4 results
Comparison of conventional and hypofractionated radiation after mastectomy in locally advanced breast cancer: a prospective randomised study on dosimetric evaluation and treatment outcome
- Sumana Maiti, Suman Meyur, Bidhan Chandra Mandal, Lekshmi R Shenoi, Susmita Biswas, Siddhartha Basu
-
- Journal:
- Journal of Radiotherapy in Practice / Volume 20 / Issue 1 / March 2021
- Published online by Cambridge University Press:
- 17 January 2020, pp. 30-38
-
- Article
- Export citation
-
Background:
Although hypofractionated radiotherapy has been standardised in early breast cancer, even in post-mastectomy no such consensus has been developed for locally advanced breast cancer (LABC), probably due to complex planning and field matching. This study is directed towards dosimetric evaluation and comparison of toxicity, response and disease-free survival (DFS) comparison between hypofractionation and conventional radiotherapy in post-mastectomy LABC.
Methodology:In total, 222 female breast cancer patients were randomly assigned to be treated with either hypofractionated radiotherapy (n = 120) delivering 40 Gy in 15 fractions over 3 weeks or conventional radiotherapy (n = 102) with 50 Gy in 25 fractions over 5 weeks after modified radical mastectomy (MRM) along with neoadjuvant and/or adjuvant chemotherapy. All patients were planned with treatment planning software and assessed regularly during and after treatment.
Results:Median follow-up period was 178 weeks in conventional arm (CRA) and 182 weeks in hypofractionation arm (HFA). There exists a dosimetric difference between the two arms of treatment, in spite of similar dose coverage [planning treatment volume (PTV) D90 92·04% in CRA versus 92·5% in HFA; p = 0·49], average dose in HFA is less than that of CRA (p < 0·001); so is the maximum clinical target volume (CTV) dose (p < 0·001). Similarly, average lung dose in HFA arm is significantly lower than CRA (9·9 versus 10·84; p = 0·06), but the V20Gy of lung and V30Gy of heart had no difference. The toxicity of radiation was comparable with similar mean time to produce toxicity [CRA: 7 W, HFA: 10 W; hazard ratio 0·64, 95% confidence interval (CI) = 0·28–1·45]. Three-year recurrence event was alike in two arms (CRA: 4·9%, HFA: 5·8%; p = 0·76). Mean DFS in CRA is 230 weeks and that of HFA is 235 weeks with hazard ratio 1·01 (95% CI = 0·32–3·19; p = 0·987).
Conclusion:Though biologically effective dose (BED) in hypofractionation is lesser than that of conventional fractionation, there are indistinguishable toxicity, locoregional recurrence, distant failure rate and DFS between the two modalities.
Early transition, relaminarization and drag reduction in the flow of polymer solutions through microtubes
- Bidhan Chandra, V. Shankar, Debopam Das
-
- Journal:
- Journal of Fluid Mechanics / Volume 885 / 25 February 2020
- Published online by Cambridge University Press:
- 10 January 2020, A47
-
- Article
- Export citation
-
Experiments are performed to investigate the onset of early transition and drag reduction in the flow of polymer (polyacrylamide and polyethylene oxide) solutions through rigid microtubes of diameters in the range 0.49–2.84 mm. We measure friction factor variation with Reynolds number for varying polymer concentrations and tube diameters, and the Reynolds number,
$Re_{t}$, at which the experimental data deviate from the laminar value represents the onset of transition. Crucially, owing to the high shear rates encountered in our experiments, we show that it is important to account for shear thinning of the fluid in the theoretical estimation of the friction factor in the laminar regime. We accomplish this using a Carreau model, and show that the use of laminar friction factor calculated without shear thinning leads to an erroneous overestimation of
$Re_{t}$. The
$Re_{t}$ obtained from friction factor data in the present study is in good agreement with that inferred using micro particle image velocimetry analysis in Chandra et al. (J. Fluid Mech., vol. 844, 2018, pp. 1052–1083). For smaller concentrations of the added polymer, there is a marginal delay in the onset of turbulence, but as the concentration is increased further, the transition Reynolds number decreases much below
$2000$, the usual value at which transition occurs in Newtonian pipe flows. Thus, the present study further corroborates the phenomenon of early transition leading to an ‘elasto-inertial’ turbulent state in the flow of polymer solutions. For concentrations such that there is a delay in transition, if
$Re$ is maintained above the
$Re_{t}$ for Newtonian fluids, the flow is transitional or turbulent in the absence of polymers. At such a fixed
$Re$, if the concentration of the polymer is increased gradually, the friction factor decreases and the flow relaminarizes. With further increase in polymer concentration, the flow undergoes a transition due to elasto-inertial instability. The effect of addition of small amounts of polymer on turbulent drag reduction in the flow of water through microtubes is also investigated. Increase in polymer concentration, molecular weight and decrease in tube diameter causes an increase in drag reduction. The friction factor data for different polymer concentrations, molecular weights, tube diameters and
$Re$, when plotted with
$Wi(1-\unicode[STIX]{x1D6FD})$, show a reasonable collapse, where
$Wi$ is the Weissenberg number defined as the product of the longest relaxation time of the polymer solution and the average shear rate in the tube and
$\unicode[STIX]{x1D6FD}$ is the ratio of solvent to total solution viscosity. Interestingly, the onset of the maximum drag reduction asymptote, for experiments using varying tube diameters and polymer concentrations, appears to occur at
$Wi(1-\unicode[STIX]{x1D6FD})\sim O(1)$.
