ABSTRACT
In vivo dosimetry is a method for estimation of overall error in the delivered dose to the patients at the end of radiotherapy process. In this research, two methods for target dose calculation were evaluated on midline and central axis of photon beams in in vivo dosimetry of thorax fields. Entrance and exit doses for anterior and lateral fields of thorax were measured in thorax phantom using diode dosimeter. Also, the doses of some points on midline and central axis were measured in thorax phantom using ionization chamber. The dose at these points was calculated using entrance and exit doses by geometric and arithmetic mean methods. The calculated doses were compared with measured doses. In all cases, arithmetic mean method showed errors from%8.8 to 19% for points on midline and central axis in comparison to measurements. The range of errors for geometric method was from%1.5 to%8 depending on distance from midline. The results showed that doses of points on midline and central axis can be calculated with acceptable accuracy from entrance and exit doses using geometric mean in thorax fields
Subject(s)
Humans , Radiotherapy, High-Energy , Phantoms, Imaging , Algorithms , Cobalt Radioisotopes , Radiotherapy Dosage , Thorax/radiation effects , Models, Anatomic , Monte Carlo MethodABSTRACT
Accuracy of the delivered dose to the patient is one of the most important and effective factors in radiotherapy. In vivo dosimetry is used to evaluate the accuracy of delivered dose in radiotherapy. Therefore, in this study the accuracy of delivered dose to the patients was verified using in vivo dosimetry in radiotherapy department of Tabriz lmam Hospital. Entrance doses of 320 fields treated by Cobalt-60 machine and linear accelerator including head and neck, trunk, pelvis, and extremities were measured using in vivo dosimetry system. Difference between measured entrance dose and prescribed dose for each field was determined. For all fields and also for each specific group of fields, average error and standard deviation of its distribution were determined. For whole fields, the average error of 1.34% with standard deviation [SD] of 7.12%, for [60]Co fields the average error of -0.17% with SD of 5.98% and for Linac fields, the average error of -3.56% and 7.17% were seen. In head and neck fields, the average error of -0.37% with SD of 4.73%; for trunk fields the average error of%-1.88 with SD of 7.27%, and for pelvis and extremities, the average error of -2.49% with SD of 7.79% were seen. The results show an acceptable systematic error in radiotherapy department. But standard deviation of 7.12% is slightly higher than the recommended value of 5%. It is possible to lower the uncertainty in delivered dose to recommended value by optimization of Linac function, regular quality control, and workload reduction
Subject(s)
Humans , Quality Control , HospitalsABSTRACT
With promising results from several institutions, many centers began to treat patients with esophageal squamous cell carcinoma [SCC] with neoadjuvant chemoradiotherapy followed by esophagectomy. The aim of this research is to determine the feasibility of this method in our selected patients. In this prospective phase I clinical trial, 10 patients [7 male, 3 female; 58.4 +/- 2.5 Y/O] with stage III and VIA lower thoracic esophageal SCC, were treated with intravenous infusion of 1000 mg/m[2]/day 5-flourouracil during day 1 to 4, 75 mg/m[2] cisplatin in day 1, and a total dose of 18 Gray external beam radiation during day 1 to 6 and underwent transhiatal esophagectomy during day 7 till 10. This group was compared with a retrospective group of 61 patients which treated with surgery alone. Age, sex, duration and grading of the dysphagea, differentiation and staging of the tumor were not different in these two groups. There is no complete pathologic response in the study group. One patient died because of severe leukopenia and sepsis and other because of azygos vein rupture. Other complications were: chylothorax which required later thoracotomy [10%], recurrent nerve paresis [10%], superficial wound infection of the neck incision [10%]. All patients had mild to moderate leukopenia [2600'400/mm3] during days 11 to 16. Total postoperative intensive care unit stay was 2.2 +/- 0.5 days and postoperative hospitalization was 15.7 +/- 1.8 days and in-hospital operative mortality was 20% and total morbidity was 50% which were not significantly different from control group [p<0.05]. Postoperative blood transfusion was 5.3 +/- 0.8 unit per patient which was significantly greater than control group[P<0.05]. The perioperative mortality and morbidity of this neoadjuvant protocol is acceptable comparing with our control group and we can propose phase II and III studies for determining the long-term effect of these protocol