Journal of Clinical and Diagnostic Research, ISSN - 0973 - 709X

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On Sep 2018




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"Journal of Clinical and Diagnostic Research is at present a well-known Indian originated scientific journal which started with a humble beginning. I have been associated with this journal since many years. I appreciate the Editor, Dr. Hemant Jain, for his constant effort in bringing up this journal to the present status right from the scratch. The journal is multidisciplinary. It encourages in publishing the scientific articles from postgraduates and also the beginners who start their career. At the same time the journal also caters for the high quality articles from specialty and super-specialty researchers. Hence it provides a platform for the scientist and researchers to publish. The other aspect of it is, the readers get the information regarding the most recent developments in science which can be used for teaching, research, treating patients and to some extent take preventive measures against certain diseases. The journal is contributing immensely to the society at national and international level."



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On Aug 2018




Dr. Arundhathi. S
"Journal of Clinical and Diagnostic Research (JCDR) is a reputed peer reviewed journal and is constantly involved in publishing high quality research articles related to medicine. Its been a great pleasure to be associated with this esteemed journal as a reviewer and as an author for a couple of years. The editorial board consists of many dedicated and reputed experts as its members and they are doing an appreciable work in guiding budding researchers. JCDR is doing a commendable job in scientific research by promoting excellent quality research & review articles and case reports & series. The reviewers provide appropriate suggestions that improve the quality of articles. I strongly recommend my fraternity to encourage JCDR by contributing their valuable research work in this widely accepted, user friendly journal. I hope my collaboration with JCDR will continue for a long time".



Dr. Arundhathi. S
MBBS, MD (Pathology),
Sanjay Gandhi institute of trauma and orthopedics,
Bengaluru.
On Aug 2018




Dr. Mamta Gupta,
"It gives me great pleasure to be associated with JCDR, since last 2-3 years. Since then I have authored, co-authored and reviewed about 25 articles in JCDR. I thank JCDR for giving me an opportunity to improve my own skills as an author and a reviewer.
It 's a multispecialty journal, publishing high quality articles. It gives a platform to the authors to publish their research work which can be available for everyone across the globe to read. The best thing about JCDR is that the full articles of all medical specialties are available as pdf/html for reading free of cost or without institutional subscription, which is not there for other journals. For those who have problem in writing manuscript or do statistical work, JCDR comes for their rescue.
The journal has a monthly publication and the articles are published quite fast. In time compared to other journals. The on-line first publication is also a great advantage and facility to review one's own articles before going to print. The response to any query and permission if required, is quite fast; this is quite commendable. I have a very good experience about seeking quick permission for quoting a photograph (Fig.) from a JCDR article for my chapter authored in an E book. I never thought it would be so easy. No hassles.
Reviewing articles is no less a pain staking process and requires in depth perception, knowledge about the topic for review. It requires time and concentration, yet I enjoy doing it. The JCDR website especially for the reviewers is quite user friendly. My suggestions for improving the journal is, more strict review process, so that only high quality articles are published. I find a a good number of articles in Obst. Gynae, hence, a new journal for this specialty titled JCDR-OG can be started. May be a bimonthly or quarterly publication to begin with. Only selected articles should find a place in it.
An yearly reward for the best article authored can also incentivize the authors. Though the process of finding the best article will be not be very easy. I do not know how reviewing process can be improved. If an article is being reviewed by two reviewers, then opinion of one can be communicated to the other or the final opinion of the editor can be communicated to the reviewer if requested for. This will help one’s reviewing skills.
My best wishes to Dr. Hemant Jain and all the editorial staff of JCDR for their untiring efforts to bring out this journal. I strongly recommend medical fraternity to publish their valuable research work in this esteemed journal, JCDR".



Dr. Mamta Gupta
Consultant
(Ex HOD Obs &Gynae, Hindu Rao Hospital and associated NDMC Medical College, Delhi)
Aug 2018




Dr. Rajendra Kumar Ghritlaharey

"I wish to thank Dr. Hemant Jain, Editor-in-Chief Journal of Clinical and Diagnostic Research (JCDR), for asking me to write up few words.
Writing is the representation of language in a textual medium i e; into the words and sentences on paper. Quality medical manuscript writing in particular, demands not only a high-quality research, but also requires accurate and concise communication of findings and conclusions, with adherence to particular journal guidelines. In medical field whether working in teaching, private, or in corporate institution, everyone wants to excel in his / her own field and get recognised by making manuscripts publication.


