Effect of Clinician-directed Technical Specifications on Entrance Skin Doses in Neonates

Objectives: To compare the entrance skin doses (ESD) before and after implementation of a radiation safety policy in neonates (RSN), which focused on clinician-directed technical specifications on the digital X-ray machine. Methods: Prospective observations included two sets of X-rays: Before (BRSN) and after (ARSN) implementation of RSN (documented indication for Xray/expected posttest findings, settings of 40 kVp, 0.5 mAs, film-focus distance 100 cm, gonadal-shield, optimal collimation, and post-shoot image-enhancement). Results: 33 and 32 X-rays were analyzed in respective groups. Mean (SD) of calculated and machine-quantified ESD (µGy/m2) was higher in BRSN group as compared to ARSN group (P <0.001). All ARSN X-rays were interpretable for expected post-test findings. Conclusion: Clinicians’ cognizance of ability to make consequential bedside technical specifications, can reduce ESD without affecting interpretability. These single observations could have a larger impact in sick neonates, where multiple X-rays are done.

Simulated measurement of doses from kilovoltage cone beam CT based on a 5 years old pediatric anthropomorphic phantom / 中华放射医学与防护杂志

Objective To use thermoluminescense dosimeters (TLDs) to evaluate the radiation doses to various critical organs in the computerized imaging reference systems (CIRS) 5 years old pediatric anthropomorphic phantom result ing from Varian kilovohage cone beam CT (kV-CBCT) system based on the standard scanning protocols.Effective dose were also calculated based on dose measurement.Methods A batch of TLDs with consistency no larger than 2％ were selected and annealed.First,the doses in an anthropomorphic pelvic phantom were measured using a CT chamber and TLDs,respectively,based on the standard pelvic protocols.The ratio of the both measurements is the TLD conversion coefficient.Other TLDs from the same batch were placed between two tissue-equivalent inserts and placed into the pre-drilled organ cavities of the pediatric phantom.By using standard protocols,the organs dose were measured,based on which the corresponding effective doses were calculated.Results The TLD conversion coefficient was 3.91 mGy/per reading.By using the standard head,low-dose thorax,pelvis protocol,the whole body effective dose was 0.63,6.85 and 19.3 mSv,respectively.Conclusions It is feasible for using the CT chamber-calibrated TLDs to measure the radiation doses from kV-CBCT to pediatric anthropomorphic phantom.The effective dose in pelvic protocol was higher than in thorax and head protocol,indicating that the pelvic protocol has a penitential to lead to larger radiation damage and higher risk of secondary cancer.

Evaluación de riesgo de la práctica de radioterapia con rayos X de kilovoltaje / Risk evaluation of the kilovoltage radiotherapy practice

La radioterapia de kilovoltaje es una práctica de radioterapia de reciente reimplementación en el servicio de tratamiento del Instituto Nacional de Oncología y Radiología de Cuba. Uno de los aspectos relacionados con la autorización de su empleo es la evaluación de los riesgos asociados a dicha práctica. El siguiente artículo constituye un resumen del modelo de secuencias accidentales postuladas para la práctica, cuyo riesgo se cuantifica a través de la metodología de matriz de riesgo. El código SECURE-MR fue la herramienta seleccionada para implementar tal aplicación, por cuanto lo distinguen, además de las facilidades tradicionales de análisis, algunas novedosas que permiten el establecimiento de prioridades de contribuyentes. Los resultados globales de la evaluación de riesgo para el modelo postulado, así como algunas aplicaciones de optimización particulares se incluyen en el artículo

The kilovoltage radiotherapy is a recently re-implemented practice in the National Institute of Oncology and Radiology of Cuba to treat patients. One of the problems to approve its use is the assessment of risks associated to this practice. The present paper shows a summary of the pattern of accidental sequences proposed for this practice and its risk is quantified by using the risk matrix methodology. The SECURE-MR code has been used as the tool selected to implement such a practice. In addition to customary analysis facilities, this code has some other novel characteristics allowing us to establish the contributors’ priorities. The global results of the risk assessment for the proposed pattern, as well as some particular optimization practices are included in this paper

Comparison of set-up errors detected by EPID and CBCT using two different immobilization ;techniques for patients with nasopharygeal carcinoma / 中国癌症杂志

Background and purpose: With the development of therapy equipments and technology, the treatment for nasopharyngeal carcinoma(NPC) has entered into the era of precision radiotherapy, and setup errors have become a very important factor affecting treatment effects. The purpose of this study was to analyze the set-up errors detected by the kilovoltage cone beam CT(EPID) and the megavoltage electronic portal imaging device(CBCT) using 2 kinds of different immobilization techniques (pillow+head neck shoulder mask and vacuum bag+head neck shoulder mask) for NPC patients. Methods:A total number of 40 NPC patients were randomly assigned into 2 groups (pillow+head neck shoulder mask group and vacuum bag+neck shoulder mask group). Then each group was further divided into CBCT scan group and EPID group for veriifcation before treatment delivery. We matched the EPID images with the DRRs and acquired the set-up errors in x, y, z axis. Setup errors of CBCT were calculated according to its matched and planned CT images in left-right (x), superior-inferior (y) and anterior-posterior (z) directions. Paired t-test was used to evaluate the differences. Results:In the pillow+head neck shoulder mask group, the set-up errors of CBCT in the x, y, z axis were x (0.67±2.01)mm, y (0.51±1.71)mm and z (0.57±2.04)mm, respectively. The errors of EPID were x (0.69±2.19)mm, y (0.54±2.03)mm and z (0.61±2.11)mm. In the vacuum bag+head neck shoulder mask group, the set-up errors of CBCT in the x, y, z axis were x (0.42±1.81)mm, y (0.33±1.55)mm and z (0.50±1.75)mm, respectively. The errors of EPID were x (0.44±1.87)mm, y (0.43±1.70)mm and z (0.54±1.77)mm. The vacuum bag+head neck shoulder mask ifxed technique was more accurate when compared to the pillow + head neck shoulder mask ifxation method (P<0.05). Conclusion:CBCT and EPID were similar in detecting set-up errors for the NPC patients. However, the vacuum bag+neck shoulder mask ifxed technique was more accurate when compared to the pillow+head neck shoulder mask ifxation method.

