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Original article

Designing of High‑Volume PET/CT Facility with

Optimal Reduction of Radiation Exposure to the
Staff: Implementation and Optimization in a Tertiary
Health Care Facility in India
Ashish Kumar Jha, Abhijith Mohan Singh, Sneha Mithun, Sneha Shah, Archi Agrawal,
Nilendu C. Purandare, Bhakti Shetye, Venkatesh Rangarajan
Department of Nuclear Medicine and Molecular Imaging, Tata Memorial Hospital, Mumbai, Maharashtra, India

Abstract
Positron emission tomography (PET) has been in use for a few decades but with its fusion with computed tomography (CT) in
2001, the new PET/CT integrated system has become very popular and is now a key influential modality for patient management
in oncology. However, along with its growing popularity, a growing concern of radiation safety among the radiation professionals
has become evident. We have judiciously developed a PET/CT facility with optimal shielding, along with an efficient workflow to
perform high volume procedures and minimize the radiation exposure to the staff and the general public by reducing unnecessary
patient proximity to the staff and general public.

Keywords: Nuclear medicine procedure and professional exposure, positron emission tomography/computed tomography
procedure, radiation dose, radiation safety

Introduction physiological processes of the body.[3] In the last few

years, PET/CT has made a significant impact on patient
Stand‑alone positron emission tomography (PET) management in oncology. Increasing indications of PET/
scanners have been available for more than 35 years CT in various oncological conditions have made this
but their use was not widespread as an independent system an integral part of nuclear medicine departments.
modality. The fusion of morphological imaging in the However, the increasing workload in nuclear medicine
form of computed tomography (CT), along with the departments has also increased concerns among
physiological imaging of PET as an integrated PET/ radiation professionals regarding radiation exposure,
CT scanner brought a new dimension in imaging.[1,2] and thereby the responsibilities of a Radiation Safety
This technique, being a noninvasive diagnostic imaging Officer  (RSO) to minimize radiation exposure for the
tool, takes advantage of certain metabolites in the professionals, the patients, and the general public.
form of radiopharmaceuticals to trace the abnormal International Council on Radiological Protection (ICRP),
metabolic activity in the body. At the same time, the International Atomic Energy Agency (IAEA), and other
small quantity of tracer dose not alter the normal national agencies have published guidelines to limit
occupational radiation exposure and prescribed the
Access this article online
maximum radiation exposure limit for the professionals,
Quick Response Code:
Website:
the general public, and the environment. [4,5] These
www.wjnm.org agencies advocate the implementation of “As Low As
Reasonably Achievable” (ALARA). In order to achieve
DOI:
ALARA at workplace, the radiation safety aspect has to be
10.4103/1450-1147.163252 implemented at each and every stage of project planning
and implementation. Proper layout and workflow design

Address for correspondence:

Mr. Ashish Kumar Jha, Department of Nuclear Medicine and Molecular Imaging, Tata Memorial Hospital, Parel ‑ 400 012, Mumbai, Maharashtra, India.
E‑mail: ashish.kumar.jha.77@gmail.com

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Jha, et al.: Designing of high‑volume PET/CT facility

