Ontogeny and tissue specific expression profiles of recombination activating genes (RAGs) during development in Nile tilapia, Oreochromisniloticus.

Recombination activating genes (RAGs) mediates the process of rearrangement and somatic recombination (V(D)J) to generate different antibody repertoire. Studies on the expression pattern of adaptive immune genes during ontogenic development are crucial for the formulation of fish immunization strategy. In the present study, Nile tilapia was taken to explore the relative expression profile of RAG genes during their developmental stages. The developmental stages of Nile tilapia, i.e., unfertilized egg, 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28 and 30 days post-hatch (dph) and kidney, blood, gill, liver and spleen tissues from adult fish were collected and the cDNA synthesis was carried out. Gene specific primers for RAG-1 and RAG-2 of Nile tilapia were designed and their annealing temperature (Tm) was optimized by gradient PCR. Consequently, PCR was performed to confirm the specific amplification of RAG-1 and RAG-2 genes. Quantitative real-time PCR (qRT-PCR) gene expression of RAG-1 and RAG-2 were noticed in all the developmental stages; however, a significant increase was observed after 12 dph and peaked at 24 dph, followed by a gradual decrease until 30 dph. Tissue-specific gene expression profiling revealed that the highest expression of RAG-1 and RAG-2 was observed in the kidney, followed by spleen, gill, liver and blood. The findings of the study explored the suitable timing of lymphoid maturation that could be technically used for the adoption of strategies to improve disease resistance of fish larvae for mitigating larval mortality.

L-Proline: A Versatile Organo-Catalyst in Organic Chemistry.

BACKGROUND: L-proline is a natural amino acid having secondary amine functionality and acts as a bifunctional catalyst (organo-catalyst). The amino-functional group acts as Lewis base type while carboxylic acids act as Brønsted acid type catalysts. It catalyzed different asymmetric syntheses, including known reactions such as Aldol condensation, Mannich reaction, Michael Addition, Knoevenagel condensation, Hantzsch synthesis, OXA-Michael Henry tandem, Ullmann reactions, Wieland-Miescher ketone synthesis, Robinson annulation, Biginelli reaction, α- amination. It is also an essential catalyst for synthesizing heterocyclic skeletons such as coumarin, spiro-oxindoles, imidazoles, benzimidazoles, quinoxalines, podophyllotoxin, benzothiazoles, isoxazolidines, phenothiazines, aziridine, indole, 1,5-benzodiazepines, pyridine, and quinazolines. OBJECTIVE: In this review, we had the objective to critically summarize the use of proline and proline derivatives as catalysts of multicomponent reactions performed in various media and leading to synthetically and biologically relevant heterocycles, a very important class of compounds that constitutes over 60% of drugs and agrochemicals. METHODS: All scholarly articles for L-Proline catalyzed reactions were retrieved from ScienceDirect, Google Scholar , PubMed, etc. Results and Conclusion: Given the importance of L-Proline based reactions, it has been observed to have tremendous applications in organic chemistry. It can also act as a 'Green catalyst'.

Cytokine profile and induction of T helper type 17 and regulatory T cells by human peripheral mononuclear cells after microbial exposure.

The immunomodulatory effects of probiotics were assessed following exposure of normal peripheral blood mononuclear cells (PBMC), cord blood cells and the spleen-derived monocyte/macrophage cell line CRL-9850 to Lactobacillus acidophilus LAVRI-A1, Lb. rhamnosus GG, exopolysaccharides (EPS)-producing Streptococcus thermophilus St1275, Bifidobacteriun longum BL536, B. lactis B94 and Escherichia coli TG1 strains. The production of a panel of pro- and anti-inflammatory cytokines by PBMC following bacterial stimulation was measured, using live, heat-killed or mock gastrointestinal tract (GIT)-exposed bacteria, and results show that (i) all bacterial strains investigated induced significant secretion of pro- and anti-inflammatory cytokines from PBMC-derived monocytes/macrophages; and (ii) cytokine levels increased relative to the expansion of bacterial cell numbers over time for cells exposed to live cultures. Bifidobacteria and S. thermophilus stimulated significant concentrations of transforming growth factor (TGF)-ß, an interleukin necessary for the differentiation of regulatory T cells (T(reg) )/T helper type 17 (Th17) cells and, as such, the study further examined the induction of Th17 and T(reg) cells after PBMC exposure to selected bacteria for 96 h. Data show a significant increase in the numbers of both cell types in the exposed populations, measured by cell surface marker expression and by cytokine production. Probiotics have been shown to induce cytokines from a range of immune cells following ingestion of these organisms. These studies suggest that probiotics' interaction with immune-competent cells produces a cytokine milieu, exerting immunomodulatory effects on local effector cells, as well as potently inducing differentiation of Th17 and T(reg) cells.

