Lateral decubitus positioning for cervical nerve root block using CT image guidance minimizes effective radiation dose and procedural time

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.

Diagnosis and Treatment of Cervical Spondylotic Radiculopathy Using Selective Nerve Root Block (SNRB): Where are We Now?

Cervical spondylotic radiculopathy (CSR) is one of the most common degenerative diseases of the spine that is commonly treated with surgery. The primary goal of surgery is to relieve symptoms through decompression or relieving pressure on compressed cervical nerves. Nevertheless, cutaneous pain distribution is not always predictable, making accurate diagnosis challenging and increasing the likelihood of inadequate surgical outcomes. With the widespread application of minimally invasive surgical techniques, the requirement for precise preoperative localization of the affected segments has become critical, especially when treating patients with multi-segmental CSR. Recently, the preoperative use of a selective nerve root block (SNRB) to localize the specific nerve roots involved in CSR has increased. However, few reviews discuss the currently used block approaches, risk factors, and other aspects of concern voiced by surgeons carrying out SNRB. This review summarized the main cervical SNRB approaches currently used clinically and the relevant technical details. Methods that can be used to decrease risk during cervical SNRB procedures, including choice of steroids, vessel avoidance, guidance with radiographs or ultra-sound, contrast agent usage, and other concerns, also are discussed. We concluded that a comprehensive understanding of the current techniques used for cervical SNRB would allow surgeons to perform cervical SNRB more safely.

Development of in-house RIA kit for progesterone in cow's skim milk

A radioimmunoassay (RIA) method for progesterone has been developed. It has been validated for the determination of progesterone in cow skim milk. The main reagents used in the development work were prepared and characterized in-house. The assay uses a radioiodinated tracer purified by gel filtration on Sephadex G-25, standards prepared in skim milk and coated tubes with specific antibodies as the solid phase (separation system). The radiochemical purity of the tracer was greater than 95%, the maximum binding using solid phase reached 43% and the nonspecific binding didn't exceed 5%. Series of progesterone standards using milk matrix with concentration ranging from 0 to 40ng/mL were prepared. Detection limit of the assay was 0.13ng/mL and the precision evaluation gives an intra and inter-assay coefficient variations between 4.94% and 12.66%. The recovery obtained with skim milk samples was 84% to 119% and the parallelism test indicated good linearity (R² > 0.99). The clinical tests give high correlation coefficient (r = 0.998) between progesterone concentrations of cow's skim milk assayed using developed progesterone RIA kit and commercial progesterone RIA kit.

Paravertebral Collateral Arteries in Patients with Carotid Stenosis: Is There a Safe Space for Transforaminal Cervical Nerve Root Injections?

AIM

Image-guided cervical nerve root injections can cause serious complications including spinal cord infarction. This risk may be increased in patients with carotid stenosis who develop collateral arteries. The aim of this study is to describe the prevalence, and anatomical location, of arterial collateral vessels in relation to the optimal needle tip position in cervical nerve root injections.

MATERIALS AND METHODS

This retrospective study included 25 patients who had > 70% stenosis on a carotid CT angiogram. For each foramen the position of collateral arteries and the most anterior point of the facet joint were recorded, as Cartesian coordinates, by two independent observers. Descriptive statistics were used to analyse and present the results.

RESULTS

14 patients had unilateral and 11 had bilateral stenoses. A total of 85 collaterals were identified at all levels, the most common being C2/3. The median distance from collateral to optimal needle tip placement was 9.6 mm (95% CI median: 6.7-12.4, IQR: 5.6-15.6). The minimum distance was 2.9 mm. Inter-observer reliability was "substantial" (ICC 0.78, 95% CI 0.71-0.83).

CONCLUSION

Collateral arteries were common in our cohort of patients with carotid artery stenosis and half lay within 10 mm of the optimal position for transforaminal cervical nerve root injection.

