ABSTRACT
Objective:To investigate the effect of dwell time deviation constraint of inverse optimization on the quality and position error robustness of three-dimensional (3D) brachytherapy plans for cervical cancer.Methods:A total of 20 patients with cervical cancer receiving 3D brachytherapy treatment in Xiangya Hospital Central South University from August 2020 to August 2021 were retrospectively selected. All plans were designed using the Eclipse treatment planning system, and the dwell time deviation constraint parameter smooth value in the system were set to 0.00, 0.25, 0.50, 0.75, and 1.00, respectively. An inverse dose volume optimization algorithm was used to generate plans with various smooth values, and the optimization conditions were the same as the original clinical plans. Key dosimetric metrics and total dwell time differences were comparatively analyzed. The applicators were intentionally subjected to position errors (0.2-1.0 cm) in 6 directions (left-right, anterior-posterior, head-foot), and the effect of various smooth values on plan quality and robustness was assessed. There were 133 plans per case and 2 660 plans for 20 patients. The results were statistically analyzed using the Wilcoxon signed-rank nonparametric test.Results:As the smooth value was increased, the modulation factor was gradually decreased and the D 2 cm3 of the bladder and rectum was increased. Plans with smooth values of 0.25, 0.50, 0.75, 1.00 had modulation factors of 0.72±0.09, 0.63±0.08, 0.55±0.08, 0.51±0.06, respectively, lower than 0.75±0.05 of the plan with the smooth value of 0.00, and all differences were statistically significant ( P=0.004, 0.002, 0.002, 0.002). The bladder D 2 cm3 of plans with smooth values of 0.50, 0.75, 1.00 were (475.4±41.0) cGy, (483.7±46.2) cGy, and (489.0±46.8) cGy, respectively, higher than (469.8±41.8) cGy of the plan with the smooth value of 0.00, with statistically significant differences (all P=0.002). The rectum D 2 cm3 of plans with smooth values of 0.50 and 0.75 plans were (413.2±93.3) cGy and (418.6±96.4) cGy, both higher than (410.2±91.5) cGy of the plan with the smooth value of 0.00, with statistically significant differences ( P=0.006, 0.010). When positional errors were introduced, the high risk clinical target volume (HR-CTV) D 90% was close for different smooth plans at most positional errors, and the differences were not statistically significant. The organs at risk D 2 cm3 of plans with the smooth value of 0.00 was lower than those of plans with other smooth values, and for the bladder and rectum, the differences were statistically significant at most positional errors (all P<0.01). Conclusions:The dwell time deviation constraint parameter exerts significant effect on the plan quality, and the smaller the value of the constraint parameter, the higher quality of the plan. The dwell time deviation constraint parameter has slight impact on the positional error robustness of dosimetric indices of targets and key organs at risk.
ABSTRACT
The central line-associated bloodstream infection (CLABSI) is a common and serious complication of central venous catheterization, which can lead to various short-term and long-term adverse outcomes. Neonatal CLABSI did not increase linearly with the prolongation of peripherally inserted central catheter (PICC). When the umbilical venous catheter (UVC) is retained for more than 1-2 weeks, the incidence of neonatal CLABSI may increase significantly; PICC replacement at 7-10 days after UVC indwelling may reduce the incidence of CLABSI, but it has not been supported by evidence-based medicine. This article reviews the related studies between neonatal CLABSI and catheter dwell time, in order to plan the indwelling time more reasonably and prevent CLABSI better.
ABSTRACT
Purpose: High Dose Rate (HDR) remote afterloading brachytherapy machine and advanced treatment planning system have made it possible to make variations in individual dwell times across a catheter according to tumour density and for sparing normal structures. New inverse planning technique such as Inverse Planning Simulated Annealing (IPSA) has also been introduced. But very few institutions are venturing towards volume based IPSA optimised intracavitary brachytherapy. This study focuses on dwell time deviation constraint (DTDC) feature of IPSA based optimization which restricts the large variation of dwell time across the catheter. Methods and Material: For this retrospective study we have generated IPSA optimised intracavitary brachytherapy plans for 20 cancer cervix applications. The initial DTDC value of each IPSA plan was kept 0.0. Later on gradual increment was made in DTDC values in step of 0.2. Plan modulation index (M) defined by Ryan L. Smith et al was used for characterising the variation of dwell time modulation with respect to gradual increase in DTDC parameter. Results: Plan modulation index gradually decreases with increasing value of DTDC from 0.0 to 1.0. There was the 83% decrease in M value from IPSA of DTDC 0.0 to fully constrained IPSA of DTDC1.0. There is reduction of 8.26% and 6.95% for D2cc values of rectum and bladder respectively for DTDC 1.0 compared to DTDC 0.0. Conclusions: One of the benefits of applying DTDC constrained in IPSA plan is that, it removes local hot spots. It's another advantage is the reduction in rectum and bladder dose.
ABSTRACT
Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) is a new tool that can provide the element composition, size distribution, and number concentration of nanoparticles. Here we discussed the effects of dwell time and settling time on analysis of nanoparticles by SP-ICP-MS. We analyzed standard materials of gold nanoparticles (30, 40 and 60 nm AuNPs, from NIST and NCNST), showing that better signal-to-noise ratio and higher determination efficiency could be achived when using shorter dwell time and settling time. We utilized a nano mode for SP-ICP-MS, in which the dwell time was set as 0. 05 ms and the settling time was 0. The size of NIST AuNP standard material determined here was in accord with the certified size using the developed method. The detection limits of size and number concentration of AuNPs were 8 nm and 1. 1×105 particle / L, respectively.
ABSTRACT
In the current study, we report a new technique to place a tunnelled peripherally inserted central catheter (PICC) at the upper arm of patient under real-time ultrasound-guided venipuncture using disposal equipment provided within a standard PICC set. The tunnelling of the PICC required an extra time of 5 minutes but was well tolerated by all patients involved in the study. The tunnelled PICC was applied on 50 patients and the infection rate as well its catheter dwell time were compared to another 50 patients with conventional PICC. The rate of patients who developed infection decreased from 34% for conventional PICC to 16% in tunnelled PICC patients. The central line-associated blood stream infections rate was also decreased from 4.4 per 1000 catheter-days for conventional PICC to 1.3 per 1000 catheter-days for tunnelled PICC. The mean time to infection development for tunnelled PICC (24 days) was longer than those observed with conventional PICC (19 days). Tunnelled PICC has also increased the mean catheter dwell time from 27 days (for conventional PICC) to 47 days. Tunnelling a PICC has the potential to reduce the infection rate while increase the catheter dwell time.