This past week has seen an unprecedented level of attention over the potential cancer risk posed to patients who undergo CT (Computed Tomography) scans as a result of exposure to ionizing radiation.
Two multicenter studies published in this week’s Archives of Internal Medicine suggest that clinical CT radiation doses are much higher than previously expected, resulting in an increased lifetime potential cancer risk. The statistics supporting these claims are troubling, although perhaps not unexpected.
Dr. Smith-Bindman & colleagues used clinical data from national databases to evaluate the level of radiation dose associated with several common CT imaging exams in a sample of 1119 patients. Their results showed a high degree of variability in dose between different types of CT studies, overall doses which were much higher than previously thought, as well as doses which differed significantly within and across institutions, with a mean 13-fold variation between the highest and lowest dose for each study type
In the second study, Dr. Berrington de Gonzalez & colleagues, using risk models based on the 2006 Biological Effects of Ionizing Radiation VII, estimated that approximately 29,000 future cancers could be related to CT scans that were performed in the US in 2007 alone. Their study suggested that the largest contributors to radiation dose are abdominal and pelvic scans, followed by chest studies.
These two ground-breaking studies have shed light on what many radiologists and physicians have been speaking to for years. While there is significant utility for CT scans in the acute trauma setting and for identifying solid tumours of the chest & abdomen, it is important to acknowledge the risk-benefit ratio when considering this imaging technique. According to the Canadian Institute for Health Information, there were 3.4 million CT scans performed in Canada in 2007. The Canadian Association of Radiologists asserts that up to one-third of CT scans are inappropriate. In light of the studies published this past week, it is reasonable to consider the value of utilizing alternate imaging techniques that do not expose a patient to ionizing radiation when appropriate.
A sound alternative can be found in Magnetic Resonance Imaging (MRI). MRI uses non-ionizing radio frequency signals to acquire its images, utilizing a magnetic field, radio waves and computer technology to generate detailed three-dimensional images of body tissue and anatomy.
While CT provides good spatial resolution (the ability to distinguish two structures an arbitrarily small distance from each other as separate), MRI provides comparable resolution with far better contrast resolution (the ability to distinguish the differences between two arbitrarily similar but not identical tissues). In the case of tumour detection, imaging of the brain, spinal cord & vertebral applications, blockages in the vascular system, and soft tissue injury, MRI, in non-acute circumstances, is documented clinically to be generally superior to CT.
While CT may continue to be relied upon in the hospital setting because of its ease of access, it is important for patients to weigh all the circumstances and consider other perhaps safer and better imaging alternatives. Both the American College of Radiology and the Canadian Association of Radiologists are encouraging physicians to be more accountable in this regard and to seek out imaging techniques, such as MRI, which provide a greater benefit/harm ratio to the patient.
In British Columbia, it has just been announced that the B.C. Liberals have ordered Vancouver Coastal Health (VCH) to drastically reduce patient services and specifically, that VCH plans to perform only 18,000 MRIs in the coming year, down from 27,000 in 2008 and 20,500 in 2009. Similar cuts have been announced on Vancouver Island. These cuts are expected to increase wait-times in the public system by approximately 20%. Depending on your location within the province, this could mean wait times in excess of 18 months for a routine MRI.
The impact that this will have on patients is significant. A patient who is on a long-term waiting list may be forced to miss numerous days of work/school and wait for the appropriate treatment because their physician does not yet have the diagnostic answers that they require to treat them. This extended wait contributes to deferment of appropriate treatment, lost wages, and a negative impact a patient’s daily health & well-being.
In British Columbia, unlike some of the other provinces, patients do have options. Within 24-48 hours patients can obtain their MRI scan, with the report sent immediately to their physician. All that is required to start this process is a physician’s referral. Once you have your diagnosis you can also expedite an appointment with a specialist and/or surgeon at one of the private surgical centers in B.C. and see them in a matter of days instead of months.
So instead of waiting for months for the appropriate diagnostic exam, you can have an MRI, specialist consult and (if required) surgery in a matter of days.
There are costs associated with this expedited care but perhaps not as much as you think. What is important to know is that the choice is yours as to whether the costs for expedited care are worth it to you. You do have a choice.
