Purpose:
An innovative, simple, and fast method to optimize the number and position of catheters is presented for prostate and breast high dose rate (HDR) brachytherapy, both for arbitrary templates ...or template-free implants (such as robotic templates).
Methods:
Eight clinical cases were chosen randomly from a bank of patients, previously treated in our clinic to test our method. The 2D Centroidal Voronoi Tessellations (CVT) algorithm was adapted to distribute catheters uniformly in space, within the maximum external contour of the planning target volume. The catheters optimization procedure includes the inverse planning simulated annealing algorithm (IPSA). Complete treatment plans can then be generated from the algorithm for different number of catheters. The best plan is chosen from different dosimetry criteria and will automatically provide the number of catheters and their positions. After the CVT algorithm parameters were optimized for speed and dosimetric results, it was validated against prostate clinical cases, using clinically relevant dose parameters. The robustness to implantation error was also evaluated. Finally, the efficiency of the method was tested in breast interstitial HDR brachytherapy cases.
Results:
The effect of the number and locations of the catheters on prostate cancer patients was studied. Treatment plans with a better or equivalent dose distributions could be obtained with fewer catheters. A better or equal prostate V100 was obtained down to 12 catheters. Plans with nine or less catheters would not be clinically acceptable in terms of prostate V100 and D90. Implantation errors up to 3 mm were acceptable since no statistical difference was found when compared to 0 mm error (p > 0.05). No significant difference in dosimetric indices was observed for the different combination of parameters within the CVT algorithm. A linear relation was found between the number of random points and the optimization time of the CVT algorithm. Because the computation time decrease with the number of points and that no effects were observed on the dosimetric indices when varying the number of sampling points and the number of iterations, they were respectively fixed to 2500 and to 100. The computation time to obtain ten complete treatments plans ranging from 9 to 18 catheters, with the corresponding dosimetric indices, was 90 s. However, 93% of the computation time is used by a research version of IPSA. For the breast, on average, the Radiation Therapy Oncology Group recommendations would be satisfied down to 12 catheters. Plans with nine or less catheters would not be clinically acceptable in terms of V100, dose homogeneity index, and D90.
Conclusions:
The authors have devised a simple, fast and efficient method to optimize the number and position of catheters in interstitial HDR brachytherapy. The method was shown to be robust for both prostate and breast HDR brachytherapy. More importantly, the computation time of the algorithm is acceptable for clinical use. Ultimately, this catheter optimization algorithm could be coupled with a 3D ultrasound system to allow real-time guidance and planning in HDR brachytherapy.
To present the algorithm of a modification to the inverse planning simulated annealing (IPSA) optimization engine that allows for restriction of the intracatheter dwell time variance.
IPSA was ...modified to allow user control of dwell time variance within each catheter through a single parameter, the dwell time deviation constraint (DTDC). The minimum DTDC value (DTDC = 0) does not impose any restriction on dwell time variance, and the maximum value (DTDC = 1) restricts all dwell times within each catheter to take on the same value. The final optimization penalty function value was evaluated as a function of DTDC.
The algorithm proposed fully preserves the inverse planning nature of the IPSA algorithm along with the penalty-based dose optimization workflow. Increasing DTDC creates less variance in dwell time between dwell positions in each catheter and may be used to induce a more smooth change in dwell time with dwell position in each catheter. Nonzero DTDC values always increased the optimization penalty function value.
The DTDC was developed as an extension to IPSA to allow restriction of the difference in dwell time between adjacent dwell positions. This results in less variation between neighboring dwell positions which can be clinically desirable. However, the impact of this restriction needs to be considered for its clinical relevance on a case-by-case basis because considerable degradation in dose-volume histogram metrics can result for large DTDC values.
Purpose
The purpose of this study is application of a numerical simulation for determination of the influence of geometric parameters of a furnace and hydrodynamics of the gas introduced by a ...vertical submerged lance on the process of feed mixing and temperature distribution.
Design/methodology/approach
A numerical simulation with Phoenics software was applied for modeling of liquid phase movement and heat exchange between the gas supplied through a lance and the slag feed in a top submerged lance (TSL) furnace. The simulation of a two-phase flow of a slag–gas mixture based on the inter phase slip algorithm module was conducted. The influence of selected parameters, such as depth of lance submergence, gas flow rate and change of furnace geometry, on the phenomena of movement was studied.
Findings
Growth of dynamics of mixing with the depth of lance submergence and with increase of gas velocity in the lance was observed. Formation of a recirculation zone in the liquid slag was registered. Movement of the slag caused by the gas flow brought homogenization of the temperature field.
Originality/value
The study applied the simulation of a two-phase flow in the liquid slag–gas system in steady state, taking into account heat transfer between phases. It provides possibilities for optimization and selection of process parameters within the scope of the developed new technology using a TSL furnace.
