The presence of artificial implants complicates the delivery of proton therapy due to inaccurate characterization of both the implant and the surrounding tissues. In this work, we describe a method to characterize implant and human tissue mimicking materials in terms of relative stopping power (RSP) using a novel proton counting detector. Each proton is tracked by directly measuring the deposited energy along the proton track using a fast, pixelated spectral detector AdvaPIX-TPX3 (TPX3). We considered three scenarios to characterize the RSPs. First, in-air measurements were made in the presence of metal rods (Al, Ti and CoCr) and bone. Then, measurements of energy perturbations in the presence of metal implants and bone in an anthropomorphic phantom were performed. Finally, sampling of cumulative stopping power (CSP) of the phantom were made at different locations of the anthropomorphic phantom. CSP and RSP information were extracted from energy spectra at each beam path. To quantify the RSP of metal rods we used the shift in the most probable energy (MPE) of CSP from the reference CSP without a rod. Overall, the RSPs were determined as 1.48, 2.06, 3.08, and 5.53 from in-air measurements; 1.44, 1.97, 2.98, and 5.44 from in-phantom measurements, for bone, Al, Ti and CoCr, respectively. Additionally, we sampled CSP for multiple paths of the anthropomorphic phantom ranging from 18.63 to 25.23 cm deriving RSP of soft tissues and bones in agreement within 1.6% of TOPAS simulations. Using minimum error of these multiple CSP, optimal mass densities were derived for soft tissue and bone and they are within 1% of vendor-provided nominal densities. The preliminary data obtained indicates the proposed novel method can be used for the validation of material and density maps, required by proton Monte Carlo Dose calculation, provided by competing multi-energy computed tomography and metal artifact reduction techniques.
- MeSH
- Phantoms, Imaging * MeSH
- Humans MeSH
- Monte Carlo Method * MeSH
- Prostheses and Implants * MeSH
- Proton Therapy instrumentation MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- MeSH
- Basement Membrane immunology MeSH
- Pemphigoid, Bullous diagnosis immunology MeSH
- Fluorescent Antibody Technique MeSH
- Immunoglobulins analysis MeSH
- Humans MeSH
- Aged MeSH
- Check Tag
- Humans MeSH
- Aged MeSH
- Female MeSH
- Publication type
- Case Reports MeSH
PURPOSE: Thrombolytic therapy in patients with acute ischemic stroke is contraindicated when the infarction core exceeds a given threshold. To date, there are no standardized guidelines for computed tomography infarction core assessment. Current practice involves use of thresholding methods, where the results are further adjusted by an experienced physician. An automated method for infarction core delineation and volume measurement was developed and tested. MATERIALS AND METHODS: CT postprocessing software was developed for analysis of whole brain perfused blood volume (PBV) and cerebral blood volume (CBV) maps. The program was designed for potential use with mean transit time (MTT) or cerebral blood flow (CBF) maps. The proposed method was tested on a set of 12 patients on both PBV and CBV maps with whole brain coverage by comparison with the results of a simple thresholding method and with manually marked findings provided by two independent physicians. RESULTS: The proposed method produced a marked infarct core volume corresponding to 53 % of the manually delineated volumes. The simple thresholding method with the optimal threshold, using the same dataset, marked 15[Formula: see text] larger volume compared to the volume delineated by physicians. CONCLUSION: An automated infarction core segmentation method based on local neighborhood features was developed and tested, demonstrating its utility in distinguishing between infarcted and non-infarcted areas, as well as reduction in the number of false positives and volume error.
- MeSH
- Blood Volume * MeSH
- Humans MeSH
- Brain physiopathology radiography MeSH
- Brain Infarction diagnosis physiopathology MeSH
- Cerebrovascular Circulation physiology MeSH
- Tomography, X-Ray Computed methods MeSH
- Regional Blood Flow physiology MeSH
- Software * MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
BACKGROUND: The spatially varying mechanical properties in finite element models of bone are most often derived from bone density data obtained via quantitative computed tomography. The key step is to accurately and efficiently map the density given in voxels to the finite element mesh. METHODS: The density projection is first formulated in least-squares terms and then discretized using a continuous and discontinuous variant of the finite element method. Both discretization variants are compared with the nodal and element approaches known from the literature. FINDINGS: In terms of accuracy in the L2 norm, energy distance and efficiency, the discontinuous zero-order variant appears to be the most advantageous. The proposed variant sufficiently preserves the spectrum of density at the edges, while keeping computational cost low. INTERPRETATION: The continuous finite element method is analogous to the nodal formulation in the literature, while the discontinuous finite element method is analogous to the element formulation. The two variants differ in terms of implementation, computational cost and ability to preserve the density spectrum. These differences cannot be described and measured by known indirect methods from the literature.
