What’s the best imaging technique to detect cancer?

A patient recently approached me to know which medical imaging modality was the best to detect cancer, if any, within her.

March 13, 2019 Health, Wellness

By dr alex khoo cheen hoe

Imaging modalities are important to allow doctors to see what’s going on inside our bodies. — Photos.com

This question has always been asked and will continue to boggle the minds of many.

First and foremost, there is no universal imaging modality that can detect everything.

It is also important to know what are the underlying health issues (if any), which organ is involved, what needs to be assessed and why is the imaging needed.

There are many medical imaging modalities available, including ultrasound, echocardiography, conventional x-rays, computed tomography (CT), magnetic resonance imaging (MRI) and nuclear medicine imaging (gamma imaging and positron emission tomography, or PET).

Each of these imaging modalities has their own strengths and weaknesses.

For example, ultrasound, which basically uses attenuation and deflection of sound waves for tissue mapping, is very useful in assessing superficial soft tissue organs.

Women who undergo antenatal follow-up are quite familiar with the use of this imaging modality to evaluate their baby in the womb.

However, it is difficult to get good quality images of organs in certain areas and in obese patients with an ultrasound.

The widely available conventional radiography (or more commonly known as x-ray) has been used since its first discovery by Wilhelm Roentgen in 1895.

Most people will remember undergoing chest x-rays for their pre-employment screening test.

On the other hand, CT scans, which also use x-rays , are able to visualise the body in three dimensions (3D).

This imaging modality is available in most hospitals and has become an important tool in clinical practice.

It has been used to detect cerebrovascular accidents (strokes), lung diseases, cancers and fractures.

However, this scan is limited when it comes to visualising soft tissue lesions, particularly in the brain, spinal cord and pelvic organs.

The good news is that the days where radiation from the CT machines was an issue are gone, as newer CT machines are able to produce better quality images with much lower radiation.

MRI, which uses magnetic resonance of the protons within the body, is basically free of ionising radiation.

It is able to visualise soft tissues within the body with better resolution compared to a CT scan.

Unfortunately, the lungs and bone structures are not well visualised on MRI.

Patients with non-MRI compatible implants, like a non-compatible pacemaker or implantable cardioverter defibrillator (ICD), are also not allowed to undergo the scan.

Fortunately, the newer generation of such implants are now MRI-compatible.

Though uncommon, the side effects related to the use of gadolinium-based contrasts – used in x-rays, CT scans and MRIs to help visualise the targeted area – are real and the search for better alternative contrast agents is underway.

A PET scan of a head. This nuclear medicine imaging has a high sensitivity in detecting cancers. — Photos: AFP

Nuclear medicine imaging

Being in the field of nuclear medicine, I am frequently asked to comment if nuclear medicine imaging is still relevant when we already have other good imaging modalities.

The answer is simple: Nuclear medicine imaging has its strength in functional imaging.

In nuclear medicine imaging, small doses of radioactive substances are used either independently or paired with special pharmaceuticals to visualise the organ of interest.

If doctors need to evaluate the skeletal system, a radioactive bone scan using Technetium-99m methylenediphosphonate (Tc-99m MDP) can be done.

This radiopharmaceutical will be distributed within the bones in such a way that any abnormalities will cause either an increase or decrease in its levels, which can be detected.

In fact, Tc-99m MDP is so sensitive that a 5% change in bone turnover can be detected, compared to 40%-50% on conventional radiograph or even a CT scan.

And early detection means early intervention.

Nuclear medicine is also unique as some radioactive substances not only treat diseases, but are also able to provide images at the same time – hence the word “theranostic”, a portmanteau of “therapy” and “diagnostic”.

For example, not only can radioactive iodine-131 be used for the treatment of well-differentiated thyroid cancer, but imaging of the cancer distribution can also be done – literally “killing two birds with a stone”.

PET pros and cons

PET imaging is currently the “in-thing” in cancer management.

Whether used with CT or MRI (PET/CT or PET/MRI), the high sensitivity in detection of cancers, and most uniquely, the determination of the level of metabolic activity within the cancer is very useful to clinicians.

Though some cancers are already dead after treatment, the physical aspect of the cancer may still be seen on conventional radiographs and CT for a period of time, analogous to a dead tree stump.

