Radiation Dose Reduction in CT Fluoroscopy-Guided Lumbar Interlaminar Epidural Steroid Injection by Minimizing Preliminary Planning Imaging

Patient Dose Estimation in Computed Tomography-Guided Biopsy Procedures

This study establishes typical Diagnostic Reference Levels (DRL) values and assesses patient doses in computed tomography (CT)-guided biopsy procedures. The Effective Dose (ED), Entrance Skin Dose (ESD), and Size-Specific Dose Estimate (SSDE) were calculated using the relevant literature-derived conversion factors. A retrospective analysis of 226 CT-guided biopsies across five categories (Iliac bone, liver, lung, mediastinum, and para-aortic lymph nodes) was conducted. Typical DRL values were computed as median distributions, following guidelines from the International Commission on Radiological Protection (ICRP) Publication 135. DRLs for helical mode CT acquisitions were set at 9.7 mGy for Iliac bone, 8.9 mGy for liver, 8.8 mGy for lung, 7.9 mGy for mediastinal mass, and 9 mGy for para-aortic lymph nodes biopsies. In contrast, DRLs for biopsy acquisitions were 7.3 mGy, 7.7 mGy, 5.6 mGy, 5.6 mGy, and 7.4 mGy, respectively. Median SSDE values varied from 7.6 mGy to 10 mGy for biopsy acquisitions and from 11.3 mGy to 12.6 mGy for helical scans. Median ED values ranged from 1.6 mSv to 5.7 mSv for biopsy scans and from 3.9 mSv to 9.3 mSv for helical scans. The study highlights the significance of using DRLs for optimizing CT-guided biopsy procedures, revealing notable variations in radiation exposure between helical scans covering entire anatomical regions and localized biopsy acquisitions.

Next Level in Computed Tomography-Guided Periradicular Infiltration Therapy: Same Efficiency with Less Radiation Exposure

OBJECTIVE

This retrospective cohort study investigated the radiation exposure and clinical efficiency of a new institutional low-dose protocol for computed tomography (CT)-guided lumbar periradicular infiltration (PRI).

METHODS

This was a retrospective matched-pair comparison of patients undergoing single-level lumbar PRI therapy employing a new low-dose CT protocol consisting of a helical scan with reduced energy levels and tube current versus the institutional standard CT protocol. The following variables were collected: dose-length product for the planning step, interventional step, and total examination, number of CT guidance scans, examination time, and postprocedural improvement on the numerical rating scale for radicular pain.

RESULTS

Forty-five patients were allocated to each group. A sufficient radiation dose reduction of 30% during PRI was achieved with the low-dose protocol with a median dose-length product of 9.8 mGy∗cm compared to 32.9 mGy∗cm with the standard protocol (P < 0.001). No need for additional multiple scans during the interventional mode was observed in the low-dose group, resulting in a comparable procedure time between the groups. Furthermore, the short-term pain-reducing effect of PRI was comparable between the low-dose and standard protocols (median delta numerical rating scale = 4 in both groups).

CONCLUSIONS

Our low-dose protocol with less tube voltage and lower electric current leads to less radiation exposure with the same safety and efficiency. In conclusion, every facility that performs CT-based procedures should check whether a further dose reduction is applicable to avoid stochastic radiation damage to the patient.

Computed Tomography of the Spine

The introduction of the first whole-body CT scanner in 1974 marked the beginning of cross-sectional spine imaging. In the last decades, the technological advancement, increasing availability and clinical success of CT led to a rapidly growing number of CT examinations, also of the spine. After initially being primarily used for trauma evaluation, new indications continued to emerge, such as assessment of vertebral fractures or degenerative spine disease, preoperative and postoperative evaluation, or CT-guided interventions at the spine; however, improvements in patient management and clinical outcomes come along with higher radiation exposure, which increases the risk for secondary malignancies. Therefore, technical developments in CT acquisition and reconstruction must always include efforts to reduce the radiation dose. But how exactly can the dose be reduced? What amount of dose reduction can be achieved without compromising the clinical value of spinal CT examinations and what can be expected from the rising stars in CT technology: artificial intelligence and photon counting CT? In this article, we try to answer these questions by systematically reviewing dose reduction techniques with respect to the major clinical indications of spinal CT. Furthermore, we take a concise look on the dose reduction potential of future developments in CT hardware and software.