- MeSH
- Finite Element Analysis MeSH
- Bone and Bones * diagnostic imaging MeSH
- Bone Density MeSH
- Humans MeSH
- Tomography, X-Ray Computed * methods MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
VÝCHODISKA: Snaha o zmapování situace v lékárnách a jejich propojení se službami harm reduction v Plzni vycházela ze spolupráce Terénního programu Ulice s lékárnou v Rokycanech. Protože ne všichni PUD jsou v kontaktu s nízkoprahovými programy, byl zájem zacílen zvláště na lékárny. Kromě lékáren se v Plzni na distribuci injekčních stříkaček podílejí také tři neziskové organizace. CÍLE: Zjistit množství injekčních stříkaček, které se pohybuje na drogové scéně v Plzni, a to oběma směry. Zvláštní zřetel byl kladen na zjištění role lékáren v tomto koloběhu. METODY: Krátký průzkum formou dotazování lékáren, prodejen zdravotnických potřeb, neziskových organizací pracujících s PUD a Městské policie. Získaná data byla zpracována popisnou statistikou. SOUBOR: Výzkumný soubor tvořilo 45 lékáren, 7 prodejen zdravotnických potřeb, 4 nízkoprahové programy tří neziskových organizací pracujících s PUD a Městská policie. VÝSLEDKY: Celkový objem vydaného injekčního materiálu v 1. pololetí roku 2010 činil 94 791 kusů stříkaček. Objem přijatého injekčního materiálu, který byl bezpečně likvidován, činil 81 527 kusů stříkaček. ZÁVĚRY: V plzeňských lékárnách se prodává 10 % z celkového počtu vydaného injekčního materiálu. Tento počet není vysoký, pokrytí populace injekčních uživatelů nízkoprahovými službami se zdá být dostatečné. Na území Plzně neprodává injekční materiál 39 % lékáren, což odpovídá trendům v České republice. Během výzkumu se nám podařilo navázat spolupráci se třemi lékárnami, což je 6,7 %. To je méně, než kolik vyšlo v celorepublikovém výzkumu. Absence standardů spolupráce s lékárnami a neexistence definice úlohy lékáren v adiktologických službách vede k nesystematičnosti a nedostatečnému využití potenciálu lékáren při práci s problémovými uživateli drog.
BACKGROUND: the attempt to map the situation in pharmacies and their connection to the harm reduction service in Pilsen stemmed from the cooperation between the Ulice Outreach Programme and a pharmacy in Rokycany. As not all PDUs are in contact with the low-threshold programmes, the focus was placed especially on pharmacies. The distribution of syringes is provided not only by pharmacies but also by three non-profit organisations. AIMS: to find out the number of syringes circulating on the Pilsen drug scene in both directions, with special regard to understanding the role of pharmacies in this circulation. DESIGN AND MEASUREMENTS: a short survey in the form of questions addressed to pharmacies, medical supplies shops, non-profit organisations working with PDUs, and the Municipal Police. The data generated by the survey were processed by descriptive statistics. PARTICIPANTS: the research sample consisted of 45 pharmacies, 7 medical supplies shops, 4 low-threshold programmes of 3 non-profit organisations working with PDUs, and the Municipal Police. RESULTS: the total amount of injecting material issued in the first six months of 2010 was 94,791 syringes. The amount of injecting material received and safely disposed of was 81,527 syringes. CONSLUSIONS: Pharmacies in Pilsen sell 10% of the total amount of injecting material issued. This number is not high; the coverage of the population of injecting users by lothreshold services seems to be sufficient. 39% of the pharmacies in Pilsen do not sell injecting material, which corresponds with the overall trends in the Czech Republic. During the survey, we managed to establish cooperation with three pharmacies, which account for 6.7% of the pharmacies. This number is below the average of nationwide survey results. The absence of standards for cooperation with pharmacies and the lack of a definition of the role of pharmacies in relation to addictological services lead to the lack of a systematic approach and insufficient utilisation of pharmacies’ potential for work with problem drug users.
- Keywords
- distribuce injekčního materiálu,
- MeSH
- Epidemiologic Studies MeSH
- Syringes statistics & numerical data MeSH
- Cooperative Behavior MeSH
- Pharmacies * MeSH
- Humans MeSH
- Substance-Related Disorders epidemiology MeSH
- Needle-Exchange Programs * statistics & numerical data trends MeSH
- Harm Reduction MeSH
- Drug Users MeSH
- Health Services Research statistics & numerical data MeSH
- Check Tag
- Humans MeSH
- Geographicals
- Czech Republic MeSH
xx, 669 s. : il.
Statistics in practice
1st ed. xiii, 277 s.
1st ed. vii, 647 s. : il. ; 29 cm
- MeSH
- Brain Mapping MeSH
- Publication type
- Monograph MeSH
- Conspectus
- Statistika
- NML Fields
- statistika, zdravotnická statistika
