Keywords:
Neuroradiology spine, Interventional non-vascular, CT, Imaging sequences, Dosimetry, Image verification
Authors:
D. Brand1, R. Davies1, J. Kew2; 1SA/AU, 2Woodville, SA/AU
DOI:
10.1594/ranzcr2018/R-0115
Methods and materials
Study Design: Retrospective case note and image audit of 200 consecutive patients presenting over 2 months with intention to treat by epidural or perineural steroid injection,
irrespective of spinal level,
pathology involved and first time or repeat intervention.
There was one exclusion where the treatment DLP was not recorded.
Radiation dose was collected prospectively.
Technical factors and clinical notes were recorded prospectively.
Technical success was based on review of images demonstrating epidural contrast opacification after CT guided needle placement.
In all cases CT guidance was by several acquisitions of a stack of 4 axial slices using a partial scan low mAs technique.
For lumbar epidural injection,
the needle orientation was adjusted after each slice acquisition in order to place the needle tip immediately superficial to the epidural space under CT guidance.
A 22g 9 or 12cm spinal anaesthesia needle and a 1 or 2.5cc syringe was employed with injection of 0.1 to 0.5cc of contrast to confirm epidural positioning followed by 1-2cc of dexamethasone (4mg/ml) infused into the epidural space at the selected spinal level.
For cervical injection,
CT guided 25g 38mm needle placement within the right or left target facet joint was followed by contrast injection to confirm perineural and epidural spread of contrast in each case at the target level.
Scanners were either 16 slice or 160 slice with scan protocols varied as follows.
For 16 slice machines,
a sectored half scan was acquired in 0.3s,
as a 2,4 or 8mm scan thickness,
reconstructed into 4 by 0.5,
1 or 2mm axial slices.
For 160 slice machines,
a sectored half scan was acquired in 0.23s,
as a 2,4 or 8mm scan thickness,
reconstructed into 4 by 0.5,
1 or 2mm axial slices for cervical and 4 by 2mm slices for lumbar needle placement.
The radiation dose differences between 16-slice and 160-slice scanners was compared.
A minimum of 2 and a median of 4 image acquisitions was used to confirm needle position in the target space.
Radiation doses recorded were compared with published data in the literature.
Shepherd et al [1] reported a mean procedural dose length product (DLP) of 199 +/- 101 mGy.cm.
Chang et al [2] reported a mean DLP of 89.6 +/- 3.33 mGy.cm representing an average effective dose of 1.34 +/- 0.05mSv per interlaminar epidural steroid injection in the lumbar spine.
Amrhein et al [3] reported a radiation exposure DLP of 94.2 +/- 52 mGy.cm.