Radiation dose of fluoroscopy-guided versus ultralow-dose CT-fluoroscopy-guided lumbar spine epidural steroid injections

OBJECTIVE

Compare radiation dose of lumbar spine epidural steroid injections (ESIs) performed under fluoroscopy guidance and ultralow-dose CT-fluoroscopy guidance.

MATERIALS AND METHODS

Retrospective review of consecutive lumbar ESIs performed using fluoroscopy, between May 2017 and April 2019, and using ultralow-dose CT-fluoroscopy, between August 2019 and February 2021, was performed. Ultralow-dose CT-fluoroscopy technique omits a planning CT scan, utilizes CT-fluoroscopy, and minimizes radiation dose parameters. Patient characteristics (age, sex, height, weight, body mass index (BMI)), procedural characteristics (anatomic level, type of ESI, procedure time, pain reduction, complications, trainee participation), and radiation dose were compared. Chi-square tests and two-sample t-tests were performed for statistical analysis.

RESULTS

One hundred and forty-seven patients (mean age 55.8 ± 16.7; 85 women) underwent ESIs using fluoroscopy. Sixty-six patients (mean age 60.9 ± 16.7; 33 women) underwent ESIs using ultralow-dose CT-fluoroscopy. The effective dose for the fluoroscopy group was 0.30 mSv ± 0.34, compared to 0.15 mSV ± 0.11 for ultralow-dose CT-fluoroscopy (p < 0.001). The average age in the CT-fluoroscopy group was older (p = 0.04), and there was more trainee participation in the fluoroscopy group (p < 0.001); otherwise there was no statistically significant difference in patient or procedural characteristics between the conventional fluoroscopy group and the ultralow-dose CT-fluoroscopy group. There was no statistically significant difference in immediate post-procedure pain reduction between the groups (p = 0.16). Four intrathecal injections occurred only in the fluoroscopy group, though this difference was not significant (p = 0.18).

CONCLUSION

Ultralow-dose CT-fluoroscopy technique for image-guided lumbar spine ESIs can lower radiation dose compared to fluoroscopy-guided technique.

Low-dose multi-detector computed tomography for periradicular infiltrations at the cervical and lumbar spine

Periradicular infiltrations are frequently performed in daily neuroradiological routine and are often guided by multi-detector computed tomography (MDCT), thus leading to radiation exposure. The purpose of this study was to evaluate MDCT with low dose (LD) and model-based iterative reconstruction for image-guided periradicular infiltrations at the cervical and lumbosacral spine. We retrospectively analyzed 204 MDCT scans acquired for the purpose of cervical or lumbosacral periradicular interventions, which were either derived from scanning with standard dose (SD; 40 mA and 120 kVp) or LD (20–30 mA and 120 kVp) using a 128-slice MDCT scanner. The SD cases were matched to the LD cases considering sex, age, level of infiltration, presence of spinal instrumentation, and body diameter. All images were reconstructed using model-based iterative image reconstruction and were evaluated by two readers (R1 and R2) using 5- or 3-point Likert scales (score of 1 reflects the best value per category). Furthermore, noise in imaging data was quantitatively measured by the standard deviation (StDev) of muscle tissue. The dose length product (DLP) was statistically significantly lower for LD scans (6.75 ± 6.43 mGy*cm vs. 10.16 ± 7.70 mGy*cm; p < 0.01; reduction of 33.5%). Image noise was comparable between LD and SD scans (13.13 ± 3.66 HU vs. 13.37 ± 4.08 HU; p = 0.85). Overall image quality was scored as good to very good with only minimal artifacts according to both readers, and determination of the nerve root was possible in almost all patients (LD vs. SD: p > 0.05 for all items). This resulted in high confidence for intervention planning as well as periprocedural intervention guidance for both SD and LD scans. The inter-reader agreement was at least substantial (weighted Cohen’s κ ≥ 0.62), except for confidence in intervention planning for LD scans (κ = 0.49). In conclusion, considerable dose reduction for planning and performing periradicular infiltrations with MDCT using model-based iterative image reconstruction is feasible and can be performed without clinically relevant drawbacks regarding image quality or confidence for planning.

