Measurement of the Ambient and Extremity Doses in Clinical Oncology Hospital, Menoufia University, Egypt

The ambient dose of radiation therapy and nuclear medicine units of Clinical Oncology Hospital, Menoufia University were investigated using thermoluminescence dosimeter MTS-700 and surveymeter (Inspector Radiation Alert). The maximum% difference between read out of both MTS-700 (TLD) and surveymeter did not exceed 6% and 8% for the two hospital units respectively. Values of the annual ambient dose received in both hospital units were found to be incompliant with radiation protection regulations. In addition, the extremity effective dose Hp (0.07) of staff in nuclear medicine unit was measured using wrist and finger techniques. Results indicate in-homogenies distribution of fingertips doses. Radiation doses received by the wrists and fingertips of radiopharmaceutical staff preparing Tc syringe were observed to be higher by a factor of about 1.41 and 1.44 respectively than those for the administrating staff whom injecting patients by Tc syringe, but also still in congruent with international radiation protection regulations.


Introduction
The use of ionizing radiations widely applied, especially in the context of medical diagnostics and therapy as well as for material testing and many other purposes [1] [2]. Radiation has been used in medicine. Between 30 and 50 percent of medical decisions, especially the critical ones, are made after studying the results of radiological examinations [3] [4]. In medicine, the most important requirement is the radiation dosimetry for surveillance of radiation workers in radiology, nuclear medicine and radiation oncology. In addition, its importance was defined for quality assurance (i.e. Precise estimation of delivering dose to the patient) in both external beam radiation therapy and brachytherapy as well [5].
Because of the large and growing number of patients undergoing radiation therapy and the multiple nuclear medicine procedures, continued efforts are required to improve the quality of treatment, diagnosis and to reduce the associated radiological risk [6]. So, multiple therapeutic and diagnostic procedures in radiation therapy and nuclear medicine units of Clinical Oncology Hospital, Menoufia University, Egypt require proper attention.
In the present work, an ambient radiation monitoring program is assessed.
Knowledge of ambient dose values is relevant to the occupational exposure personnel who may limit the time spent at high dose areas. Recommendations were given to the departmental authorities to implement actions in order to reduce doses at high dose sites in order to comply with the ALARA principle [7]. This will be discussed whether the exposed doses at the work places are acceptably and safe or not. The investigated sites at radiation therapy unit are a radiation therapy clinic, 60 Cocontrol, patient waiting, long hall, worker path room, linear accelerator control, simulator control and 60 Co treatment room. Moreover, other selected sites in the nuclear medicine unit are chosen, physician station, technician station, X-ray room, injection room, preparing material, patient path room, external hall and patient waiting room. In addition, determination and investigation of the effective skin dose at depth 0.07 mm (Hp (0.07)) of the body of medical and paramedical staff in the nuclear medicine unit will be done using wrist and finger MTS-700 (TLD). Special attention has been paid to the exposure of nuclear medicine worker hands. The radio pharmacists who label various ligands can be exposed to high radiation doses to their fingertips (primarily of the thumb, index finger and middle finger). Quite frequently, the Hp (0.07) to the fingertips of those three fingers may exceed the dose limit, i.e. value of 500 mSv/y for the skin of human fingers; this dose limit refers to the maximum dose recorded [8].

Experimental Procedure for Ambient Dose Measurements
In radiation therapy unit some radiation sources are in use; these are 60 Co (Cobalt-60) gamma source (Theratronics 780-E (1.25 MeV). This teletherapy unit was manufactured in Canada by Theratronics International Limited for Oncology System and used for radiation therapy treatment of cancer patients.
X-ray Photon beam from medical linear accelerator (Varian Clinac 600-C with nominal energy 6 MeV) was used in radiation therapy unit for radiation therapy treatment of cancer patients. This device provides rectangular, symmetric and asymmetric fields and generates therapeutically useful megavoltage X-rays with  give dose rate. MTS-700 is tissue equivalent, its Z eff (effective atomic number) is 8.13 [12]. In order to investigate the dosimetric characteristics of MTS-700 (TLD), 60 Co γ-source with dose rate = 48.08 cGy/min and radiation field size of

