CT-guided spinal injections are minimally invasive procedures used to treat pain by delivering medication, typically corticosteroids and local anesthetics, into the epidural space, neural foramina, or facet joints. At our institution, these procedures are performed under CT guidance, as it offers more precise needle positioning compared to fluoroscopy [1-5]. However, some concerns about radiation exposure remain.
The necessity of dose reduction in CT-guided spinal injections stems from the need to minimize patient exposure to ionizing radiation while maintaining procedural efficacy. High doses can increase cancer risk and other health issues [6,7], prompting the medical community to adopt strategies like reducing tube current, using axial acquisitions for short scan lengths, and eliminating nonessential imaging. These methods significantly decrease radiation exposure without compromising procedural success [8-10]. Implementing low-dose protocols aligns with the “as low as reasonably achievable” (ALARA) principle for patient safety.
This prospective study, conducted between January and September 2024, included 229 adult patients who underwent CT-guided injections at our institution. After excluding 39 patients due to incomplete data and 19 patients who underwent CT-guided procedures other than epidural/foraminal/facet injections (sacroiliac, pyriformis, pudendal, lumbosacral plexus, and sacrococcygeal), 171 CT-guided procedures were analyzed.
CT protocol:
The standard protocol includes AP and lateral scout views, a helical diagnostic scan covering one vertebral body above and one below the target level(s), followed by targeted axial acquisitions with dose reduction as per the manufacturer's protocol, which includes lowering the tube voltage to 100 kV and using automated current modulation (control group).
To further reduce radiation exposure, we modified the protocol for the study group as follows (Table 1):
- Helical diagnostic scan: Limited to the target injection area whenever possible, determined based on prior diagnostic MRI.
- Axial acquisitions: Restricted to the minimum necessary coverage in the Z-plane.
- Tube voltage (kV): Manually adjusted to 80 or 100 kV based on patient body habitus.
- Tube current (mAs): Manually set after deactivating automated current modulation to prevent compensation of reduced kV with increased mAs.
In both groups, iterative image reconstruction was used as per the manufacturer's protocol.
The study group included 126 scans, while the control group contained 45 scans.
Interventions were performed by one of four radiologists with varying levels of experience, ranging from 1 year to over 25 years.
A single investigator collected Dose-Length Product (DLP) measurements from the dose sheet, including total DLP (mGy.cm), DLP of the diagnostic scan, and the minimum and maximum DLP of the axial scans. Additionally, data on the type of injection (epidural, foraminal, facet), number of injections per procedure, and vertebral level(s) were extracted.
A radiology resident, who did not participate in the procedures, evaluated needle tip visibility on the final image before injection.
Data were organized in Excel sheets, and descriptive statistics were performed. A p-value of <0.05 was considered statistically significant.