Authors are the souls of any journal, and deserve much respect. To publish a journal manuscripts are needed from authors. Authors have a great responsibility for producing facts of their work in terms of number and results truthfully and an individual honesty is expected from authors in this regards. Both ways its true "No authors-No manuscripts-No journals" and "No journals–No manuscripts–No authors". Reviewing a manuscript is also a very responsible and important task of any peer-reviewed journal and to be taken seriously. It needs knowledge on the subject, sincerity, honesty and determination. Although the process of reviewing a manuscript is a time consuming task butit is expected to give one's best remarks within the time frame of the journal.
Salient features of the JCDR: It is a biomedical, multidisciplinary (including all medical and dental specialities), e-journal, with wide scope and extensive author support. At the same time, a free text of manuscript is available in HTML and PDF format. There is fast growing authorship and readership with JCDR as this can be judged by the number of articles published in it i e; in Feb 2007 of its first issue, it contained 5 articles only, and now in its recent volume published in April 2011, it contained 67 manuscripts. This e-journal is fulfilling the commitments and objectives sincerely, (as stated by Editor-in-chief in his preface to first edition) i e; to encourage physicians through the internet, especially from the developing countries who witness a spectrum of disease and acquire a wealth of knowledge to publish their experiences to benefit the medical community in patients care. I also feel that many of us have work of substance, newer ideas, adequate clinical materials but poor in medical writing and hesitation to submit the work and need help. JCDR provides authors help in this regards.
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Indexation and online availability: Indexation transforms the journal in some sense from its local ownership to the worldwide professional community and to the public.JCDR is indexed with Embase & EMbiology, Google Scholar, Index Copernicus, Chemical Abstracts Service, Journal seek Database, Indian Science Abstracts, to name few of them. Manuscriptspublished in JCDR are available on major search engines ie; google, yahoo, msn.
In the era of fast growing newer technologies, and in computer and internet friendly environment the manuscripts preparation, submission, review, revision, etc and all can be done and checked with a click from all corer of the world, at any time. Of course there is always a scope for improvement in every field and none is perfect. To progress, one needs to identify the areas of one's weakness and to strengthen them.
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Every one of us: authors, reviewers, editors, and publisher are responsible for enhancing the stature of the journal. I wish for a great success for JCDR."



Thanking you
With sincere regards
Dr. Rajendra Kumar Ghritlaharey, M.S., M. Ch., FAIS
Associate Professor,
Department of Paediatric Surgery, Gandhi Medical College & Associated
Kamla Nehru & Hamidia Hospitals Bhopal, Madhya Pradesh 462 001 (India)
E-mail: drrajendrak1@rediffmail.com
On May 11,2011




Dr. Shankar P.R.