Experimental Procedure for Extremity Dose Measurements of Medical and Paramedical Staff in Nuclear Medicine Unit
Nuclear medicine implies the manipulation of unsealed radioactive sources. Labelle 99m Tc in hospital divided into three steps kit preparation, dispensing syringes and administration as described in Table 1 work table for nuclear medicine unit workers. In this research, the workers did so by volunteering for their colleague, the second author, to complete his Ph.D. They were divided into two groups, the first group called preparing radiopharmaceuticals group (physicists) and the second group called injecting radiopharmaceuticals group (nurses). In nuclear medicine procedures, radiation exposure of hands, especially in fingertips, is much higher than that of the thorax. [14] [15]. If the dose to any part of the extremities of a worker is likely to exceed three tenths of the annual dose limit, an additional dosimeter should be placed on the part of the extremity where the dose is expected to have its highest value. In practice, extremity monitoring is carried out by measuring the personal dose equivalent Hp (0.07) [16]. The work load includes numbers of patients and the scan type during one week the period of investigation described in Table 2. Two pairs of gloves equipped with eight chips of MTS-700 (TLD) were fixed in a certain position as in Figure 3 in a palm side of the two hands of the two groups at the centers of the wrists and fingertips of middle, index, and thumb fingers.  2) Determining specific activity in dose calibrator.
3) Drawing from elution vial and adding saline 2 Dispensing Syringes 1) Dispensing in syringes from kit vial.
2) Checking activity in dose calibrator.
3) Transfer of unshielded syringes to lead transport box.
3 Administration 1) Remove needle and mounting syringe shield.
2) Inject patient with 10 mm saline to check the cannula before inject with radiopharmaceutical and again injected with 10 mm saline after radiopharmaceutical for washing.

Results
The element correction coefficient (ECC) was calculated for a set of measurements carried out on 15 pieces from MTS-700 (TLD) irradiated at dose of 2 Gy The mean value of relative ECF was found to be ranged between 0.96 and 1.04 with standard deviation (SD) 0.02 and coefficient of variance (CV) 2.28% (see Table 3). In order to assess the repeatability of the dose measurements attainable using the MTS-700 (TLD) a set of repeated readouts, 15 chips for each cycle,   [18]. The dosimeters showed high resistance to adverse effects caused by handling procedures (see Table 4). Variance in sensitivity of a typical batch of TL dosimeters is unavoidable but can be reduced from 10% -15% to 1% -2% when dosimeters are calibrated [19]. A calibration factor (nC/mGy) was assigned to each one. This process of calibration was repeated for two times to seven groups      Table   5 and Table 6, respectively.
The results of extremity dose measurements using MTS-700 (TLD) for nuclear medicine workers shown in Table 7 and Table 8 respectively.

Discussion
A comparison between the values of the annual ambient doses measured with surveymeter and MTS-700 (TLD) in the radiation therapy working area is shown in Table 4. The working areas are radiation therapy clinic, 60 Co Control room, patient waiting, long hall, worker path room, linear control, simulator control and 60 Co room. Values obtained by MTS-700 (TLD) are slightly higher than those obtained by surveymeter. The maximum% difference between read out of both the surveymeter and MTS-700 (TLD) did not exceed 6%, which indicates good agreement between both of them. In addition, doses measured in the nuclear medicine unit were gathered in Table 5. Measuring sites are physician   station, technician station, X-ray room, injection room, preparing material, patient path room, external hall and patient waiting room. The maximum% difference between measurements with the above mentioned techniques not exceed 8%.This difference between two different measurement methodologies may be resulted from the fact that only fifteen measurements were taken in a month with surveymeter, while MTS-700 (TLD) responded for whole time exposure.
Results given in both Table 5 and Table 6  The dose values of wrists and fingertips personal dose Hp (0.07) for nuclear medicine unit worker using MTS-700 (TLD) are displayed in Table 7 and Table   8. Table 7 shows radiation doses to right and left wrists of group one (preparing 99m Tc) and group two (injecting 99m Tc). Radiation doses received by the wrists of radiopharmaceutical staff preparing, dispensing syringe were observed to be higher by a factor of about 1.41 than those for the administrating staff whom injected patients by 99m Tc. The annual wrists doses were calculated for group 1 and  staff preparing will receive dose more than 3/10 th of the limit, which legally require routinely monitoring. With this work conditions, the equivalent dose limit will not be reached. These results are in agreement with the findings of Gauri, S. et al. [23] and Chruscielewski, W. et al. [24]. The maximum expected annual dose to the fingers appeared to be less than the annual limit (500 mSv/y) because all of workers are on rotation and do not constantly handle radioactivity throughout the year but if the workload is increased and the protection measures stays as they are doses can reach the equivalent dose limit. So, we recommend increase the radiation protection precautions as, using the automatic injector, increasing the patient waiting area and adding a new patient bathrooms. The extent of the annual radiation exposure of the workers depends on several factors within the workplace [25] [26] [27]. These factors include, but are not limited to, the annual workload, the distribution of the workload among workers, the radiation protection practices followed by the workers, and the radiation safety facilities provided by the employers. An evaluation of how such factors affect occupational exposure will be our future study after the development of radiation therapy and nuclear medicine units of Clinical Oncology Hospital Menoufia University, Egypt.

Conclusions
MTS-700 (TLD) was subjected to several systematic investigations carried out using γ-ray doses range from 100 to 2000 mGy. These TLDs were applied in clinical radiotherapy and nuclear medicine dose measurements. Results showed that MTS-700 (TLD) has a good reproducibility, an extended range of linearity, high sensitivity, and no significant variation in response over a wide range of Egypt has radiation protection maps for worker, patients and visitors.