D50 Values Research Articles

Comparative study of late rectal toxicity in prostate cancer patients treated with low-dose-rate brachytherapy: With or without supplemental external beam radiotherapy

PurposeSupplemental external beam radiation therapy (sEBRT) is often prescribed in men undergoing low-dose-rate (LDR) brachytherapy. A population of patients was analyzed to assess the effect of sEBRT on late rectal toxicity. It was hypothesized that sEBRT + LDR would be associated with a higher risk of late rectal toxicity. Methods and MaterialsThis retrospective cohort study examined LDR brachytherapy patients, treated with or without sEBRT, with a minimum of 5-year followup. Longitudinal assessments were evaluated using the computerized patient record system. The Kaplan–Meier method was used for analysis. ResultsMedian followup was 7.5 years for 245 patients from 2004 to 2007. sEBRT was administered to 33.5%. Followup beyond 5 years was available for 89%. Overall rates of Grade ≥2 and ≥3 rectal toxicities were 6.9% and 2.9%, respectively. The risk of Grade ≥2 rectal toxicity was 2.8-fold higher for patients receiving sEBRT (95% confidence interval: 1.1–7.2; p = 0.02). The risk of Grade ≥3 rectal toxicity was 11.9-fold higher for patients who received sEBRT (1.5–97.4, 95% confidence interval; p = 0.003). Six of seven patients with a Grade ≥3 rectal toxicity received sEBRT, including one who required an abdominoperineal resection. Median post-LDR D90, V150, V200, and R100 values were 103.3%, 59.4%, 30.1%, and 0.5 cc. ConclusionsIn a cohort of LDR brachytherapy patients with high rates of followup, sEBRT + LDR was associated with significantly higher risk of Grade ≥2 and ≥3 late rectal toxicity. This analysis supports previous findings and maintains concern about the supplemental use of external beam radiation therapy with LDR brachytherapy while its benefit for tumor control has yet to be prospectively validated.

Long term experience with 3D image guided brachytherapy and clinical outcome in cervical cancer patients

Background and purposeTo report our 10years’ experience and learning curve of the treatment of cervical cancer patients with chemo radiotherapy and MRI (or CT in 9 selected patients) guided brachytherapy using pulsed dose rate (PDR) brachytherapy (BT). Methods and materialsHundred and seventy consecutive patients with cervical cancer FIGO stage IB–IVB (without metastases beyond the para-aortic nodal region) were treated in our institute between 2002 and 2012. Patients received external beam radiotherapy (nodal boost to the lymph nodes positive at diagnosis)±chemotherapy followed by a pulsed or low dose rate brachytherapy boost. MRI (or CT) images were taken with the applicator in situ. The first 16 patients were treated according to X-ray-based plans, optimized on MRI. High-risk CTV, intermediate-risk CTV, bladder, rectum and sigmoid were retrospectively contoured according to the GEC-ESTRO recommendations. In all other patients, treatment plans were optimized after delineation of the target volumes and organs at risk at MRI (or CT). Doses were converted to the equivalent dose in 2Gy (EQD2) by applying the linear quadratic model. The median age of the patients was 55years (range 16–88). 41% had stage III or IV disease. Of the 170 patients, 91 patients had on imaging metastatic lymph nodes at diagnosis (62 patients pelvic lymph node involvement and 29 para-aortic). In 27 (16%) patients the intracavitary technique was combined with interstitial brachytherapy. ResultsThe mean D90 and D100 for the high-risk CTV were 84.8±8.36Gy and 67.5±6.29Gy for the entire patient group. Mean D90 and D100 values for the IR CTV were 68.7±5.5Gy and 56.5±6.25Gy. There was an important learning curve between both patient groups, with an increase in mean D90 of 75.8Gy for the first 16 patients compared to 85.8Gy for the second group. At the same time, the mean dose to 2cm3 of bladder and sigmoid decreased from 86.1Gy to 82.7Gy and from 70Gy to 61.7Gy, respectively. At a median follow-up of 37months (range 2–136months), local control rate for all patients was 96%, the regional control (pelvic and para-aortic) rate 81% and crude disease free survival rate 55%. The overall survival at 5years is 65%. The higher dose to the target volume resulted in an increase in local control from 88% in the first 16 patients compared to 97% in the second patient group. Regarding late toxicity, 21 patients (12%) presented grade 3–4 late morbidity. Rectal, urinary, sigmoid and vaginal morbidity was 5%, 6%, 2% and 5%, respectively. A correlation between rectal D2cm3 >65Gy and grade >3 late morbidity was found (p=0.006). ConclusionAlthough the majority of the patients presented with locally advanced carcinoma, excellent local and regional control rates were achieved. Rectal, urinary, sigmoid and vaginal grade 3–4 morbidity was 5%, 6%, 2% and 5%, respectively. A correlation between rectal D2cm3 >65Gy and grade >3 late morbidity was found (p=0.006).

