Dosimetric comparison of 60Co and 192Ir high dose rate source used in brachytherapy treatment of cervical cancer

Purpose: The study purpose included dosimetric comparison of cobalt 60 (60Co) and iridium 192 (192Ir) high dose rate (HDR) source used in brachytherapy treatment of cervical cancer. Materials and Methods: Computed tomography (CT) scans for 15 patients of carcinoma of uterine cervix using 3-mm slice thickness were considered for the study The contouring of high-risk clinical target volume (HRCTV), bladder, and rectum on CT images was done as per the GEC ESTRO guidelines with the help of magnetic resonance imaging images in the treatment planning system. All parameters were kept the same for 60Co (3.5 mm active length, 0.5 mm active dia, Bebig) and 192Ir (3.5 mm active length, 0.6 mm active dia, Bebig) HDR source with 2.5-mm step size and dose prescription to Point A. As per the International Commission on Radiation Unit (ICRU)-89 guidelines, the dose–volume parameters such as D50(Gy), D90(Gy), and D98(Gy) for HRCTV and D0.1cc (Gy), D1cc (Gy), D2cc (Gy), and D5cc (Gy) to the bladder and rectum were calculated for both the HDR sources. Results: The difference in dose–volume histogram parameters such as D50,D90,and D98 of HRCTV was 3.19%, 1.13%, and 0.50%, respectively, for the two radioisotopes. The difference in dose values of D0.1cc, D1cc, D2cc, D5cc, and ICRU reference points of bladder was –0.58%, –0.67%, –0.99%, –0.94%, and –1.75%, respectively. On the other hand, dose difference for D0.1cc, D1cc, D2cc, D5cc, and ICRU reference points of rectum was 0.67%, 0.26%, 0.56%, 0.63%, and –0.33%, respectively. Conclusions: The present study results show that all the dose parameters of HRCTV, bladder, and rectum with 60Co were comparable with those of 192Ir HDR source. The isodose distribution is more bulge out for 60Co in cranial-caudal direction compared to that of 192Ir. However, these differences can be reduced by treatment planning optimization techniques. The clinical plan evaluation in each slice and plane is necessary to explore the logistic and financial benefits of miniaturized 60Co source over 192Ir HDR source

A 3-year follow-up cytogenetic observation on victims exposed to iridium-192 in a radioactive sourcer-loss accident in Nanjing City / 中国职业医学

OBJECTIVE: To observe the decay law of chromosome aberrations after 3 years iridium-192 radiation exposure in victims of Nanjing “5.7” radiation accident. METHODS: The peripheral blood of victims was collected 3 years after iridium-192 radiation exposure. The routine chromosome aberration analysis, micronucleus analysis and G-banding karyotype analysis were used to detect the chromosomal instability rate, the binuclear micronucleus rate and the stability distortion rate. A dose reconstruction was carried out based on the distortion results. RESULTS: The aberration frequency of dicentric(dic) and centric rings(r) was 6.5% after 3 years iridium-192 radiation exposure, which decreased to 31.0% at 6 days after exposure(the aberration frequency of dic and r was 21.0%). The estimated biological dose based on the aberration frequency of dic and r was 0.75 Gy, which is about 50.0% of the initial estimated dose(1.52 Gy) at 6 days after exposure. The micronucleus rate of the binuclear lymphocytes was 63.0‰, and the estimated biological dose based on the micronucleus rate was 0.71 Gy, which was similar to the estimated dose of aberration frequency of dic and r. The total frequency of chromosome aberration observed by karyotype analysis of G-bands by trypsin using Giemsa was 41.0%, the stability aberration frequency was 30.0%, and the translocation frequency was 15.0%. The result of dose reconstruction based on the translocation frequency was 1.50-1.89 Gy, which was very close to the initial estimated dose(1.52 Gy). CONCLUSION: The decay of unstable chromosome aberration may be influenced by many factors, more detailed data need to be accumulated to study the decay law. The use of stable chromosomal aberrations, especially translocation frequencies used in dose reconstruction in earlier exposures, is an ideal method.

Exploring the possibility of radiography in emission mode at higher energies: Improving the visualization of the internal structure of paintings / Explorando las posibilidades de la radiografía en modo de emisión a altas energías: Cómo optimizar la visualización de la estructura interna en pinturas

Summary We demonstrated in previous investigations that the internal structure of paintings can be visualized with conventional radiography in transmission mode when paintings have the proper stratigraphy. Unfortunately, there are many paintings that do not result in useful images. This problem can be solved by using radiography in emission mode. With this technique, the painting is irradiated with high energetic X-rays originating from an X-ray tube operating at 100 keV - 320 keV while inside the painting low energetic signals such as photoelectrons or characteristic photons are being generated. These signals escape from the top 10 µm of the painting and are able to illuminate the imaging plate. However, this technique has also some disadvantages. One of them is that it is not able to visualize underlying paintings. In this study, we explored the possibility to enhance the information depth by increasing the energy of the photon source from 100 keV up to 1.3325 MeV (i.e., 60Co source). At the same time, we also studied how the contrast between pigments is generated in emission mode. For this, we used mathematical simulation of particle transport in matter to understand the relation between input particle (particle type such as photon, electron or positron and the energy of the particle), the material being irradiated (element from which it is composed, thickness and density) and the output signal (generated particle types and energy). Finally, we will show that it is possible to image paintings using a 192Ir and even a 60Co source.

