Sanjay S. Supe

Consistency and reproducibility of the VMAT plan delivery using three independent validation methods

The complexity of VMAT delivery requires new methods and potentially new tools for the commissioning of these systems. It appears that great consideration is needed for quality assurance (QA) of these treatments since there are limited devices that are dedicated to the QA of rotational delivery. In this present study, we have evaluated the consistency and reproducibility of one prostate and one lung VMAT plans for 31 consecutive days using three different approaches: 1) MLC DynaLog files, 2) in vivo measurements using the multiwire ionization chamber DAVID, and 3) using PTWseven29 2D ARRAY with the OCTAVIUS phantom at our Varian Clinac linear accelerator. Overall, the three methods of testing the reproducibility and consistency of the VMAT delivery were in agreement with each other. All methods showed minimal daily deviations that contributed to clinically insignificant dose variations from day to day. Based on our results, we conclude that the VMAT delivery using a Varian 2100CD linear accelerator equipped with 120 MLC is highly reproducible. PACS numbers: 87.55.Qr and 87.56.Fc

Prevalence of fatigue among cancer patients receiving various anticancer therapies and its impact on Quality of Life: A cross-sectional study

Background: Fatigue is disabling and continuous phenomenon in cancer patients during and after various anticancer treatments which can continue for many years after treatment and definitely it has profound effect on Quality of Life (QOL). However, determining its severity is still underestimated among the cancer patients and also very few studies in the literature exist reporting on Cancer-Related Fatigue (CRF) among Indian population. Aims: To find out the prevalence of rate of fatigue in cancer patient receiving various anti cancer therapies. To find out the relative impact of fatigue on QOL. Materials and Methods: This cross-sectional observational study included a total 121 cancer patients receiving radiotherapy, chemotherapy, and concurrent chemo-radiation with the age group of above 15 years who fulfilled the inclusion and exclusion criteria. All the patients were assessed for severity of fatigue using Brief Fatigue Inventory (BFI) and for QOL using FACT-G scale while they were receiving the anticancer therapies as an in-patient in the regional cancer centers in Madhya Pradesh, India. Results: The severe fatigue was more prevalent in chemotherapy [58/59 (98.30%)], and concurrent chemo-radiation (33/42 (78.57%)) as compared to radiotherapy (Moderate-9/20 (45%) and Severe-9/20 (45%)). Moderate correlations were exhibited between fatigue due to radiotherapy and QOL (r = -0.71, P < 0.01), whereas weak correlation was found between fatigue due to chemotherapy and concurrent chemo-radiation (r = -0.361, P < 0.01 and r = -0.453, P < 0.01, respectively). Conclusion: Severity of fatigue was found more after chemotherapy and concurrent chemo-radiation therapy while impact on QOL was more after the radiotherapy.

Backscattered dose perturbation effects at metallic interfaces irradiated by high-energy X- and gamma-ray therapeutic beams.