"On looking back through my Gmail archives after being requested by the journal to write a short editorial about my experiences of publishing with the Journal of Clinical and Diagnostic Research (JCDR), I came across an e-mail from Dr. Hemant Jain, Editor, in March 2007, which introduced the new electronic journal. The main features of the journal which were outlined in the e-mail were extensive author support, cash rewards, the peer review process, and other salient features of the journal.
Over a span of over four years, we (I and my colleagues) have published around 25 articles in the journal. In this editorial, I plan to briefly discuss my experiences of publishing with JCDR and the strengths of the journal and to finally address the areas for improvement.
My experiences of publishing with JCDR: Overall, my experiences of publishing withJCDR have been positive. The best point about the journal is that it responds to queries from the author. This may seem to be simple and not too much to ask for, but unfortunately, many journals in the subcontinent and from many developing countries do not respond or they respond with a long delay to the queries from the authors 1. The reasons could be many, including lack of optimal secretarial and other support. Another problem with many journals is the slowness of the review process. Editorial processing and peer review can take anywhere between a year to two years with some journals. Also, some journals do not keep the contributors informed about the progress of the review process. Due to the long review process, the articles can lose their relevance and topicality. A major benefit with JCDR is the timeliness and promptness of its response. In Dr Jain's e-mail which was sent to me in 2007, before the introduction of the Pre-publishing system, he had stated that he had received my submission and that he would get back to me within seven days and he did!
Most of the manuscripts are published within 3 to 4 months of their submission if they are found to be suitable after the review process. JCDR is published bimonthly and the accepted articles were usually published in the next issue. Recently, due to the increased volume of the submissions, the review process has become slower and it ?? Section can take from 4 to 6 months for the articles to be reviewed. The journal has an extensive author support system and it has recently introduced a paid expedited review process. The journal also mentions the average time for processing the manuscript under different submission systems - regular submission and expedited review.
Strengths of the journal: The journal has an online first facility in which the accepted manuscripts may be published on the website before being included in a regular issue of the journal. This cuts down the time between their acceptance and the publication. The journal is indexed in many databases, though not in PubMed. The editorial board should now take steps to index the journal in PubMed. The journal has a system of notifying readers through e-mail when a new issue is released. Also, the articles are available in both the HTML and the PDF formats. I especially like the new and colorful page format of the journal. Also, the access statistics of the articles are available. The prepublication and the manuscript tracking system are also helpful for the authors.
Areas for improvement: In certain cases, I felt that the peer review process of the manuscripts was not up to international standards and that it should be strengthened. Also, the number of manuscripts in an issue is high and it may be difficult for readers to go through all of them. The journal can consider tightening of the peer review process and increasing the quality standards for the acceptance of the manuscripts. I faced occasional problems with the online manuscript submission (Pre-publishing) system, which have to be addressed.
Overall, the publishing process with JCDR has been smooth, quick and relatively hassle free and I can recommend other authors to consider the journal as an outlet for their work."



Dr. P. Ravi Shankar
KIST Medical College, P.O. Box 14142, Kathmandu, Nepal.
E-mail: ravi.dr.shankar@gmail.com
On April 2011
Anuradha

Dear team JCDR, I would like to thank you for the very professional and polite service provided by everyone at JCDR. While i have been in the field of writing and editing for sometime, this has been my first attempt in publishing a scientific paper.Thank you for hand-holding me through the process.


Dr. Anuradha
E-mail: anuradha2nittur@gmail.com
On Jan 2020

Important Notice

Original article / research
Year : 2022 | Month : June | Volume : 16 | Issue : 6 | Page : XC01 - XC04 Full Version

A Systematic Approach to Optimise the Number of Beams for Intensity Modulated Radiotherapy in Pituitary Adenoma using Radiobiological Parameters


Published: June 1, 2022 | DOI: https://doi.org/10.7860/JCDR/2022/52570.16441
Richa Sharma, Sunil Dutt Sharma, Devesh Kumar Avasthi, Rohit Verma

1. Research Scholar, Department of Applied Physics, Amity Institute of Applied Sciences, Amity University, Noida, Uttar Pradesh, India. 2. Head, Medical Physics Section, Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Mumbai, Maharastra, India. 3. Dean, Research and Development, School of Engineering, University of Petroleum and Energy Studies, Dehradun, Uttarakhand, India. 4. Assistant Professor, Department of Applied Physics, Amity Institute of Applied Sciences, Amity University, Noida, Uttar Pradesh, India.

Correspondence Address :
Richa Sharma,
Department of Applied Physics, Amity Institute of Applied Sciences,
Amity University Uttar Pradesh, Noida, Uttar Pradesh, India.
E-mail: richa035@gmail.com

Abstract

Introduction: The number of beams used in a Radiotherapy (RT) plan effects the overall quality of the plan and hence the treatment. The inclusion of radiobiological concepts in finding the optimum number of beams for a particular planning technique has the potential to provide a step ahead of the routine clinical practice where clinical decisions are more dependent on the physical dose parameters.

Aim: To optimise the number of beams for Intensity Modulated Radiotherapy (IMRT) plan based on Tumour Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) biological parameters.