Exploring on aqueous chemistry of micron-sized lignite particles in lignite–water slurry: Effects of pH on humics dissolution

The aqueous chemistry of lignite can change the properties of coal–water slurry. The aqueous chemistry of lignite–water slurry including dissolution kinetics of humics and properties of the residual lignite was studied using optical microscope imaging, SEM, FTIR, zeta potential and contact angle analysis. Also, the influence of humics dissolution on the interaction of micron-sized lignite particles was discussed by EDLVO theory. The dissolution kinetics demonstrates that humics concentration increases with increasing the slurry pH. The outer diffusion through the product layer is the rate controlling step according to shrinking unreacted core model. The value of D50 defined as the apparent particle size relevant to 50% of cumulative distribution is decreased when the lignite slurry pH is increased. The FTIR, zeta potential and contact angle results show that humics dissolution increases the surface hydrophilicity of the residual lignite. The total energy ET of the residual lignite particles at 10nm of separation distance is enhanced from −0.70×10−17 to 0.34×10−17J with the humics concentration is increased from 2.28 to 5.33mg/L. The EDLVO calculation indicates that the dispersion stability of micron-sized lignite particles is improved with humics dissolution.

Exploration of design parameters for a dewatering structure for debris flow mitigation

A small-scale flume experiment was conducted to assess the design considerations for a horizontal dewatering debris-flow-brake. Design parameters and a design sequence are suggested, which were previously unavailable in the published literature, and are developed from comparison to other mitigation design strategies and results of laboratory flume experiments. It is concluded that the most important input parameters into the design of a debris-flow dewatering brake are the expected thickness of the debris-flow deposit and the channel shape. The volume of debris that can be stopped and stored by this mitigation design is a function of these parameters as well as channel slope. The thickness of the debris that is arrested on the grate depends on the depositional properties of the debris-flow mass, such as the unit weight of the material, but in small-scale experimentation thickness was not affected by volume of the debris available. The ideal brake is a free draining surface with an aperture smaller than the D90 value for the debris-flow grain-size distribution.

Rapid phase-correlated rescanning irradiation improves treatment time in carbon-ion scanning beam treatment under irregular breathing

To shorten treatment time in pencil beam scanning irradiation, we developed rapid phase-controlled rescanning (rPCR), which irradiates two or more isoenergy layers in a single gating window. Here, we evaluated carbon-ion beam dose distribution with rapid and conventional PCR (cPCR).4 dimensional computed tomography (4DCT) imaging was performed on 12 subjects with lung or liver tumors. To compensate for intrafractional range variation, the field-specific target volume (FTV) was calculated using 4DCT within the gating window (T20–T80). We applied an amplitude-based gating strategy, in which the beam is on when the tumor is within the gating window defined by treatment planning. Dose distributions were calculated for layered phase-controlled rescanning under an irregular respiratory pattern, although a single 4DCT data set was used. The number of rescannings was eight times. The prescribed doses were 48 Gy(RBE)/1 fr (where RBE is relative biological effectiveness) delivered via four beam ports to the FTV for the lung cases and 45 Gy(RBE)/2 fr delivered via two beam ports to the FTV for the liver cases.In the liver cases, the accumulated dose distributions showed an increased magnitude of hot/cold spots with rPCR compared with cPCR. The results of the dose assessment metrics for the cPCR and rPCR were very similar. The D95, Dmax, and Dmin values (cPCR/rPCR) averaged over all the patients were 96.3 ± 0.9%/96.0 ± 1.2%, 107.3 ± 3.6%/107.1 ± 2.9%, and 88.8 ± 3.2%/88.1 ± 3.1%, respectively. The treatment times in cPCR and rPCR were 110.7 s and 53.5 s, respectively.rPCR preserved dose conformation under irregular respiratory motion and reduced the total treatment time compared with cPCR.

