Tag: diagnostic imaging

Posted on

CT Scan versus MRI Scan – Which is Better?

A boat waiting to sail off the coast of Antigua. (Dr. Noorali Bharwani)
A boat waiting to sail off the coast of Antigua. (Dr. Noorali Bharwani)

It is hard to think that there is any adult who hasn’t had either magnetic resonance imaging (MRI) or computed tomography (CT) or both. They are complementary imaging technologies and each has advantages and limitations for particular indications.

CT is more widely used than MRI in some countries. That raises concern about the potential for CT to contribute to radiation-induced cancer. In 2007, it was estimated that 0.4 per cent of current cancers in the United States were due to CTs performed in the past. It is also estimated that in the future this figure may rise to two per cent based on historical rates of CT usage.

CT scans have many benefits that outweigh this small potential risk. Newer, faster machines and techniques require less radiation than was previously used. Still, CT is contraindicated in pregnancy.

Compare that to MRI. An advantage of MRI is that no ionizing radiation is used. MRI is recommended over CT when either approach could yield the same diagnostic information. Unfortunately, there are not many common imaging scenarios in which MRI can simply replace CT.

Although MRI can detect health problems or confirm a diagnosis, it is interesting to note that medical societies often recommend that MRI not be the first procedure for diagnosis and treatment.

CT images provide more detailed information. A CT scan combines a series of X-ray images taken from different angles and uses computer processing to create cross-sectional images, or slices, of the bones, blood vessels and soft tissues inside a body.

A CT is well suited to quickly examine people who may have internal injuries from car accidents or other types of trauma. A CT scan can be used to visualize nearly all parts of the body and is used to diagnose disease or injury as well as to plan medical, surgical or radiation treatment.

MRI scanners use magnetic fields and radio waves to form images of the body. The technique is widely used in hospitals for medical diagnosis, staging of disease and for follow-up without exposure to ionizing radiation. In certain cases MRI is not preferred as it can be more expensive, time-consuming, and claustrophobic.

To summarize, indications of doing CT scan and MRI scan are pretty similar. There is a small radiation exposure in CT compared to none in MRI. CT is slightly cheaper to do. It takes less time than MRI, especially beneficial for claustrophobic patients and time utilization in the radiology department. If you are claustrophobic then ask for a mild sedation and enjoy the ride.

Start reading the preview of my book A Doctor's Journey for free on Amazon. Available on Kindle for $2.99!

Posted on

Mammograms Lead to Many Unnecessary Breast Cancer Treatments

Woman getting a mammogram. (JupiterImages/Thinkstock)
Woman getting a mammogram. (JupiterImages/Thinkstock)

Mammography is known to be an imperfect screening tool for detecting breast cancer. Similar to the PSA test for men to detect prostate cancer. According to Wikipedia, mammograms miss cancer (false-negative) in at least 10 per cent of cases, about seven per cent will have a false-positive result which lead to biopsies and other tests. Then there are women who are over diagnosed. That means finding a cancer that does not need treatment.

Let me be clear, mammograms are still worthwhile. They do catch some deadly cancers and save lives. Not all doctors agree with the conclusions in the paper published this November in the New England Journal of Medicine titled, “Effect of Three Decades of Screening Mammography on Breast-Cancer Incidence.”

But the paper is worth discussing. According to Canadian Cancer Society website, breast cancer accounts for over a quarter (28 per cent) of new cancer cases in women. On average, 62 Canadian women will be diagnosed with, and 14 women will die of breast cancer every day.

Researchers looked at 30 years (1976 – 2008) records to examine trends in the incidence of early-stage breast cancer (ductal carcinoma-in-situ and localized disease) and late-stage breast cancer (regional and distant disease) among women 40 years of age or older.

The results of the study indicate that introduction of screening mammography in the U.S. is associated with a doubling in the number of cases of early-stage breast cancer each year, the rate at which women present with late-stage cancer has decreased by eight per cent and only eight of the 122 additional early-stage cancers diagnosed were expected to progress to advanced disease.

The researchers estimated that breast cancer was overdiagnosed in 1.3 million U.S. women in the past 30 years. These cancers would never have led to clinical symptoms. In 2008, breast cancer was overdiagnosed in more than 70,000 women; this accounted for 31 per cent of all breast cancers diagnosed.

Finding breast cancer early does not mean it will always reduce a woman’s chance of dying from breast cancer. This can change if mammograms begin to detect deadly breast cancer before they spread. Once a suspicious area is seen on a mammogram, there is no good way to tell if it is cancer, if it is an early cancer or a deadly one, until patient has had surgery. It would be nice to tell an individual woman whether her cancer needs to be treated just by looking at a mammogram.

That does not mean we stop doing mammograms. Mammograms are still worthwhile, because they do catch some deadly cancers and save lives. Do not stop going for mammograms on the basis of this paper.

Start reading the preview of my book A Doctor's Journey for free on Amazon. Available on Kindle for $2.99!

Posted on

Use of MRI in Evaluating Breast Lumps

A woman receiving a scan. (iStockphoto/Thinkstock)
A woman receiving a scan. (iStockphoto/Thinkstock)


A woman with locally advanced breast cancer.

The traditional way to assess a breast lump is to take a history, do a physical examination, do a fine needle aspiration cytology (examination of a breast lump aspirate under a microscope), mammogram and/or ultrasound, core biopsy under ultrasound control and finally, if there is no satisfactory answer then do a surgical biopsy.