Materials and Methods: This retrospective study was done on 30 patients with pituitary macro-adenoma who underwent radiotherapy with a prescribed dose of 50.4 Gy in 28 fractions in Delhi State Cancer Institutes, Delhi, India from December 2012 to August 2018. The study data was collected and analysed between June 2018 and April 2020. These patients were treated with step and shoot IMRT technique on ONCORTM Expression linear accelerator (Siemens Healthineers, USA). But, the number of beams used to deliver IMRT plans were different as decided by the medical physicist and hence planner dependent rather than the disease. Being a centrally located disease, a symmetric beam arrangement was adopted for IMRT planning. For dosimetric comparison, three IMRT plans with five, seven, and nine equispaced beams were generated in Monaco treatment planning system for each patient and thus, a total of 90 IMRT plans were created and evaluated. For fair comparison, same IMRT planning parameters were utilized in all three plans of each patient. Monte Carlo (MC) dose calculation algorithm was used for all the plans. Resulting Cumulative Dose Volume Histograms (CDVHs) were exported to MATLAB, where these cDVHs were processed as per Niemierko’s radiobiological model to calculate the values of TCP and NTCP based on the Equivalent Uniform Dose (EUD). After this, the analysis of variance, ANOVA test was conducted over the resulting values of EUD, TCP, and NTCP to assess the difference of quality among plans having different beam arrangements at 0.05 level of significance.

Results: The mean tumour control probability (TCP) for IMRT plans with seven and nine beams were found to be 89.0±0.8% and 89.1±0.9% respectively for planning target volume (PTV). These values were not significantly different from each other. However, the mean TCP value for IMRT plans with five beams was found to be 88.4±1.1% for PTV. Further, this TCP value was proved to be significantly lower as compared to IMRT plans with seven and nine beams with a p-value of 0.008 and 0.004 respectively. On the other hand, the mean Normal Tissue Complication Probability (NTCP) was assessed to be less than 1% for all critical organs irrespective of the beam arrangement, indicating almost no probability of radiation induced toxicity in any of the organ.

Conclusion: This study concludes that the plan efficiency can be improved by using optimum number of beams for IMRT planning of pituitary adenoma.

Keywords

Beam number optimisation, Dose escalation, Equivalent uniform dose, Normal tissue complication probability, Tumour control probability

Pituitary adenomas comprise of 10–15% of all intracranial tumours. Although, these adenomas are classified as benign they may be locally invasive and may cause major morbidity and mortality. Initially, surgery was the only modality used for the treatment of pituitary adenoma, but gradually it was found that surgery followed by RT was more effective than surgery alone since in 90% of the cases, only a partial resection can be performed (1). The goal of RT is to deliver lethal dose to tumour without exceeding the tolerance doses of other neighboring organs.

The RT has improved continuously with time to achieve better Therapeutic Ratio (TR) by means of more conformal planning techniques and better treatment delivery systems, having greater accuracy and precision. Inclusion of radiobiological concepts in routine practice can provide a step forward in the direction of further improvement (2). Complicated radiobiological calculations are no more cumbersome in today’s era due to the availability of high speed computers that are common in RT departments. Although, the radiobiological concepts like EUD, TCP and NTCP are decades old, yet they are underutilized in routine practice. Even though, EUD is being used as an optimization constraint in many commercial Treatment Planning Systems (TPSs) where the option of radiobiological optimization is available, the clinical decision still depends on physical dose distribution and physical Dose Volume Histogram (DVH) rather than on the values of TCP and NTCP while selecting one plan over the other (3),(4). Even the dosimetric comparison studies between different planning techniques are based on physical dosimetric parameters (5),(6). The inclusion of radiobiological parameters is required to further improving the clinical practice in RT. As per the International Commission on Radiation Units and Measurements (ICRU) 83, NTCP and EUD are also to be included for level three reporting of IMRT plans (4).

Since the advent of RT, the selection of an optimal number of beams for different clinical cases has been dependent either upon the trial and error process or on the clinical experience of the planner. Although, using an optimal number of beams is an important step of planning which directly affects the quality of a plan but even after decades of practice, planners do not have a case specific and systematic method to define an optimum number of beams in IMRT (7).

