Poisson Twister Generator by Cumulative Frequency Technology

The widely known generators of Poisson random variables are associated with different modifications of the algorithm based on the convergence in probability of a sequence of uniform random variables to the created stochastic number. However, in some situations, this approach yields different discrete Poisson probability distributions and skipping in the generated numbers. This article offers a new approach for creating Poisson random variables based on the complete twister generator of uniform random variables, using cumulative frequency technology. The simulation results confirm that probabilistic and frequency distributions of the obtained stochastic numbers completely coincide with the theoretical Poisson distribution. Moreover, combining this new approach with the tuning algorithm of basic twister generation allows for a significant increase in length of the created sequences without using additional RAM of the computer

Nonlinear photoacoustic signal amplification from single targets in absorption background

AbstractPhotoacoustic (PA) detection of single absorbing targets such as nanoparticles or cells can be limited by absorption background. We show here that this problem can be overcome by using the nonlinear photoacoustics based on the differences in PA signal dependences on the laser energy from targets and background. Among different nonlinear phenomena, we focused on laser generation of nanobubbles as more efficient PA signal amplifiers from strongly absorbing, highly localized targets in the presence of spatially homogenous absorption background generating linear signals only. This approach was demonstrated by using nonlinear PA flow cytometry platform for label-free detection of circulating melanoma cells in blood background in vitro and in vivo. Nonlinearly amplified PA signals from overheated melanin nanoclusters in melanoma cells became detectable above still linear blood background. Nonlinear nanobubble-based photoacoustics provide new opportunities to significantly (5–20-fold) increase PA contrast of single nanoparticles, cells, viruses and bacteria in complex biological environments

Photoacoustic Flow Cytometry for Single Sickle Cell Detection In Vitro and In Vivo

Control of sickle cell disease (SCD) stage and treatment efficiency are still time-consuming which makes well-timed prevention of SCD crisis difficult. We show here that in vivo photoacoustic flow cytometry (PAFC) has a potential for real-time monitoring of circulating sickle cells in mouse model. In vivo data were verified by in vitro PAFC and photothermal (PT) and PA spectral imaging of sickle red blood cells (sRBCs) expressing SCD-associated hemoglobin (HbS) compared to normal red blood cells (nRBCs). We discovered that PT and PA signal amplitudes from sRBCs in linear mode were 2–4-fold lower than those from nRBCs. PT and PA imaging revealed more profound spatial Hb heterogeneity in sRBCs than in nRBCs, which can be associated with the presence of HbS clusters with high local absorption. This hypothesis was confirmed in nonlinear mode through nanobubble formation around overheated HbS clusters accompanied by spatially selective signal amplification. More profound differences in absorption of sRBCs than in nRBCs led to notable increase in PA signal fluctuation (fluctuation PAFC mode) as an indicator of SCD. The obtained data suggest that noninvasive label-free fluctuation PAFC has a potential for real-time enumeration of sRBCs in vitro and in vivo

In vivo long-term monitoring of circulating tumor cells fluctuation during medical interventions

The goal of this research was to study the long-term impact of medical interventions on circulating tumor cell (CTC) dynamics. We have explored whether tumor compression, punch biopsy or tumor resection cause dissemination of CTCs into peripheral blood circulation using in vivo fluorescent flow cytometry and breast cancer-bearing mouse model inoculated with MDA-MB-231-Luc2-GFP cells in the mammary gland. Two weeks after tumor inoculation, three groups of mice were the subject of the following interventions: (1) tumor compression for 15 minutes using 400 g weight to approximate the pressure during mammography; (2) punch biopsy; or (3) surgery. The CTC dynamics were determined before, during and six weeks after these interventions. An additional group of tumor-bearing mice was used as control and did not receive an intervention. The CTC dynamics in all mice were monitored weekly for eight weeks after tumor inoculation. We determined that tumor compression did not significantly affect CTC dynamics, either during the procedure itself (P = 0.28), or during the 6-week follow-up. In the punch biopsy group, we observed a significant increase in CTC immediately after the biopsy (P = 0.02), and the rate stayed elevated up to six weeks after the procedure in comparison to the tumor control group. The CTCs in the group of mice that received a tumor resection disappeared immediately after the surgery (P = 0.03). However, CTC recurrence in small numbers was detected during six weeks after the surgery. In the future, to prevent these side effects of medical interventions, the defined dynamics of intervention-induced CTCs may be used as a basis for initiation of aggressive anti-CTC therapy at time-points of increasing CTC number

Real-time label-free embolus detection using in vivo photoacoustic flow cytometry