Dosimetric evaluation of hybrid and volumetric-modulated arc therapy plan for left-sided chest wall irradiation in MONACO treatment planning system.

Background and Objective: Radiation induced toxicities in heart and lungs are diminishes the survival rate of cancer patients. The purpose of this study is to evaluate the dosimetric parameters of hybrid plans for chest wall irradiation of left breast carcinoma patients using Monaco treatment planning system and compare with the volumetric-modulated arc therapy (VMAT) treatment plans. Materials and Methods: Fifteen carcinoma left breast patients were randomly selected to evaluate the advantage of hybrid plan over VMAT. Hybrid plans were generated with 70% and 30% dose contribution from forward intensity-modulated radiotherapy and VMAT, respectively, whereas VMAT had been done with full prescription. Conformity and homogeneity indices were evaluated for target coverage between hybrid and VMAT plans. Results: Hybrid plan has proved its superiority over VMAT in terms of better organ at risk sparing and lesser low dose spillage and at the same time providing comparable target coverage. In low-dose spectrum, VMAT showed higher dose-volume than the hybrid plan. The maximum variation was found to be 44.75% at 7 Gy and the minimum dose difference was observed at 1 Gy (6.02%). Conclusion: This study suggests that the hybrid plan could be a better option for left-sided chest wall irradiation in regular clinical practice.

Oral Nano-Curcumin in a Model of Chronic Gulf War Illness Alleviates Brain Dysfunction with Modulation of Oxidative Stress, Mitochondrial Function, Neuroinflammation, Neurogenesis, and Gene Expression.

Unrelenting cognitive and mood impairments concomitant with incessant oxidative stress and neuroinflammation are among the significant symptoms of chronic Gulf War Illness (GWI). Curcumin (CUR), an antiinflammatory compound, has shown promise to alleviate brain dysfunction in a model of GWI following intraperitoneal administrations at a high dose. However, low bioavailability after oral treatment has hampered its clinical translation. Therefore, this study investigated the efficacy of low-dose, intermittent, oral polymer nanoparticle encapsulated CUR (nCUR) for improving brain function in a rat model of chronic GWI. Intermittent administration of 10 or 20 mg/Kg nCUR for 8 weeks in the early phase of GWI improved brain function and reduced oxidative stress (OS) and neuroinflammation. We next examined the efficacy of 12-weeks of intermittent nCUR at 10 mg/Kg in GWI animals, with treatment commencing 8 months after exposure to GWI-related chemicals and stress, mimicking treatment for the persistent cognitive and mood dysfunction displayed by veterans with GWI. GWI rats receiving nCUR exhibited better cognitive and mood function associated with improved mitochondrial function and diminished neuroinflammation in the hippocampus. Improved mitochondrial function was evident from normalized expression of OS markers, antioxidants, and mitochondrial electron transport genes, and complex proteins. Lessened neuroinflammation was noticeable from reductions in astrocyte hypertrophy, NF-kB, activated microglia with NLRP3 inflammasomes, and multiple proinflammatory cytokines. Moreover, nCUR treated animals displayed enhanced neurogenesis with a normalized expression of synaptophysin puncta, and multiple genes linked to cognitive dysfunction. Thus, low-dose, intermittent, oral nCUR therapy has promise for improving brain function in veterans with GWI.

