Ionizing radiation gives immense benefit to patients in the hospital through diagnosis & therapy practices but intolerable radiation may affliction to healthcare worker & public. Computed Tomography (CT) in the hospital is contributed maximum part of annual effective dose to healthcare worker & public (NCRP, 2009; Mettler F A Jr, 2009). MMCH is a large gov-ernment hospital that has 39 departments including cardiology, radiology and imaging, radiotherapy, surgery. MMCH has various types of radiation generating equipment such as CT, X-ray, fluoros-copy, etc. Institute of Nuclear Medicine and Allied Sciences (INMAS) was established in the MMCH campus where different types of radioactive mate-rials & radiation generating equipment including SPECT CT used for diagnosis and treatment to patient.  Gamma radiation has sufficient energy to ionize the atoms of the material, because it is the most energetic radiation of the electromagnetic spectrum which is 10,000 times higher than that of visible light (Eslami A, 2017; Eslami A, 2016). Gamma radiation gives maximum part of the public exposure that emits from the natural radionuclides. The leading three natural radionuclides are the primordial radionuclides such as 238U, 232Th & their decay products & 40K that exists trace amount in earth formation. The cosmic rays and terrestrial radiation are responsible for maximum part of the public exposure (Charles M, 2000). Public exposure from the terrestrial radiation stands on originally on geo-logical features of the place such as altitude, latitude & solar system (Agency for Toxic, 1999). Normally, radiation effective dose of the healthcare worker & public at indoor position is higher than that of the outdoor position because building mate-rials contribute few portions of radiation exposure to healthcare worker & public. Building materials, namely rod, brick, concrete, marble, gypsum, sand, granite, lime-stone, aggregate, etc. hold initially natural primordial radionuclides, for example, 238U, 232Th & their decay products and 40K. The know-how of the natural radionuclides of the building materials is important for assessment of the effective dose to healthcare worker & public since human beings spent about 80% time at indoor position and leftover 20% time at outdoor position (UNSCEAR, 2000; UNSCEAR, 2008; UNSCEAR, 1982; Taskin H, 2009). Gamma radiation provides higher part of the effective dose to human beings from all types of the ionizing radiation as it has the longest pene-tration ability comparing to others (Al-Saleh FS, 2007). Considerable variation of the real-time dose rates was noticed at indoor & outdoor positions of the nuclear installations and hospitals (Al-Ghorable FH, 2005; Arvela H, 2002; Rybach L, 2002; Sagnat-chi F, 2008; Tavakoli MB, 2003; Svoukis E, 2007; Rangas-wamy R, 2005; Ononugbo CP, 2015; Ala-sadi AH, 2016; Ali et al., 2022; Biswas et al., 2021).    

Healthcare worker and public are exposed to radia-tion externally & internally in the MMCH campus due to the existence of natural and man-made radio-nuclides. Calculation of the effective dose per year on healthcare worker & public arising from the hospital radiation is very substantial since it is asso-ciated with the probability of getting cancer on heal-thcare worker & public. Estimation of the excess life-time cancer risk (ELCR) on healthcare worker & public due to discharge of ionizing radiation from the large hospital is necessary since those give to collective dose on healthcare worker & public (UNSCEAR, 2008). The objective of the study is to monitor the real-time radiation in the MMCH cam-pus, Bangladesh and to estimate the excess life-time cancer risk on healthcare worker and public based on the annual effective dose. 

Radiation Monitoring Equipment

Real-time digital movable radiation monitoring instruments were utilized to collect the dose rates at 1 meter over the ground level. The monitoring ins-truments were set up on the tripod. The radiation monitoring instruments were designed and fabricated by Germany. A non-mandatory intensified leather case including belt connection can redundant pro-tection the monitoring instrument. The monitoring instrument is a Geiger counter with competent form so that human beings can utilize it most effortlessly and safely. The monitoring instrument holds a bat-tery gauge, different unit conversion, real-time radia-tion dose rate and collective dose demonstration positions and timetable for registering and aware functions. Revolutionary guides hold PC data down-load via USB cable and extremely small electric power circuit for lengthening battery life. The moni-toring instrument registers the prevalence radiation promptly, continually, and steadily. Alteration of pulses per minute to dose rate based on the magni-tude of the pulse input. For typical environmental condition, input usually (~ 0.200 μSv/h) the change-over is 142 pulses/minute (User Manual, 2014). The monitoring instrument has the quality for voice signal when the dose rate exceeds the precise level. The default voice signal level is 5µSv/h. If the radi-ation level in any area beyond the 5 µSv/h, the dose rate will be showed including an additional sign in the display. 