Thromboembolic events are one of the world’s leading causes of death among patients. Embolus or clot formations have several etiologies including paraneoplastic, post-surgery, cauterization, transplantation, or extracorporeal circuits. Despite its medical significance, little progress has been made in early embolus detection, screening and control. The aim of our study is to test the utility of the in vivo photoacoustic (PA) flow cytometry (PAFC) technique for non-invasive embolus detection in real-time. Using in vivo PAFC, emboli were non-invasively monitored in the bloodstream of two different mouse models. The tumor-free mouse model consisted of two groups, one in which the limbs were clamped to produce vessel stasis (7 procedures), and one where the mice underwent surgery (7 procedures). The melanoma-bearing mouse model also consisted of two groups, one in which the implanted tumor underwent compression (8 procedures), and one where a surgical excision of the implanted tumor was performed (8 procedures). We demonstrated that the PAFC can detect a single embolus, and has the ability to distinguish between erythrocyte–rich (red) and leukocyte/platelet-rich (white) emboli in small vessels. We show that, in tumor-bearing mice, the level of circulating emboli was increased compared to tumor-free mice (p = 0.0013). The number of circulating emboli temporarily increased in the tumor-free control mice during vessel stasis (p = 0.033) and after surgical excisions (signed-rank p = 0.031). Similar observations were noted during tumor compression (p = 0.013) and after tumor excisions (p = 0.012). For the first time, it was possible to detect unlabeled emboli in vivo non-invasively, and to confirm the presence of pigmented tumor cells within circulating emboli. The insight on embolus dynamics during cancer progression and medical procedures highlight the clinical potential of PAFC for early detection of cancer and surgery-induced emboli to prevent the fatal thromboembolic complications by well-timed therapy

Relationship between embolus and melanoma.

<p>Detection rate of white emboli in 16 melanoma-bearing mice and 14 tumor-free mice (<i>p</i> = 0.0013). Values and error bars represent the mean and the standard error of the mean (SEM) of embolus counts.</p

Tumor-positive margin and IVIS image after partial tumor resection.

<p>(A) Histological Image of the resected tumor from mouse S5 with tumor-positive margin. (B) IVIS image of three different mice two weeks after receiving a tumor resection. The IVIS image from mouse S4 shows a positive bioluminescent signal in the previous tumor area (ROI 1) two weeks after receiving a tumor resection. In this mouse, the histological exam showed tumor-free margin from the resected tumor. The IVIS image of positive bioluminescent signal in the previous tumor area near the tail is due to skin shifting after stitching. In the IVIS image of mouse S5 no residual tumor was observed two weeks after receiving a tumor resection but the histology exam of the resected tumor showed a positive tumor margin.</p

CTC dynamics change after tumor pressure.

<p>(A) Profile plot of CTC detection rates (in CTCs/minute) measured weekly from six mice inoculated with breast cancer cells (MDA-MB-LUC2-GFP) during the eight weeks after tumor inoculation. Pressure was applied at week 2. (B) Profile plot of the average number of CTC signals per minute and average tumor volume during the same eight weeks. Values and error bars represent the averages and SDs of CTC counts from n = 6 mice. (C) Individual tumor volumes from six mice after tumor inoculation. Pressure was applied at week 2 after tumor inoculation. (D) Profile plot of average number of CTC signals per minute from 60 min before, 15 min during, and 120 min after removing pressure provided by a cylindrical 400 g weight with 10-mm diameter. (E) Image of the tumor after 15 minutes of compression using digital pressure-controller software (Loadstar Sensor, DI-100).</p

Embolus dynamics in control mice before, during and after compression and surgery.

<p>(A) Profile plot of average detection rate (emboli per hour) from before, 30 minutes during (red region) and after compression with a clamp (400 g) (7 procedures). Detection-rate values and error bars represent the mean and SEM of detection rates during successive 10-minute time intervals, and are positioned at the intervals’ midpoints. (B) Effects of compression effect on embolus detection rates. Values (error bars) represent the estimates (90% confidence intervals) of detection rates (emboli per hour) before compression vs. during and after compression and during vs. after compression as determined from mixed-models Poisson-regression analysis (7 procedures). (C) Profile plot of average detection rates (emboli per hour) for 30 minutes before and 190 minutes after surgery. Values and error bars represent the mean and SEM of detection rates during successive 10 minute time intervals (N7 procedures). Red arrow indicates initiation of the surgery (duration ~3 min). (D) Embolus detection rates in counts per hour before vs. after surgery. Values (error bars) represent estimated detection rates (SEM) (7 procedures).</p

Embolus dynamics in tumor-bearing mice before, during and after compression and biopsy.

<p>(A) Profile plot of average detection rate (emboli per hour) from before, during (red region) and after tumor compression with a clamp (8 procedures). Detection-rate values and error bars represent the mean and SEM of detection rates during successive 10-minute time intervals, and are positioned at the intervals’ midpoints. (B) Effects of compression on embolus-detection rates. (C) Profile plot of average embolus-detection rate (counts per hour) for before, during and after a biopsy incision. Red arrow indicates initiation of the procedure (8 procedures). (D) Embolus-detection rates in counts per hour before vs. after a surgical tumor excision. (E) Sample trace of PA signals before and after a representative biopsy. Red arrow indicates initiation of the biopsy procedure. (F) Sample PA signal trace with detection of embolus in the blood vessel of a melanoma-bearing mouse after application of a 120-g weight on the tumor. (G) Shows details of combined PA contrast. (A,C) Values and error bars represent the mean and SEM of embolus detection rates during each 10-minute bin. (B,D) Values (error bars) represent the estimates (90% confidence intervals) determined from mixed-models Poisson-regression analysis.</p