Resumen En investigaciones previas se ha demostrado que la estructura interna de las pinturas se puede visualizar satisfactoriamente con la radiografía convencional en modo de transmisión, siempre y cuando dichas pinturas tengan la estratigrafía adecuada. Desafortunadamente, hay muchos casos en los que la aplicación de este método no resultan en imágenes útiles. Este problema puede ser resuelto usando la radiografía en modo de emisión. Con esta técnica, la pintura se irradia con rayos X de alta energía originados en un tubo de rayos X trabajando entre 100 keV y 320 keV. Esto genera señales de baja energía (fotoelectrones o fotones característicos) en el interior de la pintura que, al escapar de las 10 μm superiores, pueden iluminar una placa de imágenes. No obstante, su aplicación también implica ciertas desventajas. Una de ellas es la incapacidad de visualizar las pinturas subyacentes. En este estudio, exploramos la posibilidad de incrementar la información obtenida a mayores profundidades aumentando la energía de la fuente de fotones desde 100 keV hasta 1.3325 MeV (fuente de 60Co). También estudiamos el impacto de esta energía en el contraste obtenido entre los pigmentos. Para esto, utilizamos la simulación matemática del transporte de partículas en la materia para comprender la relación entre partículas de entrada (fotones, electrones o positrones y la energía de las partículas), el material que se irradia (elemento del que está compuesto, espesor) y la señal de salida (tipos de partículas generados y energía). Finalmente, mostraremos que es posible crear imágenes de pinturas usando una fuente 60Co.

Treatment outcomes of high-dose-rate intracavitary brachytherapy for cervical cancer: a comparison of Ir-192 versus Co-60 sources / 부인종양

OBJECTIVE: To determine and compare treatment outcomes between cobalt-60 (Co-60) and iridium-192 (Ir-192) high dose rate (HDR) brachytherapy in stage IB2–IIIB cervical cancer patients at Department of Radiology, Faculty of Medicine Vajira Hospital, Navamindrahiraj University. METHODS: A retrospective cohort study of patients diagnosed with cervical cancer and treated with radiotherapy at the Department of Radiation Oncology, Faculty of Medicine Vajira Hospital between 2004 and 2014. Survival rate was analyzed by Kaplan-Meier method and were compared between groups with log-rank test. Multivariate analysis was performed using Cox proportional hazards model. RESULTS: A total of 480 patients with cervical cancer and treated with radiotherapy were included, 274 patients for Ir-192 group and 206 patients for Co-60 group. The 2- and 5-year disease-free survival rate in Ir-192 group were 80.4% and 73.1% and in Co-60 group were 82.5% and 74.7%, respectively (p = 0.365). Overall survival rates at 2 and 5 years were 89.4% and 77% of the Ir-192 group, and 91.6% and 81.9% in the Co-60 group, respectively (p = 0.238). The complications were primarily grade 1 or 2. Grade 3 and 4 complications were found in 13 of 274 and 7 of 206 in Ir-192 and Co-60 groups, respectively (p = 0.232). Grade and clinical stage of cancer significantly affected the survival outcome. CONCLUSION: Cervical cancer patients who were treated with HDR Co-60 brachytherapy were comparable in survival and toxicity outcomes of those with HDR Ir-192 brachytherapy. Co-60 source has lots of economic advantages over Ir-192 and hence suitable for low resource radiotherapy setting.

Proficiency test for calibration of well-type chambers using two types of 192Ir sources / Ensayo de aptitud para la calibración de cámaras de pozo usando dos tipos de fuentes de 192Ir

The Secondary Standard Dosimetry Laboratory of Cuba has implemented the calibration methodology of well-type chambers using the high dose rate sources. The use of different source types, at the hospital site as a modification of the procedure using other source types in a permanent facility of the primary laboratory leads to the need to evaluate the performance of the secondary procedure for calibration. The present paper describes the proficiency test to Cuban laboratory by making a comparison of dosimetry standards used in Germany and Cuba.

El Laboratorio Secundario de Calibración Dosimétrica de Cuba ha implementado una metodología para calibrar cámaras de pozo utilizando fuentes de de altas tasas de dosis. El uso de diferentes tipos de fuentes, como parte de una modificación del procedimiento con otro tipo de fuente usada en una instalación permanente del laboratorio primario, provocó la necesidad de evaluar el desempeño del procedimiento secundario de calibración. El trabajo describe el ensayo de aptitud al laboratorio cubano mediante un ejercicio de comparación entre los patrones dosimétricos de Alemania y Cuba.