of nuclear medicine facility, along with an optimal The calculated values for expected annual radiation
isotope procurement and consumption planning may exposure were compared with the actual readings of
reduce the radiation burden on the professionals, the the staff for 2012 and 2013 to assess the effectiveness of
patients, the general public, and the environment at the workflow and facility design in reducing radiation
large.[6] National and international enforcement agencies exposure.
have prescribed the layout design of PET/CT and nuclear
medicine facility for better workflow management. In Design of PET/CT facility
India, the Atomic Energy Regulatory Board (AERB) The initiative of radiation safety should start at the
has prescribed the model layout plan for PET/CT time of designing of the radiation facility and radiation
facility.[7,8] However, in our existing tertiary health care safety must be guaranteed by the facility design itself.
facility with old infrastructure and the unavailability The layout plan, patient movement plan, construction
of space, implementation of these prescribed layouts materials, and workplace shielding have to be decided
was not possible. So we had to design a layout plan keeping in mind radiation safety of the professionals, the
in the available space for better implementation of patients, and the general public as well as the workload
radiation safety norms to achieve ALARA. The new and workflow to achieve the concept of ALARA.
PET/CT facility was to be added to the existing  PET/CT
and single photon emission computed tomography We have designed the PET/CT layout keeping in mind
(SPECT)/CT facilities. the high throughput with ALARA as the central focus of
the concept. A dose constraint of 0.1 mSv per year was
Materials and Methods adopted in occupied areas. Figure 2 shows the layout
plan of our newly developed PET/CT facility. The design
The new PET/CT facility was designed in the allotted was developed taking into consideration the movement
156 m2 (6 m × 26 m) area across the corridor of our existing of the patient through the unit and the relative positions
department. The model plan [Figure 1] provided by the of the injected patients with reference to the staff and
competent authority in our country, i.e. AERB is meant members of the public, which also included those staff
for a site measuring about 12 m × 13 m (total 156 m2). working in adjacent departments of the hospital. The
So, though the area was adequate for a PET/CT facility, layout consists of the nursing station, the radiopharmacy
the model plan could not be implemented because of room, the injection room, the postinjection patient
its size. Hence, we modified the plan and developed a waiting room, the radioactive toilet, the postscan holding
radiation safety compliant department and designed room, the PET/CT scanner room, and the operating
the entire workflow to perform high‑volume work, console room.
i.e. around 35 PET/CT procedures every day. We
also planned fludeoxyglucose (FDG) procurement Design of work area
schedule, patient appointment for high throughput There are two types of radiation sources present in
with minimum amount of radiation exposure to the the nuclear medicine department: (i) radioisotope and
professionals and the patients. We calculated the (ii) the injected patients. The radioisotope present in the
expected radiation exposure to the radiation worker department can be confined and shielded to achieve
working in this department. We also compared negligible radiation exposure from it when not in use but
radiation exposure received by the radiation workers during handling, it is necessary to minimize the exposure
working in the new and old PET/CT facilities together by means of proper planning of the work by using remote
in 2013 with that of the old PET/CT facility in 2012. handling equipments and good work practice. Emphasis
has been placed on developing each area of the facility
keeping in mind the nature of radiation exposure. The
source of radiation in various parts of the design is as
follows: On the dispensing table, radioactivity in the
vials and syringes; in the injection area, radioactivity in

Figure 1: Model plan provided by AERB Figure 2: Layout plan of our newly developed PET/CT facility

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Jha, et al.: Designing of high‑volume PET/CT facility

the syringes and the injected patients; in the postdose are made up of 300‑mm‑thick RCC, resulting in an
waiting area, the injected patients; and in console, the exposure rate of about 1.22 uSv/h (for a patient injected
injected patients and scatter from CT. with 300 MBq of 18F radiopharmaceutical at a distance
of about 1 m).
Dispensing table
We used 100‑mm‑thick lead bricks to shield the entire Operating console room
dispensing area from all around and L‑bench with The wall separating the console room from the PET/CT
50‑mm lead equivalent lead glass [Figure 3], along with scanner room is a 300‑mm‑thick RCC wall with 4‑mm
a 40‑mm‑thick dispensing module. Dose vial is directly lead equivalent lead glass window.
delivered from the on‑site cyclotron to our dispensing
area by pneumatic chute in a 25‑mm‑thick lead container The shielding effectively reduces the exposure to about
in the form of lots. Each lot contains 1850 MBq of 0.19 µSv/h (RCC) and 3.1 µSv/h (lead glass).
18
F isotope. Six lots amounting to 11.1 GBq are received
in total. The surface dose rate from the container
containing 1850 MBq of 18F isotope is 2.48 mSv/h and Workflow management
at 50 cm, the exposure rate is 0.009 mSv/h that is within Planning and streamlining the workflow properly and
the prescribed limits. The dose vial is then transferred consistently can effectively minimize radiation exposure
into the dispensing module and individual doses are to the professionals [Figure 5]. At the same time, effective
dispensed. sharing of the workload among the professionals may
also be introduced to minimize individual radiation
exposure.
Injection area
The injection room is constructed separately with
220‑mm‑thick reinforced cement concrete (RCC) wall. All The patients referred for a PET/CT study are attended
the injections are injected in this room. Intravenous (IV) at a dedicated counter for appointments. Appointment
access is obtained and the radiopharmaceutical is injected is scheduled by the trained staff present at the counter
through an aperture between the injection room and and detailed scan‑specific instructions are provided to
the adjoining radiopharmacy [Figure 4]. The physician the patient at the time of appointment. On the appointed
and the nursing staff stand in the radiopharmacy room date, the patient reports at nursing station where the
throughout the procedure and are able to inject and nurse in charge verifies the patient details and tests
monitor the patient through the aperture. This keeps prescribed, and refers him/her to the resident doctors
radiation exposure to the professionals at a minimum for documenting relevant clinical history. Relevant
as they are shielded from the injected patient by the instructions are provided to the patient regarding the
220‑mm‑thick RCC wall.[9] prescan and postscan precautions. He/she then proceeds
to the injection room. A continuous flow of patients is
maintained with a patient being injected approximately
Postdose waiting area every 20 min.
The injected patient is then directed to the postdose
waiting area where he/she can rest comfortably during
the uptake period. The walls of postdose waiting area