In situ sulfur isotopes (δ34S and δ33S) analyses in sulfides and elemental sulfur using high sensitivity cones combined with the addition of nitrogen by laser ablation MC-ICP-MS

The sulfur isotope is an important geochemical tracer in diverse fields of geosciences. In this study, the effects of three different cone combinations with the addition of N2 on the performance of in situ S isotope analyses were investigated in detail. The signal intensities of S isotopes were improved by a factor of 2.3 and 3.6 using the X skimmer cone combined with the standard sample cone or the Jet sample cone, respectively, compared with the standard arrangement (H skimmer cone combined with the standard sample cone). This signal enhancement is important for the improvement of the precision and accuracy of in situ S isotope analysis at high spatial resolution. Different cone combinations have a significant effect on the mass bias and mass bias stability for S isotopes. Poor precisions of S isotope ratios were obtained using the Jet and X cones combination at their corresponding optimum makeup gas flow when using Ar plasma only. The addition of 4–8 ml min−1 nitrogen to the central gas flow in laser ablation MC-ICP-MS was found to significantly enlarge the mass bias stability zone at their corresponding optimum makeup gas flow in these three different cone combinations. The polyatomic interferences of OO, SH, OOH were also significantly reduced, and the interference free plateaus of sulfur isotopes became broader and flatter in the nitrogen mode (N2 = 4 ml min−1). However, the signal intensity of S was not increased by the addition of nitrogen in this study. The laser fluence and ablation mode had significant effects on sulfur isotope fractionation during the analysis of sulfides and elemental sulfur by laser ablation MC-ICP-MS. The matrix effect among different sulfides and elemental sulfur was observed, but could be significantly reduced by line scan ablation in preference to single spot ablation under the optimized fluence. It is recommended that the d90 values of the particles in pressed powder pellets for accurate and precise S isotope analysis should be less than 10 μm. Under the selected optimized analytical conditions, excellent agreements between the determined values and the reference values were achieved for the IAEA-S series standard reference materials and a set of six well-characterized, isotopic homogeneous sulfide standards (PPP-1, MoS2, MASS-1, P-GBW07267, P-GBW07268, P-GBW07270), validating the capability of the developed method for providing high-quality in situ S isotope data in sulfides and elemental sulfur.

Comparative study of late rectal toxicity in veterans undergoing low-dose rate prostate brachytherapy treated with or without supplemental external beam radiotherapy.