A simple, 10-minute procedure for transforaminal injection under ultrasonic guidance to effect cervical selective nerve root block

The aim is to provide a detailed procedure of a simple and 10-minute cervical nerve root block (CNRB) under ultrasonic guidance, and to report the clinical outcomes, disorders, and complications. Records of patients who had undergone CNRB, were reviewed under ultrasonic guidance at the hospital from 2010 through 2012. The procedure is described in detail. Arm and shoulder pain was evaluated by use of the visual analogue scale (VAS). Forty-three patients agreed to undergo CNRB under ultrasonic guidance. Nerve roots from C5 to C8 were affected in 41, and these nerve roots were readily distinguished. Two of the 43 participants did not receive injections because impediments in visualizing the affected nerve root. Of the 41 who received injections, radicular pain immediately disappeared in 39, who continued to feel pain relief 1 month later. However, pain recurred in 15 patients (38%), of whom 11 underwent cervical spine surgery. The rest of 24 patients felt sustained pain relief longer than 3 months after the injection, significantly. Although one patient had recurrent radicular pain 10 months later, the pain could be controlled by medication. At the final follow-up periods, 17.2 (10–24 months), the median VAS score of the patients, 23 (0 to 71 mm), was significantly improvement (P = 0.001) in comparison to before injection 88 (range; 56–100). No complications occurred. The cervical nerve root block under ultrasonic guidance simply, safely, and efficaciously decreased radicular pain for 17.2 months in 62% patients with intolerable radicular pain.

Radiation dose for 345 CT-guided interlaminar lumbar epidural steroid injections

BACKGROUND AND PURPOSE

CT guidance is increasingly being used to localize the epidural space during epidural steroid injections. A common concern is that CT may be associated with significantly higher radiation doses compared with conventional fluoroscopy. The goal of this retrospective study was to determine the average dose-length product and effective dose delivered while interlaminar epidural steroid injections are performed and allow comparison with other modalities.

MATERIALS AND METHODS

A total of 281 patients who had undergone 345 consecutive CT-guided epidural steroid injections of the lumbar spine were evaluated for radiation exposure. The dose-length product for each scan was derived from the CT dose index volume and scan length. Effective dose was then calculated from the dose-length product and a κ coefficient of 0.015. Procedure time was calculated from the PACS time stamp on the scout image to the last CT image of the last image series.

RESULTS

The average dose-length product across all procedures was 89.6 ± 3.33 mGy·cm, which represents an effective dose of 1.34 ± 0.05 mSv. No complications from the procedure were observed, and average procedure time was 8 minutes.

CONCLUSIONS

The use of a stationary table and an intermittent scanning technique allow for short procedures and doses that are significantly lower than those of conventional diagnostic CT scans. Furthermore, because CT dose index overestimates radiation dose in stationary table procedures, the actual radiation dose may be even lower than stated here.

Optimal contrast concentration for CT-guided epidural steroid injections

BACKGROUND AND PURPOSE

Contrast is used in CT-guided epidural steroid injections to ensure proper needle placement. Once injected, undiluted contrast often obscures the needle, hindering subsequent repositioning. The purpose of this investigation was to establish the optimal contrast dilution for CT-guided epidural steroid injections.

MATERIALS AND METHODS

This investigation consisted of an initial phantom study, followed by a prospective, randomized, single-center trial assessing a range of contrast dilutions. In the phantom study, a phantom housing a chamber containing a 22-gauge needle and various dilutions of contrast was scanned, and images were evaluated for needle visibility. On the basis of these results, concentrations of 66, 100, 133, and 150 mg/mL iodine were selected for evaluation in a clinical study. Patients presenting for CT-guided epidural steroid injections were randomly assigned to a contrast dilution, and images from the procedure were evaluated by 2 readers blinded to the contrast assignment. Needle visibility was scored by use of a 5-point scale.

RESULTS

In the phantom study, the needle was not visible at contrast concentrations of ≥133 mg/mL. In the clinical study, needle visibility was strongly associated with contrast concentration (P < .0001). Significant improvements in visibility were found in 66 mg/mL and 100 mg/mL compared with higher iodine concentrations; no difference was found comparing 66 mg/mL with 100 mg/mL iodine. Neither injection location (cervical versus lumbar) nor technique (interlaminar versus transforaminal) influenced visibility scores.

