Ignacio Rosbaco1, Fiorela Merma2, Cristian Sosa3, Ian Pasquevich2, Angela Tissone, Pablo Andrés2
ORCID
Recibido:
Aceptado: 2026-07-09
©2026 El(los) Autor(es) – Esta publicación es Órgano oficial de la Sociedad de Anestesiología de Chile
Revista Chilena de Anestesia Vol. 55 Núm. 5 | https://doi.org/10.25237/revchilanestv55n5-14
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Evaluación de la dosis de radiación en pacientes sometidos a procedimientos intervencionistas para la patología lumbar
Abstract
Resumen
ABSTARCT
Purpose: Interventional pain-management procedures have increased in number and complexity in recent years. Consequently, both patients and healthcare staff are receiving higher radiation doses. The aim of this study was to estimate the kerma-area product (PKA) delivered to patients and the effective dose associated with the procedures performed. Materials and Methods: Individual doses were measured and estimated using thermoluminescent dosimeters and a NOMEX PTW multimeter. In accordance with international protocols such as IAEA TRS 457 and IAEA TECDOC 1641, PKA was estimated. It was then compared with the reference level suggested by the UK Health Protection Agency (6 Gy^cm2, 88 seconds of fluoroscopy). Results: The PKA values obtained were below 1 Gy^cm2, ranging from 0.17 Gy^cm2 to 0.72 Gy^cm2 (k = 2), with corresponding fluoroscopy times between 28 and 70 seconds. The effective doses (ranged 0.04 mSv – 0.15 mSv) were estimated using conversion factors suggested by NCRP Report No. 160 and taking into account the recommendations of UNSCEAR 2000. Conclusions: PKA values below the established reference levels support the performance of effective and optimised procedures, consistent with the professional judgement of the evaluating expert. Lower PKA values reduce the probability of occurrence of stochastic effects in both patients and healthcare personnel and help prevent the occurrence of tissue reactions. This study represents an initial approach to patient dosimetry in interventional procedures for lumbar pain treatment in the national clinical setting.
Keywords: Fluoroscopy, pain management, in vivo dosimetry, radiation protection, patient safety.
Introduction
Pain is a clinical syndrome associated with a broad spectrum of benign and malignant conditions and represents a major determinant of impaired quality of life. The increasing prevalence of degenerative skeletal disorders, osteoporosis, and oncological diseases has resulted in a growing demand for effective pain management strategies. In many cases, optimal pain control requires a multidisciplinary approach, particularly for patients who show insufficient response to conventional pharmacological or conservative therapies. Within this context, image-guided interventional pain management techniques have emerged as valuable therapeutic options[1].
Over recent decades, interventional radiologists and interventional pain physicians have assumed an increasingly prominent role in the treatment of pain syndromes. This evolution is largely attributable to the ability of interventional techniques to deliver minimally invasive, image-guided treatments directly to the target anatomical region, often resulting in rapid, safe, and clinically effective outcomes[2],[3]. Amongst these conditions, chronic lumbar pain is especially prevalent in the adult population and constitutes a major cause of long-term disability and reduced quality of life.
Consequently, millions of image-guided interventional pain management procedures are performed worldwide each year. Although fluoroscopy-guided techniques provide important benefits, they also raise concerns regarding patient exposure to ionising radiation[4]. During these procedures, patients are exposed to scattered and primary radiation resulting from interactions between the X-ray beam and body tissues. While reported dose levels for fluoroscopy-guided pain procedures are generally considered acceptable, uncertainties related to the health effects of low-dose radiation exposure persist. Therefore, rigorous application of the optimisation principle of radiation protection as expressed by the ALARA criterion (“as low as reasonably achievable”) remains essential in clinical practice[5],[6],[7].
In addition to optimisation, justification constitutes a fundamental principle of radiological protection in medical exposures involving ionising radiation. The inappropriate, excessive, or non-optimised use of fluoroscopic and other radiological procedures may result in avoidable radiation exposure and increased healthcare costs. Although the true magnitude of the risk associated with unjustified medical exposures remains uncertain, ensuring that interventional procedures are properly justified and optimised is crucial for minimising unnecessary radiation doses to patients and healthcare personnel. The availability of reliable dosimetric data is therefore an important component in supporting informed decision-making and improving radiation protection strategies in interventional prac- tice[8],[9],[10],[11],[12],[13].
Within this framework, the aim of the present study is to estimate the kerma-area product (PKA) and the effective dose received during routine interventional pain management procedures. The dosimetric information obtained provides an additional tool to support the justification and optimisation of these procedures.
