CT scan series part 15 – generic CT scan assessment (for copy)

What can you, the patient, do to find out if your medical facility is complying to the highest standards for radiation dose reduction and safety from CT scanners?

Virtually all US facilities may report use of “Low Dose” software. All CT machines now manufactured and sold in the US are of the helical design and capable of supporting the latest version of Low Dose software. Older CT scanners and earlier versions of software remain problematic at some institutions and I will almost guarantee that your doctor will not know or admit to knowing the status of CT technology at their institution. This is due in part to the number and variety of machines. As one example; At the OSU medical center they have currently 14 CT scanners that will be increasing to 17.

The term “Low Dose” is not specific enough and various manufacturers of CTs are continually leapfrogging better machines into the market for me to recommend a specific machine. “The soul is in the Software” and I believe I have reduced the low dose and safety issues to 4 questions you will want answered in the affirmative the next time you are scanned. Ask the following at the time of your being scheduled or inform your scheduling contact that you need to be assured of the following:

1)Does the scanner use iterative image reconstruction software?

2)Does the Scanner I will be scanned on have kV modulation? kV stands for kilovolt

3)Does the Scanner I will be scanned on have mA modulation? The mA stands for miliampere. Note: One of the basic parameters affecting radiation dose for a smaller patient is in the hands of the CT operator adjusting mAs. For those who have a need to know more about kV & mA - en.wikibooks.org/wiki/Basic...

4)Does the Scanner I will be scanned on have organ-based modulation? scitation.aip.org/content/a... & ncbi.nlm.nih.gov/pubmed/225... The organ based modulation capability is particularly important if you are a younger patient or plan on living, secondary cancer free, over 20 years after scanning;-)

Not all organs are equally sensitive to radiation and the “organ-based modulation” feature insures lowest radiation to the most radiation sensitive organs, i.e. breast and gonads, eyes and thyroid.

You now have a simple way to find out if the CT scan you are about to get is giving you the lowest reasonable dose of ionizing radiation irrespective of the Brand of CT scanner.

Updates will follow if I learn anything that requires modification of this recommendation.


10 Replies

  • Easy... two sources...or split beam... 8 slices per rotation... Like SOMATOM Definition Flash, or the new GE Lightspeed Ultras... with organ based modality..

    In Canada these are used primarily for cardio or kids... life time exposure is what matters...

    I'm glad to drive a 4 on the floor 1980's CTscan machine if my grandkids get the ultra low dose...

    Definition Flash brochure


    Choices... The new Defintion Edge is coming to a show room near you... :-)

    New ASH 'Choose Wisely' on CLL scans...



  • Chris, the HU site doesn't handle links that include the apostrophe character, so I renamed your referenced post, editing your reply above accordingly. I have also included a reference to your post in the Related Posts section of Part 1 of Wayne's series.


  • Wayne, I've edited part 1 of your series to include a link to this your latest post in this series. While doing so, I found that you never published a part 14 on this site...


  • Recently I heard that the number CT scans required for those involved in trials such as Ibrutinib is actually thought to be unnecessary and possibly dangerous giving rise to other issues the point I believe of your comment. So I understand it after the first twelve months of treatment if nodes are within tolerance or negligible then scans can be reduced to one or two a year to evidence whether or not there is any return. I also believe that companies undertaking the trials are giving thought to a revision of their requirements.

  • Hi Berrytog,

    The necessity issue for frequency of CT scans in Clinical Trials is in the eye of the beholder. The drug developer wants clear objective evidence of efficacy that the drug is working and in the case of KIs (Kinase Inhibitors) like Ibrutinib, Idelalisib etc. where the drug actually causes an increase in the ALC (Absolute Lymphocyte Count), that evidence is not possible to obtain without imaging. From a Researcher point of view it is useful to see just how the drug is acting on internal lymphnodes and to catch any cases of relapse as early as possible. In that scenario CT scans are indispensable as relapse is often initiated in the internal nodes. From the one being scanned however, the concern is legitimate to the question of cumulative ionizing radiation that is known to cause double breaks in DNA that are difficult to repair. In CLL with so many patients having defective TP53 and ATM genes that are critical to the task of cellular damage repair it is logical that frequent CT scans will increase secondary cancer risks, especially in younger patients and patients who are female.

    I am on an early Phase I Clinical Trial with Ibrutinib and we lab rats are scanned every 6 months.