When dealing with cancers, time is essential and any residual metabolically-active disease should be dealt with swiftly.

Hence, information of the metabolic activity of the tumour is very useful – no metabolic activity means dead tissue.

Furthermore, the radioactive substance can be used safely in patients with renal (kidney) impairment without causing further deterioration.

Then again, PET/CT or PET/MRI is not the ultimate imaging modality.

There are limitations to using PET as not all tumours take up the radioactive substance and there might be masking by physiological uptake by normal cells.

The fear of having radioactive substances within the body is also a major deterrent in many patients.

However, with proper counselling, they will realise that the radioactive substance used will basically decay exponentially and wash out from the body, similar to any other medical imaging contrasts.

Imaging is necessary

The ultrasound is one of the more commonly experienced imaging modalities as pregnant women are required to undergo them as part of their regular check-ups.

Once again, I highlight that no imaging modality is perfect.

Not all clinical information can be gathered from non-ionising medical imaging such as ultrasounds and MRI, and neither are all patients suitable to undergo them.

Patients undergoing x-rays, CT and nuclear medicine imaging, including PET/CT and PET/MRI, are exposed to certain levels of radiation.

Technological advancement has significantly reduced the radiation exposure to the least possible, compared to many years ago.

Even though the radiation exposure is minimal, many people still harbour the unfounded fear of it possibly triggering or exacerbating cancer.

In actual fact, the radiation exposure from medical imaging is negligible in the course of medical treatment.

Cost is no doubt an issue in this day and age. It goes without saying, that the more expensive the imaging is, the more likely that patients will try to avoid it.

Better equipment and technology comes with a price.

One needs to consider the investment, equipment costs, research and clinical trials involved before an imaging modality is approved, similar to how smartphones are being improved and made.

The better the specifications of the phone, the pricier it is. But with time, prices will fall due to increasing demand and availability.

Nuclear medicine imaging is relatively expensive due to the scanner, as well as the radioactive substances needed for the imaging.

These substances need to be specially ordered and are not widely available.

Nonetheless, it is a small price to pay for crucial clinical information needed to manage our own health.

In short, it is important for patients to understand that doctors choose imaging modalities to help diagnose, stage, plan, evaluate and monitor their condition.

There are times when doctors will order multiple imaging modalities in the course of their management.

The risk and benefits for each imaging is always taken into account before subjecting patients to them. Each and every person is unique and every disease is different.

Whenever I hear patients sharing their medical conditions, I do sometimes wonder if they actually realise that they are unique individuals with different medical issues and their experience may not be applicable to their listeners.

In the era of precision medicine, there is no one imaging that fits all. To achieve the best treatment, it is important to tailor the treatment according to the patient and underlying condition.

If in doubt, discuss with your doctor. I end with a quote from Ralph Waldo Emerson: “Don’t waste life in doubts and fears.”

https://www.star2.com/health/2019/03/13/whats-the-best-imaging-technique-to-detect-cancer/

The Ultra-High-Field MRI Scanner, The Siemens Magnetom Terra

Siemens Healthineers just won the first European regulatory approval for an ultra-high-field MRI scanner to be used in clinical practice. The Magnetom Terra sports a magnetic field strength of 7 Tesla, which is considerably more powerful than 3 Tesla, the current high-end standard. MRIs of such strength have been used in research hospitals for years, so it’s a welcome sign that they’re going to be used in more routine applications. Additionally, the new scanner can be easily switched from clinical protocols to those used in research and back, as needed, providing the greatest applicability to hospitals that would be ordering such an advanced device.

A greater field strength results in a higher image resolution as well as improved contrast, allowing one to see more details, be it in neurological or musculoskeletal exams. A Siemens Healthineers announcement points to the device’s ability to help identify white and gray matter in patients with epilepsy, which may be used to better diagnose and manage their condition. Similarly with folks who have multiple sclerosis, the new scanner can help spot lesions in the gray matter with greater ease.