Onset of transition in the flow of polymer solutions through microtubes
- Bidhan Chandra, V. Shankar, Debopam Das
-
- Journal:
- Journal of Fluid Mechanics / Volume 844 / 10 June 2018
- Published online by Cambridge University Press:
- 16 April 2018, pp. 1052-1083
-
- Article
- Export citation
-
Experiments are performed to characterize the onset of laminar–turbulent transition in the flow of high-molecular-weight polymer solutions in rigid microtubes of diameters in the range
$390~\unicode[STIX]{x03BC}\text{m}{-}470~\unicode[STIX]{x03BC}\text{m}$ using the micro-PIV technique. By considering flow in tubes of such small diameters, the present study probes higher values of elasticity numbers (
$E\equiv \unicode[STIX]{x1D706}\unicode[STIX]{x1D708}/R^{2}$) compared to existing studies, where
$\unicode[STIX]{x1D706}$ is the longest relaxation time of the polymer solution,
$R$ is the tube radius and
$\unicode[STIX]{x1D708}$ is the kinematic viscosity of the polymer solution. For the Newtonian case, our experiments indicate that the natural transition (without the aid of any forcing mechanism) occurs at Reynolds number (
$Re$)
$2000\pm 100$. As the concentration of polymer is increased, initially there is a delay in the onset of the transition and the transition Reynolds number increases to
$2500$. Further increase in concentration of the polymer results in a decrease in the Reynolds number for transition. At sufficiently high concentrations, the added polymer tends to destabilize the flow and the transition is observed to happen at
$Re$ as low as
$800$. It is also observed that the addition of polymers, regardless of their concentration, reduces the magnitude of the velocity fluctuations after transition. Dye-stream visualization is further used to corroborate the onset of transition in the flow of polymer solutions. The present work thus shows that addition of polymer, at sufficiently high concentrations, destabilizes the flow when compared to that of a Newtonian fluid, thereby providing additional evidence for ‘early transition’ or ‘elasto-inertial turbulence’ in the flow of polymer solutions. The data for the transition Reynolds number
$Re_{t}$ from our experiments (for tubes of different diameters, and for two different polymers at varying concentrations) collapse well according to the scaling relation
$Re_{t}\propto 1/\sqrt{E(1-\unicode[STIX]{x1D6FD})}$, where
$\unicode[STIX]{x1D6FD}$ is the ratio of solvent viscosity to the viscosity of the polymer solution.
Environmental and Familial Risk Factors of Parkinsons Disease: Case-Control Study
- Jaya Sanyal, D. P. Chakraborty, Biswanath Sarkar, Tapas Kumar Banerjee, Subhash Chandra Mukherjee, Bidhan Chandra Ray, V. R. Rao
-
- Journal:
- Canadian Journal of Neurological Sciences / Volume 37 / Issue 5 / September 2010
- Published online by Cambridge University Press:
- 02 December 2014, pp. 637-642
-
- Article
-
- You have access Access
- Export citation
-
Background:
While the cause of Parkinson's disease (PD) remains unknown, evidence suggests certain environmental factors, such as well water drinking, herbicides, pesticides exposure and neurotoxins, may trigger the chain of oxidative reactions culminating in the death of dopaminergic neurons in substantia nigra to cause Parkinsonism. To investigate the possible impact of environmental risk factors for idiopathic PD, a case-control study was performed in the Eastern India.
Methods:During the period from January 1st, 2006 and December 10th, 2009, 175 PD patients (140 men, 35 women) and 350 non-Parkinson age-sex matched controls were included in the study. Subjects were given a structured neurological examination and completed an administered questionnaire which elicited detailed information on demographic data, pesticides, herbicides family history, occupation, dietary and smoking habits.
Results:The multivariate analysis revealed that family history of PD, pesticide exposure, exposure to toxins other than pesticides and herbicides, rural living and previous history of depression were associated with increased risk of PD, whereas, smoking appeared to be a protective factor. Well water drinking for at least five years, though a significant risk factor on univariate analysis (OR=4.5, 95% CI=2.1-9.9), could not be proved significant in multivariate analysis. Head trauma, vegetarian dietary habit, occupation involving physical exertion and exposure to domestic pets were not as significant risk factors.
Conclusion:Results of our study support the hypothesis of multifactorial etiology of PD with environmental factors acting on a genetically susceptible host.
![](/core/cambridge-core/public/images/lazy-loader.gif)