112 Background: Supplemental external beam radiation therapy (sEBRT) is often prescribed in men undergoing low dose rate (LDR) brachytherapy for prostate cancer. A population of patients was analyzed to assess the effect of sEBRT on late rectal toxicity. It was hypothesized that sEBRT+LDR would be associated with a higher risk of late rectal toxicity, compared to LDR brachytherapy alone. Methods: This retrospective cohort study examined LDR brachytherapy patients, treated with or without sEBRT, with a minimum of 5 years follow-up. All were treated at a credentialed Veterans Affairs medical center that enrolled many of these patients on RTOG 0234. Longitudinal assessments were evaluated using the Computerized Patient Record System, and toxicities were coded using the CTCAE v4.0. The Kaplan-Meier method was used for analysis. Results: Median follow-up was 7.5 years for 245 consecutive patients from 2004 and 2007. sEBRT was administered to 33.5%. Follow-up beyond 5 years was available for 89%. Overall rates of grade ≥ 2 and ≥ 3 rectal toxicities were 6.9% and 2.9%, respectively. The risk of grade ≥ 2 rectal toxicity was 2.8-fold higher for patients receiving sEBRT (1.1 - 7.2, 95% CI, p = 0.02). The risk of grade ≥ 3 rectal toxicity was 11.9-fold higher for patients who received sEBRT (1.5 - 97.4, 95% CI, p = 0.003). Six out of 7 patients with a grade ≥ 3 rectal toxicity received sEBRT, including one who required an abdominoperineal resection due to radiation proctopathy. The median post-LDR D90, V150, V200, and R100 values were 103.3%, 59.4%, 30.1%, and 0.5 cc. The minimum R100 associated with a grade ≥ 2 toxicity was 0.2 cc, and the minimum R100 for a grade ≥ 3 toxicity was 0.4 cc. Grade ≥ 2 rectal toxicity was seen in 3% vs 13% of patients who had post-implant dosimetry of R100 < 1 cc vs R100≥ 1 cc, respectively. Conclusions: In a cohort of LDR brachytherapy patients with high rates of follow-up, sEBRT+LDR was associated with significantly higher risk of grade ≥ 2 and ≥ 3 late rectal toxicity. This analysis supports previous findings and maintains concern about the supplemental use of EBRT with LDR brachytherapy while its benefit for tumor control has yet to be prospectively validated.

The influence of particle size on some physicochemical, rheological and melting properties and volatile compound profile of compound chocolate and cocolin samples

Compound chocolate and cocolin are widely used chocolate-derived products. However, we have not encountered any study about the influence of the particle size on the various quality parameters of these products. The aim of this study was to determine the effects of particle size on some physical (color properties, particle size distribution, rheology, microstructure and melting properties) and chemical properties (phenolic content, volatile composition and also FT-IR spectra of fats) of compound chocolate and cocolin samples. Refining level did not significantly affect color and melting properties, total phenolic content, thermal properties and FT-IR spectra of the fats extracted from the samples. D 90 values of compound chocolates and cocolins changed between 58.3–18.6 and 60.5–18.2 µm, respectively. Surface area of the samples also increased with refining process. Obtained rheological data were fitted to the Casson model with R 2 values ranged between 0.9863 and 0.999, and the corresponding parameters of the model, namely yield stress (τ 0) and plastic viscosity (η pl), significantly increased with decreasing particle size of the samples. Temperature sweep test was also performed, and temperature dependency of apparent viscosity of the samples changed with respect to refining process applied. Volatile composition of the samples was also determined by HS-SPME–GC/MS, and it concluded that both desired such as pyrazines and undesired such as acetic acid compounds for chocolate changed inversely proportional to particle size. According to the findings of the present study, it can be concluded that refining process and particle size are very substantial factors affecting the quality characteristics of the compound chocolate and cocolin samples.

Experimental investigation of fracture width limitations of granular lost circulation treatments

Drilling fluid losses into fractured shales is a major challenge. Lost circulation treatments are widely applied to mitigate the losses; however, the effectiveness of these treatments is affected by different physical properties of the used lost circulation materials (LCM). This paper presents an experimental investigation to study the effect of LCM type, concentration, particle size distribution, temperature, and LCM shape on the formed seal integrity, with respect to differential pressure, at different fracture widths. The overall objective of this study is to address the effectiveness of LCM treatments in sealing fractured shales, with specific application to the over consolidated Barents Sea overburden. Three commonly used LCMs that vary in size were used to formulate and evaluate the effectiveness of nine LCM blends. Nutshell blends effectively sealed different fracture widths with high seal integrities. Examination of the formed seal under an optical microscope and a scanning electron microscope revealed that this performance is due to the irregular shapes of these materials as well as their ability to deform under elevated pressure. Based on the results, it has been found that to effectively seal fractures using granular LCM treatments, the D90 value should be equal or slightly larger than the anticipated fracture width. However, due to both the increased risk of plugging downhole tools and the availability of larger LCM, granular LCM treatments can only be used to seal fractures up to 2000 microns. With the current limitations, other unconventional treatments are required to seal fractures wider than 2000 microns.