CONCLUSIONS

For CT-guided epidural steroid injections, the optimal contrast concentration is 66-100 mg/mL iodine. Because these concentrations are not commercially available, proceduralists must dilute their contrast for such procedures.

Laser-guided cervical selective nerve root block with the Dyna-CT: initial experience of three-dimensional puncture planning with an ex-vivo model

Background

Cervical selective nerve root block (CSNRB) is a well-established, minimally invasive procedure to treat radicular cervical pain. However, the procedure is technically challenging and might lead to major complications. The objective of this study was to evaluate the feasibility of a three-dimensional puncture planning and two-dimensional laser-guidance system for CSNRB in an ex-vivo model.

Methods

Dyna-CT of the cervical spine of an ex-vivo lamb model was performed with the Artis Zee® Ceiling (Siemens Medical Solutions, Erlangen, Germany) to acquire multiplanar reconstruction images. 15 cervical nerve root punctures were planned and conducted with the syngo iGuide® laser-guidance system. Needle tip location and contrast dye distribution were analyzed by two independent investigators. Procedural, planning, and fluoroscopic time, tract length, and dose area product (DAP) were acquired for each puncture.

Results

All 15 punctures were rated as successful with 12 punctures on the first attempt. Total procedural time was approximately 5 minutes. Mean planning time for the puncture was 2.03 (±0.39) min. Mean puncture time was 2.16 (±0.32) min, while mean fluoroscopy time was 0.17 (±0.06) min. Mean tract length was 2.68 (±0.23) cm. Mean total DAP was 397.45 (±15.63) µGy m².

Conclusion

CSNRB performed with Dyna-CT and the tested laser guidance system is feasible. 3D pre-puncture planning is easy and fast and the laser-guiding system ensures very accurate and intuitive puncture control.

Comparison of CT and fluoroscopic guidance for lumbar puncture in an obese population with prior failed unguided attempt

BACKGROUND AND PURPOSE

In the past 50 years, fluoroscopic guidance has been used to improve upon lumbar puncture (LP) technique that was unchanged for over a century. Recently, CT has seen increasing use as a guidance modality due to its ability to demonstrate soft tissue contrast and provide millimeter accuracy with needle targeting. This study compared procedure time and radiation dosages for fluoroscopic and CT guided LP.

MATERIALS AND METHODS

This institutional review board and Health Insurance Portability and Accountability Act (HIPAA) compliant study was a retrospective review of a consecutive cohort referred for image guided LP. For CT, 45 patients aged 49 years (range 20-78, SD 14) with body mass index (BMI) values of 33 kg/m(2) (range 20-50, SD 12) were included. For fluoroscopy, 100 patients aged 47 years (range 18-88, SD 17) with BMI values of 29 kg/m(2) (range 15-56, SD 9) were included. CT procedure time was determined using picture archiving and communication system (PACS) image time stamps. Radiation dose was determined using the CT dose report and effective dose conversion factors. Fluoroscopic procedure time was determined from nursing. Fluoroscopic radiation dose was calculated from dose-area product (DAP) and fluoroscopy times, with effective dosage calculated using simulation software.

RESULTS

For CT, procedure time average was 14 min (range 5-42, SD 8.5). Average dose-length product was 120 mGy×cm (range 39-211, SD 43) and average effective dose was 1.98 mSv (range 0.2-8.18, SD 4.4). For fluoroscopy, procedure time averaged 12 min (range 12-30, SD 6). Average DAP was 10 Gy×cm(2) (range 0.1-70, SD 11) and effective dose estimate averaged 2.9 mSv (range 0.9-9.4, SD 1.9). There were no unsuccessful taps or complications.

CONCLUSIONS

Both fluoroscopic and CT guidance may be used to perform an LP in an obese population with a short procedure time and low radiation dose.