Critical Appraisal of Paediatric Embryonal Cancers Treated with Image-guided Intensity-modulated Proton Therapy.

AIM: To carry out a comprehensive critical appraisal of image-guided intensity-modulated proton therapy practice for craniospinal irradiation (CSI). MATERIALS AND METHODS: An image-guided intensity-modulated proton therapy database of 45 consecutive paediatric patients with central nervous system embryonal malignancies treated between January 2019 and April 2022 were critically appraised for demography, diagnosis, treatment planning strategy and treatment delivery accuracy. RESULTS: Most patients (median age: 7.5 years; male:female ratio: 34:11) had medulloblastoma (56%), followed by recurrent ependymoma (19%), pinealoblastoma (5%), germ cell (5%) and others (15%). The dose to the planning target volume-craniospinal (PTV-CS; length 39.06-79.59 cm) varied from 21 to 35 GyRBE, whereas the combined median dose to craniospinal and boost was 54 GyRBE. In all patients, the 95% isodose line covered the cribriform plate completely and optic nerves mostly, with a median V95% of 100% and 82.96%, keeping Dmax to the lens <3.9 GyRBE. In skeletally immature patients (88.38%), the anterior vertebral body was completely covered in 18.18% and underdosed in 70.15% of the cases, resulting in a median Dmean of 10.11 GyRBE to the oesophagus. Lateral spine coverage was maintained on the edges of the vertebral body in 52.2%, whereas it extended beyond in 48.8%. The median V98% for clinical target volumes and V95% for PTVs of the brain, spine and craniospinal were >97%, with excellent conformity (0.89) and homogeneity (0.07) indices for PTV-CS. All neurological organs at risk received a median Dmax ranging from 36 to 44 GyRBE from the combined CSI and boost regimens. Analysis of patient-specific quality assurance results revealed that 545 (97.67%) planar dosage verification had gamma (3% at 3 mm) values >95%. The online patient set-up verification showed translational and rotational deviation within 2 mm and 0.5° in 88-94% and 97% of the cases. Systematic and random error were within 0.90 mm and 1.71 mm in translation and 0.1° and 0.2° in rotation. CONCLUSION: A change in practice pattern was observed. The findings from our comprehensive critical appraisal add to the growing library of CSI practice and may serve as a reference for inter-institutional comparison.

Antibacterial Efficacy of Pastes Against E Faecalis in Primary Root Dentin: A Confocal Microscope Study.

OBJECTIVES: Management of abscessed primary teeth often present endodontic failure owing to questioned efficiency of dressings or obturating pastes to eliminate Enterococcus faecalis, a resistant bacterium, residing in depth of dentinal tubules. The present study evaluates the antimicrobial efficacy of two antibacterial and two obturating pastes in dentinal tubules of primary teeth infected with Enterococcus faecalis using viability stain and confocal laser scanning microscope (CLSM). STUDY DESIGN: Total 28 samples were prepared.Four groups with 6 samples each were made according to antibacterial pastes i.e. 1% or 2%Chlorhexidine (CHX) + calcium hydroxide (CH), CH + iodoform (Metapex) and Zinc Oxide Eugenol (ZOE). Dentinal tubules from the root canal side were infected with E. faecalis by centrifugation of the bacterial suspension. Two specimens from each group were subjected to 1, 7 and 15 days antibacterial pastes exposure. Viability staining followed by CLSM were used to quantitatively analyze the dead cell count directly inside dentin. RESULT: Univariate analysis showed that all medicaments were significantly effective (p<.05). Kruskal wallis ANOVA test did not show significant difference among four medicaments at day 1 while it was significantly different at day 7 & 15. Paired sample student's t-test revealed significant difference in efficacy between 1& 15 days for 1%CHX+CH; between 1&15,and 7&15 days; between all days for ZOE. Ranking of antimicrobial efficacy of tested medicament was (most effective to the least): 1%CHX+CH(15)> ZOE(15)> Metapex(15)> 2%CHX+CH(15)> 2%CHX+CH(7)> 2%CHX+CH(1)> 1%CHX+CH(7)> 2%CHX+CH(15)> Metapex(1)> ZOE(1)> ZOE(7). CONCLUSIONS: All medicaments were effective against E. faecalis in dentine of primary teeth and their efficacy increased with longer contact with 1%CHX+CH being most effective at day 15. Inclusion of 1% CHX in dressings or obturating pastes might minimize the endodontic relapse and maximize the tooth retention in functional state in pediatric dentistry.