Mixing phenomena in metallurgical steel ladles by bottom gas injection involves three phases namely, liquid molten steel, liquid slag and gaseous argon. In order to numerically solve this three-phase ...fluid flow system, a new approach is proposed which considers the physical nature of the gas being a dispersed phase in the liquid, while the two liquids namely, molten steel and slag are continuous phases initially separated by a sharp interface. The model was developed with the combination of two algorithms namely, IPSA (inter phase slip algorithm) where the gas bubbles are given a Eulerian approach since are considered as an interpenetrating phase in the two liquids and VOF (volume of fluid) in which the liquid is divided into two separate liquids but depending on the physical properties of each liquid they are assigned a mass fraction of each liquid. This implies that both the liquid phases (steel and slag) and the gas phase (argon) were solved for the mass balance. The Navier–Stokes conservation equations and the gas-phase turbulence in the liquid phases were solved in combination with the standard k-ε turbulence model. The mathematical model was successfully validated against flow patterns obtained experimentally using particle image velocimetry (PIV) and by the calculation of the area of the slag eye formed in a 1/17th water–oil physical model. The model was applied to an industrial ladle to describe in detail the turbulent flow structure of the multiphase system.
Nearly all states and provinces have laws mandating licensed healthcare professionals to report to law enforcement suspicions and allegations of the abuse of children, older adults, and disabled ...persons and all incidents of violence by a deadly weapon. However, a few states in the United States additionally mandate providers to report all injuries resultant from reported or suspected domestic/intimate partner violence. This can present a challenge to forensic nurses seeking to protect patient confidentiality and autonomy. This challenge becomes further compounded when a patient desiring to remain anonymous reports sexual assault by their partner, accompanied by bodily injury. This case report explores one such scenario that occurred in a rural Colorado Emergency Department, the issues this presents to forensic nurses, and possible responses.
SUMMARY
Section 1502 of the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 (Dodd-Frank Act) created a reporting requirement for publicly traded companies that manufacture products ...using “conflict minerals” from the Democratic Republic of the Congo (DRC) or adjoining countries. Under certain circumstances, companies must file a Conflict Minerals Report (CMR) in addition to a Specialized Disclosure Report (Form SD). Companies that claim their products are free of conflict minerals from the DRC must have an audit of their CMR. We investigate the extent to which companies have complied with the new disclosure requirements as well as the current and future auditing implications.
To present clinical outcomes and dose-volume histogram parameters of three-dimensional image-based high-dose-rate interstitial brachytherapy (HDR-ISBT) in patients with primary or recurrent ...gynecologic cancer unsuitable for intracavitary brachytherapy (ICB).
Records of 43 women treated between 2001 and 2009 with iridium-192 gynecologic HDR-ISBT boost, using a Syed-Neblett template and inverse planning simulated annealing dose optimization, were reviewed. Median HDR-ISBT dose was 30Gy, delivered in 4-6Gy/fraction. Dose-volume histogram parameters recommended by the Groupe Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology for image-based ICB were analyzed. Total doses were normalized to 2Gy fractions (biologically equivalent dose in 2Gy fractions). Local control (LC) and survival were calculated using Kaplan-Meier method. Toxicities were defined according to Common Terminology Criteria for Adverse Events v3.0.
There were 34 primary malignancies (cervix=12, vagina=15, Bartholin's gland=5, and vulva=2) and 9 recurrences. International Federation of Gynecology and Obstetrics stage distribution for primary cancers was I=2, II=13, III=15, and IV=4. Median followup was 19.3 months (range, 0-92.2). Two-year LC was 87% for primary cancers, and 45% for recurrent cancers, respectively (p=0.0175). Median V(100), D(90), and D(100) for clinical target volume were 97.6%, 90.2, and 68.7Gy(10), respectively. Median bladder and rectal D(2)(cc) were 76.6 and 79.5Gy(3), respectively. Median urethral D(10) was 80.6Gy(3). Twelve patients experienced Grades 3 and 4 late morbidity, but toxicities were transient. Only 2 patients had persistent severe toxicities. A trend toward increased risk for vaginal necrosis was observed with a clinical target volume >84cc.
HDR-ISBT may achieve good LC in gynecologic cancer unsuitable for ICB, especially in primary malignancies with a 2-year LC rate higher than 85%. Delivery of such high doses has potential advantages but may predispose to adverse effects, reversible in most cases.
