Differences/Benefits of MRI, Pet Scan, Cat Scan, etc.??

weezie1053 · 08-01-2007, 04:10 PM

You senior members are a wonderful resource of information. I just started following these threads a few months ago, and I am realizing how much I don't know.

Can someone explain to me why some members have MRI's, others Pet Scans and other Cat Scans? What the differences and the benefits of each one. What is the most beneificial for screening?

I am scheduled for my second ever MRI, and I was just wondering.

Thanks.

Louise

fauxgypsy · 08-02-2007, 11:53 AM

I am hoping someone will answer this as well. If no one answers it soon I will try but there are others on this board with much more experience than I have. I do think that some of the difference is the doctor's preference. With one Dr. I had CT scans, MRIs, and PET scans. With the other I had CT scans and bone scans. I know each one may be better at detecting a certain type of metastasis. But some of it is preference. Some people have MUGA scans while they are on the herceptin, some have echocardiograms.

Leslie

Becky · 08-02-2007, 12:28 PM

CT scans are xrays taken in small "slices" so there are many of the pictures and together they represent the organ or area being viewed.

A Pet/CT is the same thing but you are given an injection of radioactive glucose (a sugar). Theory is that cancer, since it is growing faster than normal cells, takes up this glucose and the special xrays picks up a glow if cancer is there (false positives include injury or infection since your body is rapidly "growing" in those situations - ie: healing). A CT could show a tumor but a PET/CT would tell you if that tumor is alive or dead. Therefore, a PET might be better to track a tumor you know you have but you don't know if the chemo has worked its magic.

An MRI uses no radiation as PET or CT does. It uses magnetic waves. The waves pass through your body (or organ) and make a picture. Some tissues, like the brain, don't xray well. Also, if you have a brain tumor and your doctor is tracking its regression or progression, an MRI is better as you are not radiating the brain over and over again - especially since it is radiation that is the cure for the tumor. MRI is a good method to track some tumors. They work well to diagnose both breast cancer and DCIS but MRI does not work as well as mammograms to uncover calcifications - especially calcifications that might be hiding a small DCIS (therefore, both used together could be best).

PET/CT is probably best for the body (as you will be able to tell if the mass detected is cancer) and MRI for the brain.
I hope this helps

Brenda_D · 08-02-2007, 02:14 PM

Very well put, Becky.

I was wondering what my next scan should be. It seems a Pet may be the best for to see if the chemo and rads killed the ca in my IM node.

Thanks!

weezie1053 · 08-02-2007, 06:52 PM

Thanks, Becky. Since my BC was confined to the right breast and had not spread to the lymph nodes, the MRI would make sense. I plan on having the mammo each spring, and continue to have the MRI ilate summer/fall. Had a MRI today, and it will probably be several days before I have the results since my Onc is on vacation.

Thanks again.

Louise

hutchibk · 08-02-2007, 09:22 PM

According to my onc, each scan shows different things more effectively: (let's see if I can remember this and not make a fool of myself...)

CT - good for looking at organs and bones. One of the best tools for studying the chest and abdomen and skeletal structures because it provides detailed, cross-sectional views of all types of tissue. Often the preferred method for diagnosing many different cancers, including lung, liver and pancreatic cancer, since the image allows a physician to confirm the presence of a tumor and measure its size, precise location and the extent of the tumor's involvement with other nearby tissue.

MRI - Magnetic Resonance Imaging. Not radiation, uses magnetic field and radio waves. It is good for looking at soft tissue and brain. Detailed MR images allow physicians to better evaluate parts of the body and certain diseases that may not be assessed adequately with other imaging methods such as x-ray, ultrasound or CT Scan. Because protons are most abundant in water molecules, MR images show differences in water content between various body tissues. As a result, MRI is especially suited to detecting disorders that increase fluid in diseased areas of the body, for example, areas affected by tumors, infection and inflammation. Overall, the differentiation of abnormal (diseased) tissue from normal tissues is significantly easier with MRI than with other imaging modalities such as x-ray, CT and ultrasound.