“This ability to use 7 Tesla technology in the clinical realm is a breakthrough into broader clinical 7 Tesla MR applications. This CE certificate is now well-supported by the remarkable progress with respect to novel radio-frequency technologies and MR methods that will make whole-body MRI at 7 Tesla feasible in the future. It will definitely foster the translation of research into clinical applications,” in a statement said Professor Dr. Siegfried Trattnig, M.D., Director of the MR Centre of Excellence at the Medical University of Vienna, “And, the higher signal to noise ratio, the improved contrast, and non-proton MR at 7T will translate into better spatiotemporal resolution, but even more importantly into enhanced biochemical and metabolic tissue characterization en route to clinical noninvasive personalized medicine.”

In terms of installation, Siemens Healthineers touts that it’s the world’s lightest 7 Tesla whole-body magnet, being half the weight of similar actively shielded devices. This makes it similarly difficult to install as more common 3 Tesla scanners.

Product page: MAGNETOM Terra…

Via: Siemens Healthineers…

https://www.medgadget.com/2017/08/eu-gives-first-approval-ultra-high-field-mri-scanner-siemens-magnetom-terra.html

When The Best Tests Fail

Medical Tests That Can Save Your Life

Health screenings can save your life—if they work right. What you do can make all the difference

By Beth Howard 
Published November 2011, Prevention

When it comes to protecting your health, few advances pack the oomph of a good screening test.

Take a look at the taming of cervical cancer: Fifty years ago, the disease claimed the lives of more women each year than any other cancer. Then doctors started using the Pap test, which can catch cervical cancer before it starts. And now cervical cancer has dropped to number 15 on the list of cancer killers of American women.

Yet even a great screening test can have crucial weaknesses. The Pap isn't perfect. And a recent study on the colonoscopy found that some doctors do the exam so quickly that their patients don't get the procedure's full lifesaving benefit.

Fortunately, you don't have to lose out—if you know what to do and say. Make sure you get the best from four common screenings.

Prevent Colon Cancer

Katie Couric's colonoscopy on Today in 2000 prompted 20% more people than expected to get the exam in the nine months that followed. After that, the increase tapered off—but didn't disappear. That makes doctors happy: In part because of increased screening, deaths from colon cancer dropped from more than 57,000 in 2000 to 53,580 in 2004, according to the CDC.

During a colonoscopy, a doctor inserts a flexible, lighted tube into the rectum and guides it into the colon to look for and remove growths called polyps, which are the source of most colon cancers.
But the test may not always catch a patient's cancer. One reason: A New England Journal of Medicine study of one gastroenterology practice found that doctors who rush find fewer polyps.

"If you spend more time looking for weeds in a garden, you're going to find more weeds," says Robert L. Barclay, MD, the lead author of the research, which examined his own office in Rockford, IL. "The physician in our practice who averaged the longest inspection time [nearly 17 minutes] found 10 times as many polyps as the physician with the shortest average time [about 3 minutes]."

Because colonoscopies are recommended just once a decade, a slower test could make a critical difference.

Tune Up Your Test

Ask how many colonoscopies your physician typically does before lunch. Ten is a reasonable number.

Encourage your doctor to watch the clock: In the Rockford practice, setting a minimum of eight minutes for withdrawing the scope increased the overall detection rate by 40%.

Make the prep more palatable with a pill. Before the exam, patients generally drink large quantities of a nasty tasting, laxative-like substance to clean out the colon; simply consuming the liquid is such an unpleasant experience that it can keep people from getting screened. But research shows that a new tablet called OsmoPrep is just as effective—and much easier for the patient. (Some conditions, like kidney disease or cardiovascular problems, rule out OsmoPrep; check with your doctor.)

Ward Off Cervical Cancer

Between 1955 and 1992, the death rate from cervical cancer dropped by 74%, thanks to the Pap test, in which doctors take a sample of cells from the cervical area and send it to a lab for evaluation. But for every five women who have cancerous or precancerous cervical cells, at least one will have a test mistakenly reported as normal, according to the National Institutes of Health.

Because cervical cancer develops slowly, the woman's next test should catch the problem in time. Still, getting one of these "false negatives" sometimes means a dangerous delay in diagnosis and treatment.

Tune Up Your Test

Ask about the tools your doctor uses. Studies show that doctors get a better sampling of cells when they use a "spatula" (for the opening to the cervix) in combination with a cytobrush, which looks like a mascara wand (for the opening of the uterus). An instrument called a "broom"—like a miniature janitor's broom—is less effective, says Lucille Marchand, MD, a professor in the Department of Family Medicine at the University of Wisconsin School of Medicine and Public Health. If your doc uses the broom, it's a sign that he or she isn't up-to-date, Marchand says—good reason to consider a switch.