Comparison of acquisition and iterative reconstruction parameters in abdominal computed tomography-guided procedures: a phantom study

BACKGROUND

Many computed tomography (CT) navigation systems have been developed to help radiologists improve the accuracy and safety of the procedure. We evaluated the accuracy of one CT computer-assisted guided procedure with different reduction dose protocols.

METHODS

A total of 128 punctures were randomly made by two operators on two different anthropomorphic phantoms. The tube voltage was fixed to 100 kVp. Tube currents (mAs) were defined to obtain 4 dose levels: 180 mAs (D1.00), 90 mAs (D0.50), 45 mAs (D0.25) and 15 mAs (D0.10) with respective volume CT dose index (CTDIvol) of 7.02, 3.52, 1.75 and 0.59 mGy. The raw data were reconstructed using level 2 of advanced model-based iterative reconstruction (ADMIRE) (A2) for D1.00, A3 for D0.50, A4 for D0.25 and A5 for D0.10. Two 12-mm targets per phantom were selected. The mean Euclidean distance (EuD) between the tip of the needle and the isocenter of the target was measured for each puncture. The different measures were compared by paired Student's t-tests.

RESULTS

The mean EuD was 7.0±3.1 mm for the 128 punctures performed. Regardless of which phantom was considered, no significant difference in accuracy occurred between the 4 dose levels, which were 7.1±3.5 mm for D1.00; 7.1±3.1 mm for D0.50; 7.2±3.0 mm for D0.25 and 6.6±2.6 mm for D0.10.

CONCLUSIONS

Abdominal CT-guided procedures, using computer-assisted navigation and iterative reconstruction algorithms, allow precise punctures on anthropomorphic phantoms with a dose reduction of -92% compared to a standard protocol.

Comparison of low-dose CT with CT/CT fluoroscopy guidance in percutaneous sacral and supra-acetabular cementoplasty

PURPOSE

Percutaneous cementoplasty is a minimally invasive treatment modality for painful osteoporotic and pathologic sacral and supra-acetabular iliac fractures. This study compares the use of low-dose CT guidance with CT/CT fluoroscopy in sacral and supra-acetabular cementoplasty.

METHODS

A retrospective review of patients who had undergone sacral or supra-acetabular cementoplasty was performed with patients grouped by use of CT/CT fluoroscopy or low-dose CT guidance during the procedure. Parameters evaluated included type of fracture, laterality of lesions, pain scores, pain medication use, imaging parameters, procedure time, dose-length product, effective dose, cement volume, and complications.

RESULTS

There were 17 patients identified who underwent cementoplasty utilizing dual CT/CT fluoroscopy, while 13 patients had their procedures performed with low-dose CT. There was a statistically significant decrease in radiation dose in the low-dose CT group (1481 mGy•cm) compared with the CT/CT fluoroscopy group (2809 mGy•cm) (P = 0.013). There was a significant decrease in procedure time with low-dose CT for bilateral lesions (P = 0.016). There was no significant difference between groups in complication rate (P = 0.999). Clinically nonsignificant cement extravasation occurred in two patients (10%) in the CT/CT fluoroscopy group and in one patient (8%) in the low-dose CT group (P = 0.999). There was a significant decrease in pain scores compared with baseline on the visual analogue scale in both groups at 1 week (low-dose CT P = 0.002, CT/CT fluoroscopy P = 0.008) and 1 month postprocedure (low-dose CT P = 0.014, CT/CT fluoroscopy P = 0.004), but no difference between groups at 1 day (P = 0.196), 1 week (P = 0.368), or 1 month (P = 0.514).