PET - good for deeper reference when you can't determine what you are seeing on a CT or MRI, or when tumor markers indicate activity but CT and MRI don't show anything. PET can often see the smallest spots that the others don't as it shows anotomic as well as metabolic information. PET scans are used most often to detect cancer and to examine the effects of cancer therapy by characterizing biochemical changes in the cancer. These scans can be performed on the whole body. PET scans of the brain are used to evaluate patients who have memory disorders of an undetermined cause, suspected or proven brain tumors or seizure disorders that are not responsive to medical therapy and are therefore candidates for surgery.

(OK, I cheated a little and googled for more factual info)

Lala · 08-03-2007, 01:32 AM

Now to add my 2 cents. Here's how the scans are used in a stage 4 case.
Every 2 to 3 months I have various scans to see the response to treatment. The Catscan of the Abdomen and Chest are used to monitor my Liver mets. I have the Bone Scan for a full skeletal picture to monitor my bone mets. In addition, I have a MRI of the Thoracic and Lumbar region of the Spine, this offers a far better view than the bone scan. I have a Brain MRI every 6 months as per the request of my oncologist whom thinks all Stage 4 Her2+ need to do this schedule. I have recently changed that schedule. I now have a Brain MRI every few months to make sure I am NED in the Brain.
I have a Pet Scan after every treatment course is completed in order to see the total response of the treatment, this is usually every 6 months or even yearly.

Every person is different, I believe every newly diagnosed cancer patient needs baseline scans to insure proper staging.

anotherone · 08-03-2007, 09:29 AM

It is not inocuous - to have those scans ( apart from MRI I guess). I was told not to hold a baby on my lap for a couple of days after either bone scan or CT scan - I don't remember. And when I compare radiation received from a intraoral dental radiogram to CT scan - CT scans produce hundreeds thousands times more radiation.
Oncologist told me initial staging CT and bone scans find methastasis in only 5% of women with stage 3, and as far as I remember about 30% of us will develop them in either 5 year time or 10 year time. It does meen the disease is still undetected in majority of cases. I don't know, probably PET is more sensitive and statistics for it are different.

Lala · 08-03-2007, 10:29 AM

I have to add I am a strong advocate that all Her2+ upon diagnosis get a base line PET Scan. In my opinion, I think it is needed to help with the staging process.

When I was diagnosed I was thought to be only Stage 1 based upon my Tumor size being under 2 cm. Although I had no symptoms of pain I felt I needed to be tested head to toe before I had a lumpectomy. I requested and fought for a PET Scan.

The PET Scan revealed that I had Bone mets. Later tests showed Liver mets. I learned that Her2 is aggressive and being properly diagnosed is the key to proper treatment. Thankfully that PET Scan was the key to a proper diagnosis for me. I was then able to get the proper treatment quickly.

It is extremely important that if you are scheduled for a PET Scan, Please ask your imaging center for the Special PET Scan Diet.
This Diet needs to be done prior to your scan appointment. This is a diet that removes all glucose the from your body, enabling the PET Scan to properly work. The night before and day of your test you have a list of foods you must avoid. It is so crucial to do this diet as it enables the proper results. Sadly some people do not know this and the PET scan results can be affected by your diet. My cancer center sends out instructions on how to prepare for all diagnostic tests.

weezie1053 · 08-06-2007, 09:51 PM

Good news. After waiting 3 agonizing days, my Oncologist's office called, and my MRI was clean. No sign of invasive cancer on either breast. It was worth the wait. Thank you for your prayers and support.

Every day is a gift.

Louise

Chelee · 08-06-2007, 11:44 PM

Louise, That is just fantastic news. You can't ask for better then that. Its always so nice to get the all clear. Yeah...go out and celebrate a bit....you deserve it after stressing for a few days. Its so nice to come here and find GOOD news.

Chelee

Esther · 08-07-2007, 01:57 AM

Does anyone know how small a mass the pet scan can detect? Just wondering if there is a lower limit. The MRI machine that Cedars-Sinai uses can detect brain lesions as small as 1 mm.

Are different pet scan machines more sensitive than others, or do they all have the same limitations?