Dosimetric study for cervix carcinoma treatment using intensity modulated radiation therapy (IMRT) compensation based on 3D intracavitary brachytherapy technique.

PurposeIntensity modulated radiation therapy (IMRT) compensation based on 3D high-dose-rate (HDR) intracavitary brachytherapy (ICBT) boost technique (ICBT + IMRT) has been used in our hospital for advanced cervix carcinoma patients. The purpose of this study was to compare the dosimetric results of the four different boost techniques (the conventional 2D HDR intracavitary brachytherapy [CICBT], 3D optimized HDR intracavitary brachytherapy [OICBT], and IMRT-alone with the applicator in situ).Material and methodsFor 30 patients with locally advanced cervical carcinoma, after the completion of external beam radiotherapy (EBRT) for whole pelvic irradiation 45 Gy/25 fractions, five fractions of ICBT + IMRT boost with 6 Gy/fractions for high risk clinical target volume (HRCTV), and 5 Gy/fractions for intermediate risk clinical target volume (IRCTV) were applied. Computed tomography (CT) and magnetic resonance imaging (MRI) scans were acquired using an in situ CT/MRI-compatible applicator. The gross tumor volume (GTV), the high/intermediate-risk clinical target volume (HRCTV/IRCTV), bladder, rectum, and sigmoid were contoured by CT scans.ResultsFor ICBT + IMRT plan, values of D90, D100 of HRCTV, D90, D100, and V100 of IRCTV significantly increased (p < 0.05) in comparison to OICBT and CICBT. The D2cc values for bladder, rectum, and sigmoid were significantly lower than that of CICBT and IMRT alone. In all patients, the mean rectum V60 Gy values generated from ICBT + IMRT and OICBT techniques were very similar but for bladder and sigmoid, the V60 Gy values generated from ICBT + IMRT were higher than that of OICBT. For the ICBT + IMRT plan, the standard deviations (SD) of D90 and D2cc were found to be lower than other three treatment plans.ConclusionsThe ICBT + IMRT technique not only provides good target coverage but also maintains low doses (D2cc) to the OAR. ICBT + IMRT is an optional technique to boost parametrial region or tumor of large size and irregular shape when intracavitary/interstitial brachytherapy cannot be used.

Preparation, characterization, and in vivo evaluation of valsartan porous matrices using emulsion solvent evaporation technique.

Introduction:Valsartan is a type II Biopharmaceutics Classification System (BCS) classified drug. The poor aqueous solubility restricts its use in developing sustained or controlled release systems for the treatment of chronic hypertensive conditions. The present investigation was conducted with an objective to formulate porous matrices (PMs) of valsartan in order to enhance aqueous solubility.Materials and Methods:Polyvinylpyrrolidone (PVP) K30 and poloxamer 407 were used as hydrophilic carriers; hexane was used as a pore-forming agent, ethanol was used as a solvent, and tween 20 was used as an emulgent. The prepared porous matrices were characterized and based on the maximum slope obtained from the Washburn method and other characterization results; the drug PVP K30 (1:1.5) was selected and further evaluated in vivo by the rat gut method.Results:The prepared porous matrices are white, free-flowing powders. Among prepared formulations drug PVP K30 (1:1.5) showed maximum Washburn slope of 0.0103. The mean particle size was found to be 0.82 μ and D50 (median) value was found to be 0.55 μ. The scanning of particles at various magnifications by scanning electron microscopy (SEM) analysis revealed that the method had effectively induced porosity. The Q value of valsartan from porous matrices was observed at 20 min with a first order regression value of 0.917. The calculated difference factor (F1) when compared with pure valsartan was observed to be 63.32%. From the values obtained, it was evident that the method amplifies the percentage of drug dissolution between sixfold and eightfold when compared to pure drug. From the absorption studies by the rat gut method, the absorption of porous matrices increased threefold.Conclusion:Porous matrices of valsartan: PVP K30 (1:1.5 ratio) hold promise for the enhancement of solubility and consecutive formulation of controlled release systems even with poorly soluble drugs.

Salvage interstitial brachytherapy based on computed tomography for recurrent cervical cancer after radical hysterectomy and adjuvant radiation therapy: case presentations and introduction of the technique.