CONCLUSION

Sacral and supra-acetabular cementoplasties can be performed safely and precisely using low-dose multiple-acquisition CT guidance while providing significant radiation dose reduction with no difference in extravasation rates, postprocedural pain reduction, and complications compared with CT/CT fluoroscopy.

Radiation exposure of radiologists during different types of CT-guided interventions: an evaluation using dosimeters placed above and under lead protection

Background

Computed tomography (CT) is widely used not only for diagnostic purposes but also for image guidance during different types of interventions. Therefore, radiation exposure of both patients and interventional radiologists remains a much-discussed topic.

Purpose

To quantify radiation exposure of interventional radiologists during multiple CT-guided interventions using dosimeters placed under and outside standard protective lead clothing.

Material and Methods

A total of 113 consecutive interventions covering three different types of procedures (grouped as periradicular infiltration therapy, biopsies, and drain placement) and performed using routine clinical protocols were prospectively analyzed. The interventions were performed by two radiologists of different experience levels with identically placed dosimeters outside and underneath their protective clothing. Personal doses (right hand, eye lens, thyroid gland, thorax, gonads) were cumulatively measured for each type of intervention and separately for the two radiologists.

Results

Personal dose was below the detection limit of the dosimeters during periradicular infiltration therapy. In the biopsy and drain placement groups, the highest dose was found for the right hand (maximum cumulative dose = 1.84 ± 1.30 mSv in 19 consecutive drain placements). Under the protective gear, exposure was only observed for drain placements performed by the less experienced radiologist (maximum = 0.05 ± 0.04 mSv for the eye lens).

Conclusion

Personal doses measured here were far below annual thresholds published by the International Commission on Radiological Protection. Therefore, performing multiple CT-guided interventions appears to be safe for interventional radiologists in terms of radiation exposure.

Is There a Relationship Between Body Mass Index and Fluoroscopy Time During Cervical Interlaminar Epidural Steroid Injections?

Background

The challenge of obtaining medical imaging in individuals with higher body mass index (BMI) is described, but there is minimal data regarding the relationship between BMI and fluoroscopy time during cervical interlaminar epidural steroid injection (CIESI).

Objective

To determine the relationship between BMI and fluoroscopy time during CIESI.

Methods

Retrospective cohort study of patients who underwent fluoroscopically guided CIESI between January 2014 and February 2015 at an academic pain medicine center. Fluoroscopy time data were collected. Comparisons based on analysis of variance were made between patients with normal (<25.0 kg/m 2 ), overweight (25.0-29.9 kg/m 2 ), and obese (≥30.0 kg/m 2 ) BMI.

Results

Of 399 procedure encounters, 366 had documented BMI and fluoroscopy time data and were included for analysis. Mean age (± SD) in this cohort was 53 ± 13 years, including 189 females (52%) and 205 first-time injections. Mean fluoroscopy time for all injections was 18 ± 10 seconds. Separated by categorical BMI class, the mean fluoroscopy time was 18 ± 9 seconds for normal weight patients, 17 ± 10 seconds for overweight patients, and 20 ± 11 seconds for obese patients, respectively. Post hoc analysis showed that fluoroscopy time was significantly longer only in obese compared with overweight patients ( P  = 0.02). Trainee involvement and first-time vs repeat injection did not significantly alter fluoroscopy time ( P  = 0.17 and P  = 0.12, respectively).

Conclusions

The findings of this study indicate that BMI does not appear to have a clinically significant impact on fluoroscopy time during cervical interlaminar epidural steroid injection procedures. Future study is needed to directly quantify radiation exposure in patients and practitioners, as well as the associated health risk.

