There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Co-Planar Stereotaxic Atlas of the Human Brain—3-Dimensional Proportional System: An Approach to Cerebral Imaging, J. Talairach, P. Tournoux. Georg Thieme Verlag, New York (1988), 122 pp., 130 figs. DM 268

“Unpaired Image-to-Image Translation using Cycle-Consistent Adversarial Networks”の学習報告

NOTE The report of the Committee without its annexes appears as Official Records of the General Assembly, Sixty-third Session, Supplement No. 46. The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The country names used in this document are, in most cases, those that were in use at the time the data were collected or the text prepared. In other cases, however, the names have been updated, where this was possible and appropriate, to reflect political changes. Scientific Annexes Annex A. Medical radiation exposures Annex B. Exposures of the public and workers from various sources of radiation INTROdUCTION 1. In the course of the research and development for and the application of atomic energy and nuclear technologies, a number of radiation accidents have occurred. Some of these accidents have resulted in significant health effects and occasionally in fatal outcomes. The application of technologies that make use of radiation is increasingly widespread around the world. Millions of people have occupations related to the use of radiation, and hundreds of millions of individuals benefit from these uses. Facilities using intense radiation sources for energy production and for purposes such as radiotherapy, sterilization of products, preservation of foodstuffs and gamma radiography require special care in the design and operation of equipment to avoid radiation injury to workers or to the public. Experience has shown that such technology is generally used safely, but on occasion controls have been circumvented and serious radiation accidents have ensued. 2. Reviews of radiation exposures from accidents have been presented in previous UNSCEAR reports. The last report containing an exclusive chapter on exposures from accidents was the UNSCEAR 1993 Report [U6]. 3. This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices. Its conclusions are to be seen in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation. 4. The Committee's evaluations of public, occupational and medical diagnostic exposures are mostly concerned with chronic exposures of …

sources and effects of ionizing radiation

This study sought to systematically assess the influence of partial-volume effect (PVE) and segmentation on PET quantitative measures, hinging on lesion geometry. How this affects, e.g., prevalent maximum standardised uptake values, $SUV_{\max}$, and potentially impact clinical applications, e.g., response evaluation has yet to be fully discerned. From PET simulations with open-source software of variable-sized ellipsoidal lesions inserted in an anthropomorphic phantom, images of two contrasts and resolutions were generated. $SUV_{\max}$ and volumetric indices extracted with six different segmentations were compared for variability and test-retest repeatability. The study showed similar or larger shape dependent variability and lower repeatability in $SUV_{\max}$ than $SUV_{m\mathrm{e}an}$. Alternative volumetric indices might provide more robust measures but require better contouring than common thresholding. Thus findings suggested significant impact of PVE and segmentation in clinically relevant lesion sizes that can bias interpretation of SUV changes.

Clinical Relevance of Partial-Volume Effect: Dependence on Lesion size and Shape

Objective: To develop and validate an independent Monet Carlo dose calculation engine to support for software verification of treatment planning systems and quality assurance workflow. Method: GATE Monte Carlo toolkit was employed to simulate a fixed horizontal active scan-based proton beam delivery. Within the nozzle, two primary and secondary dose monitors have been designed allowing to compare the accuracy of dose estimation from MC simulation with respect to physical quality assurance measurements. The developed beam model was validated against a series of commissioning measurements using pinpoint chambers and 2D array ionization chambers in terms of lateral profiles and depth dose distributions. Furthermore, beam delivery module and treatment planning has been validated against the literature deploying various clinical test cases of AAPM TG-119 and a prostate patient. Result: MC simulation showed an excellent agreement with measurements in the lateral depth-dose parameters and SOBP characteristics within maximum relative error of 0.95% in range, 3.4% in entrance to peak ratio, 2.3% in mean point to point, and 0.852% in peak location. Mean relative absolute difference between MC simulation and the measurement in terms of absorbed dose in SOBP region was $0.93\% \pm 0.88\%$. Clinical phantom study showed a good agreement compared to a commercial treatment planning system (relative error for TG-119 PTV-D${}{95}$ $\mathrm{\sim}$ 1.8%; and for prostate PTV-D$_{95}$ $\mathrm{\sim}$ -0.6%). Conclusion: The results confirm the capability of GATE simulation as a reliable surrogate for verifying TPS dose maps prior to patient treatment.