Synthesis, Molecular Docking, and In vitro Antimycobacterial Studies on N'-arylidene-4-nitrobenzohydrazides.

BACKGROUND: Mycobacterium tuberculosis (Mtb) is an organism that causes tuberculosis (TB). In 2019, 10 million individuals worldwide contracted tuberculosis, with 1.4 million people dying from the disease each year (World Health Organization, 2021). Hydrazones- hydrazide-based drugs have been shown to be bactericidal against M. tuberculosis replication. OBJECTIVES: We herein intended to synthesize a series of acid hydrazones (3a-3l) by condensing 4-nitrobenzohydrazine with substituted aromatic acids in ethanol at room temperature. MATERIALS AND METHODS: All newly synthesized compounds were characterized by standard spectroscopic techniques. Synthesized compounds were then tested for anti-mycobacterial activity against H37Rv strains. Molecular docking analysis was performed for three crystal structures of 1ENY, 1TED and 2FUM Mycobacterium tuberculosis receptors. RESULTS: Among all tested molecules, 3i (MIC: 50 µg/mL) and 3b (MIC: 50 µg/mL) were found to be the best ligands for further development of new anti-TB drug. We found that our proposed molecules have higher docking scores, corresponding standard anti-TB agents, such as ciprofloxacin and isoniazid. Synthesized compounds were found to have druglikeness properties when tested with Lipinski's filter for drug-likeness. CONCLUSION: Our current study proposes N'-arylidene-4-nitrobenzohydrazides as anti-TB agents. Agents with such system can be developed in future for development into active lead molecules.

Coma falsely attributed to Lyme disease.

Neuroborreliosis has very low prevalence in Kentucky and coma due to Lyme disease is uncommon in North America. A patient diagnosed with Lyme disease in Kentucky, based on coma, typical inflammatory changes on brain imaging, and a positive ELISA resulted in an erroneous clinical impression. Diagnosis should have been confirmed by a positive result on Western Blot, polymerase chain reaction (PCR), or real-time polymerase chain reaction (RT-PCR) testing. Physicians must apply careful consideration before diagnosing a rare disease in areas where that condition is uncommon without first eliminating other differential options. Neuroborreliosis clinicalfindings are nonspecific and often require confirmatory testing, especially in nonclassical case presentations.

Enhancement of the production of L-glutaminase, an anticancer enzyme, from Aeromonas veronii by adaptive and induced mutation techniques.

Microbial anti-cancer enzymes have been proven to be effective and economical agents for cancer treatment. Aeromonas veronii has been identified as a microorganism with the potential to produce L-glutaminase, an anticancer agent effective against acute lymphocytic leukaemia. In this study, a selective medium of Aeromonas veronii was used to culture the microorganism. Strain improvement was done by adaptive and induced mutational techniques. A selective minimal agar media was incorporated for the growth of the strain which further supports adaptive mutation. Strains were also UV-irradiated and successively treated with N-methyl-N'-nitro-N-nitrosoguanidine to find a resilient strain capable of producing L-glutaminase efficiently. The Plackett-Burman design and central composite designs were used to screen and optimize additional carbon and nitrogen sources. Adaptive mutation resulted in promising yield improvements compared to native strain (P<0.001). The mean yield of 30 treated colonies from the induced mutation was significantly increased compared to the non-induced strain (P< 0.001). The economically feasible statistical designs were found to reinforce each other in order to maximize the yield of the enzyme. The interactions of nutrient factors were understood from the 3D response surface plots. The model was found to be a perfect fit in terms of maximizing enzyme yield, with the productivity improving at every stage to a fourfold output of enzyme (591.11 ±7.97 IU/mL) compared to the native strain (135±3.51 IU/mL).

Long-term results of radiofrequency ablation of slow pathway in patients with atrioventricular nodal reentrant tachycardia: single-center experience.

