Occupational Radiation Exposure to Fingers Using Thermoluminescent Ring Dosimeters in Healthcare Personnel at AEMCK

1. Introduction

Occupational exposure to ionizing radiation in nuclear medicine (NM) is a concern due to handling unsealed radio-pharmaceuticals such as technetium-99m (⁹⁹ᵐTc) and iodine-131 (¹³¹I).¹ While whole-body monitoring with film badges has been routine at AEMCK for over a decade, extremity (finger) monitoring was absent until 2020.

In NM, staff frequently handle high-activity Radio pharmaceuticals , such as technetium-99m (99mTc) and iodine- 131 (¹³¹I)), during patient preparation and administration. These procedures often involve direct finger contact with unshielded vials and syringes. Therefore the fingers often receive higher doses than the torso during direct handling of vials/syringes.² placing the extremities at elevated risk of radiation exposure. Recent studies confirm that extremity doses can exceed whole-body doses significantly without proper shielding or monitoring.^3,4

To comply with PNRA regulations and IAEA recommendations ⁵, AEMCK introduced ring TLDs for Hp(0.07) measurement. This first local implementation provides data on dose variation by job role (Hot Lab vs. Gamma/Stress Lab), supporting work practice optimization and alignment with ICRP extremity limit (500 mSv/year).⁶

1. Material and Method.

• Study Design and Participants

Observational study at AEMCK NM Department, conducted over a year in many cycles (November-December 2020, January 2021-February 2021, March21-April21,May21-June21,July21-August21, September-October21 and November- December 2021).

• Participants

Five occupationally exposed NM workers:

Group 1(RW1/2) : Two staff members from the Hot Laboratory (Hot Lab)

Group 2(RW3/4/5): Two Tech operating gamma cameras, and one from the Stress Lab

These participants regularly handled technetium-99m (⁹⁹ᵐTc) and iodine-131 (¹³¹I) for diagnostic and therapeutic procedures.

• Dosimetry and Dosimeter Description

To monitor extremity dose,TLDs were used:

Ring Design:Ring TLDs (TLD-100 chips in custom plastic holders) worn on dominant hand's index/ring finger base. Control TLD stored in low-background area for background subtraction. Calibration used Cs-137 source (1 mGy) in KANUPP SSDL, traceable to IAEA standards. Readout via RADOS RE-2000 reader under nitrogen, with annealing and element correction coefficients. Doses in mrem (Hp(0.07)). Gloves worn over rings to prevent contamination. No syringe shields used during study (though recommended).

• TLD Calibration and Readout

A RADOS TLD reader model RE-2000 at KANUPP-1 was used to process exposed TLDs. This service provided by KANUPP-1. For calibration, a known dose of 1 mGy was delivered to a batch of TLDs using a Cs-137 source. This dose level was chosen to represent the typical range of occupational exposures and falls within the linear response range of the dosimeters. The resulting glow curve data were used to construct calibration curves for dose-to-light-output conversion.

Readout protocol: Pre-read annealing was conducted to eliminate low-temperature peaks. TLD glow curves were recorded under nitrogen atmosphere. Light output was converted into dose using pre-established element correction coefficients (ECCs) and calibration factors. Doses were expressed in mrem, representing Hp(0.07) the operational quantity for skin dose equivalent at 0.07 mm tissue depth, Table-3.

• Work Procedures and Source Handling

Radioisotopes handled: ⁹⁹ᵐTc (from ⁹⁹Mo/⁹⁹ᵐTc generator) used for routine SPECT imaging ¹³¹I used for treatment of thyrotoxicosis and differentiated thyroid cancer

Tasks performed by NM Technician included:

• Generator elution Radiopharmaceutical preparation and labeling.

• Syringe loading and patient administration.

• Patient positioning and imaging (Gamma Camera and Stress Lab).

• Dose Evaluation and Grouping

Workers were monitored over multiple monthly cycles. Doses were averaged across months and grouped based on role:

Group 1 (Hot Lab): Higher handling of unshielded radioactivity

Group 2 (Gamma/Stress Lab): Indirect contact, occasional administration

All doses were compared with the annual dose limits recommended by the International Commission on Radiological Protection (ICRP) and Pakistan Nuclear Regulatory Authority (PNRA) 5 .