Development and validation of an optimal GATE model for proton pencil-beam scanning delivery

Tumour classification and quantification in positron emission tomography (PET) imaging at early stage of illness are important for radiotherapy planning, tumour diagnosis, and fast recovery. Analysing large medical volumes using traditional techniques requires a decent amount of time, and in some approaches poor accuracy is achieved. Artificial intelligence (AI) technologies can provide better accuracy and save decent amount of time. Artificial neural network (ANN), as one of the best AI technologies, has the capability to classify, measure precisely the region of interest, and model the clinical evaluation for a specific problem. This paper presents a novel application of the ANN in the wavelet domain for PET volume segmentation. ANN performance evaluation using different number of hidden neurons is also considered. The proposed intelligent system outputs are compared with the outputs of thresholding, and clustering based approaches. Two PET phantom data sets and real PET volumes have been utilised to validate the proposed system which has shown promising results.

Intelligent approach for PET volume analysis

The number of patients undergoing diagnostic radiology and radiation therapy procedures has increased drastically owing to improvements in cancer diagnosis and treatment, and consequently, patient survival. However, the risk of secondary malignancies owing to radiation exposure remains a matter of concern. We previously published three hybrid computational fetal phantoms, which contained 27 fetal organs, as a starting point for developing the whole hybrid computational pregnant phantom set, which is the final objective of this study. An International Commission on Radiological Protection (ICRP) reference female voxel model was converted to a non-uniform rational B-spline (NURBS) surface model to construct a hybrid computational female phantom as a pregnant mother for each fetal model. Both fetal and maternal organs were matched with the ICRP- 89 reference data. To create a complete standard pregnant computational phantom set at 20, 30, and 35 weeks of pregnancy, the model mother’s reproductive organs were removed, and fetal phantoms with appropriate placental and uterine models were added to the female pelvis using a 3D-modeling software. With the aid of radiological image sets that had originally been used to construct the fetal models, each fetal position and rotation inside the uterus were carefully adjusted to represent the real fetal locations inside the uterus. The major abdominal soft tissue organs below the diaphragm, namely the small intestine, large intestine, liver, gall bladder, stomach, pancreas, uterus, and urinary bladder, were removed from non-pregnant females. The resulting fetal phantom was positioned in the appropriate location, matching the original radiological image sets. An obstetrician-gynecologist reviewed the complete internal anatomy of all fetus phantoms and the pregnant women for accuracy, and suggested changes were implemented as needed. The remaining female anatomical tissues were reshaped and modified to accommodate the location of the fetus inside the uterus. This new series of hybrid computational pregnant phantom models provides realistic anatomical details that can be useful in evaluating fetal radiation doses in pregnant patients undergoing diagnostic imaging or radiotherapy procedures where realistic fetal computational human phantoms are required.

https://iopscience.iop.org/article/10.1088/2057-1976/ac9414/pdf

Hybrid computational pregnant female phantom construction for radiation dosimetry applications

In this study, two proton beam delivery designs, passive scattering proton therapy (PSPT) and pencil beam scanning (PBS), were quantitatively compared in terms of dosimetric indices. The GATE Monte Carlo code was used to simulate the proton beam system; and the developed simulation engines were benchmarked with respect to the experimental measurements. A water phantom was used to simulate system energy parameters using a set of depth-dose data in the energy range of 120-235 MeV. To compare the performance of PSPT against PBS, multiple dosimetric parameters including FWHM, peak position, range, peak-to-entrance dose ratio, and dose volume histogram have been analyzed under the same conditions. Furthermore, the clinical test cases introduced by AAPM TG-119 were simulated in both beam delivery modes to compare the relevant clinical values obtained from DVH analysis. The parametric comparison in the water phantom between the two techniques revealed that the value of peak-to-entrance dose ratio in PSPT is considerably higher than that from PBS by a factor of 8%. In addition, the FWHM of the lateral beam profile in PSPT was increased by a factor of 7% compared to the corresponding value obtained from PBS model. TG-119 phantom simulations showed that the difference of PTV mean dose between PBS and PSPT techniques are up to 2.9% while the difference of max dose to organ at risks (OARs) exceeds 33%. The results demonstrated that the PBS proton therapy systems was superior in adapting to the target volume, better dose painting, and lower out-of-field dose compared to PSPT design.

/pdf/dosimetric-comparison-of-passive-scattering-and-active-2pbw6mtnu9.pdf

Habib Zaidi

Papers

Clinical Relevance of Partial-Volume Effect: Dependence on Lesion size and Shape

Development and validation of an optimal GATE model for proton pencil-beam scanning delivery

Intelligent approach for PET volume analysis

Hybrid computational pregnant female phantom construction for radiation dosimetry applications

Dosimetric Comparison of Passive Scattering and Active Scanning Proton Therapy Techniques Using GATE Simulation