Calibration of the Equipment

The monitoring instrument was calibrated in a laboratory with ISO certificate after fabricating. The counter tube is not tending to fatigue in usual envi-ronmental condition and hence, it will not obligatory for re-calibration. Nevertheless, if the user country has an ISO certification laboratory, regular calibra-tion is essential. To deal a muster handling, tests should be accomplished for 72 hours against a pri-mary standard. The primary is calibrated against a standard reference source, namely Cs-137. A data log is then created. The monitoring instrument was calibrated after manufacturing. The monitoring ins-trument was also calibrated in the calibration labo-ratory, namely the Secondary Standard Dosimetry Laboratory (SSDL) of Bangladesh Atomic Energy Commission (BAEC) by the gamma-ray standard sources (137Cs, 60Co, etc.) and X-ray Unit. The SSDL under BAEC has been operating since 1991. The SSDL under BAEC is traceable to the Primary Stan-dard Dosimetry Laboratory (PSDL) of the National Physical Laboratory (NPL), United Kingdom. The SSDL under BAEC has X-ray Unit (30 kV-225 kV) for calibration of radiation generating equipment. The management of SSDL under BAEC is protected fulfilling the requirement of the Inter-national Ato-mic Energy Agency (IAEA)/ World Health Organ-ization (WHO) network of the SSDLs. Hence, the real-time dose rates of the monitoring instrument have been achieved to meet the inter-national moni-toring system. The monitoring instrument has the capacity to exactly monitor the dose rates in the range of 0.01-5000 µSv/hr (User Manual, 2014). 

Radiation Monitoring Procedure

The real-time radiation monitoring in the MMCH campus was accomplished in August-September 2022 following In-Situ method. The real-time radia-tion monitoring in the MMCH campus was per-formed at various outdoor places such as nearby positions of the radiation generating equipment rooms, for example, X-ray Machines, CT scan mach-ines, CT angiogram, etc. & outside of the INMAS building where different types of radioactive subs-tances were stored. The real-time radiation moni-toring was completed at 32 choosing locations in the MMCH campus and data acquiring time for one monitoring point (MP) was almost 1 hour. The digital movable monitoring instrument was posi-tioned on tripod at 1meter over the ground level. The MP was recorded using a GARMIN eTrex HC Series Personal Navigator. The instrument shows the ace-ptable effectiveness of Garmin high-detectable GPS and the outermost distance mapping to make an unparallel handy GPS receiver (Owners Manual-GARMIN eTrex HC Series, 2007).

Radiation Monitoring Site

32 MPs were selected in the MMCH campus and those MPs are marked out using Garmin HC series Personal Navigator. The longitude/latitude of the study is varied from N: 24.44669 to N: 24.44503 and from E: 90.24678 to E: 90.24483. MMCH has 39 departments, namely, radiology & imaging, radio-therapy, cardiology, anatomy, physiology, bioche-mistry, pathology, microbiology, pharmacology, forensic medicine, community medicine, medicine, respiratory medicine, neurology, physical medicine, nephrology, gastroenterology, endocrinology, heap-tology, hematology, surgery, urology, ortho-surgery, burn & plastic surgery, ortho-tromatology, neuro-surgery, paediatrics surgery, gynae & obs., paedia-trics, paediatrics nephrology, paediatrics hematology & oncology, neonatology, ophthalmology, ENT & head neck surgery, anesthesiology, dermatology, psychiatry, blood transfusion medicine, dental unit. The MPs were chosen at outdoors adjacent to the radiation generating equipment rooms and radio-active material handling & storage rooms.  

Estimation of Radiological Risk

Effective dose is generally applied for calculation of the healthcare worker & public exposure and possi-ble biological effects in regard to public exposure that is achieved from the equation underneath:

For outdoor position, AED=D_out×〖OF〗_out×T   (1)

For indoor position, AED=D_in×〖OF〗_in×T         (2)

Here, AED is the annual effective dose, Din and Dout are the mean absorbed dose rates in air at indoor & outdoor positions respectively, T is the time in hour, OFin and OFout is the indoor and outdoor positions occupancy factors that is the part of time (%) exhausting of human beings. Generally, the value of OFin and OFout are 80% and 20% respectively (UNS-CEAR, 1988). 

