Background
Monte Carlo (MC) simulations or measurements in anthropomorphic phantoms are recommended for estimating fetal dose in pregnant patients in radiotherapy. Among the many existing phantoms, ...there is no commercially available physical phantom representing the entire pregnant woman.
Purpose
In this study, the development of a low‐cost, physical pregnant female phantom was demonstrated using commercially available materials. This phantom is based on the previously published computational phantom.
Methods
Three tissue substitution materials (soft tissue, lung and bone tissue substitution) were developed. To verify Tena's substitution tissue materials, their radiation properties were assessed and compared to ICRP and ICRU materials using MC simulations in MV radiotherapy beams. Validation of the physical phantom was performed by comparing fetal doses obtained by measurements in the phantom with fetal doses obtained by MC simulations in computational phantom, during an MV photon breast radiotherapy treatment.
Results
Materials used for building Tena phantom are matched to ICRU materials using physical density, radiation absorption properties and effective atomic number. MC simulations showed that percentage depth doses of Tena and ICRU material comply within 5% for soft and lung tissue, up to 25 cm depth. In the bone tissue, the discrepancy is higher, but again within 5% up to the depth of 5 cm. When the phantom was used for fetal dose measurements in MV photon breast radiotherapy, measured fetal doses complied with fetal doses calculated using MC simulation within 15%.
Conclusions
Physical anthropomorphic phantom of pregnant patient can be manufactured using commercial materials and with low expenses. The files needed for 3D printing are now freely available. This enables further studies and comparison of numerical and physical experiments in diagnostic radiology or radiotherapy.
Assessment of legal age, also known as age of majority, is a controversial issue as there are few body biomarkers or evidence during late adolescence differentiating a subject from being a minor or ...adult. The third molar was recognized as a suitable site for age examination in late adolescence. We analyzed the development of the left mandibular third molar by the third molar maturity index (I
3M
) and a specific cut-off value of I
3M
= 0.08, established by Cameriere et al. in 2008 and used it for discriminating between minors and adult black Africans from Gaborone, Botswana. A final sample of panoramic radiographs (OPTs) of 1294 people (582 males and 712 females) aged between 13 and 23 years was evaluated. The real age decreased as I
3M
gradually increased. There was no statistically significant difference in the third molar development evaluated using I
3M
between males and females (
p
> 0.05) across different I
3M
classes. Results of 2 × 2 contingency tables for different cut-off values indicated that I
3M
= 0.08 was useful in discriminating between adults and minors. Precisely, for I
3M
= 0.08, the values of accuracy or overall fraction of correctly classified were 0.91 in males with a 95 % confidence interval (95 % CI) of 0.88 to 0.93 and 0.92 (95 % CI, 0.90 to 0.93) in females. Values of sensitivity of the test or the proportion of participants being 18 years and older were 0.88 (95 % CI, 0.87 to 0.90) in males and 0.88 (95 % CI, 0.90 to 0.93) in females, while values of specificity or proportion of individuals younger than 18 who have I
3M
<0.08 were 0.94 (95 % CI, 0.91 to 0.96) in males and 0.96 (95 % CI, 0.94 to 0.98) in females. Positive predictive values of the test, where the participants whose I
3M
<0.08 were adults, were 0.94 (95 % CI 0.91 to 0.96) in males and 0.97 (95 % CI, 0.94 to 0.98) in females, while negative predictive values of the test, where the participants whose I
3M
was ≥0.08 were minors, were 0.88 (95 % CI 0.85 to 0.90) in males and 0.97 (95 % CI, 0.94 to 0.98) in females. The likelihood ratios of the positive test (LR+) were 13.67 (95 % CI, 9.21 to 21.02) in males and 23.73 (95 % CI, 14.20 to 42.28) in females, while likelihood ratios of the negative test (LR−) were 0.12 (95 % CI 0.10 to 0.16) in males and 0.12 (95 % CI, 0.11 to 0.15) in females. Bayes post-test probabilities,
p
, were 0.94 (95 % CI 0.90 to 0.98) in males and 0.97 (95 %CI, 0.93 to 1.00) in females. These results indicate with high accuracy that I
3M
may be a useful alternative method in legal and forensic practice to discriminate individuals of black African origin who are around the legal adult age of 18 years in Botswana. Further studies should address the usefulness of this method and specific cut-off for different adolescent populations.
The calculation algorithm for intensity modulated radiotherapy (IMRT) built in the Elekta Monaco treatment planning system (TPS) is based on Monte Carlo (MC) simulation. Absorbed dose is calculated ...as dose to medium in medium (Dm,m), but the conversion from Dm,m to dose to water in medium (Dw,m) is enabled. According to published data, differences between these two options exist, particularly in bony structures. In this study, comparisons between dose calculation options built in Elekta Monaco TPS and Monte Carlo N-Particle transport code® (MCNP) in different materials are shown. Furthermore, the majority of clinical experience is based on the dose to water in water (Dw,w) concept provided by analytical algorithms and has represented the standard for dose calculation over the past few decades. Additionally, MCNP calculation was performed to simulate the Dw,w concept. Therefore, the correlation between Dw,w concept, and both calculation options provided by the Elekta Monaco TPS was determined.