Periradicular infiltration of the lumbar spine: testing the robustness of an interventional ultra-low-dose protocol at different body mass index levels

Background Computed tomography (CT)-guided periradicular infiltration remains a frequent interventional procedure for treatment of low back pain. Purpose To present an interventional ultra-low-dose protocol for CT-guided periradicular infiltration therapy and assess its application at different body mass index (BMI) levels. Material and Methods Over a period of 14 months, 79 patients underwent 183 CT-guided interventions for single-site lumbar periradicular therapy using an ultra-low-dose protocol with a basic setup of 100 kV and 5 mAs. Procedures were performed via intermittent fluoroscopy. A retrospective review was performed to analyze the parameters tube current and tube voltage, dose-length product, and BMI. Results The interventional ultra-low-dose protocol allowed safe treatment of 91.1% of the patients without a need for adapting the protocol. In seven patients with a higher BMI (range, 31-38 kg/m²; mean, 34 kg/m²), the tube current had to be increased to retain sufficient image quality. Only patients with a BMI of 30 and higher showed a significant correlation between BMI and dose-length product ( P value = 0.02), resulting in a slightly increased dose ( P value = 0.002). Conclusion The protocol presented for the interventional part of CT-guided periradicular infiltration allows to safely treat patients with a median calculated effective dose of 0.045 mSv (converted from a dose-length-product of 2.26 mGy*cm). Patients with a BMI of 30 and higher required a higher calculated effective dose with just one patient slightly exceeding 0.1 mSv.

"Scout No Scan" Technique Reduces Patient Radiation Exposure During CT-Guided Spine Biopsy

OBJECTIVE

The objective of this article is to report our experience with a technique for CT-guided spine biopsies that we refer to as the "scout no scan" technique.

CONCLUSION

The scout no scan technique can significantly lower radiation exposure while maintaining high diagnostic yields for CT-guided spinal biopsies.

Ultra-low-dose periradicular infiltration of the lumbar spine: spot scanning and its potential for further dose reduction by replacing helical planning CT

PURPOSE

Computed tomography (CT)-guided periradicular infiltration has become an accepted procedure for treating radiculopathy-associated low back pain. The purpose of this study is to compare spot scanning and segmental helical planning CT in terms of dose reduction.

MATERIALS AND METHODS

Eighty-five patients underwent CT-guided single-site lumbar periradicular therapy. Prior imaging was not available for planning. Sixty-three patients were examined with a new dedicated spot scanning technique (group I), and twenty-two patients underwent conventional segmental planning CT examinations with helical image acquisition serving as controls (group II). Examinations were reviewed retrospectively for dose-length product (DLP) and number of acquisitions required for intervention. Pain reduction accomplished with the intervention was recorded for quality assurance.

RESULTS

Median DLP was 0.80 mGy cm for spot scanning versus 6.50 mGy cm for segmental planning CT. Thus, the contribution of the planning scan to the total interventional dose decreased from 73 to 25%. As a result, the total interventional dose was reduced significantly from a median DLP of 8.90 mGy cm to 3.20 mGy cm (-64%). Acquisitions required during the intervention had a median DLP of 2.40 mGy cm for group I and 2.35 mGy cm for group II, showing no significant difference. Median pain reduction in both groups was two points on the numeric rating scale.

CONCLUSION

Dedicated spot scanning for planning reduced the total median effective dose of the intervention by more than 64% without increasing the number of images required during the interventional procedure. Significant pain reduction was achieved with both approaches. Spot scanning is recommended for dose reduction.

The effect of body mass index on fluoroscopic time and radiation dose during lumbar transforaminal epidural steroid injections

OBJECTIVE

Transforaminal epidural steroid injections (TFESIs) are a commonly used, effective treatment for radicular pain. Accurate delivery of the injected medication helps to ensure maximum therapeutic efficacy and to decrease possible adverse events, and fluoroscopy is the preferred and most common image-guidance modality used to ensure accurate needle placement during lumbar TFESIs. However, fluoroscopic-guided lumbar TFESIs put patients at risk because of radiation exposure. The purpose of this study was to determine the relationship between body mass index (BMI) and fluoroscopy time and radiation dose during lumbar TFESIs.