PurposeLocally recurring cervical cancer after surgery and adjuvant radiotherapy remains a major therapeutic challenge. This paper presents a new therapeutic technique for such patients: interstitial brachytherapy (BT) guided by real-time three-dimensional (3D) computed tomography (CT).Material and methodsSixteen patients with recurrent cervical cancer after radical surgery and adjuvant external-beam radiotherapy (EBRT) were included in this study. These patients underwent high-dose-rate (HDR) interstitial BT with free-hand placement of metal needles guided by real-time 3D-CT. Six Gy in 6 fractions were prescribed for the high-risk clinical target volume (HR-CTV). D90 and D100 for HR-CTV of BT, and the cumulative D2cc for the bladder, rectum, and sigmoid, including previous EBRT and present BT were analyzed. Treatment-related complications and 3-month tumor-response rates were investigated.ResultsThe mean D90 value for HR-CTV was 52.5 ± 3.3 Gy. The cumulative D2cc for the bladder, rectum, and sigmoid were 85.6 ± 5.8, 71.6 ± 6.4, and 69.6 ± 5.9 Gy, respectively. The mean number of needles was 6.1 ± 1.5, with an average depth of 3.5 ± 0.9 cm for each application. Interstitial BT was associated with minor complications and passable tumor-response rate.ConclusionsInterstitial BT guided by real-time 3D-CT for recurrent cervical cancer results in good dose-volume histogram (DVH) parameters. The current technique may be clinically feasible. However, long-term clinical outcomes should be further investigated.

Dosimetry study of three-dimensional print template-guided precision 125I seed implantation.

This study aimed to compare the dose difference in 125 I seed implantation between three-dimensional (3D) print template-guided operation and traditional implantation. This study retrospectively analyzed 27 patients who underwent 125I seed implantation from August 2015 to December 2015 in Hebei General Hospital. Of these, 13 underwent seed implantation guided by a 3D print template, named the template group, and 14 underwent traditional implantation, named the traditional group. All patients underwent computed tomography (CT) scan. Then, 3D templates were printed in the template group. The implantation was guided by CT and 3D templates. The patients in the traditional group underwent implantation with free hands guided by CT scan. Postplan was performed after the operation. The dose-volume histogram, D90, and V90 were calculated. The D90 values pre- and post-operation were compared in each group. The postoperation V90 values of the two groups were also compared. The mean D90 values pre- and post-operation in the template group were (87.09 ± 33.63) Gy and (85.31 ± 34.40) Gy, respectively, with no statistically significant difference. The mean D90 values pre- and post-operation in the traditional group were (86.04 ± 29.93) Gy and (74.96 ± 46.10) Gy, respectively, with a statistically significant difference. The mean V90 values postoperation in the template and traditional groups were (92.76% ± 1.89%) and (84.59% ± 7.56%), respectively, with a statistically significant difference. The postplan and preplan dose parameters of 3D print template-guided seed implantation were nearly consistent. The dose parameters of template group superior to the traditional group. The seeds can be implanted accurately with 3D print template.

Tungsten carbide powder obtained by direct carburization of tungsten trioxide using mechanical alloying method

Tungsten carbide is widely used in the production of cutting tools and parts with very good resistance to wear. It is well known that the properties of sintered carbides are closely related to the carbide particles size. Tungsten carbide production is a laborious process, which always includes a milling step. This article aims to study the manufacturing of tungsten carbide by carburizing tungsten trioxide using mechanical alloying (MA) method, thus concentrating the process in one step. Experimental tests were performed with a Fritch planetary mill and complete conversion of tungsten trioxide in carbide was observed after 30 h of milling. The average value of D50 for the synthetized WC is 6.73 ± 0.62 μm.