a b

c d
Figure 4: Injection area with aperture for injections (a) staff nurse
is fixing IV line, (b) patient is extending hand through aperture,
(c) doctor is injecting radiopharmaceutical, and (d) injection process
Figure 3: Radioisotope dispensing table is finished

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Jha, et al.: Designing of high‑volume PET/CT facility

dose to the individuals drawing up and administering

PET radiopharmaceuticals can be substantial. The dose
rate at 5 cm from an unshielded syringe source with the
typical administered activity of 225 MBq is

D = (Γ*A)/(d2)

= (0.000139 mSv m2/hMBq*275MBq)/(0.05 * 0.05)

=15.29 mSv/h

where,
D = dose rate at 5 cm
Γ = dose rate constant of 18F isotope at 1 cm[10]
A = total activity
Figure 5: Workflow design of department d = distance.
After injection, the patients wait in the postinjection
waiting area in isolation during the uptake period. Technologists
During this time, the patient is monitored on closed Transferring radioactivity container (hot capsule)
circuit television (CCTV). The patient can communicate from pneumatic chute to L‑Bench
with the staff at any time using an audio system remotely. Assuming that all hot capsules contain 1850 MBq of
After 60 min of injection, the patient is instructed on the activity and the time taken to transfer the capsule from
audio system to void his/her bladder and come to the pneumatic chute station to L‑Bench is 10 s,
machine room for scan.
t = 10 s = 10/(60 * 60) h
Subsequent to the scan, the patient is instructed to wait in
the postscan waiting area until the acquired images are Hot capsules are received six times in a day and 240 days
verified by the physician. Once the study is deemed to in a year, resulting in a total of 1,440 times in a year (T)
have been acquired adequately, the patient is instructed
to leave the department. The surface dose rate from hot capsule (R) =2.48 mSv/h
(for extremity dose calculation)
Planning workflow and dose calculation
We planned for 35 patients per day for 5 days a week and The dose rate at 50 cm from hot capsule (R1) =0.009 mSv/h
with 52 weeks in a year, with the total number of patients (for whole body dose calculation)
to be scanned per year as 35*5*52 = 9100. Each patient
is injected on an average of 225 MBq. The approximate So, the annual dose received by the technologists in
time required for dispensing one dose of isotope is 15 s. transferring the hot capsule is
The time for injection is again 15 s. The time required to
remove the IV cannula is 15 s. The total time spent with Extremity = (T*R*t)
one patient for patient positioning is 60 s. The average
time spent by the technologists or the nurses with = (1440 * 2.48 mSv/h*10)/(60 * 60)
the patient during uptake time for giving any special
instruction is around 60 s. The average time spent by the =9.92 mSv
nuclear medicine physician with the patient after imaging
to take any important clinical history is around 60 s. Whole body = (T*R1*t)

Dose calculation = (1440 * 0.009 mSv/h*10)/(60 * 60)

Prior to the injection, the required dose of
radiopharmaceutical has to be transferred from the vial =0.036 mSv
to the syringe. This operation is carried out behind the
lead shield. The shields used in this case are lead bricks Transferring radioactivity vial from hot capsule to
and lead glass, but the hands remain unprotected. dispensing module in L‑Bench
Assuming that all hot capsules contain 1,850 MBq of
Because of the high effective dose rate constant activity and the time taken to transfer the capsule from
associated with positron‑emitting radionuclides, hand the hot capsule to dispensing module is 10 s.

