis patients and the influence of dialysis in its levels.

The determination of prostate-specific antigen (PSA) is a useful tool in the diagnosis and follow-up of prostate cancer in males, but its diagnostic validity is uncertain in hemodialysis patients. We prospectively evaluated PSA in male hemodialysis patients as well as the influence of a single dialytic session on its levels. We measured pre- and postdialysis total PSA (tPSA) in 63 hemodialysis patients (mean age 68.44 +/- 11.16 years, range 33-86 years) who had received dialysis with low flux membranes as well as in 729 normal subjects (mean age 63.22 +/- 16.85 years, range 28-92 years). We also measured pre- and postdialysis hematocrit (Hct) in patients in order to estimate the degree of hemoconcentration after the dialysis session. If any of the examined patients or subjects had abnormal tPSA levels then free PSA (fPSA) and the f/tPSA ratio were additionally measured. Patients had lower levels of tPSA compared with those of the subjects (2.41 +/- 4.06 vs. 3.76 +/- 7.16 ng/ml, p < 0.05) while both of the two groups had near equal prevalence of individuals with abnormal values of tPSA or f/tPSA ratio (patients 12.69 and 7.93%, subjects 11.01 and 7.11%, respectively; nonsignificant. Dialysis resulted in a 9.48% increase in mean tPSA levels (2.41 +/- 4.06 vs. 2.69 +/- 4.06 ng/ml, nonsignificant) and in a 10.09% increase in mean Hct; the correlation between these increases was significant (r = 0.79, p < 0.001). In conclusion, our male hemodialysis patients had lower PSA levels compared with the general population, while both groups of individuals had a similar prevalence of abnormal values of tPSA and f/tPSA ratio. Dialysis with low flux membranes does not eliminate PSA and its postdialysis increase is due to hemoconcentration.