Associations between Classroom Conditions and Teacher's Voice Production

In this study, associations between classroom conditions and teachers’ voce use were researched (N=40). Acoustic variables were reverberation time (T60), early decay time (EDT), sound strength (G), the ratio of early and late sound energy arriving to a listener (C50), the ratio of early arriving sound energy to overall sound energy (D50), speech transmission index (STI) and rate of spatial decay of sound pressure levels (DL2). Indoor climate was also evaluated. Voice variables measured were sound pressure level (SPL), fundamental frequency (F0) and spectrum slope. According to findings when the values of T60, EDT and DL2 were lower or the values of C50, D50 and G higher, teachers’ voice SPL was higher. When reverberation times were longer, F0 increased and when the values of C50 and D50 were higher, men's F0 was higher. Poor indoor air increased occurrence of laryngitis. The results showed that indoor environment affects voice use and thus, is associated with the health of voice organs.

Hepatic reaction dose for parenchymal changes on Gd-EOB-DTPA-enhanced magnetic resonance images after stereotactic body radiation therapy for hepatocellular carcinoma.

The present study evaluated the threshold dose for hepatic parenchymal changes on gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) images after stereotactic body radiation therapy (SBRT) for hepatocellular carcinoma (HCC). Twenty patients with available data of follow-up MR images acquired 2-4 months after completion of SBRT were selected among the registered patients. SBRT was performed using multiple coplanar and non-coplanar beams with energies of 6 or 15 MV. All patients were treated with doses of 45 Gy administered in three fractions over 3 consecutive days. For image registration between planning computed tomography (CT) and MR images, landmark-based rigid body registration was performed using MIM software. Seventeen patients were included in the analysis. The median discrepancies between planning CT and MR images in the left-right, anterior-posterior and superior-inferior directions were 1.38 mm, 1.24 mm and 1.72 mm, respectively. The median D50 value for the defect in the hepatobiliary phase of Gd-EOB-DTPA-enhanced MR images after SBRT was 19.8 Gy (range, 14.2-28.7 Gy), with R(2) values ranging from 0.76 to 0.99. The threshold dose for parenchymal changes in the hepatobiliary phase of Gd-EOB-DTPA-enhanced MR images performed 2-4 months after 45 Gy of SBRT in three fractions was approximately 20 Gy. Our results provide the basis for further research on the functional loss of liver parenchyma after SBRT.

Novel latex particles and aluminum complexes as potential shale stabilizers in water-based drilling fluids

Abstract In this paper, novel latex particles and aluminum complexes as potential shale stabilizers in water-based drilling fluids were successfully synthesized and characterized in detail. The spherical latex particles were prepared by emulsifier-free polymerization of styrene and methyl methacrylate, and it possessed uni-modal distribution from 80 nm to 345 nm with the D90 value of 276 nm. The aluminum complexes were synthesized through the complexation reaction of humic acid with sodium aluminate and it could be completely soluble under alkaline conditions, and aluminum hydroxide and humic acid flocculate would precipitate from the filtrate under neutral or acidic conditions or interacting with magnesium or calcium ion. The synergistic effect on shale stability of latex particles and aluminum complexes was investigated quantitatively through the pressure transmission and membrane efficiency tests. The pore structure of shale cores before and after testing was also characterized via nuclear magnetic resonance core analysis and scanning electron microscope analysis. The results indicated that the latex particles as physical shale stabilizer could be deformable to internally bridge and seal micro–nano scale pore-throats and fractures of shale, and the aluminum complexes as chemical shale stabilizer would precipitate from the filtrate when exposed to pore–fluids and the precipitation could also plug and seal pore-throats and micro-fractures. The latex particles work synergistically with aluminum complexes to impart shale stability due to superior properties of decreasing shale permeability and increasing shale membrane efficiency. Furthermore, the compatible test results confirmed that novel latex particles and aluminum complexes could be alternatives to standard shale stabilizers in water-based drilling fluids.