Feasibility of using orthogonal kilo-voltage fluoroscopic imaging for setup correction in the liver-cancer radiotherapy / 中华放射肿瘤学杂志

Objective The aim of this study is to evaluate the feasibility of using orthogonal kilo voltage fluoroscopic imaging(OKVFI)for setup correction in image guided radiotherapy of the liver.Methods After positioned the patients with liver cancer implanted with silver rings on the accelerator equipped with kilo voltage X-ray volume imaging(XVI),averaged OKVFI and cone beam CT(CBCT) volumetric images were acquired.A total of 90 datasets of averaged OKVFI and 90 datasets of volumetric images for 10 patients were obtained.The couch shifts obtained by the matching between OKVFI and digitally reconstructed radiograph were compared tu those achieved by the registration between CBCT and 4D reference average CT.On the comparison of the two different matching metheds.the Pearson coefficient was used to analyzed the correlation and Bland-Altman analysis to discern the consistence.Results The Pearson coefficient of correlation for the patient position shifts were R2=0.821.0.771 and 0.909 in the left-right (LR),anterior-posterior(AP)and superior-inferior(SI)directions respectively.95% CI were-2.30 -1.53(LR),-2.06-3.01(AP)and-2.69-1.53(SI)respectively.Within a±3 mm tolerance were 97.78%.95.56%and 96.67%respectively.Conclusions OKVFI has hish correlation and consistence with CBCT image on the setup correction.It is feasible to implement position correction with OKVFI in clinic practice.

Influência do tempo de exposiçãoe da kVp na radiopacidade de cimentos endodônticos / Influence of time exposure and kVp on endodontics sealers radiopacity

Este estudo avaliou a radiopacidade dos cimentos endodônticos FillCanal®, Apexit®, Vidrion Endo® e Endométhasone®, variando o tempo de exposição (0,3 e 0,4s) e quilovoltagem (50 e 70 kVp). Para cada material estudado foram confeccionados cinco corpos-de-prova, os quais foram radiografados, juntamente com um dente, nos tempos de exposição e quilovoltagens determinados. Em cada imagem do corpo-de-prova e do dente foram realizadas cinco medidas da densidade óptica. Foram utilizados os testes de Kruskal-Wallis, para avaliar a influência dos fatores quilovoltagem, tempo de exposição e cimento, e de Mann-Whitney, para comparações múltiplas (p,0,05). Nas condições avaliadas, todos os materiais foram mais radiopacos que o dente. Com exceção do Endométhasone®®, que apresentou radiopacidade inferior em relação aos demais materiais nos dois tempos de exposição estudados, não houve diferença significativa entre os outros cimentos endodônticos avaliados quando a quilovoltagem empregada foi de 50 kVp. Quando os materiais foram expostos utilizando-se a quilovoltagem de 70 kVp, houve maior densidade óptica para o tempo 0,4 s e, nos dois tempos de exposição empregados, os valores de densidade apresentados pelos cimentos Vidrion Endo® e FillCanal® e Endométhasone® e Apexit® foram semelhantes. Concluiu-se que o fator quilovoltagem apresentou maior influência na radiopacidade dos materiais do que o tempo de exposição. Da mesma forma, pode-se dizer que a quilovoltagem de 70 kVp permite que a radiopacidade do material se diferencie pela densidade e composição deste.

Optimal Beam Tube Potential for the CsI/a:Si Flat Panel Digital Chest Radiography:Whether High KV Technique Still Suitable for Digital Equipment / 实用放射学杂志

Objective To investigate the optimal beam tube potential for amorphous silicon/cesium iodide flat panel digital chest radiography(indirect DR). Methods(1)60 healthy adults were undergone digital posteroanterior(PA) chest radiography at 80,100,150 kV respectively.The images quality of these three were compared by 5 independent observers.Several normal anatomy parts of the chest and the overall impression of the images were evaluated;(2)PA chest exposures of the anthropomorphic chest phantom to produce a constant ESDs(entrance skin doses) and exit dose were made using tube potential at 80,100,120,150 kV.The simulated chest nodules were scored. Results The quality of the adult chest radiography and the manifestation of the simulated chest nodules were superior at the lower tube voltages.The contrast of the images were best at 80 kV,while the appearance of the images look like that of the low potential radiography. Conclusion The optimal tube potential for chest DR is considered to be 80~100 kVp,while the high KV technique is no longer suitable for digital equipment.