Many studies have been done to investigate the optimum number of beams for IMRT and even for conventional planning technique, but all of them were based on concepts like conformity index, homogeneity index, normal tissue integral dose etc. which are ultimately based on physical doses only (7),(8),(9),(10). None of these studies was based on the radiobiological concept. Moreover, these studies were done on a small group of patients (less than or equal to six) and hence their results were more prone to statistical fluctuations. In this article, a systematic method is proposed to find the optimum number of beams for IMRT of pituitary adenoma based on the radiobiological concepts. Although, the method is illustrated via the case of pituitary adenoma treated with IMRT. The proposed method in this study is a generalized one and is applicable to all external beam RT plans irrespective of the treatment site and planning technique e.g. Three Dimensional Conformal Radiotherapy (3DCRT), IMRT, Volume Modulated Arc Therapy (VMAT) etc.

Material and Methods

This retrospective study was performed on data of 30 patients with pituitary adenoma who were treated with step and shoot IMRT technique on ONCORTM Expression (Siemens Healthineers, USA) linear accelerator (LINAC) machine with a prescribed dose of 50.4 Gy in 28 fractions (i.e., with 1.8 Gy dose per fraction) in Delhi State Cancer Institute, Delhi, India from December 2012 to August 2018. The study data was collected and analysed between June 2018 and April 2020. The number of beams used for IMRT plan were different as decided by the medical physicist and hence was planner dependent rather than the disease. The pituitary adenoma was thought to be an ideal case for demonstrating the proposed method as this case involves many critical organs.

Inclusion criteria: The patients with known primary pituitary macro-adenoma (both secreting and nonsecreting tumours) were included in the study. The postoperated patients with residual disease were also included.

Exclusion criteria: Pituitary micro-adenoma patients were not included in the study. The patients with large macro-adenomas invaded in surrounding Organs At Risk (OARs) e.g. optic nerves were also excluded.

Imaging and Contouring

Computed Tomography (CT) scan of each patient was acquired on Somatom Definition AS+ 128 slice (Siemens Healthineers, USA) CT scan machine in supine position with 3 mm slice thickness. These acquired images were exported in Digital Imaging and Communication in Medicine (DICOM) format to Monaco TPS (version 5.00.04, Elekta Medical Systems, Stockholm, Sweden) where the target and nearby critical organs were contoured on CT images of each patient.

Planning

After contouring, three IMRT plans with five, seven, and nine equispaced beams (starting from 0° gantry angle) were created for each patient in Monaco TPS and hence a total of 90 plans were made and evaluated. Since pituitary adenoma is a centrally located tumour, hence a symmetric beam arrangement was preferred. All plans were made for a prescribed dose of 50.4 Gy in 28 fractions. The planning optimization constraints for normal organs were based on Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) and the dose was calculated with a constant dose calculation grid size of three mm using MC dose calculation algorithm for each plan (11). DVHs were generated with a constant dose bin width of 10 Centigray (cGy). Resulting cumulative DVH (cDVH) data was exported in comma separated value (.csv) format from Monaco TPS to MATLAB (2) (version R2015a) software.

MATLAB

MATLAB is a matrix laboratory developed by The MathWorks, Inc. (Natick, MA). MATLAB was used to create a program that calculates the values of TCP and NTCP as per Niemierko’s radiobiological model. At first, this MATLAB (.m) program converts cDVH data into a differential one. Then, it makes use of withers formula to convert physical doses of DVH into biologically equivalent doses for each dose bin (12). Withers formula is also known as isoeffect formula and is given by

where EQD2 is the biologically equivalent dose in fraction size of 2 Gy, n is the total number of fractions, d is the physical dose per fraction, and α/β is the amount of dose at which type A damage is equal to type B damage according to the Linear Quadratic (LQ) model. α/β is a tissue specific parameter.

After this, MATLAB program computes the equivalent uniform dose (EUD) using the following equation

where i varies from 1 to N dose bins of DVH, vi is the volume corresponding to the ith dose bin, EQD2i is the biologically equivalent dose corresponding to the ith dose bin, and a is the tissue specific parameter, which is negative for the target structure and positive for OAR (12). For a=1, EUD is the mean dose and for a=8, EUD is the maximum dose.