Association between long-term erectile dysfunction and biochemical recurrence after permanent seed I125 implant brachytherapy for prostate cancer. A longitudinal study of a single-institution

We aimed to investigate the predictive factor of erectile dysfunction (ED) in prostate cancer (PCa) patients who underwent low-dose permanent I125 seed implant brachytherapy and to investigate if ED could represent a patient’s reported outcome measures (PROMs) of efficacy of BT and indirectly associated with biochemical recurrence free survival (BRFS). From 2000 to 2012, 176 consecutive patients with low-risk PCa underwent BT. ED was evaluated with the International Index of Erectile Function (IIEF-5). Cox regression analysis was performed to assess significant predictors of mild-to-severe ED and BRFS after BT, including covariates. The 10-year actuarial rate of ED was 66%. Subjects with severe ED had higher values of D90 (183.0 versus 177.0; p < 0.05) and V100% (40.1 versus 31.4; p < 0.05) compared with normal. At the multivariate logistic regression analysis, D90 (OR: 1.10; p < 0.05) was an independent predictor of ED. Multivariate Cox-regression analysis did not demonstrate significant association between erectile preservation and biochemical recurrence (BCR) after 10 years of follow up (HR: 2.15; p = 0.20), while D90 ≤ 180 Gy independently predicted BCR (HR: 4.65; [95%CI: 1.25–17.34]; p < 0.05). Erectile preservation should be addressed as valuable PROMs after permanent seed I125 implant, but it is not associated with better BRFS.

Use a survival model to correlate single-nucleotide polymorphisms of DNA repair genes with radiation dose–response in patients with non-small cell lung cancer

PurposeThis study utilizes a survival model and clinical data with various radiation doses from prospective trials to determine radiation dose–response parameters, such as radiosensitivity, and identify single-nucleotide-polymorphism (SNP) biomarkers that can potentially predict the dose response and guide personalized radiotherapy. MethodsThe study included 92 consecutive stage-III NSCLC patients with doses varying from 60 to 91Gy. Logistic regression analysis of survival varying with SNP genotype and radiation dose was used to screen candidates for dose–response analysis. The dose–response parameter, represented by D50, was derived by fitting survival data into a model that takes into account both tumor control and treatment mortality. A candidate would be considered as a predictor if the 90% confident intervals (90% CIs) of D50 for the 2 groups stratified by the SNP genotype were separated. ResultsOne SNP-signature (combining ERCC2:rs238406 and ERCC1:rs11615) was found to predict dose–response. D50 values are 63.7 (90% CI: 53.5–66.3) Gy and 76.1 (90% CI: 71.3, 84.6) Gy for the 2 groups stratified by the genotypes. Using this biomarker-based model, a personalized dose prescription may be generated to improve 2-year survival from ∼50% to 85% and ∼3% to 73% for hypothetical sensitive and resistant patients, respectively. ConclusionsWe have developed a survival model that may be used to identify genomic markers, such as ERCC1/2 SNPs, to predict radiation dose–response and potentially guide personalized radiotherapy.

Single-Isocenter Multiple-Target Stereotactic Radiosurgery: Risk of Compromised Coverage

To determine the dosimetric effects of rotational errors on target coverage using volumetric modulated arc therapy (VMAT) for multitarget stereotactic radiosurgery (SRS). This retrospective study included 50 SRS cases, each with 2 intracranial planning target volumes (PTVs). Both PTVs were planned for simultaneous treatment to 21 Gy using a single-isocenter, noncoplanar VMAT SRS technique. Rotational errors of 0.5°, 1.0°, and 2.0° were simulated about all axes. The dose to 95% of the PTV (D95) and the volume covered by 95% of the prescribed dose (V95) were evaluated using multivariate analysis to determine how PTV coverage was related to PTV volume, PTV separation, and rotational error. At 0.5° rotational error, D95 values and V95 coverage rates were ≥95% in all cases. For rotational errors of 1.0°, 7% of targets had D95 and V95 values <95%. Coverage worsened substantially when the rotational error increased to 2.0°: D95 and V95 values were >95% for only 63% of the targets. Multivariate analysis showed that PTV volume and distance to isocenter were strong predictors of target coverage. The effects of rotational errors on target coverage were studied across a broad range of SRS cases. In general, the risk of compromised coverage increased with decreasing target volume, increasing rotational error and increasing distance between targets. Multivariate regression models from this study may be used to quantify the dosimetric effects of rotational errors on target coverage given patient-specific input parameters of PTV volume and distance to isocenter.