DESIGN

A retrospective study design was used.

SETTING

The study was conducted at an academic orthopedic center. All procedures were performed by physicians board-certified in Physical Medicine and Rehabilitation (PM&R) and with subspecialty certification in sports medicine, or by a trainee under close supervision from an attending physician.

PARTICIPANTS

Participants were patients who underwent fluoroscopic-guided lumbar TFESIs between February 2013 and March 2015 with a documented height/weight, fluoroscopy time, and radiation dose.

INTERVENTIONS

All patients received unilateral or bilateral lumbar TFESIs with fluoroscopic guidance. Fluoroscopy time and dose were recorded.

MAIN OUTCOME MEASURES

The main outcome measures were fluoroscopy time and radiation dose. A Bonferroni correction was implemented for multiple comparisons, defining statistical significance at p<.01.

RESULTS

A total of 2,443 injections were performed on 1,548 patients. There were 419 normal, 572 overweight, and 557 obese patients, respectively. There were 1,426 first-time injections and 1,017 repeat injections. Sixty-nine percent (1,681) were unilateral injections, and 26.4% (645) were single level injections. A trainee was involved in 1,361 (55.7%) of the injections performed. The mean fluoroscopy time for all injections was 30.0±17.5 seconds, and the mean radiation dose was 2,164±1,484 mGy-cm(2). The mean fluoroscopy time was 27.7±15.2 seconds for normal weight patients, 30.0±21.0 seconds for overweight patients, and 32.2±15.1 seconds for obese patients, showing a significant difference between groups (p<.001). The mean radiation doses for each group were 1,376±450, 1,911±653, and 3,029±640 mGy-cm(2), respectively, with a significant increase in radiation dose with increasing BMI (p<.001).

CONCLUSIONS

The findings of this study demonstrate that fluoroscopy radiation dose and fluoroscopy time during lumbar TFESIs are increased in patients with an elevated BMI, and in patients of greater age, but the presence of a trainee had no effect on fluoroscopy time.

Reducing Patient Radiation Exposure From CT Fluoroscopy-Guided Lumbar Spine Pain Injections by Targeting the Planning CT

OBJECTIVE

CT fluoroscopy-guided lumbar spine pain injections typically include a preprocedural planning CT that contributes considerably to patient dose. The purpose of this study was to quantify the degree of radiation exposure reduction achieved by modifying only the planning CT component of the examination.

MATERIALS AND METHODS

A retrospective review was performed of 80 CT fluoroscopy-guided lumbar spine injections. Forty patients were scanned with a standard protocol using automatic tube current modulation (method A). Another 40 patients were scanned using a new technique that fixed the tube current of the planning CT to either 50 or 100 mA on the basis of the patient's anteroposterior diameter and that reduced the z-axis coverage (method B). Dose-length products (DLPs) were compared for the two methods.

RESULTS

The mean maximal tube current for the planning CT was 435.0 mA for method A and 67.5 mA for method B. The mean z-axis was shorter for method B at 6.5 cm than for method A at 9.6 cm (p < 0.0001). The mean DLP for the planning CT was 11 times lower for method B than for method A: 27.9 versus 313.1 mGy × cm, respectively (p < 0.0001). When method B was used, the mean DLP for the total procedure (i.e., planning CT plus CT fluoroscopy components) was reduced by 78%. There was no significant difference between methods A and B in CT fluoroscopy time (p = 0.37). All procedures were technically successful.

CONCLUSION

A nearly fivefold reduction in radiation exposure can be achieved in CT fluoroscopy-guided lumbar spine pain injections through modifications to the planning CT alone.