BACKGROUND: This study sought to evaluate the long-term recurrence rate of atrioventricular nodal reentrant tachycardia (AVNRT) after radiofrequency catheter ablation. The clinical and electrophysiological features of patients with AVNRT and their immediate outcomes after undergoing slow pathway ablation/modification were also studied. METHODS AND RESULTS: The study included 264 consecutive patients with AVNRT (mean age 46 -/+ 15 years, 143 women, 121 men) who underwent slow pathway ablation/modification using a combined electrophysiological and anatomical approach. The primary endpoint of ablation procedure was non- inducibility of the arrhythmia. The primary endpoint of the study was the recurrence of AVNRT on follow-up. Acute success was achieved in 262 (99.6%) patients. Complication rate of the ablation procedure was 2.6% and the average fluoroscopy time was 18.3 -/+ 11 minutes. The patients were followed up for a mean duration of 20 -/+ 9 months during which there was only one case of recurrence. CONCLUSION: Radiofrequency ablation or modification of slow pathway is highly effective in the treatment of AVNRT. The technique has a high initial success rate and a low complication rate. The recurrence rates are extremely low (0.3%) on long-term follow-up.

Analysis of small field percent depth dose and profiles: Comparison of measurements with various detectors and effects of detector orientation with different jaw settings.

The advent of modern technologies in radiotherapy poses an increased challenge in the determination of dosimetric parameters of small fields that exhibit a high degree of uncertainty. Percent depth dose and beam profiles were acquired using different detectors in two different orientations. The parameters such as relative surface dose (D S), depth of dose maximum (D max), percentage dose at 10 cm (D 10), penumbral width, flatness, and symmetry were evaluated with different detectors. The dosimetric data were acquired for fields defined by jaws alone, multileaf collimator (MLC) alone, and by MLC while the jaws were positioned at 0, 0.25, 0.5, and 1.0 cm away from MLC leaf-end using a Varian linear accelerator with 6 MV photon beam. The accuracy in the measurement of dosimetric parameters with various detectors for three different field definitions was evaluated. The relative D S(38.1%) with photon field diode in parallel orientation was higher than electron field diode (EFD) (27.9%) values for 1 cm ×1 cm field. An overestimation of 5.7% and 8.6% in D 10 depth were observed for 1 cm ×1 cm field with RK ion chamber in parallel and perpendicular orientation, respectively, for the fields defined by MLC while jaw positioned at the edge of the field when compared to EFD values in parallel orientation. For this field definition, the in-plane penumbral widths obtained with ion chamber in parallel and perpendicular orientation were 3.9 mm, 5.6 mm for 1 cm ×1 cm field, respectively. Among all detectors used in the study, the unshielded diodes were found to be an appropriate choice of detector for the measurement of beam parameters in small fields.

Biodegradable block copolymers.

Recently, block copolymers have got tremendous impetus on the ongoing research in the area of drug delivery technology, due to their capability to provide a biomaterial having a broad range of amphiphilic characteristics, as well as targeting the drugs to specific site. This article is an attempt to review applications of block copolymers in surface modification, drug targeting, nano and microparticles, hydrogels, micelles etc. The physicochemical properties of block copolymers and various synthetic routes for block copolymers are also discussed.

Solution structure of d-GAATTCGAATTC by 2D NMR. A new approach to determination of sugar geometries in DNA segments.

A new approach based on the correlated spectroscopy (COSY) in 2D NMR has been described for determination of sugar geometries in oligonucleotides. Under the usual low resolution conditions employed in COSY, the intensities of cross peaks depend on the magnitudes of coupling constants. There are five vicinal coupling constants in a deoxyribose ring which are sensitive to the sugar geometry. The presence, absence and rough comparison of relative intensities of COSY cross peaks arising from such coupling constants enable one to fix the sugar conformation to a fair degree of precision. The methodology has been applied to d-GAATTCGAATTC. It is observed that ten out of the twelve nucleotide units in this sequence exhibit a rare O1'-endo geometry. The EcoRI cleavage sites (between G and A) in the dodecanucleotide show an interesting variation in the conformation with the two sugars attached to the Gs acquiring a geometry between C2'-endo and C4'-endo.