1. Statistical Analysis and Significance Testing

Means ± SD calculated per group (Group 1: 14 data points; Group 2: 21data points). Unpaired two-tailed Welch’s t-test assessed inter-group difference (Excel 2016; confirmed via t-distribution calculator). Significance at p < 0.001.Data collected from the ring TLDs worn by five nuclear medicine (NM) staff members over mentioned period were statistically analyzed to evaluate the difference in extremity radiation exposure between job roles. Descriptive and inferential statistics were used.

• Software Used

The Finger doses data were entered and statistically analyzed using Microsoft Excel 2016 (Microsoft Corp., USA) and validated using https://stattrek.com/online-calculator/t-distribution for statistical testing.

• Descriptive Statistics

For each group Group 1 and Group 2 of staff members from NM division ,the mean (average) and standard deviation (SD) were calculated :

• Group 1 (Hot Lab): 2 workers × 7 datapoint= 14 data points

• Group 2 (Gamma Camera/Stress Lab): 3 workers × 7 datapoint = 21 data point,Table-1

• Inferential Statistics: Unpaired Two-Tailed t-Test

For showing the statistically significance (p<0.001) between two groups of staff members, an unpaired two-tailed t-test with unequal variances (Welch’s t-test) was applied.

• Formula for the t-statistic:

t= ———(a)

Where:

X1,X2: sample means

s1,s2 = sample standard deviations

n1, n2 = sample sizes

• Degrees of Freedom (Welch–Satterthwaite equation)

df= ———-(b)

• p-Value Calculation

The p-value was computed using the t-distribution with df ≈ 14 f0r a two-tailed test:

p = 2 * P(T > |t) (T follows t-distribution). ——- (c)

This was confirmed using online t-distribution calculators.

• Conclusion of Statistical Testing

As in Table 2, the p-value = 0.038 < 0.05, so the difference in finger doses between Group 1 and Group 2 is statistically significant. This significance indicates that Hot Lab staff received significantly higher extremity radiation doses compared to other NM personnel.

1. RESULTS

1. Overview of Measured Extremity Doses

in this study the extremity radiation doses measured using ring TLDs were recorded for five nuclear medicine (NM) radiation workers over mentioned period between 2020 and 2021. Table 1 presents the monthly ring dose values for Group 1 (RW1 and RW2) assigned to the Hot Lab and Group 2 (RW3, RW4, and RW5), assigned to the Gamma Camera and Stress Lab.

2. Description of Table 1 (Group 1 & Group 2)

As shown in Table 1, Group 1 exhibited the highest extremity dose values, as expected due to direct handling of unshielded radio-pharmaceuticals. The recorded doses for RW1 ranged

Table:1 Finger Doses for Group 1 & Group 2 Radiation Workers of Nuclear Medicine
Radiation Worker	NM Area		Monthly Ring Dose (mRem)	Dose Range	Mean+ Standard Deviation (mrem)
		Nov-Dec 2020	Jan-feb21	Mar-Apr2021	May-Jun21	Jul-Aug-21	Sep-Oct-21	Nov-Dec21	(mrem)	Mean	SD
RW1	Hot Lab	78	0	50	40	70	68	78	78.00	54.86	28.07
RW2	Hot Lab	100	19	110	80	51	48	30	91.00	61.29	33.31
RW3	Infinia	15	24	10	28	28	20	15	18.00	20.43	6.73
RW4	E-Cam	10	28	12	30	30	25	15	20.00	22.86	7.31
RW5	Stress Lab	10	15	10	15	15	15	12.00	5.00	12.43	3.82

from 0 to 78 mrem/month, and for RW2 from 19 to 110 mrem/month.The highest single dose was recorded for RW2 (100 mrem) during Jan–Feb 2021, indicating high exposure, possibly during ¹³¹I handling.The lowest dose (0 mrem) recorded for RW1 suggests either

non-participation or procedural variation in that period.The mean ± SD finger dose for Group 1 was 58.79 ± 30.48 mrem, highlighting both a high average and substantial dose variability. Group 2 workers, with indirect exposure roles, received consistently lower doses. RW3’s doses ranged between 15 and 28 mrem, RW4 between 10 and 30 mrem, and RW5 between 10 and 15 mrem. The highest dose in this group was 30 mrem. The mean ± SD for Group 2 was 18.19 ± 7.30 mrem, confirming their lower exposure profile as compared to Group 1.