Thereafter, MATLAB program uses EUD value to calculate TCP for the target structure as per Niemierko’s radiobiological model using the following equation

where TCD50 (i.e., tumour control dose50) is the dose at which there is 50% probability of tumour control, EUD is the equivalent uniform dose, and γ50 is the slope of the sigmoidal dose response curve of the tumour at 50% control probability (12). Radiobiological parameters that were used in MATLAB program to find TCP value of pituitary adenoma are listed in (Table/Fig 1) (13),(14),(15),(16).

Similarly, MATLAB program uses EUD value to calculate NTCP for the OAR as per Niemierko’s radiobiological model using the following equation

where TD50 is the dose at which there is 50% probability of normal tissue complication, EUD is the equivalent uniform dose, and γ50 is the slope of the sigmoidal dose response curve of the normal tissue at 50% complication probability (12). Oinam AS et al., was referred for a and γ50 values of all critical organs (12). Similarly, the values of TD50 and α/β were obtained from Emami B et al., (whole organ value) and Kehwar TS respectively (17),(18).

Processing of DVH Data by MATLAB Program

Exported cDVH data of Monaco TPS was imported in MATLAB. MATLAB program processed DVH data of one contoured structure at a time. Hence, the program was made to run several times to evaluate each of the contoured target and organ. Resulting values of EUD, TCP, and NTCP were noted and the average values were calculated for each beam arrangement for all targets and organs.

STATISTICAL ANALYSIS

The data was analyzed with ANOVA: single factor and Fisher’s Least Significant Difference (FLSD) tests using data analysis tool of Microsoft Excel 16 software package. Moreover, one-tail t-test: two sample assuming unequal variances was also performed using the same software at 0.05 level of significance (α).

Analysis of variance: ANOVA test is used to compare the mean values of several populations (19). The hypothesis (H0) for this test is based on the assumption that the mean (μ) values of all populations are the same, i.e.,, μ12=…=μn for all n populations that are compared. The alternative hypothesis (H1) is that at least one of the population has a different μ value. This test was used to verify whether the differences among mean EUD values for different beam arrangements were statistically significant? For this, a hypothesis H0: All the beam arrangements are equally efficient to deliver the same EUD to the target and an alternative hypothesis H1: At least one of the beam arrangements is not equally efficient to deliver the same EUD to the target were made and test was performed using the data analysis tool of Microsoft Excel 16 software, at 0.05 level of significance. Similarly, this test was repeated for TCP and NTCP values as well.

Fisher’s Least Significant Difference (FLSD): Once H0 is rejected, one is confident that at least one of the populations has a different mean value. However, ANOVA test does not tell which of the mean value is different, i.e., if μ1 ? μ2 or μ2 ? μ3 or … μn-1 ? μn. In such condition, post hoc test such as FSLD is used to identify which of the mean value is different from others (20). For those cases where H0 was rejected, FLSD test was used to identify the beam arrangement which has a significantly different mean value compared to other beam arrangements.

Results

It can be observed that all three beam arrangements deliver approximately the same EUD to target structures (Table/Fig 2). Further evaluation of EUD data with ANOVA and FLSD tests indicated insignificant difference in mean EUD values and hence equal efficiencies of seven and nine beam plans as indicated by the high p-value (p>0.05) as showed in (Table/Fig 3). It also indicates a significantly lower efficiency of five beam plans as shown by p-value (<0.05), when compared to plans having seven and nine beams. Similar results were obtained for mean TCP values (Table/Fig 4).

Equal efficiency of plans with seven and nine beams while showing significantly lower efficiency of plans having 5 beams is demonstrated in (Table/Fig 5).

Moreover, we can see from that NTCP value <1% for all critical organs irrespective of the beam arrangement, indicating almost no probability of radiation-induced toxicity in any of the organ (Table/Fig 6).

Discussion

The selection of optimum number of beams has been a topic of interest not only for advanced planning techniques like IMRT but for conventional plans as well (10). Now-a-days, various beam angle optimization algorithms are available to provide an optimized number of beams with corresponding angles for a plan (7),(8). However, the selection of an appropriate number of beams is still an important step since many of such algorithms need an adequate number of beams as an input (7).