Design and testing of indigenous cost effective three dimensional radiation field analyser (3D RFA).

The aim of the study is to design and validate an indigenous three dimensional Radiation Field Analyser (3D RFA). The feed system made for X, Y and Z axis movements is of lead screw with deep ball bearing mechanism made up of stain less steel driven by stepper motors with accuracy less than 0.5 mm. The telescopic column lifting unit was designed using linear actuation technology for lifting the water phantom. The acrylic phantom with dimensions of 800 x 750 x 570 mm was made with thickness of 15 mm. The software was developed in visual basic programming language, classified into two types, viz. beam analyzer software and beam acquisition software. The premeasurement checks were performed as per TG 106 recommendations. The physical parameters of photon PDDs such as Dmax, D10, D20 and Quality Index (QI), and the electron PDDs such as R50, Rp, E0, Epo and X-ray contamination values can be obtained instantaneously by using the developed RFA system. Also the results for profile data such as field size, central axis deviation, penumbra, flatness and symmetry calculated according to various protocols can be obtained for both photon and electron beams. The result of PDDs for photon beams were compared with BJR25 supplement values and the profile data were compared with TG 40 recommendation. The results were in agreement with standard protocols.

Impact of cutout off axis on electron beam dosimetric parameters.

Dosimetric changes caused by the positional uncertainty of centering a small electron cutout to the machine central axis (CAX) of the linear accelerator (linac) were investigated. Six circular cutouts with 4 cm diameter were made with their centres shifted off by 0, 2, 4, 6, 8 and 10 mm from the machine CAX. The 6 x 6 cm(2) electron applicator was used for the measurement. The percentage depth doses (PDDs) were measured at the Machine CAX and also with respect to cutout centre for 6, 9, 12, 16 and 20 MeV electron beams. The in-line and cross-line profiles were measured at the depth of maximum dose (R100). The relative output factor (ROF) was measured at the reference depth. All the measurements were made at nominal source to surface distance (100 cm SSD) as well as at extended SSDs (100, 102, 106 and 110 cm). When the cutout centre was shifted away from the machine CAX for low energy beams the depth of 100% dose (R(100)), the depth of 90% dose (R(90)) and the depth of 80% dose (R(80)) had no significant change. For higher energies (>9 MeV) there was a reduction in these dosimetric parameters. The isodose coverage of the in-line and cross-line profile was reduced when the cutout centre was shifted away from the machine CAX. At extended SSDs the dosimetric changes are only because of geometric divergence of the beam and not by the positional uncertainty of the cutout. It is important for the radiation oncologist, dosimetrist, therapist and physicist to note such dosimetric changes while using the electron beam to the patients.

Peripheral dose from a dual energy linear accelerator equipped with tertiary multileaf collimators and enhanced dynamic wedge.

Peripheral dose (PD) or the dose outside the geometrical boundaries of the radiation field is of clinical importance when anatomical structures with low dose tolerances might be involved(1). It is the aim of this study is to estimate the PD on linear accelerators on different wedge systems without multileaf collimator (MLC). Measurements were performed on a dual energy linear accelerator equipped with tertiary MLC and enhanced dynamic wedge (EDW). Measurements were made using an ionization chamber embedded in a Radiation Field Analyser (RFA-300) with the secondary collimator and MLC setting of 5x5, 10x10, 15x15, and 20x20 cm2, and with the MLC fully retracted. The effects of SSD on PD were measured at three SSDs of 90, 100, and 110 cm for the irradiation fields of 5x5, 10x10, 15x15, and 20x20 cm2 and the effects of the three different wedges (Upper wedge, Lower Wedge and Enhanced Dynamic Wedge) on PD were measured for 45° wedges with field size of 15x15 cm2. Data were taken from 3 cm to 24 cm away from the field edge. Results show that due to tertiary MLC, PD can be reduced by means of a factor of two to three at certain distance from the edge of the field compared with TG-36 data. In between the wedges, the PD was less for the EDW when compared with the upper and lower physical wedges. We conclude that the reduction in PD is significant in reducing or eliminating the need for external peripheral shielding to reduce the dose on affected critical organs.