4. Statistical Comparison (Between Groups)

The t-test analysis, Table-2, shows the difference between Group 1 and Group 2 mean doses was statistically significant (p = 0.000238, t = 4.89).Since p < 0.0001 the difference between groups is statistically highly significant. This validates that Hot Lab workers (Group 1) are receiving significantly higher finger doses than Group 2.

Table-2: statistical t-valué and P-valud
Group	n	Mean Dose (mrem)	Standard Deviation (mrem)
Group 1 (Hot Lab)	14	58.79	30.48
Group 2 (Gamma/Stress Lab)	21	18.19	7.30
aDegree of Freedom (df)			14
bt-value			4.89
cTwo tailed p-value		<0.0001 highly significance	0.000238

5. Interpretation of Figure 1 (Graphical Comparison)

The comparative extremity doses for Group 1 and Group 2 is illustrated in Figure 1, Group1 shows more fluctuation and generally higher bar heights, indicating greater dose variance and overall exposure. Group 2 shows tighter clustering and shorter bars, consistent

Figure1: Extremity Dose of Group1 and Group2 RW

with their controlled and indirect handling of radio-pharmaceuticals. This graphical representation visually supports the statistical conclusion that the nature of task (i.e., direct vs indirect handling of unsealed sources) influences extremity dose.

6. Comparison to Regulatory Limits

As it has seen that the observed variability and exposure in Group 1, none of the workers exceeded the annual dose limit of 500 mSv/year (50,000 mrem/year) for extremities, as set by ICRP and PNRA. The maximum monthly dose (100 mrem) observed in RW2 remains well below the permissible threshold when annualised.

• Conclusion of Results

The study shows the clarity of extremity exposure during handling of un-sealed radio-pharmaceuticals that:

• Work type significantly impacts finger dose.

• Hot Lab staff require more rigorous protection and training.

• Current safety protocols are adequate but could be improved with the implementation of syringe shields and other mitigation strategies.

Table-3: Trade Names and Origins of Materials and Equipment Use
Item/Material	Trade Name/Model	Purpose/Use
Thermoluminescent Dosimeter (TLD) Chips	TLD-100 (LiF:Mg,Ti)	Extremity dose at (Hp(0.07))
TLD Ring Holders	Custom Plastic Adjustable Rings	placement of TLD on finger. Fabricated Locally
TLD Reader	RADOS RE-2000	Reading and analyzing TLD glow curves
Calibration Radiation Source	Cs-137 Standard Source	Standardized irradiation for TLD calibration
Radiopharmaceuticals	Technetium-99m, Iodine-131	Diagnostic and therapeutic procedures
Radiopharmaceutical Generator	99Mo/99mTc Generator from PINSTECH	Elution of Tc-99m for radiopharmaceutical preparation
Ring Dosimeter Calibration Service	N/A	Calibration of TLDs using Cs-137 source in KANUPP
Radiation Protection Regulations	PAK-904 Rev. 1	Regulatory compliance and dose limits of PNRA
Software Used	Microsoft Excel	Dose tabulation, graphs, and statistical analysis

1. DISCUSSION

The Hot Lab personnel (RW1 and RW2), who routinely handle unsealed high-activity radio-pharmaceuticals such as Iodine-131 (¹³¹I), received significantly higher finger radiation doses compared to NM technologists working in the Gamma Camera and Stress Lab (RW3–RW5), consistent with global reports.⁷,⁸. Figure 1 shows that, the average extremity dose for Hot Lab workers was 58.79 ± 30.48 mrem, while that for other technologists was 18.19 ± 7.30 mrem, a difference found to be statistically significant (p = 0.000238). These findings confirm that direct manual handling of therapeutic isotopes results in elevated finger exposure. To mitigate such extremity exposure and making safety culture, following Radiation safety practices recommended;

• All workers used ring dosimeters placed at the base of the index or ring finger on the dominant hand for monthly dose accumulation.:

• Use of syringe shields 8,9 during injection procedures can reduce finger doses by 75%–85%, particularly during ¹³¹I handling.

