For clients without access to suitable digital data of past CTs, MRIs and MRAs, 3D Volume Renderings are impossible. In this event an attorney should consider sending the client — with these printed guidelines – for a new scan at a radiological facility that is suitable (has the ability to provide the patient’s digital data on CD in uncompressed DICOM files). Fresh scans often make superior renderings, as the radiologist knows to obtain additional data for a truly superior rendering. New data and any Volume Renderings should then be sent to the client’s treating physician or to an expert witness, which will ultimately facilitate admissibility at trial. Consult with a radiologist first. A scan, contrast-enhanced or not, could be medically contraindicated (ex. allergy to contrast).
Specify the scan will be for a 3D Volume Rendering. The more slices and data generated, the better the Volume Rendering will be. Provide the client’s medical history and the area(s) of anatomical interest.
A multi-slice CT scanner is optimal; a helical (spiral) scanner is sufficient.
The scanner should be set for thinner slices:
Body – 5 mm maximum thickness
Head – 2 mm maximum thickness
Bone – 1 mm maximum thickness
Thin-sliced axial (horizontal) views are best for 3D Volume Renderings. Request 50% slice overlap to avoid potential data loss.
We recommend these scanning parameters:
3D/volumetric scans with isotropic resolution of 1x1x1 mm or better yield the best renderings. Ex. a 256mm FOV could be used with a 256×256 matrix and 1mm slice/partition thickness. Thus voxels will have 1mm isotropic resolution (1x1x1mm).
The scan should be performed using a dedicated surface coil whenever appropriate.
The ENTIRE body part should be covered, plus a few “air” slices at either end, in order to make sure that the volume does not look clipped when rendered in 3D.
For T1-weighted scans, 3D gradient echo techniques are best, such as MP-RAGE or FSPGR.
If 3D/volumetric scans are not possible and 2D MRI scans are to be done, the interslice gap MUST be 0 and slices should be as thin as possible.
Request a 3D MRA scan (vs. a 2D scan). Be sure to obtain all the source images.