A surgical biopsy gives us a definitive answer. But there are drawbacks to sending every patient with a breast lump for surgery. To start with it causes severe anxiety. You have to take a day off work. It requires local or general anaesthetic. There may or may not be postoperative complications like bleeding, bruising, discomfort, infection and pain.

On a long term basis, surgical biopsy will leave you with a scar and may be another lump which may be just a scar tissue but could be suspicious for cancer. Then you have to go through the whole process all over again.

Is there anything else we can do before going for surgery to make sure that there is no cancer in the breast?

You can ask for a second opinion. If all investigations are negative then there is a less than five per cent chance that cancer has been missed. In that case, we can leave the lump alone and provide follow up care with clinical examination and mammography or ultrasound, on a case by case basis. Sometimes a patient will ask for MRI.

MRI (magnetic resonance imaging) is a procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. MRI does not use any x-rays.
MRI is not available for routine screening. It is expensive and requires specialized equipment and personnel with good solid training to read the images. Hence, it is available in bigger cities only and is not covered by government insurance plans. MRI is more often used for breast imaging in the US than Canada because of the prevalence of private health care.

MRI is sensitive to small abnormalities in breast tissue. MRI also has limitations. For example, MRI cannot detect the presence of calcium deposits, which can be identified by mammography and may be a sign of cancer.

The value of breast MRI for breast cancer detection remains uncertain. And even at its best, MRI produces many uncertain findings. Some radiologists call these “unidentified bright objects,” or UBOs.

In women with a high inherited risk of breast cancer, screening trials of MRI breast scans have shown that MRI is more sensitive than mammography for finding breast tumors. Screening studies are ongoing.

Breast MRI is not recommended as a routine screening tool for breast cancer. However, for women at high risk, women with previous breast cancer, MRI can be useful in certain circumstances.

Start reading the preview of my book A Doctor's Journey for free on Amazon. Available on Kindle for $2.99!

Posted on

M.R.I.

If you listen carefully, then you can almost hear Dr. Ken Blair, Palliser Health Authority’s Director of Diagnostic Imaging, say with pride: “Heeeeere’s is MRI!”

Besides Blair, there are numerous people who are proud of successfully bringing the MRI service to Palliser Health Authority (PHA). We tend to criticize our health care system a lot. Perhaps with good intentions. We want more of everything. The human desire for more is some time insatiable. Some times that is good and some times not so good.

In case of MRI, it was good! Certainly the Government of Alberta and our local MLAs deserve a big “Thank you”. So do the public, the health authority, the health care providers and Dr. Ken Blair and his team of tireless people in the x-ray department (oops! it is called the Department of Diagnostic Imaging).

What is MRI?

MRI stands for Magnetic Resonance Imaging. In 1946, Bloch and Purcell demonstrated that some atomic nuclei respond to the application of particular magnetic fields by emitting or absorbing electromagnetic field. This was then used for analytic chemistry.

A Swedish physicist, Erik Odeblad, pioneered the medical application of this technique in the 1950s. In the next 30 years, much work was done on the MRI images showing human pathology. Initial emphasis was placed on imaging of the brain. But since 1980, studies of other organs have also been performed.

All MRI machines are constructed around a large magnet that provides a uniform, static magnetic field. There are no adverse effects reported from this and there are guidelines designed to prevent possible hazards. The only adverse effect reported is three to four percent incidence of claustrophobia.

Dr. Jay Daniels, PHA’s Director of MRI Services, says the technology uses a super conducting magnet which is kept to a temperature approximately four degrees above absolute zero, with a resulting magnetic field over 50,000 times stronger than the earth’s. No ferrous metal is allowed in the examination room as it could become a very dangerous missile in the presence of the magnetic field!

Within a week or so, the first MRI images will roll out of the new addition to the Medicine Hat Regional Hospital. Daniels predicts excellent availability for the patients of our Region with lower waiting lists than has traditionally been the case in Alberta. The examination time will vary from few minutes to 40 minutes depending on the body part being imaged.

Common indications for the tests are: chronic headaches, family history of brain aneurysms, possible spinal disc diseases, and arthritis of the back, knees and shoulders. Other indications depend on the clinical situations. Daniels says the MRI is safer than using ionizing radiation as in the case with x-rays. Patients with metal in the eyes, pacemakers, and cardiac leads however cannot be imaged. Orthopaedic hardware like metals in the knees and hips can distort the pictures if they are too close to the organ being imaged

Blair is very proud of “the first class state of the art physical facility, which includes not only the room for the scanner, but also an excellent patient reception and waiting area”. There is a great lack of trained MRI technologists in Canada. PHA was fortunate to recruit an experienced technologist for the position of supervisor and have trained two of the local staff as MRI technologists.

Blair is worried that public’s perception and expectation on what an MRI can do may be too high. MRI is not indicated for all undiagnosed conditions and is not a “magic answer” to people’s anxiety about their health. Each request for MRI will be carefully screened, says Blair.

And he is serious. He will not accept my request for a total body MRI to see why my golf swing is so bad! For that I may have to go to a private clinic! But seriously, MRI will make a difference to the health of PHA residents. So be proud and make judicious use of the new service!

Start reading the preview of my book A Doctor's Journey for free on Amazon. Available on Kindle for $2.99!