In-Vivo Dosimetry with Diode for the Treatment of Pelvic Malagnancies

Research Article

Austin Oncol Case Rep. 2016; 1(1): 1004.

In-Vivo Dosimetry with Diode for the Treatment of Pelvic Malagnancies

Gadhi MA1,2,3*, Buzdar SA² and Fatmi S³

¹Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX, USA

²Medical Physics Research Group, Department of Physics, The Islamia University of Bahawalpur, Pakistan

³Bahawalpur Institute of Nuclear Medicine and Oncology (BINO), Bahawalpur, Pakistan

*Corresponding author: Muhammad Asghar Gadhi, Bahawalpur Institute of Nuclear Medicine and Oncology (BINO), Noor Mahal Road, Bahawalpur, Pakistan

Received: July 29, 2016; Accepted: August 23, 2016; Published: August 26, 2016


The ±3% overall tolerance limit in absorbed radiation dose delivery has been recommended by The International Commission of Radiological Units (ICRU). In-Vivo Dosimetry (IVD) is one of the best Quality Assurance (QA) tool to check the dose delivered to the patients being treated with radiation. The aim of the current investigation is to check the diode IVD system to measure the entrance and exit dose in radiation therapy for pelvic malignancies during treatment and its implementation as a patient-specific QA tool for the verification of the dose delivery. During February 2014 to December 2015, the entrance & exit dose of 254 pelvic patients have been measured using diode IVD system and compared these with calculated corresponding values. Totally 1,614 radiation fields have been monitored. The analysis of data showed the percentage Δ±0.083% with α ±2.179% between measured and prescribed dose. It was observed that 99.814% measurements using diode remained within the action level i.e. within ±5% and 86.493% within ±3%. Larger deviations have been observed in lateral and wedged fields as compared to anterior-posterior fields. The positioning of patients and diode has been noticed as the common source of errors for variation, alone or in combination with other sources. The measurements repeated after the rectification of error(s), were found within action level. The current investigation revealed that diode IVD is simple, cost effective, offers immediate outcomes and can function as a suitable patient specific-quality assurance tool in radiotherapy.

Keywords: In-vivo Dosimetry; Diode; Pelvis; Radiation Therapy; Co-60


Cancer, possibly more than any other term, has the impact to make one’s blood run cold. It is a cruel killer, and nearly nothing can block its path once it has spread. Regardless of our technologies and developments, our research institutes, and myriad researchers devoted to eradicate the cause, cancer remains an actual threat. Pelvic cancer is the common malignancy. It is anticipated that almost 22.2 million new cancer cases will be noticed yearly over the world by 2030 [1]. Radiotherapy is needed for the treatment of 80% cancer patients [2,3]. Radiation therapy is an effective treatment modality for both palliative and curative treatment of cancer along with surgery and chemotherapy.

The local tumor control depends on the accurate delivery of radiation dose to patients being treated with radiation therapy. The ±3% overall tolerance limit in absorbed radiation dose delivery in radiation therapy has been recommended by ICRU [4,5]. IVD is the key technique to assure the exact dose delivery during radiation therapy to a patient [6]. Entrance dose measurements verify the patient set-up, the radiation output, and performance of the radiation equipment. Exit dose measurements additionally verify the dose calculation algorithm and determine the effect of various factors like the contour of the treatment portal, patient’s thickness and tissue in-homogeneities and calculation of absorbed dose for radiation therapy of cancer patient [7-11]. The diodes and thermoluminescent dosimeters are the most common detectors being used for IVD [8- 10,12,13]. Metal oxide semiconductor[8], alanine/gel [14,15], plastic scintillators [16,17], Presage dosimeter [18], radiochromic films [19] and conventional portal films or electronic portal imaging devices [20] are other detectors being used for dose verification in clinical radiation therapy practice. The preference for particular detector influenced by various aspects, for example, type of measurement, training of the radiation personnel, cost, personal preference and availability (key factor) [21]. Although it is recommended by various international organizations [9,10,22-26] for routine verification of the dose delivery for all groups of patients undergoing radiotherapy but IVD is rarely used in our country for routine verification of absorbed radiation dose in clinical radiation oncology practice [2].

This investigation was performed to check the utilization of diode IVD for in vivo verification of entrance & exit dose in radiation therapy for pelvic (prostate, bladder, rectum and cervix) malignancies being treated in our institute and comparison with the calculated values of the absorbed dose for corresponding radiation portals.

Materials and Methods

Entrance & exit dose for patients undergoing pelvic (prostate, rectum, cervix, endometrium and urinary-bladder cancers) radiation therapy on Co-60 photons beam has been measured using diode IVD system. The Co-60 photons beam has been calibrated using an ionization chamber (TN30013-03936 PTW, Freiburg, Germany) positioned at 5cm depth in water phantom according to IAEA TRS- 398 protocol [27]. The IVD system used in this study consisted of PDM Model No. 37-721 and ISORAD n-type diode Model No. 117009 (Nuclear Associates, NY, USA). The detailed characterization of diode IVD system has been performed as per procedure outlined in the literature [2]. The action level is set ±5% for pelvic patients initially for the period of six months and then it has been decided to lower down the action level to ±3%. The diode has been positioned onto the skin of the patient in center of the radiation field as shown in the figure 1. All fields have been monitored in first week of treatment. Entrance dose has been calculated at a depth of 0.5cm from entrance surface. Exit dose has been calculated at a depth of 0.5cm from beam exit point. Entrance & exit dose has been calculated as per procedure outlined in the literature [8].