Definitions
The kerma-area product (PKA) measures the total radiation energy incident on a patient during a fluoroscopy procedure, calculated as the radiation’s air kerma (energy per unit mass) multiplied by the beam’s cross-sectional area (Gy
The effective dose (E) is a radiation protection quantity intended to represent the overall stochastic health risk to a reference person from exposure to ionising radiation. It is calculated as the sum of equivalent doses to individual tissues and organs, each multiplied by a tissue-weighting factor that reflects the relative radiosensitivity of that tissue; it is expressed in Sievert (Sv)[15]. The effective dose allows comparison of different diagnostic or occupational exposures on a common risk-related scale, but should not be used for patient-specific risk prediction or epidemiological dose reconstruction, as stated in the discussion section of this manuscript.
Study design
This was an observational, descriptive study conducted in patients undergoing fluoroscopy-guided interventional procedures for lumbar pain management.
Study population: The participants’ pool consisted of patients who underwent these procedures at Hospital Zonal Bariloche, San Carlos de Bariloche, Argentina, during the second half of 2021 and who provided informed consent to participate in this study.
Inclusion criteria: Adult patients involved in interventional techniques for pain treatment in lumbar pathology who provid
ed written informed consent to participate in the project.
Exclusion criteria: Patients involved in pain treatment techniques in lumbar pathology other than interventional procedures, or those who underwent these procedures but declined to participate or did not provide informed consent for inclusion in this project.
Sample size: The sample size was constrained by the feasibility of performing measurements at the hospital under pandemic conditions. Nevertheless, despite these constraints, a recruitment rate of approximately two patients per week was achieved, which was considered sufficient given the standardised nature of the procedures and the reproducibility of the procedural steps. This resulted in a total sample of 24 patients: 16 females (median age: 44 years old (range: 30 to 77 years old); mean weight: 78.6 kg ± 16.2 kg) and eight males (median age: 53 years old (range: 40 to 68 years old); mean weight: 86.8 kg ± 11.4 kg). No statistically significant sex-related differences were found.
Dose assessment
A dosimetry survey was carried out using thermoluminescent dosimeters (TLDs) to estimate the doses received by patients during interventional procedures for the treatment of lumbar pain. The dosimeters were calibrated using a 137Cs (cesium-137) radioactive source, and energy correction factors were subsequently applied[16]. In addition, a PTW NOMEX multimeter was used in the survey, with the capability to determine parameters such as dose, tube voltage (maximum and mean), exposure time (total and per pulse), amongst others.
Nine irradiations were performed on an adult phantom to estimate the magnitude of the kerma-area product (PKA) during a standard diagnostic procedure. From the measurement of air kerma at the entrance surface, the entrance surface dose (ESD), the PKA, and the effective dose were estimated.
In accordance with the definition of PKA[14], this quantity was calculated by multiplying the air kerma measured at the centre of the X-ray beam plane by the area of the X-ray field, expressed in Gy-cm2. The phantom used had the standard dimensions required to simulate the thorax of an adult individual and consisted of a water filled PMMA (Poly(methyl meth
acrylate)) structure. The fluoroscopic system employed was a Siemens Siremobil unit.
The ESD was calculated using equation 1 as suggested in the literature[14]:
where:
f (E): is the energy-dependent conversion factor that converts air kerma to absorbed dose in the skin.
B (A,E): is the backscatter factor, which accounts for radiation backscattered from the patient and contributing to the ESD. It depends on the radiation field area and the bremsstrahlung spectrum. Typical values range from 1.1 to 1.4.
Air kerma values were measured at the surface of the phantom and on the patients’ skin using the mean of the reading obtained from the dosimeters (each dosimeter consisting of three TLDs), which were calibrated in terms of air kerma. The dosimeters were positioned on the patient as shown in Figure 1. In addition, the number of exposures, exposure time, tube voltage, and tube current were recorded.
The effective dose was calculated from the PKA by applying a conversion coefficient of 0.21 mSv-mGy-1-cm-2, as recommended in the literature for this type of procedure[17],[18]. A PKA value of 6 Gy
Results
Table 1 presents the measurements performed using an adult patient phantom, TLDs, and the PTW NOMEX system, together with the calculated quantities, as well as the number of exposures and the fluoroscopy time for each measurement. The PKA values obtained for all measurements are below the adopted reference level (6 Gy-cm2). Uncertainty assessment was carried out as stated in the literature[20].