Purpose:To analyze backscattered dose enhancements near different metallic interfaces for cobalt-60 (60Co) gamma rays and 6- and 18-MV photon beams.Material and Methods:Measurements were carried out with a PTW thin-window, parallel-plate ionization chamber and an RDM-1F electrometer. Thin sheets of aluminum, mild steel, copper, cadmium and lead were used as inhomogeneities. The chamber was positioned below the inhomogenities with the gantry maintained under the couch.Results:It can be noticed that the backscatter dose factor (BSDF) reaches the saturation value within few millimeters of all inhomogeneities and the thickness at which the saturation value is reached depends on the atomic number of the inhomogeneity. The amount of backscattered radiation was noticed to be greater with lesser-energy photons (60Co) compared to the higherenergy photons. The BSDF varies across the beam when the inhomogeneity is present due to the change in beam quality. The backscattered electrons from lead inhomogeneity have a range in the order of 5–7 mm.Conclusion:Higher atomic number inhomogeneities result in an increase in BSDF, as they have higher scattering cross section for the secondary electrons. The increase in dose was noticed for few millimeters upstream from the metallic inhomogeneity, which suggests that the range of backscattered electrons is very small. Since the factors affecting the BSDF at the interface are energydependent, it is expected that the variation in BSDF will also be sensitive to the beam energy.Ziel:Analyse der Verstärkung der Rückstreudosis an unterschiedlichen metallischen Grenzflächen für Kobalt-60-(60Co-)Gamma-Strahlen sowie für 6- und 18MV-Photonen-Strahlung.Material und Methode:Die Messungen wurden in einer dünnwandigen PTW-Parallelplatten-Ionisationskammer mit einem RDM- 1F-Elektrometer durchgeführt. Dünne Platten aus Aluminium, Weichstahl, Kupfer, Cadmium und Blei dienten als Grenzflächen. Die Ionisationskammer wurde unterhalb der Grenzflächen platziert, wobei sich die Gantry unter der Liegefläche befand.Ergebnisse:Es wurde festgestellt, dass der Rückstreudosisfaktor (BSDF) seinen Sättigungswert innerhalb weniger Millimeter aller Grenzflächenmaterialien erreicht, wobei die Dicke, bei der der Sättigungswert erreicht wird, von der Kernladungszahl des Grenzflächenmaterials abhängt. Weiter wurde festgestellt, dass der Anteil rückgestreuter Strahlung bei weniger energiereichen Photonen (60Co) geringer ausfällt im Vergleich zu höherenergetischen Photonen. Der BSDF variiert in Gegenwart der Grenzfläche innerhalb des Strahlenbündels aufgrund von Veränderungen der Strahlenqualität. Die Elektronen, die von der Blei-Grenzfläche rückgestreut werden, haben eine Reichweite von 5–7 mm.Schlussfolgerung:Grenzflächenmaterialien mit höherer Kernladungszahl bewirken eine Zunahme des BSDF, da sie für die Sekundärelektronen einen höheren Streuquerschnitt aufweisen. Die Dosiszunahme wurde wenige Millimeter vor der metallischen Grenzfläche festgestellt, was auf eine sehr geringe Reichweite der rückgestreuten Elektronen hinweist. Da die Faktoren, die den BSDF an der Grenzfläche beeinflussen, energieabhängig sind, ist zu erwarten, dass die Variabilität des BSDF auch auf die Strahlungsenergie reagiert.

Influence of intraluminal brachytherapy dose on complications in the treatment of esophageal cancer

PURPOSE Demonstration of the influence of intraluminal brachytherapy dose on complications in the treatment of esophageal carcinoma. METHODS AND MATERIALS Between January 1990 and June 1991, 75 patients with esophageal cancer were treated with external radiotherapy followed by intraluminal brachytherapy. Patients had a Karnofsky score of over 70, with no supra-clavicular nodal or distant disease. An external radiotherapy dose between 40 and 55 Gy (mean 52 Gy), 5 times a week, 2 to 2.06 Gy/fraction, followed by a single session of Intraluminal brachytherapy using a locally developed, manual, afterloading applicator with Cs-137 sources with dose ranges of 8-10 Gy (Group 1: 42 patients), 10-12 Gy (Group 2: 11 patients), and 12-15 Gy (Group 3: 22 patients) at a mean dose rate of 2.09 Gy/hr was delivered. RESULTS The actuarial figures at 1 year were 39% for overall survival, 29% for disease-free survival, and 38% for local control. Fourteen patients (18.6%) developed complications of either an esophageal stricture or fistula. These were dependent on intra-luminal brachytherapy dose, whereas external radiotherapy and intra-luminal brachytherapy doses did not contribute significantly to local control. For Groups 1, 2, and 3, actuarial local control were 28%, 45%, and 63% (p < 0.1) and of complications were 6%, 20%, and 70% (p < 0.001), respectively. Also, on applying the Time/Dose/Fractionation formula on brachytherapy doses, it was found that the complication rate was 6% for TDF of < 31, 25% for TDF of 32-37, and 70% for TDF of > 38 (p < 0.001). CONCLUSION External radiotherapy doses in the range of 50 to 55 Gy followed by a dose of 10-12 Gy of intraluminal brachytherapy was found optimal with respect to complications and local control in the radiotherapeutic management of esophageal cancer.