Variation of beam characteristics between three different wedges from a dual-energy accelerator.

The use of megavoltage X-ray sources of radiation, with their skin-sparing qualities in radiation therapy, has been proved useful in relieving patient discomfort and allowing higher tumor doses to be given with fewer restrictions due to radiation effects in the skin. The purpose of this study was to compare the dosimetric characteristics of a physical and enhanced dynamic wedge from a dual-energy (6 and 18 MV) linear accelerator such as surfaces doses with different source to surface distances (SSD), half value layer (HVL) in water and peripheral doses for both available energies. At short SSD such as 85 cm, higher surface doses are produced by the lower wedges by the short wedge-to-skin distance. For physical wedged field, at heel edge side HVL value was high (17 cm) compared with the measured that of EDW (15.1 cm). It was noticed that, the HVL variation across the beam was significantly higher for 6 MV X-rays than for 18 MV X-rays. The lower wedge has the maximum variation of peripheral dose compared to other wedges. The three wedge systems discussed in this work possess vastly different dosimetric characteristics. These differences will have a direct impact on the choice of the wedge system to be used for a particular treatment. Complete knowledge of the dosimetric characterisitics, including the surface and peripheral doses, is crucial in proper choice of particular wedge systems in clinical use.

Comparison of IMRT and Rapidarc treatment plans using AAPM task group test suites.

The purpose of this study is to examine the plan quality and monitor unit with sliding window IMRT and RapidArc (RA) treatment plans using American Association Physicists in Medicine TG119 test suite DICOM-RT images and structure sets. The structure set includes multi-target (superior, central, inferior), prostate, head and neck and C-shape. Plans were performed with Eclipse planning system using AAA algorithm with the plan goals specified in TG119. The plan results for multitarget shows that the D99 is greater than the plan goal for all the targets. The D10 is less than the plan goal for superior and inferior targets in both IMRT and RA plans. The D10 is 5% more with IMRT plan and 7% more with RA plan for central target in comparison with plan goal. The plan results for prostate shows that D95 is greater than the plan goal for both IMRT and RA plans. The D5 is less than the plan goal for IMRT plan and almost equal to plan goal for RA plan. The D30 is less than the plan goal for bladder and rectum in both the plans. The D10 is higher than the plan goal by 1.9% and 2.5% in IMRT and RA plan for rectum. The plan results for head and neck shows that the D99 and D90 were greater than the plan goal for PTV. The spinal cord and parotid doses were less than the plan goal in both the plans. The plan results for C-shape shows that the D95 was greater than the plan goal and D10 was less than the plan goal for PTV. The dose to central core was less than the plan goal in both IMRT and RA plans. Both the IMRT and RapidArc plans have met the plan goal for all the target and normal structures. RapidArc optimization and treatment planning requires more time than the IMRT plan. The monitor unit calculated by the RapidArc plan is less compared to IMRT plan, which reduces the treatment error caused by patient motion during treatment and integral dose.

Dosimetric comparison of high dose rate brachytherapy and intensity-modulated radiation therapy for cervical carcinoma.

Intracavitary brachytherapy is an integral part of radiotherapy for locally advanced gynecologic malignancies. A dosimetric intercomparison of high dose rate intracavitary brachytherapy (HDR_BT) and intensity-modulated radiotherapy in cervical carcinoma has been made in the present study. CT scan images of 10 patients treated with HDR_BT were used for this study. A sliding-window IMRT (IMRT_SW) and step-and-shoot IMRT plans were generated using 6-MV X-rays. The cumulative dose volume histograms of target, bladder, rectum and normal tissue were analyzed for both techniques and dose distributions were compared. It was seen that the pear-shaped dose distribution characteristic of intracavitary brachytherapy with sharp dose fall-off outside the target could be achieved with IMRT. The integral dose to planning target volume was significantly higher with HDR_BT in comparison with IMRT. Significant differences between the two techniques were seen for doses to 1 cc and 2 cc of rectum, while the differences in 1 cc and 2 cc doses to bladder were not significant. The integral doses to the nontarget critical and normal structures were smaller with HDR_BT and with IMRT. It is concluded that IMRT can be the choice of treatment in case of non-availability of HDR brachytherapy facilities or when noninvasive treatments are preferred.