Get a "liquid-based" test such as Thin Prep or Sure Prep. Cells are less apt to clump together or be obscured by mucus with these methods, so it's easier to detect cancer if it's present, according to Kenneth L. Noller, MD, president-elect of the American College of Obstetricians and Gynecologists. About 80% of gynecologists use this more accurate technology.

Consider getting an HPV test. The human papilloma virus is the culprit behind most cases of cervical cancer. The HPV test, used with the Pap to screen women over age 30, assesses whether you're infected with any of the 13 HPV types that are linked to the cancer; a positive result on both tests may lead your doctor to perform a colposcopy, in which your cervix is inspected through a kind of magnifying glass.

The HPV test is also approved for younger women if a Pap test indicates a possible problem. (Most women are able to fight off the virus; only those who are unable to get rid of it go on to develop pre-cancer of the cervix.) For women over age 30, says Dr. Noller, "having this test along with a Pap smear once every three years is more accurate in picking up cancer than getting a Pap every year."

Watch the calendar to keep your smear clear. It's best to schedule your test when you're not menstruating—day 10 to 14 of your cycle (day 1 is the first day of your period). Avoid tampons, douches, contraceptive jellies, yeast creams, and sexual intercourse for 72 hours prior to your exam. Go ahead with the exam if that's the only time you can do it—but "these make it more likely there will be a suspicious finding that's not actually cancer," says Dr. Noller, which can lead to unnecessary follow-up tests.

Detect Breast Cancer

The most basic breast cancer screening test, the mammogram, stirred a lot of controversy a few years ago when Danish researchers argued that there was no good evidence behind its widespread use. After analyzing the studies, the American Cancer Society and the National Cancer Institute came out soundly in favor of the test for women starting at age 40.

For women 50 and older, the US Preventive Services Task Force says an annual mammogram cuts the risk of dying of breast cancer by 16% or more; in one large study, the risk was cut by up to 45%.

Still, the test has flaws. It can indicate an abnormality when one isn't really there, leading to lots of worry and more tests—including biopsy. Out of every three women screened over a period of 10 years, one gets a false alarm. Scarier, studies have shown that in about 20% of cases where cancer is present, a mammogram doesn't detect it.

Tune Up Your Test

Ask for a double-check of your x-ray. When you call for an appointment, ask the imaging facility about its reading practices: Ideally, your films will be read by two radiologists or scanned by computer-assisted detection (CAD) technologies. "These provide a second set of eyes, and studies suggest they can make a difference," says Daniel C. Sullivan, MD, director of the Cancer Imaging Program of the National Cancer Institute. "CAD improves diagnosis as much as 20% for some radiologists."

Take your x-rays with you if you change imaging facilities. Screening is more powerful if your doctor can compare new images against old ones to track the changes over time.

Consider going high tech if you're at increased risk. Women who have a mutation in the genes known as BRCA 1 or 2 should have an MRI each year along with their mammogram, according to Ellen Warner, MD, a medical oncologist at Toronto Sunnybrook Regional Cancer Centre in Ontario. In her study of 236 high-risk women, MRI found 77% of cancers, compared with 36% detected by mammography. Despite these impressive stats, women at average risk are not encouraged to get an MRI because of its high false-positive rate—it often signals cancer when none is present.

Schedule your mammogram strategically. It's best to get a mammogram during the first 2 weeks of your cycle if you're premenopausal to avoid the hormonal shifts that can make breasts more sensitive, says Barbara Jaeger, MD, director of women's imaging at Mercy Medical Center in Baltimore. Also, lay off caffeine for a week before the test—it increases tenderness, too.

Cushion your breasts to ease the pressure. In studies of more than 1,300 women, a cushion called the MammoPad reduced discomfort by nearly half for 70% of women, Jaeger says. In her research, that relief let technologists compress women's breasts more, producing better pictures. The MammoPad is used in about 1,500 imaging centers across the country.

Skip deodorant—and powders, creams, and perfume—on the day of the mammogram. These can interfere with the reading.