  • I asked the head radiology tech about alternatives to CT for lymph size tracking. His first reaction was PET scan. It's more expensive. But he's a tech, and certainly not a CLL oncologist. Each modality (PET, CT, MRI, etc) has its strengths and weaknesses based on tissue type.

    I'll run this past a few radiologists next time I'm in the neighborhood.


  • There are two areas of basic concern regarding CT scan use. The first is overuse in patient W&W and particularly with patients being prescribed for a CT as part of the diagnostic workup. A CT should not be used to diagnose CLL. The second issue is the frequency of CT scanning to confirm drug efficacy and has legitimacy for KIs (Kinase Inhibitors) due to rising lymphocytosis where a method to assess internal non palpable nodes is needed. The question here is How many and how frequently? PET scans are a bad idea for assessing node size in a Clinical Trial context or to just check around for the curiosity of the oncologist. If indicators such as unexplained rise in LDH (Lactate Dehydrogenase) or rapid lymphnode enlargement is out of the CLL pattern then a PET can be useful to see if the metabolic level of node activity is consistent with CLL or is indicative of a faster breed of cancer, commonly discovered to be Richter's. Even then it is only used to determine the best target for a biopsy. Do check out my other essays which give some detail on proper use of which type of scan.


  • WWW -

    I'm still catching up on some of your posts. This reply is a bit of a tangent, and my deserve a thread of its own regarding patient medical record management.

    I worked in IT at a community hospital as the network guy for 10 years. I got to know the folks in radiology really well, because they sometimes had problems sending images from one vendor or hospital's equipment to another. The vendors or hospitals would point fingers at each other. So I would sniff the network traffic, give the results to the tech support at each end, and settle the bets.

    I wasn't involved in dosage issues per-se, but radiology PACS (Picture Archiving and Communication Systems) were part of what I maintained. I'm not at the stage of treatment requiring multiple CT's at intervals, and I push back on all requests for imaging on the basis of cost and dosage.

    I still know the folks in the radiology department, and I try to get all my imaging done there, so it's all in the same PACS system. This makes it much easier for various specialties who want access to my info to get all of it from a single place. With US HIPAA privacy laws, this means only 1 form I have to fill out. Doctors often have their favorite imaging provider, but if you insist on a specific one, citing the reason I mention, they are generally obligated to go with your wishes, I believe. Once the form is done, all of your studies can be easily transferred from one hospital to another via network or DVD.

    Most patients are totally unaware that in the US, and I imagine elsewhere, the patient can ask for a copy of their CT, MRI, PET, X-Ray, Sonogram on a DVD for a small fee. The Medical Records Department at the hospital I use charges $5. The DVD works in both Mac and PC's, and has the program to display the info on it. I bring the DVDs with me to some appointments if I think the doctor might want to see them. Less paperwork, less delay, fewer followup visits. Be sure to get the DVD made AFTER the radiologist does the report if you can, because most PACS systems put the report on the DVD. If it isn't on the DVD, ask the Medical Records Department for a paper copy. It takes 24-48 hours for some radiology departments to do the report - depending on day of the week and patient load. The DVDs are importable into most other PACS systems.

    Get a paper copy of the radiologist's report no matter what. I've saved a lot of time by simply handing a specialist my test results even if they don't want to see the imaging. This can save weeks of waiting for forms and reports to be sent to the wrong fax machine between appointments.

    I think maintaining good personal medical records avoids the cases where the doctor simply orders a new CT or whatever study because they don't know where your last one was. It's sad that the data sharing standards have not advanced more, but in PACS systems, they're further along than the rest of your medical record.


  • Excellent advice that I should have emphasized in my CT-scan essays. My DVD discs are begining to outnumber my movie discs. I had not been aware that the report is included if one is willing to wait. I always got a paper copy.

    I have run into problems getting them to run on my Mac.


  • Yeah, and to be fair, sometimes it's a problem on Windows, too. It depends a lot on the hospital staying up to date with versions. Let them know you have a Mac and have trouble. Sometimes, the files on the disk are clearly MP4 and JPEG, but then you miss the additional info encoded with each image - settings of the modality.

    Have a look at Osirix:


    There's a free version. There may be better free ones. Look for DICOM viewers or readers.

    The radiologist report often takes time, at least at the hospital where I worked. It doesn't make economic sense to keep a bunch of radiologists idle. If it's an emergency, they have someone oncall to read it immediately. Some of the reading is moving offshore or to the web.

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