A comprehensive review of head and neck cancer rehabilitation: physical therapy perspectives.

Rehabilitation in relation to cancer can be preventative, restorative, supportive, and palliative. It is recognized that patients may have rehabilitation needs throughout their care pathway. The role of physiotherapy in the cancer rehabilitation is less understood and particularly in the head and neck cancer (HNC) patients. This results in various residual deformities and dysfunctions for the patients with HNC. The objective of this review is to provide detailed information regarding the problems faced after the cancer treatments and rehabilitation of patients who suffered with HNC. The fact that cancer patients are facing several months of chemotherapy and/or radiotherapy and usually major surgery, as well as the direct effect of immobility due to pain, means that muscle wasting, joint stiffness, as well as de-conditioning and fatigue are inevitable. The absence of physiotherapy intervention would be detrimental to patient care and the ability of the patient/family to cope with the effects of the disease or its treatment on their functional capacity and quality of life. Following any treatment for HNC, physical therapy may play an essential role in preventing various complications and helping patients to mitigate impairments, and restoring function of the shoulder joint, neck, and face.

Cyberknife: A double edged sword?

The Cyberknife represents a new, frameless stereotactic radiosurgery system which efficiently incorporates advance robotics with computerized image reconstruction to allow highly conformal image guided radiation delivery. This review focus is on the pros and cons of this new radiotherapy tool, its current indications, safety profile and future directions. A literature search of Medline, Pubmed, Biomed, Medscape and Cancer lit database were referred to retrieve relevant data/information. The authors conclude that the use of this system offers an invaluable solution to the treatment of selective tumours/lesions located close to critical structures, salvage of recurrent and metastatic lesions and potential of treatment of selective early stage malignancies like the carcinoma prostate and lung. However, it is still too premature, with insufficient follow up data to advocate it as the treatment of choice in any set up. There are several radiobiological issues that also remain in the greyzone.

Dosimetric comparison of various optimization techniques for high dose rate brachytherapy of interstitial cervix implants.

HDR brachytherapy treatment planning often involves optimization methods to calculate the dwell times and dwell positions of the radioactive source along specified afterloading catheters. The purpose of this study is to compare the dose distribution obtained with geometric optimization (GO) and volume optimization (VO) combined with isodose reshaping. This is a retrospective study of 10 cervix HDR interstitial brachytherapy implants planned using geometric optimization and treated with a dose of 6 Gy per fraction. Four treatment optimization plans were compared: geometric optimization (GO), volume optimization (VO), geometric optimization followed by isodose reshape (GO_IsoR), and volume optimization followed by isodose reshape (VO_IsoR). Dose volume histogram (DVH) was analyzed and the four plans were evaluated based on the dosimetric parameters: target coverage (V100), conformal index (COIN), homogeneity index (HI), dose nonuniformity ratio (DNR) and natural dose ratio (NDR). Good target coverage by the prescription dose was achieved with GO_IsoR (mean V100 of 88.11%), with 150% and 200% of the target volume receiving 32.0% and 10.4% of prescription dose, respectively. Slightly lower target coverage was achieved with VO_IsoR plans (mean V100 of 86.11%) with a significant reduction in the tumor volume receiving high dose (mean V150 of 28.29% and mean V200 of 7.3%). Conformity and homogeneity were good with VO_IsoR (mean COIN=0.75 and mean HI=0.58) as compared to the other optimization techniques. VO_IsoR plans are superior in sparing the normal structures while also providing better conformity and homogeneity to the target. Clinically acceptable plans can be obtained by isodose reshaping provided the isodose lines are dragged carefully. PACS number: 87.53 Bn

Influence of photon beam energy on IMRT plan quality for radiotherapy of prostate cancer