Table 1. Measured and calculated quantities for a patient phantom.
| Results are expressed with a relative expanded uncertainty of k = 2[20]. | ||||||
|---|---|---|---|---|---|---|
| Meas | # shoots | Time [s] | K. | ESD [mGy] | PKA [Gy^cm2] | E [mSv] |
| 1 | 22 | 70 | 5.50 | 6.18 | 0.59 | 0.12 |
| 2 | 25 | 79 | 6.76 | 7.60 | 0.72 | 0.15 |
| 3 | 13 | 47 | 1.56 | 1.76 | 0.17 | 0.04 |
| 4 | 13 | 47 | 2.22 | 2.50 | 0.24 | 0.05 |
| 5 | 13 | 47 | 1.93 | 2.17 | 0.21 | 0.04 |
| 6 | 13 | 47 | 1.71 | 1.92 | 0.18 | 0.04 |
| 7 | 11 | 35 | 4.75 | 5.34 | 0.58 | 0.11 |
| 8 | 9 | 28 | 3.69 | 4.14 | 0.70 | 0.08 |
| 9 | 11 | 35 | 2.57 | 2.89 | 0.68 | 0.06 |
Kair: air kerma; ESD: entrance surface dose; PKA: air kerma-area product; E: effective dose. The “time” column indicates the fluoroscopy time.
In addition, dosimetry was performed for 24 patients at four positions, as indicated in the schematic shown in Figure 1, with the dosimeters positioned so as not to interfere with the interventional procedure. Table 2 presents the air kerma values measured at the different positions and for the type of procedure performed.
Figure 1. Scheme of the patient’s cross-sectional view. Letters A, B, C and D represent the arrangement of TLDs on the patient’s skin surface. Irradiation field diameter: 11 cm. Irradiated area: 95.03 cm2. TLD correction factor[20]: 1.06
Discussion
Dose management is a key aspect of fluoroscopy-guided interventional procedures for the treatment of lumbar pain, particularly in the context of the increasing number of interventions performed and the cumulative nature of radiation exposure. For anaesthesiologists and pain physicians, fluoroscopy is an indispensable tool that improves procedural accuracy and patient safety by facilitating correct needle placement and anatomical localization. Nevertheless, its use entails exposure to ionizing radiation, which may become clinically relevant in prolonged or technically demanding procedures. Although radiation doses per procedure are generally moderate, suboptimal technique, limited operator experience, or inadequate equipment settings may result in unnecessary patient exposure, highlighting the importance of appropriate training and adherence to radiation protection principles in interventional pain practice[21].
Patient radiation dose during interventional pain procedures shows considerable variability, influenced by factors such as the imaging modality employed, procedural complexity, patient anatomy, and operator-dependent practices, including fluoroscopy time, beam angulation, and collimation. From a clinical perspective, this variability underscores the need for systematic and practical dose monitoring strategies that can be integrated into routine anaesthesiology practice without interfering with procedural workflow. The use of surrogate dosimetric quantities, such as air kerma, kerma-area product (PKA), and fluoroscopy time, allows clinicians to monitor radiation exposure, identify high-dose procedures, and support optimisation efforts aimed at reducing patient dose while maintaining procedural efficacy[22],[23].
Dose estimates based on indirect metrics are subject to inherent uncertainties related to patient size and anatomy, beam geometry, field overlap, tube angulation, backscatter, calibration of dose indicators, and system-specific assumptions. In clinical interventional practice, these uncertainties are generally addressed implicitly and qualitatively rather than through formal uncertainty propagation, as suggested in the literature[20]. This approach reflects the primary role of surrogate dose quantities in anaesthesiology: to support dose awareness, guide optimisation strategies, and define trigger levels for follow-up, rather than to provide precise patient-specific dosimetric estimates.
Within this context, effective dose constitutes a useful radiation protection quantity for interventional pain practice. Although it is not intended for individual patient risk estimation, effective dose enables comparison of the relative radiation burden associated with different imaging techniques, procedural protocols, or institutional practices. In lumbar interventional pain procedures, it has proven particularly valuable for comparing fluoroscopy-guided and CT-guided approaches and for supporting justification and optimisation decisions. When used in conjunction with procedure-specific quantities such as PKA, effective dose contributes to a coherent dose management framework that promotes safer clinical practice and reinforces radiological protection principles in anaesthesiology and pain management.
Conclusions
Patient dosimetry should be a fundamental component of medical procedures involving ionising radiation, with the aim of maximising clinical benefits while minimising the associated risks, in particular the probability of future stochastic effectsresulting from radiation exposure.