Therapeutic efficiency of short anterior urethral stricture treated with endourethral surgery combined with iridium 192 radiotherapy / 西安交通大学学报·英文版

Objective: To assess the therapeutic efficiency of short anterior urethral stricture treated with endourethral surgery combined with iridium 192 radiation therapy in order to decrease the recurrence rate after endourethral surgery. Methods: A total of 286 patients with anterior urethral stricture (stricture length ranging from 0.5 to 2.5 cm, averaging at 1.6 cm) were divided randomly into two groups after internal urethrotomy and cicatrix electrotomy. The radiation group of 173 patients was treated as soon as possible with iridium 192 radiation therapy on the stricture sections while the control group of 113 patients was not. The recurrence rate was compared between the two groups during one year's follow-up. Results: Among all the 286 successful operations, stricture recurred in 19 patients of the radiation group (recurrence rate of 10.98%) and in 62 ones of the control group (recurrence rate of 54.86%), with a significant difference (P=0.003). Conclusion: It is an effective way to prevent recurrence by treating patients as early as possible with iridium 192 radiation on the stricture sections after endourethral operation on anterior urethral stricture.

Therapeutic efficiency of short anterior urethral stricture treated with endourethral surgery combined with iridium 192 radiotherapy / 药物分析学报

Objective To assess the therapeutic efficiency of short anterior urethral stricture treated with endourethral surgery combined with iridium 192 radiation therapy in order to decrease the recurrence rate after endourethral surgery. Methods A total of 286 patients with anterior urethral stricture (stricture length ranging from 0.5 to 2.5cm, averaging at 1.6cm) were divided randomly into two groups after internal urethrotomy and cicatrix electrotomy. The radiation group of 173 patients was treated as soon as possible with iridium 192 radiation therapy on the stricture sections while the control group of 113 patients was not. The recurrence rate was compared between the two groups during one year's follow-up. Results Among all the 286 successful operations, stricture recurred in 19 patients of the radiation group (recurrence rate of 10.98%) and in 62 ones of the control group (recurrence rate of 54.86%), with a significant difference (P=0.003). Conclusion It is an effective way to prevent recurrence by treating patients as early as possible with iridium 192 radiation on the stricture sections after endourethral operation on anterior urethral stricture.

Clinical Analysis of Stereotactic Brachytherapy with High-Activity Iridium-192 Sources for Treatment of Malignant Astrocytomas

Interstitial irradiation using high-activity Iridium-192 sources was studied clinically to treat supratentorial malignant astrocytomas(including glioblastoma multifrome). As of 1988, in attempt to define the efficacy of this technique in patients with more extensive disease, we treated patients less rigid selection criteria. 15 eligible patients have been approached and ten have accepted randomization for follow-up study over two years. Pathology was anaplastic astrocytoma in 5 patients, glioblastoma multiforme in 5 patients. Mean survival of patients treated with this procedure was 18.4 months. Continued investigation will determine which patient may benefit from this techique.

Clinical Analysis of Brachytherapy Using Iodine-125 and Iridium-192 for the Treatment of Intracranial Malignant Gliomas

Twenty-nine patients haboring primary or recurrent malignant gliomas were treated with direct implantation of radioactive sources into the tumor in afterlozded, removable catheters using stereotatic technique between November 1987 and October 1990. Indine-125(I-125) was implanted in 22 patients and high dose rate(HDR) Iridium-192(Ir-192) in 7 patients. All patients had been treated with external radiation and most had been treated with chemotherapeutic agents. one or more sources were placed in each tumor to deliver 5000-8000 cGy to the tumor's periphery for I-125 and 3000 cGy for HDR Ir-192. Eleven of 13 patients with glioblastoma multiforme were alive at 35 weeks whose mean survival was 74 weeks, and remained two were expired at 35 and 78 weeks, respectively. All 5 patients with anaplastic astrocytoma were alive at 39 weeks whose mean survival was 74 weeks. Five of 9 recurrent blioblastoma were alive at 22 weeks whose mean survival was 44 weeks, and remained three were expired at 13, 17 and 22 weeks respectively. All two patients with anaplastic astrocytoma were alive at 22 and 52 weeks, respectively. Four patients with deep seated analphastic astrocytoma(3 in the thalamus and 1 in the third ventricle) were treated successfully by brachytheray without any surgical morbidity and mortality and they were still alive 38, 48, 74 and 123 weeks after brachytherapy. There were few minor postoperative complications including 3 meningitis. 2 leak of cerebrospinal fluid and 3 radiation necrosis without any mortality. The authors conclude that the brachytherapy with temporary implanted I-125 or Ir-192 sources may provide long-term survial in selected patients with primary or recurrent malignant gliomas.

Stereotatic Interstitial Brachytheraoy with Iridium-192 in the Treatment of Brain Tumors-Report of Intial Experience

Five patients with brain tumors have been treated with an afterloaded removable Iridium-192 interstitial brachytherapy using Brown-Roberts-Wells stereotactic system. There were two cases of glioblastoma multiforme, one case of recurrent glioblastoma multiforme, one case of recurrent metastatic brain tumor and one case of recurrent astrocytoma grade II. The patients were treated by combination of surgery or stereotactic biopsy and external radiation previously. Tumor doses ranging from 4100 to 8600 cGy were delivered to these patients. There was no death and 4 patients showed definite tumor regression 3 months following interstitial brachytherapy. The method was safe and appeared to be effective madality to achieve local control of brain tumors.