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Jha, et al.: Designing of high‑volume PET/CT facility

The dose rate from dose vial at 50 cm (R) = 1 mSv/h (for K = 0.64 (patient attenuation)[11]
extremity dose calculation) Rt = dose reduction after 1 h = 0.643[11]
T = 1 (full occupancy).
So, the annual dose received by the technologists in
transferring the hot capsule is Physician
Assuming that each injection may take about 5 s, the total
Extremity = (T*R*t) hand dose received by the nuclear medicine physicians
together due to injection in 1 year would be
= (1440 * 1 mSv/h*10)/(60 * 60)
Extremity = R2*t*N
=4 mSv
=15.29 mSv/h*1/720 h/pat*9100 pat/year
The whole body dose rate outside the L‑Bench is
negligible.
=193.25 mSv/year
Dispensing of a single dose where,
Assuming that each dispensing may take 10 s (1/240 h), R2 = 15.29 mSv/h is the dose rate at 5 cm from 275 MBq
the total hand dose received by all the technologists activity (average activity of 18F radiopharmaceuticals
together during dispensing in 1 year would be for injection)
t = time in hour (5 s = 1/720 h)
Extremity = (R2*t*N)
N = number of patients in a year.
=15.29 mSv/h*1/360 h/pat*9100 pat/year
Assuming that the nuclear medicine physicians may
=386.5 mSv/year spend 1 min with every patient during the injection
process, the whole body dose would be
where,
R2 = 15.29 mSv/h is the dose rate at 5 cm from 275 MBq D = [Γ*A/(d2)*t*N*K*Rt*T]
activity (average activity of 18F radiopharmaceuticals
for injection) = ((0.000139 mSv m2/h MBq*275 MBq)/(0.5m) 2)*1/60 h/
t = time in hour (10 s = 1/360 h) pat*9100 pat/year*0.64 * 1*1
N = number of patients in a year.
=14.84 mSv/year
The whole body radiation exposure outside the lead
bench is negligible. where,
Γ =0.000139 mSv m2/h/MBq is the dose rate from the
Dose received during patient positioning injected patient at a distance of 1 m
A = injected activity (275 MBq)
and planning d = distance from the patient
Assuming that a technologist may spend a cumulative
t = time in hour (5 min = 1/12 h)
time of 5 min with every patient at 50 cm distance during
N = number of patients in a year
patient positioning, planning, or for any other purpose,
K = 0.64 (patient attenuation)[10]
the dose to the technologist would be
Rt = dose reduction just after injection = 1
T = 1 (full occupancy).
D = [Γ *A/(d2)*t*N*K*Rt*T]

= ((0.000139 mSv m2/h MBq*275 MBq)/(0.5 m) 2)*1/12 h/ Likewise, assuming that the nuclear medicine physicians
pat*9100 pat/year*0.64 * 0.643*1 may spend 2 min with every patient after scan for taking
relevant history if required, then
=47.72 mSv/year
D = [Γ*A/(d2)*t*N*K*Rt*T]
where,
Γ = 0.000139 mSv m2/h/MBq is the dose rate from the = {(0.000139 mSv m2/h MBq*275 MBq)/(0.5m) 2}*1/30 h/
injected patient at a distance of 1 m pat*9100 pat/year*0.64 * 0.643 * 1 = 19.09 mSv/year
A = injected activity (275 MBq)
d = distance from the patient where,
t = time in hour (5 min = 1/12 h) Γ =0.000139 mSv m2/h/MBq is the dose rate from the
N = number of patients in a year injected patient at a distance of 1 m

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Jha, et al.: Designing of high‑volume PET/CT facility