• Short-tubing butterfly cannulas 10 11 inserted before radiopharmaceutical administration reduce hand proximity to the source.

• Rotation-based work scheduling limits 10 cumulative exposure by distributing high-risk tasks among multiple workers.

• Hands-on practice with dummy 10 sources enhances technique, safety awareness, and confidence in real procedures.

To follow these strategies, along with regular extremity dose monitoring, can effectively minimize the risk of exceeding the annual dose limit of 500 mSv (50,000 mrem) for the fingers, while ensuring safe and compliant operation in nuclear medicine facilities like AEMCK.

1. CONCLUSIONS

It can be infer that the measured extremity doses for all five nuclear medicine workers remained well below the recommended annual limit of 500 mSv (50,000 mrem), with rotation-based duties further minimizing cumulative exposure. Periodic monitoring of finger doses is recommended to support safe work practices and maintain proper documentation of radiopharmaceutical handling protocols at AEMCK.

Note: During this study period, no syringe shields were used by staff. Workers wore gloves over the ring dosimeters to prevent radioactive contamination.

1. References:

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1. Pakistan Nuclear Regulatory Authority. Regulatory guide on radiation protection (PAK-904). Islamabad: PNRA; 2019.

1. International Commission on Radiological Protection. 1990 recommendations. ICRP Publication 60. Ann ICRP. 1991;21(1-3).

1. Struelens L, et al. How much do 68Ga-, 177Lu- and 131I-based radiopharmaceuticals contribute to extremity doses? EJNMMI Phys. 2024;11:95.

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1. Amin NAB, et al. Whole body and extremity doses of nuclear medicine personnel handling liquid I-131(¹³¹I)). Appl Radiat Isot. 2023;202:111058.

1. Martin CJ. Strategies for assessment of doses to the tips of the fingers in nuclear medicine. J Radiol Prot. 2016;36(3):405-421.

1. International Atomic Energy Agency. Occupational radiation protection in nuclear medicine. IAEA Safety Reports Series No. 90. Vienna: IAEA; 2020.

Acknowledgment

It is pleased to acknowledge that the support from the Nuclear Medicine Department staff at Atomic Energy Medical Centre, Karachi (AEMCK), for their cooperation during data collection and monitoring activities. We also thank the Secondary Standard Dosimetry Laboratory (SSDL) at KANUPP for calibration and technical support in TLD processing.

Funding

This research has no grant from different finding did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Conflicts of Interest

The authors declare that there are no conflicts of interest related to this study.

Ethical Consideration

As this involved routine occupational dose monitoring without patient intervention or additional procedures, formal Institutional Review Board approval was not required. Informed verbal consent obtained from all participants.

Author Contributions

Author	Contribution Description
Uzma Ilyas¹ (Corresponding Author)	Conceptualization, data collection, TLD analysis, manuscript preparation
Umer Hussain Hyder²	Methodology development and manuscript review
Dr. Hina Hashmi³	Institutional support, supervision, and final approval of the manuscript

¹Medical Physicist (Nuclear Medicine )Principal Scientist , Atomic Energy Medical Centre,(AEMCK) Karachi, Pakistan Atomic Energy Commission.

²Medical Physicist (Radio therapy ) Senior Scientist , Atomic Energy Medical Centre,(AEMCK) Karachi, Pakistan Atomic Energy Commission.

³Director of Atomic Energy Medical Centre,(AEMCK) Karachi, Pakistan Atomic Energy Commission.

Corresponding Author

Ms.Uzma Ilyas.PS

Email: [email protected]

Mobile: +92-3343227473

Use of AI in Manuscript Preparation

It has been confirmed that AI tools (ChatGPT/Gemini ) were used to assist in language editing, formatting, and statistical expression, but all content was developed and verified by the authors. AI was not used to generate original research content or manipulate data.