The main purpose of this study was to compare three different treatment plans for locally advanced cervical cancer: (i) the inverse-planning simulated annealing (IPSA) plan for combination ...brachytherapy (BT) of interstitial and intracavitary brachytherapy, (ii) manual optimization based on the Manchester system for combination-BT, and (iii) the conventional Manchester system using only tandem and ovoids. This was a retrospective study of 25 consecutive implants. The high-risk clinical target volume (HR-CTV) and organs at risk were defined according to the GEC-ESTRO Working Group definitions. A dose of 6 Gy was prescribed. The uniform cost function for dose constraints was applied to all IPSA-generated plans. The coverage of the HR-CTV by IPSA for combination-BT was equivalent to that of manual optimization, and was better than that of the Manchester system using only tandem and ovoids. The mean V100 achieved by IPSA for combination-BT, manual optimization and Manchester was 96 ± 3.7%, 95 ± 5.5% and 80 ± 13.4%, respectively. The mean D100 was 483 ± 80, 487 ± 97 and 335 ± 119 cGy, respectively. The mean D90 was 677 ± 61, 681 ± 88 and 513 ± 150 cGy, respectively. IPSA resulted in significant reductions of the doses to the rectum (IPSA D2cm3
: 408 ± 71 cGy vs manual optimization D2cm3
: 485 ± 105 cGy; P = 0.03) and the bladder (IPSA D2cm3
: 452 ± 60 cGy vs manual optimization D2cm3
: 583 ± 113 cGy; P < 0.0001). In conclusion, combination-BT achieved better tumor coverage, and plans using IPSA provided significant sparing of normal tissues without compromising CTV coverage.
Urethral dose is related to severity of genitourinary toxicity in patients treated with brachytherapy for prostate cancer. This work describes a dose planning method that uses inverse planning to ...create a low-dose tunnel around the urethra and presents a class solution to achieve this additional dose sparing of the urethra.
Fifteen patients on the Radiation Therapy Oncology Group (RTOG) 0321 protocol were treated for prostate cancer with a high-dose-rate brachytherapy dose boost to an external beam radiation treatment regimen. All were treated with 9.5Gy for each of the two fractions after 45Gy of the external beam radiation. The inverse-planning algorithm, inverse planning simulated annealing (IPSA), was used to create both the standard RTOG protocol (SRP) plan for treatment and the a posteriori urethra dose sparing (UDS) plan consisting of a dose tunnel along the urethra. Both plans maintained the protocol parameters: prostate V(100) (volume receiving 100% of prescribed dose)>90% and bladder and rectum V(75)<1 cm(3). In the SRP plans, the urethra surface was optimized to receive <125% of the prescription dose and in the UDS plans <100%. Dose-volume histograms for the clinical treatment volume, bladder, rectum, penile bulb, and urethra for both plans are compared using a paired sample t test with significance claimed for probability values<0.05.
UDS planning reduced the urethra V(100) from 88% to 58% on average (p<0.01) and the V(125) from 3.3% to 0.2% (p < 0.01). Bladder and rectum V(75) were maintained at <1 cm(3) and not significantly different between plans. Prostate coverage was maintained per protocol at V(100)>90%, with mean for the SRP V(100)=93% versus UDS plan V(100)=90%. Prostate D(90) for SRP was 104% versus UDS plan D(90)=101%. For all patients, the UDS achieved a dose tunnel surrounding the length of the intraprostatic urethra. The class solution for generating UDS is presented.
A urethral sparing-focused planning solution using IPSA reduces mean urethral dose by 34%, as compared with IPSA-generated plans based on the RTOG 0321 protocol. This is done while maintaining prostate coverage and critical structure dose. This technique can be applied to all patients in whom urethra toxicity is of particular concern.
The aim of this study was to compare inverse planning-simulated annealing (IPSA) with geometric optimization (GO) in high-dose-rate (HDR) prostate brachytherapy, to assess variations in dosimetric ...indices associated to catheter displacement.
We retrospectively studied the dosimetric effect of catheter displacement in 20 patients treated with HDR prostate brachytherapy with salvage intention. The catheter loadings, with optimized dwell positions, from the first fraction were transferred to the catheter positions in the second fraction.
Median catheter displacement was 8.7 ± 3.3 mm (range, 2.7 ± 1.1 mm-14.7 ± 1.7 mm). D90% median variations for IPSA and GO were -10% with a maximum of -59%, and -29% with a maximum of -63%, respectively. V100% median variation was -11% with a maximum of -37% for IPSA, and -20% with a maximum of -37% for GO. V150/V100 implant median variations were 15% and 9% for IPSA and GO with maximum values of 65% and 47%, respectively (p < 0.05). No significant differences were observed for V200/V100 indices, nor were any significant differences found for organs at risk. Correlation between mean catheter displacement and dosimetric indices was found only in the planning target volume D90% and V100%; linear regression slopes were -2.0% per mm and -2.6% per mm for IPSA vs. -2.4% per mm and -3.5% per mm for GO.
IPSA does not present any additional risk compared with GO in HDR prostate brachytherapy when catheter uncertainties are taken into account. Moreover, IPSA optimization preserves planning target volume coverage better than GO, suggesting that it may be superior when catheter displacement is considered.
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