Find Skin Cancer

Melanoma, the most dangerous form of skin cancer, has a grim distinction: Among cancers that can be screened for, it's the onlyone for which both the number of new cases and the death rate are on the rise. Yet the US Preventive Services Task Force, which sets the most widely accepted list of recommended screening tests, doesn't include a skin check in their recommendations.

In January, a study found that even a single melanoma screening at age 50 would be a cost-effective way to pick up the disease in the early stages. The American Cancer Society suggests getting a once-over at every checkup. "We know survival is much better when diagnosis is early," says lead study author Elena Losina, PhD, an associate professor of biostatistics at Boston University School of Public Health.

Tune Up Your Test

Put all your doctors to work. Melanoma can occur in surprising spots that are difficult to examine yourself, like the eyes, gums, and genitals. A full-body check is your best protection; also ask your dentist, eye doctor, and gynecologist to look for pigmented lesions or other suspicious changes during routine exams.

Know the ABCDs of healthy skin. Monitor moles and other growths for asymmetry, border (ragged or irregular), color (uneven shades of brown, black, tan, even blue), and diameter (larger than a pencil's eraser). But tell your doc about any change—even in a smaller mole, Dr. Losina says: "Self-screening is crucial—especially at midlife."

See a specialist if you spot something suspicious. A 2006 study from Emory University showed that dermatologists are best at detecting the cancer. Skin doctors picked up 89% of melanomas, compared with 80%% identified by primary care docs.

Breakthroughs You Can Use : Screen for the Silent Cancers

Some diseases are so difficult to detect that they're almost always deadly by the time they're found. But these new approaches might make a lifesaving difference in some of the toughest cases.

Ovarian Cancer

Women are scared of ovarian cancer for good reason: In 80% of cases, it isn't discovered until it's too late to cure. Yet tests—an ultrasound of the ovaries and a blood test that measures levels of CA-125, a protein known to rise when there's cancer—are useless for women at average risk.

The reason: If those exams suggest disease, the typical next step, at least for women past menopause, is to remove the ovary for biopsy. But the tests are so inexact that doctors would have to remove 100 women's ovaries to find a single case of cancer, says Edward E. Partridge, MD, interim director of the UAB Cancer Center at the University of Alabama at Birmingham.

Partridge's research holds out hope that testing will soon become less invasive and more accurate. In his study of 34,000 postmenopausal, asymptomatic women, doctors didn't do a biopsy unless a woman had a worrisome change on an ultrasound and her CA-125 level was over 65 U/ml—nearly double what's generally considered elevated. The result: Researchers found cancer in 1 out of every 5 women biopsied.

Lung Cancer

Like ovarian cancer, lung cancer in its early stages often causes no symptoms—or vague ones that are easily missed. So four out of five lung cancers are found in a late stage, often after they have spread to other places in the body, when there's little chance of a cure. Yet a recent large study showed that a CT scan of the lungs is remarkably successful at finding these cancers early.

When researchers at Cornell University scanned the lungs of 31,000 ex-smokers, they found cancer in 484 patients—85% of them at an early stage. Treatment at that point affords a 92% chance of surviving 10 years, says lead researcher Claudia Henschke, MD, a professor of radiology at Weill Medical College at Cornell University.

Why shouldn't everyone get a scan? First, it's not yet clear that the test will actually lengthen anyone's life. Further studies will show whether patients whose lung cancer is detected early live longer—or simply go through treatment longer but die at the same time as patients whose cancer was not detected this way. Also, there's concern about harm if doctors are too quick to biopsy patients with suspicious findings; a biopsy needle can collapse a lung. Still, the scan is worth considering if you're over 50 and have smoked at least half a pack a day for 20 years or more at any time in the past, according to Henschke.

http://www.prevention.com/health/health-concerns/medical-tests-can-save-your-life

Mammograms may not be suitable for high-risk group

Article rank 8 Sep 2012 The Star Malaysia — AP

Mammograms aimed at finding breast cancer might actually raise the chances of developing it in young women whose genes put them at higher risk for the disease, a study by leading European cancer agencies suggests.

 

The added radiation from mammograms and other types of tests with chest radiation might be especially harmful to them and an MRI is probably a safer method of screening women under 30 who are at high risk because of gene mutations, the authors conclude.

The study did not prove a link between the radiation and breast cancer, but is one of the biggest ever to look at the issue. The research was published on Thursday in the journal BMJ.
 