To evaluate the accuracy of TPS calculation options for 6 MV photon beam, MCNP simulation was performed for 13 different materials with mass densities ranging from 0.2 g/cm3 to 2.17 g/cm3 using simplified geometry. The simulation was performed in two ways: with standard material representation taking into account their chemical compositions and corresponding mass densities and using non-standard material representation employing chemical composition of water with varying mass densities. Depth dose curves calculated by MCNP were compared to those obtained by two calculation options Dm,m and Dw,m using root mean square (RMS) deviations.
RMS deviations between depth dose curves, for Dm,m and Dw,m become largest for mass density 2.17 g/cm3, up to RMS = 13%. Comparison for both calculation options to the MCNP defined for Dm,m shows very good agreement, with RMS deviation less than 3% for the majority of examined materials. For the Dw,m calculation option results are acceptable in mass density range from 0.5 g/cm3 (RMS = 1.4%) to 1.06 g/cm3 (RMS = 2.4%). For the rest of examined materials, RMS deviation increases, with a maximal value of 12.4%. Absorbed dose calculation comparison between Dw,m and non-standard MCNP shows large deviations for the majority of used materials, up to RMS = 13.1%. RMS deviations between Dm,m calculation option and non-standard MCNP are much lower than one might expect. For the highest mass density in this research (ρ = 2.17 g/cm3), the RMS deviation is 3.7%.
Although it does not take into account the chemical composition of the medium, TPS calculation option Dm,m shows very good agreement with standard MCNP calculations. Furthermore, it is demonstrated that the Dw,m calculation option differs substantially from Dw,w. Additionally, it was found that for different materials absorbed dose calculated as Dm,m shows better agreement to the algorithms that calculate absorbed dose using Dw,w approach. Although the research was performed on simplified geometry, the results indicate that the use of Dm,m could be preferable in order to allow better consistency with previous clinical data in radiation oncology.
•MC evaluation of Elekta Monaco algorithm for both calculation options performed.•Monte Carlo simulation using MCNP code carried out in two ways.•Dose to medium in medium and dose to water in water compared.•Dose to water in medium and dose to water in water compared.•The comparison was made for 13 materials of different mass densities.
Human dipeptidyl peptidase III (hDPP III) is a zinc-exopeptidase of the family M49 involved in final steps of intracellular protein degradation and in cytoprotective pathway Keap1-Nrf2. Biochemical ...and structural properties of this enzyme have been extensively investigated, but the knowledge on its contacts with other proteins is scarce. Previously, polypeptide aprotinin was shown to be a competitive inhibitor of hDPP III hydrolytic activity. In this study, aprotinin was first investigated as a potential substrate of hDPP III, but no degradation products were demonstrated by MALDI-TOF mass spectrometry. Subsequently, molecular details of the protein-protein interaction between aprotinin and hDPP III were studied by molecular modeling. Docking and long molecular dynamics (MD) simulations have shown that aprotinin interacts by its canonical binding epitope with the substrate binding cleft of hDPP III. Thereby, free N-terminus of aprotinin is distant from the active-site zinc. Enzyme-inhibitor complex is stabilized by intermolecular hydrogen bonding network, electrostatic and hydrophobic interactions which mostly involve constituent amino acid residues of the hDPP III substrate binding subsites S1, S1', S2, S2' and S3'. This is the first study that gives insight into aprotinin binding to a metallopeptidase.
Communicated by Ramaswamy H. Sarma
To investigate sex-specific correlations between the dimensions of permanent canines and the anterior Bolton ratio and to construct a statistical model capable of identifying the sex of an unknown ...subject.
Odontometric data were collected from 121 plaster study models derived from Caucasian orthodontic patients aged 12-17 years at the pretreatment stage by measuring the dimensions of the permanent canines and Bolton's anterior ratio. Sixteen variables were collected for each subject: 12 dimensions of the permanent canines, sex, age, anterior Bolton ratio, and Angle's classification. Data were analyzed using inferential statistics, principal component analysis, and artificial neural network modeling.
Sex-specific differences were identified in all odontometric variables, and an artificial neural network model was prepared that used odontometric variables for predicting the sex of the participants with an accuracy of > 80%. This model can be applied for forensic purposes, and its accuracy can be further improved by adding data collected from new subjects or adding new variables for existing subjects. The improvement in the accuracy of the model was demonstrated by an increase in the percentage of accurate predictions from 72.0-78.1% to 77.8-85.7% after the anterior Bolton ratio and age were added.
The described artificial neural network model combines forensic dentistry and orthodontics to improve subject recognition by expanding the initial space of odontometric variables and adding orthodontic parameters.
