[Intl_DxMedPhys] Dynamic CT Myelogram Protocol - What's a reasonable DLP?

[Szczykutowicz, Timothy P]

I def would not keep using a fixed mA, these protocols are high enough as it is, for smaller pts you could probably go lower. We do 2x passes if everything goes well, but 3 or 4 is not uncommon, especially for larger pts if they cannot roll and coat the spine with contrast.

At UW, for the dynamic we have techs use our routine spine protocols, which are basically the highest dose torso protocols we have. So DLPs of 7,8k mGy*cm are not uncommon, I am looking at a 3x repeat larger pt right now on my pacs over 12k.

I don't see much online in terms of dose data for this indication.

If anyone is interested in sending me some aggregated dose data for this, my team can compile and send back the summary stats to the list? This will really get the dose haters of the world blood rising...;) If we get some good responses, this might be good for a neuro journal to publish as a reference for setting dose in this high dose indication. If someone knows of a publication on this pls send me. I didn't find anything when we built our protocol, and I looked again today and didn't see anything more (like a multi center dose summary, just some research papers form single institution).

Proposed data fields below as a minimum:
Pts size surrogate (WED, AP, LAT, AP+LAT, ED, BMI would be good options we can translate as needed depending on what you have - we need something here), CTDIvol per pass, total number of passes, DLP per pass, DLP total.
Optional other stuff to send:
Any additional data like positioning per pass would be good. I think also details on kV, pitch, rotation time, review image kernel and slice thickness, and if you use AEC or not would be good. Since these scans are so high dose and long ranges, they can be difficult on old scanners with crappy tubes, may be good to understand how sites deal with this. For example, we do these on a newer canon, but also an older wide bore GE and you definitely see motion artifacts in the lung fields because we need to scan slow.

If your dsm doesn't separate these from limited meylo where the rads already know where the tear is... then I guess pull all of them and we can tease out based on the small scan range for the limited ones. We would have to keep these separate. I also bet your neuro people will just have a list of these, because someone is billing special for the procedure, so given the volume of these is probably very low, some manual data gathering here might also not be too difficult.

-stick



Timothy P. Szczykutowicz, Ph.D., DABR
Professor
Departments of Radiology, Medical Physics and BME
University of Wisconsin Madison
Cell# 1-716-560-7751<tel:(716)%20560-7751>
Office# 1-608-263-5729
he/him/his



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Subject: [Intl_DxMedPhys] Dynamic CT Myelogram Protocol - What's a reasonable DLP?


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Hi Everyone, A site that I recently began consulting for has a new physician who wants to perform Dynamic CT Myelograms.   The goal of the procedure is to look for CSF leaks in the spine.   The protocol that the physician provided and put on the
Hi Everyone,
A site that I recently began consulting for has a new physician who wants to perform Dynamic CT Myelograms.  The goal of the procedure is to look for CSF leaks in the spine.  The protocol that the physician provided and put on the scanner, simplified, is below:

  1.  Patient in Right lateral decubitus position.
  2.  Prep the skin and advance a 22 gauge spinal needle under serial CT guidance.
  3.  Inject 10 mL of Omnipaque-300.
  4.  Perform 3 continuous passes from sacrum to skull base, then skull base to sacrum, and then sacrum to skull base.
  5.  Rotate the patient to left lateral decubitus and do another single pass from sacrum to skull base.

The acquisition parameters for the 4 passes is 140 kVp, 250 mA, 0.625 mm slices.  They're using a GE Revolution scanner.

This protocol was loaded and they did a patient.  The total exam DLP was 7,871.89 mGy-cm.  The techs promptly freaked out and have since refused to perform the procedure.

So, for the group, what is a reasonable DLP limit for a case like this?  Are any of your sites doing this procedure and what doses are you seeing?  140 kVp seems like the wrong kVp for optimizing iodine contrast - what kVp are you using for the passes?

Thanks in advance for the wisdom I'm sure someone has out there.

Tyler Fisher
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