The present study has have tested the proposed method for just three equispaced beam arrangements having five, seven, and nine beams. The reason behind not testing for lower or higher number of beams was the observation from previous studies which have shown that plans with less than five or more than nine beams are of inferior quality compared to other equispaced beam plans (7),(8),(9). These studies have shown that an IMRT plan with three beams has the least value of conformity index and conformal index and has the highest value of inhomogeneity index, mean non target dose, average MU/segment, sensitivity of objective function, and objective function value. Similarly, for a plan with 11 or more beams, the values of conformity index and conformal index are lower compared to a plan with five beams. Furthermore, such high beam number plan has the highest number of Monitor Units (MUs), segments and mean non target dose due to increased overlapping of low dose regions. However, being in the saturation region, only slight changes in inhomogeneity index, objective function value, sensitivity of objective function, and average MU/segment are present for such plans.

Past studies on IMRT beam number comparison have been done with fewer number of patients (7),(8),(9),(10). Moreover, some of these studies incorporated patients of different sites as well. On the other hand, the present study included thirty patients with the same disease (i.e., pituitary adenoma) and therefore results are less prone to statistical fluctuations compared to the past studies. However, the present study’s results are in correlation with the past studies. In addition, the present study proved that an IMRT plan with seven or nine beams has significantly better efficiency than an IMRT plan with five beams in terms of tumour control. The results also indicate an insignificant difference between efficiencies of seven and nine beam IMRT plans.

Previous studies have reported that escalating the number of beams in a plan beyond a particular point does not improve the quality of plan (7),(8),(9). Since such unnecessary addition in the number of beams leads to more radiation leakage and hence increased normal tissue dose. Moreover, it results in an increased number of segments and MUs with a decrease in mean MU/beam that may further add to uncertainty in the delivery of treatment even for dynamic IMRT (7),(8). Higher MUs implies greater risk of secondary cancer because of irradiation to low dose and a longer treatment time that leads to more intrafraction motion of tumour as well as lesser patient comfort (5). It is also recommended to use the minimum possible number of beams that are essential to produce a good quality plan in order to reduce the overall time required for treatment delivery and dosimetric verification (8). Hence, this study indicates planning with seven equispaced beams to be the optimum choice for coplanar IMRT of pituitary adenoma.

The maximum limit of prescription dose is set by the tolerance dose of OARs since the aim of RT is not just the treatment of cancer, but the quality of life should also be high. This study suggests the possibility of dose escalation in case of pituitary adenoma. The proposed method can be used for virtually testing the same. For this, the prescription dose of pituitary adenoma can be increased while keeping an eye over NTCP values of normal organs. It means to test for the possibility of dose escalation, one can do replanning for old patients with higher doses and can use the proposed method to look for related improvements in TCP values together with the increased values of NTCP. If NTCP values are still under set limits, the virtual test accomplishes its task. Although, this study is demonstrated via the case of IMRT planning for pituitary adenoma, the proposed method can also be applied to other sites and planning techniques. More radiobiological studies for different types of tumour should be performed to generate more such data so as to facilitate the use of radiobiological dosimetric parameters in routine clinical practice.

Limitation(s)

The main limitation of the proposed method is the scarcity of radiobiological parameter data availability in literature. Most of the literature data is old and has to be collected from different studies.

Conclusion

The present study concludes that the plan efficiency can be improved by using optimum number of beams. Moreover, the use of radiobiological parameters for plan evaluation also indicates the scope of radiation dose escalation and therefore better tumour control without causing more damage to surrounding organs.

Acknowledgement

The authors would like to thank Prof (Dr.) R K Grover (Ex-Director, Delhi State Cancer Institutes) to provide MATLAB software package facility for carrying out this study.

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DOI and Others

DOI: 10.7860/JCDR/2022/52570.16441

Date of Submission: Nov 10, 2021
Date of Peer Review: Jan 17, 2022
Date of Acceptance: Mar 05, 2022
Date of Publishing: Jun 01, 2022

AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? NA
• Was informed consent obtained from the subjects involved in the study? NA
• For any images presented appropriate consent has been obtained from the subjects. NA

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