The patient phantom dosimetry performed in this study shows that all recorded values of the kerma-area product (PKA) are below the adopted reference level. This finding indicates, in principle, that it is possible to carry out successful and optimised procedures while reducing the likelihood of radiation-induced effects in patients. The interventional procedures were performed and their results analysed by a local expert. However, national diagnostic reference levels (DRLs) have not yet been established. Their development would be highly desirable to ensure standards tailored to the local context, given their dependence on the technology employed and on socio-economic and demographic factors.
The present study represents an initial step in the local dosimetric assessment of patients, contributing to increased awareness of the importance of patient dosimetry. Furthermore, from a radiological protection perspective, it provides a first picture of the current situation of interventional procedures for the treatment of lumbar pathology at a national level and serves as a starting point for future improvements.
Table 2. Air kerma values measured in 24 patients at the positions indicated in Figure 1 (0.00 indicates that the measured values is below the recording threshold of 0.1 mGy). Results are expressed with a relative expanded uncertainty of k = 2[20]
| Patient | Air kerma [mGy]; position | # shoots | Procedure | |||
|---|---|---|---|---|---|---|
| A | B | C | D | |||
| 1 | 2.85 | – | 1.60 | – | 56 | CESI |
| 2 | 1.42 | – | 1.12 | – | 31 | SIIAI L. ZAIAI L5-S1 L |
| 3 | 1.08 | 0.90 | 0.38 | – | 32 | SIIAI L |
| 4 | – | 0.00 | – | – | 53 | ZAIAI L |
| 5 | – | – | – | – | 20 | Incomplete |
| 6 | 0.37 | 0.00 | 0.25 | 6.08 | 54 | TFSI L5/S1 L + CESI |
| 7 | 0.22 | 0.69 | 1.58 | 0.28 | 42 | TFSI L5/S1 R + CESI |
| 8 | 0.75 | 0.00 | 0.25 | 0.00 | 39 | ZAIAI L5-S1 L4-L5 L |
| 9 | 4.86 | 0.00 | 0.49 | 2.58 | 47 | SIIAI L. ZAIAI L5-S1 L |
| 10 | 0.28 | 0.00 | 0.47 | 0.00 | 33 | ZAIAI L5-S1 L4-L5 R + SIIAI R |
| 11 | 0.58 | 0.00 | 0.57 | 15.65 | 59 | TFSI L5/S1 R + CESI |
| 12 | 2.75 | 0.18 | 0.67 | 0.24 | 43 | ZAIAI L5-S1 L4-L5 R + SIIAI R |
| 13 | 0.45 | 0.00 | 0.58 | 2.98 | 36 | ZAIAI L5-S1 L4-L5 L |
| 14 | 0.48 | 0.37 | 0.67 | 2.23 | 51 | TFSI L3/L4 R + CESI |
| 15 | 1.52 | 0.17 | 0.14 | 1.78 | 26 | TFSI L5/S1 R |
| 16 | 0.48 | 0.00 | 1.08 | 6.80 | 70 | TFSI L4/L5 L |
| 17 | 0.15 | 0.00 | 5.28 | 0.21 | 33 | CESI |
| 18 | 1.79 | 0.30 | 0.83 | 10.60 | 48 | Intradiscal platelet-rich plasma L5 + L4. |
| 19 | 0.17 | 0.00 | 0.39 | 0.13 | 27 | Concordance proof L5-S1 L4-L5 L3-L4 |
| 20 | 1.34 | 0.26 | 0.64 | 0.38 | 110 | TFSI L4-L5 L. |
| 21 | 0.00 | 0.00 | 0.18 | 0.00 | 51 | Concordance proof L5-S1 L4-L5 L3-L4 |
| 22 | 2.35 | 0.14 | – | 1.04 | 26 | SIIAI R. ZAIAI L5-S1 R |
| 23 | 4.82 | 0.00 | – | 1.41 | 36 | CESI |
| 24 | 1.66 | 0.00 | – | – | 32 | ZAIAI L5-S1 L4-L5 L |
CESI: Caudal epidural injection; SIIAI: Sacroiliac intra-articular injection; ZAIAI: Zygapohyseal intra-articular injection; TFSI: Transforaminal injection.
Ethical approval
This study was reviewed and approved by the Ethics Committee and Commission for the Evaluation of Human Health Research Projects (CEEPISH) of the Ministry of Health of Río Negro Province, Argentina (Resolution No. 5451/21 MS). Written informed consent was obtained from all participants prior to inclusion in the study.
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