A = injected activity (275 MBq) Total extremity (hands) radiation exposure to all the

d = distance from the patient technologists together in 1 year = 9.92 mSv/year +
t = time in hour (2 min = 1/30 h) 4 mSv/year + 386.5 mSv/year = 400.42 mSv/year
N = number of patients in a year
K = 0.64 (patient attenuation)[11] Nuclear medicine physicians
Rt = dose reduction after 1 h = 0.643[11] Total whole body radiation exposure to all the physicians
T = 1 (full occupancy). together in 1 year = 14.84 mSv/year + 19.09 mSv/
year = 33.93 mSv/year
Nurses
Assuming that the nurses may spend 2 min with every Total extremity (hands) radiation exposure to all the
patient just after injection, physicians together in 1 year = 193.25 mSv/year
D = [Γ*A/(d2)*t*N*K*Rt*T]
Nuclear medicine nurses
= ((0.000139 mSv m2/h MBq*275 MBq)/(0.5 m) 2)*1/30 h/ Total whole body radiation exposure to all the nurses
pat*9100 pat/year*0.64 * 1*1 = 41.56 mSv/year = 29.68 together in 1 year = 29.68 mSv/year + 19.09 mSv/
mSv/year year = 48.77 mSv/year.

where, The total annual extremity dose for all the nurses together
Γ = 0.000139 mSv m2/h/MBq is the dose rate from the will be equivalent to the total annual whole body dose,
injected patient at a distance of 1 m as they personally do not handle the radioisotopes.
A = injected activity (275 MBq)
d = distance from the patient Results
t = time in hour (5 min = 1/12 h)
N = number of patients in a year Our department already had PET/CT and SPECT/CT
K = 0.64 (patient attenuation)[11] facilities, operational since 2005. The new PET/CT
Rt = dose reduction just after injection = 1 facility was constructed in 2012 and started operating
T = 1 (full occupancy). from January 2013. A total of 12 nuclear medicine
physicians, 6 nurses, and 11 nuclear medicine
Assuming that the nurses may spend 2 min with technologists were deployed on radioactivity‑handling
every patient at the end of the scan at around 1 h and patient‑handling duties in 2012 in the old PET/CT
postinjection, and SPECT/CT facilities. Similarly, 13 nuclear medicine
physicians, 7 nurses, and 11 technologists were deployed
D = [Γ*A/(d2)*t*N*K*Rt*T] in 2013 in both the new as well as the existing PET/CT
and SPECT/CT facilities [Table 1]. Whole body annual
= ((0.000139 mSv m2/h MBq*275 MBq)/(0.5 m) 2)*1/30 h/ exposure to the staff was calculated for the period of
pat*9100 pat/year*0.64 * 0.643 * 1 = 19.09 mSv/year 2012 and 2013, as shown in Table 2. The total number
of nuclear medicine procedures and PET/CT scans
where, performed in 2012 and 2013 were recorded and are
Γ = 0.000139 mSv m2/h/MBq is the dose rate from the shown in Table 3. The annual average radiation dose
injected patient at a distance of 1 m received per staff is shown in Table 4. Since the staff
A = injected activity (275 MBq)
was rotated in all the three facilities (old PET/CT,
d = distance from the patient
new PET/CT, and SPECT/CT), it was not possible to
t = time in hour (2 min = 1/30 h)
calculate the dose received per PET/CT procedure.
N = number of patients in a year
Hence, the dose received was normalized to 1.657
K = 0.64 (patient attenuation)[11]
PET/CT + 1 nuclear medicine procedure in 2012 and
Rt = dose reduction after 1 h = 0.643[11]
T = 1 (full occupancy). 2.112 PET/CT + 1 nuclear medicine procedure in 2013,
as shown in Table 5. The expected exposure has been
compared with the actual exposure in Table 6.
Total estimated dose for the nuclear
medicine technologists, physicians, and
nurses are as follows:
Discussion
Nuclear medicine technologists Technetium‑99m ( 99mTc) radiopharmaceuticals are
Total whole body radiation exposure to all the the most commonly used radiopharmaceuticals
technologists together in 1 year = 0.036 mSv/year + 47.72 for diagnosis in diagnostic nuclear medicine and
mSv/year = 47.76 mSv/year iodine—131 (131I) pharmaceuticals are the most commonly