Acta stomatologica Croatisa (ASCRO) is scientific-professional magazine whose first issue was published back in 1966. Ever since the magazine publishers were the School of Dental Medicine of the ...University of Zagreb and the Croatian Dental Association of the Croatian Medical Association. Over the past fifty years two hundred regular editions were pubslihed along with three additions. The magazine has been internationally indexed and it was granted the DOI number. In this way by means of CrossCheck possible plagiarisms are being checked which aims at obtaining originality of the published results. Another peculiarity of ASCRO is bilingualism throughout the whole edition, international recognizability, open source and tradition based on sound foundations.
This study presents national surveys of patient exposure from nuclear medicine (NM) diagnostic procedures in 2010 and 2015 in the Republic of Croatia.
The survey was performed according to the ...European Commission Dose DataMed (DDM) project methodology. 28 most frequent NM diagnostic procedures were identified. Data about frequencies of procedures and average administered activities of radioisotopes used in those procedures were collected. Average administered activities were converted to effective doses according to the dose conversion coefficients. Then the collective effective dose to the population and an effective dose per capita were calculated based on the number of the most frequent NM diagnostic procedures and the average effective dose per procedure.
In 2010, 41200 NM diagnostic procedures led to 146.7 manSv collective effective dose to the population and in 2015, 42000 NM diagnostic procedures led to 146.8 manSv collective effective dose to the population. The frequencies of NM diagnostic procedures were 9.7 and 9.8 annually per 1000 population with 34.1 μSv and 34.2 μSv effective dose per capita for 2010 and 2015, respectively. The main contributors to the annual collective dose from NM in Croatia are examinations of the bone, heart, thyroid and PET/CT tumour diagnostic. Average administered activities have not changed considerably from 2010 to 2015. Nevertheless, within the frequency of some of the procedures, significant changes were found in five-year period.
Frequencies, average administered activities and collective effective dose to the population from NM diagnostic procedures in Croatia are comparable to the values reported by other European surveys. Changes were found between 2010 and 2015 and we intend to perform this study periodically to identify possible trends, but also to raise awareness about the potential dose optimization.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This paper aims to propose a statistical model to assess pubertal growth spurt using the ratio of the anterior height projection to the posterior (Vba) of the fourth cervical vertebra body (C4) on ...cephalograms and to calculate the residual proportion of skeletal maturation and the time for the pubertal growth spurt to end for a given Vba. A sample of 538 cephalograms from healthy-living children aged between 5 and 15 years was analyzed. A segmented regression model was used to explain the different Vba stages relative to the pubertal growth spurt. In addition, the time to achieve skeletal maturation was evaluated for a given Vba between the beginning (Vba1) and the end (Vba2) of the pubertal growth spurt. A longitudinal sample of 25 males and 25 females was analyzed to validate the proposed method. The values of Vba corresponding to higher pubertal development rate ranged from Vba1 = 0.677 (95%CI, 0.644–0.711) to Vba2 = 0.966 (95%CI, 0.905–1.028) and from Vba1 = 0.669 (95%CI, 0.645–0.693) to Vba2 = 1.073 (95%CI, 1.044–1.101) in males and females, respectively. The validation process results showed that our model did not produce any incorrect forecasts. The proposed method estimates the beginning and the end of the pubertal growth spurt together with the residual proportion of skeletal maturation for a given Vba.
Context: Introduction of dual-layer multileaf collimator (MLC) radiotherapy linear accelerators into clinical practice is an important development in advanced external beam radiotherapy. A method of ...delivering comparable high-resolution fluences with a single-layer MLC is presented. Aims: The aims of this study are to present new algorithms and approaches to define high-resolution hypermodulated fluences, obtain orthogonal decomposition of fluences, and deliver them on a linear accelerator with single MLC from two perpendicular collimator settings. Materials and Methods: High-resolution fluences were defined using Monte Carlo (MC) calculation. A novel use of a limited-memory, bounded, Broyden-Fletcher-Goldfarb-Shanno algorithm was used to decompose such fluences to ones deliverable with a pair of fields with mutually orthogonal collimator settings. Such a technique, here named cross motion leaf calculator (XMLC), is compared against single sliding window (SSW) technique typically used in intensity-modulated radiation therapy (IMRT). An electronic portal imaging device (EPID) is used, and the results were compared with gamma analysis. Furthermore, MC was used to determine dose distributions for computed tomography images of ten head-and-neck cancer patients. Results: Gamma analysis (3%, 3 mm) against ideal fluence is considerably more favorable to XMLC (94% ± 4%) versus SSW (76% ± 5%). Furthermore, the dose-volume histogram (DVH) analysis showed that XMLC enables delivery of fluences superior to that of IMRT and these results in clinically relevant enhancements in DVH results. Conclusions: At the time of writing of this study, there were more than 12,000 medical linear accelerators in clinical use, and XMLC can prove itself useful wherever linac is equipped with MLC but cannot delivery latest techniques, such as volumetric modulated arc therapy.
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