Effect of three different pastes on remineralization of initial enamel lesion: an in vitro study.

OBJECTIVE: Dental caries in enamel is unique as enamel is both acellular and avascular. Fluoride is one of the most effective remineralizing agents in caries prevention. The purpose of the study was to assess whether nano-hydroxyapatite and CPP-ACP can be used as an alternative to fluoride for remineralization of early carious lesions. STUDY DESIGN: Initial artificial carious lesions were prepared in enamel with demineralization solution. The treatment materials used as remineralizing agents were Nano-hydroxyapatite (10%), CPP - ACP (10%), NaF (1000 ppm) and Deionized water (negative control). Surface microhardness (SMH) measurements were performed before/after demineralization and after 3, 6, 9 and 12 days of pH cycling and the percentage surface microhardness recovery (%SMHR) was calculated. The specimens were then examined by scanning electron microscope. RESULTS: Percentage surface microhardness recovery of nano-hydroxyapatite and fluoride was significantly greater than CPP - ACP and negative control. There was no significant difference of %SMHR between n-HA and fluoride at different time periods in the pH cycling. SEM analysis revealed n-HA particles were deposited on the demineralized enamel surface which formed a new surface layer. When observed under SEM CPP - ACP failed to show any significant surface remineralization while surface globular crystal depositions with multiple discrete porosities were evident with fluoride. CONCLUSION: It was concluded that nano-hydroxyapatite and fluoride had the potential to remineralize initial enamel lesions. CPP - ACP can be used as an effective adjunct to fluoride therapy but cannot be used as an alternative to fluoride.

Biofilm associated microorganisms on removable oral orthodontic appliances in children in the mixed dentition.

OBJECTIVE: Biofilms on removable orthodontic appliances act as reservoir of microorganisms, capable of modifying the environmental condition of oral cavity and are difficult to be removed with routine hygiene measures. The present investigation includes enumeration, identification and numerical analysis of different types of cultivable bacteria associated with the biofilms on removable orthodontic appliances. STUDY DESIGN: Removable appliances of 25 healthy children among the ages of 10 to 14 years were taken to measure the prevalence of biofilms and type of microorganisms. For isolation of microorganism from biofilms different types of selective and non-selective medium based on standard methods were used. The data were further analysed by using Kolmogorov-Smirnov test, one-sample t-test and Spearman rank correlation coefficient. The percentage frequencies of isolates were also calculated RESULTS: The survey revealed the presence of both multi-species and mono species biofilms on appliances, with Non-Streptococci, anaerobic bacteria, Streptococcus spp., members of the family Enterobacteriaceae and Lactobacillus spp. as a dominant microbial flora of biofilms. Bacillus sp. and Candida sp. were isolated from one sample each. Significant positive and negative correlations were established among the species isolated from biofilms. CONCLUSION: Higher prevalence of the members of the family Enterobacteriaceae were reported during this study, advocating an extra hygienic measure is essential for this age group while wearing acrylic orthodontic appliances in oral cavity.

High-precision radiotherapy for craniospinal irradiation: evaluation of three-dimensional conformal radiotherapy, intensity-modulated radiation therapy and helical TomoTherapy.

This study aimed to establish the feasibility of intensity-modulated radiation therapy (IMRT) in craniospinal irradiation (CSI) using conventional linear accelerator (IMRT_LA) and compare it dosimetrically with helical TomoTherapy (IMRT_Tomo) and three-dimensional conformal radiotherapy (3DCRT). CT datasets of four previously treated patients with medulloblastoma were used to generate 3DCRT, IMRT_LA and IMRT_Tomo plans. A CSI dose of 35 Gy was prescribed to the planning target volume (PTV). IMRT_LA plans for tall patients were generated using an intensity feathering technique. All plans were compared dosimetrically using standardised parameters. The mean volume of each PTV receiving at least 95% of the prescribed dose (V(95%)) was >98% for all plans. All plans resulted in a comparable dose homogeneity index (DHI) for PTV_brain. For PTV_spine, IMRT_Tomo achieved the highest mean DHI of 0.96, compared with 0.91 for IMRT_LA and 0.84 for 3DCRT. The best dose conformity index was achieved by IMRT_Tomo for PTV_brain (0.96) and IMRT_LA for PTV_spine (0.83). The IMRT_Tomo plan was superior in terms of reduction of the maximum, mean and integral doses to almost all organs at risk (OARs). It also reduced the volume of each OAR irradiated to various dose levels, except for the lowest dose volume. The beam-on time was significantly longer in IMRT_Tomo. In conclusion, IMRT_Tomo for CSI is technically easier and potentially dosimetrically favourable compared with IMRT_LA and 3DCRT. IMRT for CSI can also be realised on a conventional linear accelerator even for spinal lengths exceeding maximum allowable field sizes. The longer beam-on time in IMRT_Tomo raises concerns about intrafraction motion and whole-body integral doses.