For further information relating to the specific cuts being made province-wide, visit…
In an age when we as individuals take our health seriously and make an effort to be proactive about our own physical and mental well-being, it is only natural that we want answers with respect to how medical technology & advances can impact us.
In recent months there has been significant attention provided to Whole Body Scans using Ultrasound, Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) as a preventative cancer screening tool. All of these modalities have issues as a screening tool and it is critically important to understand their limitations.
The use of imaging to screen for potentially life threatening disease is neither novel nor new. In recent years CT, due to its quick acquisition time, was utilized as a tool for whole body preventative screening. However, CT is no longer thought of as a general screening tool for two reasons. The first is that CT requires ionizing radiation which is a risk factor for cancer. In particular, if the examination needs to be periodically repeated then this should be considered an unacceptable cost to an asymptomatic patient. Additionally, CT performed without an intravenous iodine containing agent lacks contrast resolution, therefore the test’s ability to separate a kidney cyst from a solid kidney mass is far more limited than MRI. Nonetheless, CT remains a useful screening tool for heart scans which use very low amounts of radiation and yield excellent and helpful information.
Ultrasound has been used as a limited screening tool, particularly for the identification of abdominal aortic aneurysms. However, ultrasound is relatively limited in its scope in comparison to MRI. For example the spine, brain and bones cannot be assessed at all ultrasonographically. As well, even in organs that can be addressed ultrasonographically the sensitivity of MRI for the identification of lesions is superior to ultrasound. Finally, in larger patients ultrasound can be very limited for all but the most superficial structures.
The questions remains, what is different about screening with MRI which makes it superior to these other screening tests? The answer is quite a lot.
Unlike other screening tests, preventative screening with MRI concentrates on those areas which have been well documented to yield the most benefit from early detection. While not every cancer benefits from early detection, many do, such as renal cell carcinoma, liver cancer & certain gynecological cancers. In addition, whole body MRI screening focuses on life-threatening illnesses such as aneurysm, stroke, and vascular disease without exposing the patient to any harmful ionizing radiation.
From a technological standpoint, MRI has the unique ability to clearly define structures and lesions within the body in far greater detail than ever before. The additional detail obtained using MRI makes it possible for a radiologist to classify a lesion that is detected as either benign or as a lesion requiring further investigation with contrast or using other modalities. This significantly reduces the number of false positives requiring invasive follow-up endemic to the other screening modalities.
Individuals now have the opportunity to make a significant investment in their personal health utilizing whole body screening with MRI. You now have the opportunity to be proactive with your health with a safe and comprehensive test. The information obtained will provide valuable information to your physician which can significantly impact your wellbeing today or one day in the future.
Over the last decade, Magnetic Resonance Imaging (MRI) has undergone significant evolution with respect to improvements in scanner strength, enhancements in image quality and clarity, and the ability to capture images in far less time. From a radiologists’ perspective these advances have dramatically impacted their ability to discern abnormalities that may have previously gone undetected.
A further advancement in the world of MRI, now available in British Columbia, is the use of MRI as screening tool for the early detection of a number of potentially life-threatening illnesses and disease.
So – is investing in a preventive MRI screening exam a sound investment? We think so and here’s why.
It provides your physician with exceptionally detailed information about a number of body systems, allowing for the early detection of disease, cancer and other serious illnesses. It allows the opportunity for treatment at an early stage for those cancers/illnesses that are currently undetected and asymptomatic. It offers peace of mind for those patients who have concerns about certain aspects of their health based on their family history and it provides a baseline of perhaps critically important information against which all future scans will be compared.
Does this mean that whole body MRI screening is able to identify every issue within your body? Absolutely not. As with all medical examinations, it has its recognized limitations.
Whole body MRI does not have the capability to effectively diagnose coronary artery disease or evaluate the lungs for cancer (all of which are better done with CT). In addition, as a screening tool it is not optimal for the diagnosis of early colon or prostate cancer. It is also important to recognize that while whole body MRI screening has the potential to uncover a cancerous finding early, this does not guarantee that the cancer found will react successfully to treatment.
Weighing these benefits & limitations, many patients are turning to whole body MRI screening as an investment in their quest for exceptional healthcare. Though it is not, and will never be, all things to all people it is a sound, principled examination, which yields important and perhaps critical information. It is a wise investment.