The excess life-time cancer risk (ELCR) is estimated based on the equation underneath:

ELCR=AED×DL×RF (3)

Here, AED is the annual effective dose to healthcare worker & public, DL is the duration of life of Bang-ladeshi inhabitant (http://en.worldstat.info, 2023) and RF is risk factor (Sv-1) which is a fatal cancer risk per Sievert. For stochastic effects yielding from low-level radiation, ICRP 103 recom-mended the value of 0.057 per Sievert to public (ICRP, 2007).

Annual effective dose

Annual effective dose on healthcare worker and public in the MMCH campus in Bangladesh (where radiation generating equipment and radioactive subs-tances were being used for diagnosis & treatment to patient) were calculated based on the international reputation studies (UNSCEAR, 2000; Hashemi M, 2019; James IU 2015; Zarghani H, 2017; Abdullahi S, 2019; Monica S, 2016). It is supposing that Bang-ladeshi populace exhausts about 20% time at out-door position and leftover 80% time at indoor position, then annual effective dose on healthcare worker and public in the MMCH campus of Bang-ladesh were calculated. Table 1 demonstrates the annual effective dose on healthcare worker and public from August-September 2022.  The yearly effective dose to healthcare worker and public in the MMCH campus were ranged from 0.438-8.585 mSv (mean: 2.529 ± 0.627 mSv). The average yearly effective dose on healthcare worker & public due to the presence of radiation generating equipment and radioactive materials in the MMCH campus is five-fold higher than that of the global average of 0.48 mSv (ICRP, 2007). The average yearly effective doses were usually upmost at positions next to the CT rooms, CT angiogram rooms, X-ray rooms, SPECT-CT rooms and radioactive material handling, storage & dispensing rooms of the INMAS. Not-withstanding, the average yearly effective doses on healthcare worker & public next to the CT rooms, CT angiogram rooms, X-ray rooms, SPECT-CT rooms at several positions were considerably large, yet those values are smaller than the authorized limit of 20 mSv for healthcare worker (ICRP, 2007). Additionally, the yearly authorized limit to public (1 mSv) ought to be taken into consideration from plan-ned exposure situation and is not relevant to the existing exposure situation. The aforementioned yearly effective doses on healthcare worker & public were summation of the planned exposure and exis-ting exposure. The minimum yearly effective dose on healthcare worker & public were found out at position far apart from the CT rooms, CT angiogram rooms, X-ray rooms, SPECT-CT rooms and radio-active substances handling, storage and dispensing rooms. When the utmost number of radiations gene-rating equipment (CT, X-ray, SPECT-CT, etc.) in the hospital were kept in “on-state”, that moment high radiation dose rates were found out at positions next to radiation generating rooms. Table 1 Demon-strates the real-time radiation monitoring dose rates at 32 positions in the MMCH from August-Sep-tember 2022. It is observed from the Table 1 that real-time radiation dose rates & yearly effective dose on healthcare worker and public in the MMCH campus is fairly higher than those of the green field.

Table 1: Real-time radiation monitoring in the MMCH campus from August-September 2022.

Fig. 1 demonstrates the average yearly effective dose for each position on healthcare worker & public normalized to the smallest yearly effective dose. It is noticed from Fig. 1, average yearly effective dose for two positions (serial numbers 8 & 20) in the MMCH campus are practically greater than those of the other positions. The motive for greater real-time dose rates at two positions (serial numbers 8 & 20) is that these two positions are next to the CT rooms. Conversely, it is marked from Fig. 1, average yearly effective dose for two positions (serial numbers 15 & 26) in the MMCH campus are practically lesser than those of the other positions. The motive for lesser real-time dose rates at two positions (serial numbers 15 & 26) is that these two positions are very far apart from the CT rooms. 

Fig. 1: Average yearly effective dose for each position normalized to the lowest yearly effective dose.