Mammograms are most often used in women over 40, unless they are at high risk, like carrying a mutation of the BRCA1 or BRCA2 gene.

Having such a mutation increases the risk of developing cancer fivefold.

About one in 400 women has the gene abnormalities, which are more common in Eastern European Jewish populations.

Unlike mammograms, an MRI, or magnetic resonance imaging scan, does not involve radiation.

 

http://www.pressdisplay.com/pressdisplay/viewer.aspx

CT Scans Raise Cancer Risk For Children

Editor's Choice
Academic JournalMain Category: Pediatrics / Children's Health
Also Included In: MRI / PET / Ultrasound; Cancer / Oncology; Medical Devices / Diagnostics
Article Date: 08 Jun 2012 - 0:00 PDT


With MRI scans becoming cheaper and more common, perhaps the days of the CT scan that does a similar function using X-Rays rather than magnetic fields, are numbered. A report shows that the cancer risk from CT scans, especially Brain Cancer and Leukemia can triple in some cases.

The Article published in The Lancet, and written by Dr Mark Pearce and Professor Sir Alan Craft, Newcastle University, UK; Professor Louise Parker, Dalhousie University, Halifax, NS, Canada; Dr Amy Berrington de González, National Cancer Institute (NCI), National Institutes of Health (NIH), Bethesda, MD, USA, and colleagues, represents the culmination of almost two decades of research in this area, and is jointly funded by the UK Department of Health and NCI/NIH.

It shows that 2 or 3 computed tomography (CT) scans of a child's head (child meaning under 15 years old in this case), can triple the risk of brain cancer. The total dose of radiation would be around 60mGy, while 5 to 10 scans giving a dose of some 50mGy or more, triples the risk of leukemia.

The researchers go on to point out that the risks are still miniscule as the diseases are not particularly common, thus an increased risk is far from absolute certainty of contracting the disease. The CT scan is a useful and sometimes necessary diagnostic tool, and therefore physicians must weigh the risks and make patients and their parents aware.

The retrospective study used records from the radiology departments of some 70% of the UK's hospitals, and gathered data from 180,000 patients who underwent CT scans between 1985 and 2002. By looking at the number and types of CT scan from the records, the researchers estimated the dose absorbed in milli-Grays (mGy) by the brain and bone marrow in patient for each scan. The data was then cross-checked with cancer incidence and mortality reports in the UK National Health Service Registry between 1985 and 2008. It was then possible to show if a person having scans was more likely to develop cancer. From this, they calculated excess incidence of leukemia and brain tumors.

The UK has relatively low usage of CT scans due to a nationalized health service and the Ionising Radiation (Medical Exposure) Regulations, that make sure scans are only done when medically justified.

Lead author Dr Pearce says:

"The immediate benefits of CT outweigh the potential long¬term risks in many settings and because of CT's diagnostic accuracy and speed of scanning, notably removing the need for anaesthesia and sedation in young patients, it will, and should, remain in widespread practice for the foreseeable future ...

Further refinements to allow reduction in CT doses should be a priority, not only for the radiology community, but also for manufacturers. Alternative diagnostic procedures that do not involve ionising radiation exposure, such as ultrasound and MRI [magnetic resonance imaging] might be appropriate in some clinical settings. Of utmost importance is that where CT is used, it is only used where fully justified from a clinical perspective."

A patient undergoes a CT scan


In a linked Comment, Dr Andrew J Einstein, New York Presbyterian Hospital and Columbia University Medical Center, New York, NY, USA, says:

"This study should reduce the debates about whether risks from CT are real, but the specialty has anyway changed strikingly in the past decade, even while the risk debate continued. New CT scanners all now have dose-reductions options, and there is far more awareness among practitioners about the need to justify and optimise CT doses, an awareness that will surely be bolstered by Pearce and colleagues' study ...

Pearce and colleagues confirm that CT scans almost certainly produce a small cancer risk. Use of CT scans continues to rise, generally with good clinical reasons, so we must redouble our efforts to justify and optimise every CT scan.""

Reference:
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(12)60815-0/abstract

Written by Rupert Shepherd
Copyright: Medical News Today
http://www.medicalnewstoday.com/articles/246324.php