Summary Background Intensity-modulated radiation therapy (IMRT) has been widely used for prostate cancer treatments. 6MV photon beams were found to be an effective energy choice for most IMRT cases. The use of high-energy photons raise concerns about increased leakage and secondary neutron dose for the patients. Aim In this work, the effect of beam energy on the quality of IMRT plans for prostate radiotherapy was systematically studied for competing IMRT plans optimized for delivery with either 6 or 10MV beams. Materials and Methods A cohort of 20 prostate cases was selected for this study. All patients received full-course IMRT treatments to a dose of 79.2Gy to PTV in 44 fractions. For all of the cases we developed treatment plans using 6 MV and 10MV intensity-modulated beams with identical dose volume constraints. Results Percentage of doses received by the percentage volume of PTV was higher for 6MV photons compared to 10MV photons for 12 patients, less than or equal to 1% for 6 patients and 2.6%, 3.6% for the remaining 2 patients irrespective of the PTV volume. Percentage doses received by 15% of bladder volume were higher for 10 MV photons. Percentage doses received by 15% of rectum volume were also higher for 10 MV photons. Conclusions Since there is no greater advantage from 10MV photons as compared with 6MV photons in large volume pelvic IMRT dosimetry and also 10MV photons lie on the threshold energy border for the induction of photo neutrons from the accelerator components, we recommend the use of 6MV photons for IMRT of prostate cancer to achieve better results in tumour control and acceptable probability of complication rate.

Comparison of dosimetric characteristics of physical and enhanced dynamic wedges

BACKGROUND Wedge filters can be used as missing tissue compensators or wedge pairs to alter the shape of isodose curves so that two beams can be angled with a small hinge angle at a target volume without creating a hotspot. AIM In this study the dosimetric properties of Varian Enhanced Dynamic Wedge (EDW) and physical wedges (PW) were analyzed and compared. MATERIALS AND METHODS Ionometric measurements of open field output factor, physical wedge output factor, physical wedge factor and EDW factor for photon beams were carried out. A 3D scanning water phantom was used to scan depth dose and profiles for open and PW fields. The 2D ionization matrix was used to measure profiles of physical and EDW wedges. The isodose curves of physical and EDW angles were obtained using a therapy verification film. RESULTS AND DISCUSSION The PW output factors of photons were compared with the open field output factors. The physical and EDW factors were compared. The difference in percentage depth dose for open and PW fields was observed for both photon beams. The measured isodose plots for physical and EDW were compared. CONCLUSION The wedge field output factor increases with field size and wedge angle compared to that of the open field output factor. The number of MU to deliver a particular dose with the EDW field is less than that of the PW field due to a change in wedge factor. The dosimetric characteristics, like profile and isodose of EDW, closely match with that of the PW.

Influence of photon energy on the quality of prostate intensity modulated radiation therapy plans based on analysis of physical indices

The goal of the present study was to study the effects of low- and high-energy intensity-modulated photon beams on the planning of target volume and the critical organs in cases of localized prostate tumors in a cohort of 8 patients. To ensure that the difference between the plans is due to energy alone, all other parameters were kept constant. A mean dose volume histogram (DVH) for each value of energy and for each contoured structure was created and was considered as completely representative for all patients. To facilitate comparison between 6-MV and 15-MV beams, the DVH-s were normalized. The different parameters that were compared for 6-MV and 15-MV beams included mean DVH, different homogeneity indices, conformity index, etc. Analysis of several indices depicts more homogeneous dose for 15-MV beam and more conformity for 6-MV beam. Comparison of all these parameters showed that there was little difference between the 6-MV and 15-MV beams. For rectum, 2 to 4 % more volume received high dose with the 6-MV beam in comparison with the 15-MV beam, which was not clinically significant, since in practice much tighter constraints are maintained, such that Normal Tissue Complication Probability (NTCP) is kept within 5 %. Such tighter constraints might increase the dose to other regions and other critical organs but are unlikely to increase their complication probabilities. Hence the slight advantages of 15-MV beam in providing benefits of better normal-tissue sparing and better coverage cannot be considered to outweigh its well-known risk of non-negligible neutron production.