Fig. 1 & Table 1 demonstrate the fluctuation of the dose rates in the MMCH campus were contributed from the natural & man-made sources. The natural radiation is emerging from the construction materials of the building, soil and water. The man-made radia-tion is arising from the radiation generating equip-ment & radioactive material in the hospital that is being used to diagnosis and treatment to patients. The alteration of the yearly effective dose in the MMCH campus at different positions were depended on many reasons: (1) number of radiation generating equipment were remained in “on” or “off” conditions during the real-time radiation monitoring period; (2) real-time radiation monitoring positions are next-door or far away from the radiation generating equi-pment or radioactive substances handling, storage or dispensing rooms; (3) weather conditions during the real-time radiation monitoring period. It was attri-buted in the international article (Bellia S, 2001) that radiation dose rates at outdoor positions in the spring and autumn were moderately higher than those of other seasons. Aggregation of extra radon gas adjo-ining to the ground at outdoor positions throughout the winter and spring seasons were provided addi-tional gamma dose rates amid the winter and spring seasons. Again, radon emanation rates from the soil surface are reduced due to the infusing of cavity spaces in soil in the rainy season. Furthermore, radon and its by-products are generally washed out straightway for declining of its concentration in the lesser atmosphere in rainy season (Stranden E, 1985; Chandrashekara MS, 2006). The frequency distri-bution of the real-time radiation dose rates in the MMCH campus in Bangladesh is demonstrated in below Fig. 2. 

Excess life-time cancer risk (ELCR)

Excess life-time cancer risk (ELCR) on healthcare worker & public in the MMCH campus should be estimated in order to investigate the medical radia-tion hazard. The medical radiation hazard is app-eared from the natural and man-made radiation sources in the hospital. It was viewed in the inter-national papers that calculation of yearly effective dose and afterward ELCR on healthcare worker and public at indoor positions of the hospital is the modest numbers comparing to those seen at the outdoor positions.

Fig. 2: The frequency distribution of the real-time radiation dose rates at 32 positions in the MMCH campus.

It is viewed in Table 2 that the estimated ELCR on healthcare worker & public in the MMCH campus is consistent to Iran. It is perceived from Table 2, average ELCR on health-care worker & public at few areas of Iraq, Iran, India, Malaysia, Pakistan, Nigeria & Morocco are slighter than that of the MMCH campus in Bangladesh.  On the other hand, average ELCR at few areas of India are greater than that of the MMCH campus in Bangladesh. Some-what high ELCR on healthcare worker & public in the MMCH campus of Bangladesh are primarily given from the CT, CT angiogram, X-ray machine, etc. operated in the hospital to diagnosis & treat-ment to patients. In addition to that, the quite high ELCR on healthcare worker & public at indoor positions of the building persist due to the apparatus (electronics) in the laboratory of the hospital, sur-plus gorgeous stones on the structure of the walls & floor tiles & due to the nonexistence of right venti-lation system in the laboratory, working rooms, patient wards of the hospital building that enhancing the radon concentration.

Fig. 3: Excess life-time cancer risk (ELCR) on healthcare worker & public in the MMCH campus of Bangladesh.

Table 2: Yearly effective dose & ELCR on healthcare worker and Public in the MMCH campus are compared to other countries. 

The estimated average effective dose of 2.529 mSv may not be presumed to introduce weighty risk on healthcare worker from the radiological risk perspective. The motive is that average yearly effective dose limit to healthcare worker as per ICRP 103 (ICRP, 2007) is 20 mSv for 5 consecutive years & the limit is pertinent to the planned exposure practice and is not related to radiation arising from the existing exposure practice. 

CT and nuclear cardiology are liable for additional ionizing radiation effective dose on healthcare wor-ker and public in the hospital. Real-time radiation monitoring in the large hospital campus would pro-mote to minimize the ionizing radiation risk on healthcare worker & public by means of assessment of the radiation generating equipments faults and incorrect management of radioactive material in the hospital campus. The mean yearly effective dose and mean ELCR on healthcare worker & public in the MMCH campus of Bangladesh are much greater than those of the global mean values.  Study should be carried out routinely in the large hospital campus for diminishing the ELCR on healthcare worker & public which confirm the safety of their everyday work in the hospital campus against intolerable radi-ation risk. Besides, healthcare worker must be at-tentive during operation of the radiation generating equipment and handling of the radioactive subs-tances in the hospital. Additionally, healthcare wor-ker has to comply with the national rules relevant to the radiation protection and international recom-mendations (particularly IAEA and ICRP) for re-duction of the intolerable radiation risk throughout their daily work in the environment of the hospital. 

This research is funded by the Ministry of Science and Technology, Government of Bangladesh under the Special Research Allocation Project 2019-2020, 2020-2021, 2021-2022 & 2022-2023 (the grant serial no.: 523 MS, 519 MS, 572 MS & 578 MS). This research is also funded by the Ministry of Education, Government of Bangladesh under Grant of Advan-ced Research in Education Project 2020-2021, 2021-2022 & 2022-2023.

The authors declare no conflict of interest.