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CT guidance for lumber puncture. Procedure time and radiation dose 2012

Interventional Spine

Todd, S, Miller, MD
Andrew, Brook, Non ASSR Member
Judah, Burns, MD, Non ASSR Member
Amichai, Erdfarb, MD, Non ASSR Member
Richard, Zampolin, MD, Non ASSR Member
Allan, Brook, MD, Non ASSR Member

Paper/Non-Mentor

Purpose

Flouroscopic guidance has been used for LP for several decades. Previous reports have demonstrated a benefit when using flouroscipic guidance to limit the frequency of traumatic LP. Recently, several authors have reported on the benefits of US guidance for LP. CT guided LP has been reported as an alternative to or after a failed bedside LP or LP with fluoroscopic guidance in a population with cancer. CT guidance offers a map to help the physician guide the needle to the proper target. CT has the advantages over fluoroscopy of providing millimeter accuracy and soft tissue visualization. The purpose of this study was to evaluate the potential benefits of CT guidance regarding likelihood of a successful procedure and associated risks in a more general population. This guidance modality may prove revolutionary for LP performance.

Methods & Materials

Patients were referred for image guided lumbar puncture, myelogram, lumbar drain placement, and morphine test injections. The indication for each patient's procedure was noted. Data were collected retrospectively for both male and female patients from age 20 to 78. A total of 43 patients were reviewed. The radiation dose, as well as the duration of the procedure for each patient was recorded in an Excel spreadsheet. The radiation dose was calculated by machine generated CTDI vol and then multiplied with a constant to get the effective dose (mSv). The duration of the procedure was calculated by finding the difference between the recorded time that a needle first entered the patient's skin to when the needle reached the thecal sac and CSF was obtained. In addition, the needle depth and angle were recorded as well as the level which was punctured. The needle depth was measured by measuring the distance between the skin surface and the thecal sac. The deviation from a perpendicular (to the CT Table) angle of attack was measured using a tool on the PACS workstation. All procedures were intended to access the thecal sac.

Results

A total of 32 LPs, 8 myelograms, 2 Morphine test injections and 1 lumbar drain placement between December 23, 2009 and July 15, 2011 were reviewed. In all, 30 female and 13 male patients qualified for the study. The range ages of patients were 20-78. Common indications for LP included headache or pseudotumor, lumbar drain, myelography, failed bedside LP, and rule out meningitis. Common indications for myelogram were severe back pain and radiculopathy. All procedures were successful with a single needle pass. The average needle depth was 77.64mm (range 45.7mm - 127.3mm), with an average needle angle of 8.7 (range 1.5-24 degrees). Procedure time averaged 14 minutes (range 5 to 42 minuets) with a mean radiation dose of 1.12mSv (0.20-8.18mSv). Procedure time and radiation dose for uncomplicated patients by experienced operators was 11 minuets and 0.56mSv. All procedures were successful with no complications or failures.

Conclusion

This study shows the benefits of CT guidance in LP as it allows visualization of all important landmarks without putting the patient at high risk. CT guidance is a safe and effective modality for image guided LP. Procedure time and radiation dose should not limit use of CT as a guidance modality.

References/Financial Disclosures

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