Electron beam characteristics at extended source-to-surface distances for irregular cut-outs.

Electron beam therapy is widely used in the management of cancers. The rapid dose fall-off and the short range of an electron beam enable the treatment of lesions close to the surface, while sparing the underlying tissues. In an extended source-to-surface (SSD) treatment with irregular field sizes defined by cerrobend cutouts, underdosage of the lateral tissue may occur due to reduced beam flatness and uniformity. To study the changes in the beam characteristics, the depth dose, beam profile, and isodose distributions were measured at different SSDs for regular 10 × 10 cm(2) and 15 × 15 cm(2) cone, and for irregular cutouts of field size 6.5 × 9 cm(2) and 11.5 × 15 cm(2) for beam energies ranging from 6 to 20 MeV. The PDD, beam flatness, symmetry and uniformity index were compared. For lower energy (6 MeV), there was no change in the depth of maximum dose (R100) as SSD increased, but for higher energy (20 MeV), the R(100) depth increased from 2 cm to 3 cm as SSD increased. This shows that as SSD increases there is an increase in the depth of the maximum dose for higher energy beams. There is a +7 mm shift in the R(100) depth when compared with regular and irregular field sizes. The symmetry was found to be within limits for all the field sizes as the treatment distance extended as per International Electro technical Commision (IEC) protocol. There was a loss of beam flatness for irregular fields and it was more pronounced for lower energies as compared with higher energies, so that the clinically useful isodose level (80% and 90%) width decreases with increase in SSD. This suggests that target coverage at extended SSD with irregular cut-outs may be inadequate unless relatively large fields are used.

IMRT implementation and patient specific dose verification with film and ion chamber array detectors.

Implementation of Intensity Modulation Radiotherapy (IMRT) and patient dose verification was carried out with film and I'mariXX using linear accelerator with 120-leaf Millennium dynamic multileaf collimator (dMLC). The basic mechanical and electrical commissioning and quality assurance tests of linear accelerator were carried out. The leaf position accuracy and leaf position repeatability checks were performed for static MLC positions. Picket fence test and garden fence test were performed to check the stability of the dMLC and the reproducibility of the gap between leaves. The radiation checks were performed to verify the position accuracy of MLCs in the collimator system. The dMLC dosimetric checks like output stability, average leaf transmission and dosimetric leaf separation were also investigated. The variation of output with gravitation at different gantry angles was found to be within 0.9 %. The measured average leaf transmission for 6 MV was 1.6 % and 1.8% for 18 MV beam. The dosimetric leaf separation was found to be 2.2 mm and 2.3 mm for 6 MV and 18 MV beams. In order to check the consistency of the stability and the precision of the dMLC, it is necessary to carryout regular weekly and monthly checks. The dynalog files analysis for Garden fence, leaf gap width and step wedge test patterns carried out weekly were in good agreement. Pretreatment verification was performed for 50 patients with ion chamber and I'mariXX device. The variations of calculated absolute dose for all treatment fields with the ion chamber measurement were within the acceptable criterion. Treatment Planning System (TPS) calculated dose distribution pattern was comparable with the I'mariXX measured dose distribution pattern. Out of 50 patients for which the comparison was made, 36 patients were agreed with the gamma pixel match of >95% and 14 patients were with the gamma pixel match of 90-95% with the criteria of 3% delta dose (DD) and 3 mm distance-to-agreement (DTA). Commissioning and quality assurance of dMLC for IMRT application requires considerable time and effort. Many dosimetric characteristics need to be assessed carefully failing which the delivered dose will be significantly different from the planned dose. In addition to the issues discussed above we feel that individual MU check is necessary before the treatment is delivered.