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Jha, et al.: Designing of high‑volume PET/CT facility

used therapeutic radiopharmaceuticals in therapeutic Table 1: Total number of staff working in the
nuclear medicine.[12] With the advent of PET/CT imaging, department who were deployed on radioactive
an increasing number of PET radiopharmaceuticals work in 2012 and 2013
are also being used in nuclear medicine. Of these, 18F Nuclear medicine Nuclear medicine Nuclear medicine
radiopharmaceuticals are the most widely used. The dose physicians technologists staff nurses
rate constant and the penetration power of 99mTc is much 2012 12 11 6
lesser than that of the any PET radioisotope.[13] 131I also has 2013 13 11 7
a lesser dose rate and penetration power than any of the
PET radioisotopes. Thus, the increasing number of PET Table 2: Total annual whole body radiation dose 
cases adds to the radiation burden among the staff in a received by staff working in our Department of
nuclear medicine department. Considering the high dose Nuclear Medicine in 2012 and 2013
rates and transmission properties of PET radionuclides,
All nuclear All nuclear All nuclear
PET facilities require an extra amount of shielding to medicine medicine medicine staff
protect the patients, the professionals, and the general physicians (mSv) technologists (mSv) nurses (mSv)
public from radiation.[14,15] Various publications have 2012 24.42 21.19 18.3
stressed on the need for added structural shielding in PET 2013 15.9 22.8 17.4
facilities to isolate the postinjected patients from the staff
and the general public in order to minimize the radiation
Table 3: Annual number of procedures performed
dose.[11,15] Various publications have also shown that the
in the Department of Nuclear Medicine in
staff would have been exposed to an additional dose of up
2012 and 2013
to 10 mSv dose annually if the patients are not confined
in the postinjection waiting area during the uptake time. SPECT/CT Old PET/CT New PET/CT
2012 3813 6320
In our previous study we have found that, radiation
2013 4784 3612 6492
dose received by the radiation professional is significant SPECT: Single photon emission computed tomography; PET: Positron emission tomography;
during the injection process.[16] Additionally, a number of CT: Computed tomography
publications have enumerated the attenuation properties
of shielding materials for various radioisotopes.[5,8,11‑15] Table 4: Average annual WBRD received by staff
The choice of shielding material is ultimately a matter of working in the Department of Nuclear Medicine in
judgment and feasibility depending on the isotope used 2012 and 2013
and the number of studies performed. Nuclear Nuclear medicine Nuclear
medicine technologists medicine staff
Our institution is a tertiary care referral center in India physicians (mSv) (mSv) nurses (mSv)
and is one of the foremost oncology centers in Southeast 2012 2.04 1.92 3.05
Asia. The limited availability of adequate health care 2013 1.32 1.75 2.49
facilities for the diagnosis and treatment of cancer in this
region puts a significant demand on our department. Table 5: Average radiation dose received by
At our center, the number of scans performed per day staff performing PET/CT and nuclear medicine
per scanner is almost double to that of our western procedure in 2012 and 2013
counterparts. This puts the staff at an increased risk of
All nuclear All nuclear All nuclear
additional radiation exposure. medicine medicine medicine
physicians technologists staff nurses
To optimize radiation exposure to achieve ALARA, we (µSv) (µSv) (µSv)
have adhered to and implemented the radiation safety 2012 (1.657 PET/ 6.40 5.56 4.8
concept right from the initial phases of planning the CT+1 nuclear
medicine procedure)
layout and workflow design while keeping time, distance,
2013 (2.112 PET/ 3.32 4.77 3.64
and shielding as the core of our decision‑making without CT+1 nuclear
compromising on patient care. All possible methods have medicine procedure)
been implemented to achieve the goal of ALARA. The PET: Positron emission tomography; CT: Computed tomography
patient movement has been optimized to reduce the need
for unnecessary contact and interaction with the staff and be performed, and the number of staff. In order
the general public until the completion of their scans. to achieve this, we opted to build a concrete wall
(density, 2350 kg/m3) of 225‑mm thickness for shielding
In our design, we have considered the attenuation our PET/CT facility. [8] Further, the walls of the
properties of the shielding material to ascertain postinjection patient waiting area and the operating
its thickness considering the type and quantity of console were made 300 mm thick to provide additional
radioisotopes to be used, the number of studies to shielding. We have designed the dispensing and injection

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Table 6: Total annual WBRD received by all staff unnecessary patient proximity to the staff enables a
working in the Nuclear Medicine Department in reduction in professional radiation exposure.
2013 is compared with calculated radiation dose
All nuclear All All staff References
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shielding, along with an efficient workflow to reduce Source of Support: Nil. Conflict of Interest: None declared.

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