Peripheral dose from uniform dynamic multileaf collimation fields: implications for sliding window intensity-modulated radiotherapy.

The increase in the number of monitor units in sliding window intensity-modulated radiotherapy, compared with conventional techniques for the same target dose, may lead to an increase in peripheral dose (PD). PD from a linear accelerator was measured for 6 MV X-ray using 0.6 cm3 ionization chamber inserted at 5 cm depth into a 35 cm x 35 cm x 105 cm plastic water phantom. Measurements were made for field sizes of 6 cm x 6 cm, 10 cm x 10 cm and 14 cm x 14 cm, shaped in both static and dynamic multileaf collimation (DMLC) mode, employing strip fields of fixed width 0.5 cm, 1.0 cm, 1.5 cm, and 2.0 cm, respectively. The effect of collimator rotation and depth of measurement on peripheral dose was investigated for 10 cm x 10 cm field. Dynamic fields require 2 to 14 times the number of monitor units than does a static open field for the same dose at the isocentre, depending on strip field width and field size. Peripheral dose resulting from dynamic fields manifests two distinct regions showing a crest and trough within 30 cm from the field edge and a steady exponential fall beyond 30 cm. All dynamic fields were found to deliver a higher PD compared with the corresponding static open fields, being highest for smallest strip field width and largest field size; also, the percentage increase observed was highest at the largest out-of-field distance. For 6 cm x 6 cm field, dynamic fields with 0.5 cm and 2 cm strip field width deliver PDs 8 and 2 times higher than that of the static open field. The corresponding factors for 14 cm x 14 cm field were 15 and 6, respectively. The factors by which PD for DMLC fields increase, relative to jaws-shaped static fields for out-of-field distance beyond 30 cm, are almost the same as the corresponding increases in the number of monitor units. Reductions of 20% and 40% in PD were observed when the measurements were done at a depth of 10 cm and 15 cm, respectively. When the multileaf collimator executes in-plane (collimator 90 degrees) motion, peripheral dose decreases by as much as a factor of 3 compared with cross-plane data. The knowledge of PD from DMLC field is necessary to estimate the increase in whole-body dose and the likelihood of radiation induced secondary malignancy.

Performance evaluation of a dedicated computed tomography scanner used for virtual simulation using in-house fabricated CT phantoms.

Comprehensive tests on single slice CT scanner was carried out using in-house fabricated phantoms/test tools following AAPM recommended methods to independently validate the auto-performance test (APT) results. Test results of all the electromechanical parameters were found within the specified limits. Radiation and sensitivity profile widths were within ± 0.05 cm of the set slice thickness. Effective energy corresponding to nominal kVp of 80, 110 and 130 were 49.99, 55.08 and 59.48 keV, respectively. Percentage noise obtained by APT was 1.32% while the independently measured value was 0.38%. Observed contrast resolutions by independent method at 0.78% and 12% contrast difference were 4 mm and 1.25 mm (= 4 lp/cm) respectively. However, high contrast resolution (limiting spatial resolution) by APT at 50, 10 and 2% MTF levels were 9, 12.5 and 14.1 lp/cm respectively. Difference in calculated and measured CT numbers of water, air, teflon, acrylic, polystyrene and polypropylene were in the range of 0 to 24 HU, while this difference was 46 and 94 HU in case of nylon and bakelite respectively. The contrast scale determined using CT linearity phantom was 1.998×10(-4) cm(-1)/CT number. CT dose index (CTDI) and weighted CTDI (CTDI(w)) measured at different kVp for standard head and body phantoms were smaller than manufacturer-specified and system-calculated values and were found within the manufacturer-specified limit of ± 20%. Measured CTDIs on surface (head: 3.6 cGy and body: 2.6 cGy) and at the center (3.3 cGy, head; and 1.2 cGy, body) were comparable to reported values of other similar CT scanners and were also within the industry-quoted CTDI range. Comprehensive QA and independent validation of APT results are necessary to obtain baseline data for CT virtual simulation.