Brachytherapy Source Calibration

Question: Discuss about theBrachytherapy Source Calibration. Answer: Dose Combination polarity is the application of both polarities ( i.e., negative and positive for the dose in Electrometer. This makes it easier to determine and note the amount ionization of different dose at different media used be it water or Perspex. In this application we form a polar molecule when one part is positively charged while the other one has a negative charge, making it form electrical poles. In some cases, we can use water and ethanol to form a solution since both are a polar molecule(Jack Venselaar 2012, p. 112). Discussion The combination of radiography and visual picture verification very crucial in the experiment as it helped to know well-chamber ionization chamber integrity. During the expectation of radiography, there was no physical damaged noted. From our experiment, the leakage currents were recorded for the regular time of 10/(factor/100) of the well-ionization chamber of the average of 29.30nA from different readings. There was corrections elimination of the leakage current in the electrometer background during the AKS reading. The experiment was carried at a temperature of 20.80C and a pressure of 1019.7 Hpa(P Mayles 2007, p. 211). From these values we were able to calculate ptf as follows; Ptf={(temperature +273.15) * 1013}/(293.15*pressure ; Ptf={293.95*1013}/(293.15*1019.7 Ptf=297771.35/298925.055 Ptf=0.09961 We managed to calculate the amount of Air kerma strength as follows Air Kerma Strength= Average readings (A) *Nk*ptf*Pion Air kerma Strength=(29.30*0.09961*1.00*1.57) Air kerma Strength=4.582cGym2hr2 Chambers well-type ionization are made to have a high sensitivity to photons which are scattered, and it is very important to eliminate these contributions of scattered photons when readings are taken. In most cases, it is recorded that there is an overestimation of current by about 1.1% if only it is put close to the walls. And these effects increases when the well-ionization chamber is put on the floor. Our experiment we found our ion collection efficiency (Aion) to be 1.00 which is 100% and is taken to be perfect(Peter Hoskin 2011, p. 255). Our measured value is within the range of that in literature which is 98.9% for most welltype ionization types. The value of the collected current of ionization did not depend on the voltage sign of polarizing. The Air-kerma rate determined in our experiment using BDS 1000 in chambers of well-type ionization through cross-calibration which was calculated and found to be 4.582cGym2hr2 as seen above. Our calculated value is in the range of tolerance with the activity value which is 4.76 cGym2hr2 (Sonja Dieterich 2015, p. 342). We also managed to calculate the apparent Activity (Ci) as; (Ci)= Average reading* Nc*pion*ptf (Ci)= 29.3*3.85*1.00* 0.09961 (Ci)=11.23 Cl Literature value of Cl is given as 11.7 Cl , and from that we can get the percentage error ( deviation ) as For Air-kerma rate; (4.76-4.582)/ 4.76 = 0.178/4.76 0.037394*100; 3.739%. For apparent Activity (Ci) ; (11.7-11.23)/11.7. =0.47/11.7 =0.040170*100 =4.017% So for the both values of apparent Activity (Ci) and Air-kerma rate lie within the range of 5% as they have a tolerance of 3.379% and 4.017% respectively. The sensitivity of the well-type ionization chambers are affected by the by the volume and the source energy(Yves Lemoigne 2009, p. 342). Conclusion In conclusion, we were able to get more familiarized with the use and parts of farmer chambers in full-scatter photons. Good applicators adaptors and calibrations were used with commercial standard, for any reading the chamber must be connected to a sensitive PTW electrometer. We also realized that the chambers of welltype are the best for the calibration of high dose rate and pulsed dose rate. We also managed to know how to eliminate attenuations in the chambers of well-type ionization. They are made to have high sensitivity to photons which are scattered, and it is very important to eliminate these contributions of scattered photons when readings are taken(Sonja Dieterich 2015, p. 278). Bibliography Jack Venselaar, ASMDBPJH 2012, Comprehensive Brachytherapy: Physical and Clinical Aspects, Taylor Francis, Stoke. P Mayles, ANJCR 2007, Handbook of Radiotherapy Physics: Theory and Practice, CRC Press, Waashington. Peter Hoskin, CC 2011, Radiotherapy in Practice - Brachytherapy, OUP Oxford, London. Sonja Dieterich, EFDPJZ 2015, Practical Radiation Oncology Physics: A Companion to Gunderson and Tepper's Clinical Radiation Oncology, Elsevier Health Sciences, Beijing. Sun I. Kim, TSS 2007, World Congress of Medical Physics and Biomedical Engineering, Springer Science Business Medi, Tokyo. Yves Lemoigne, AC 2009, Radiotherapy and Brachytherapy, Springer Science Business Media, London.