Day: 08/04/2010

CT and CT-PET :what to expect?

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Computed Tomography (CT) Scan—What to Expect

A computed tomography (CT) scan, also called a CAT scan, is a diagnostic examination used to detect cancer and find out the cancer’s stage (a way of describing a cancer, such as where it is located, whether or where it has spread, and whether it is affecting the functions of other organs in the body). Staging helps the doctor decide what kind of treatment is best and predict a patient’s prognosis (chance of recovery). CT scans can also be used to guide some types of biopsies (the removal of a small amount of tissue for examination to determine whether cancer is present) or to evaluate the effectiveness of cancer treatments, such as chemotherapy or radiation therapy. Common areas that may be scanned include the head, neck, chest, abdomen, pelvis, or limbs.

A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a patient’s vein to provide better detail in the images. One risk of this test is radiation exposure. Usually, the potential benefit outweighs the risk; however, if you are receiving multiple CT scans and x-rays, talk with your doctor about whether another type of test that involves less exposure to radiation can be done.

In some cases, your doctor may recommend an integrated PET-CT scan. This combines the images from a positron emission tomography (PET) scan and a CT scan, performed at the same time on the same machine. Together, the two scans create a more complete image than either test can offer alone. Learn more about what to expect with an integrated PET-CT scan.

The medical team

A CT scan is performed at the radiology department of a hospital or at an outpatient imaging center. It is performed by a radiologist (a doctor who performs and interprets imaging tests to identify problems in the body) or radiologic technologist (a health care professional who is specially trained and certified to operate a CT scanner).

Preparing for the procedure

When you schedule the examination, you will get detailed instructions on how to prepare.

Tell your doctor or nurse about all medications you are taking and ask whether you should take them on the day of the test. In addition, discuss any drug allergies you have, especially any allergic reactions to iodine that you may have experienced. In addition, be sure to mention any other medical conditions you have.

Women should tell their doctors if they are breast-feeding or if there is any chance that they are pregnant because a CT scan could put the baby at risk.

You may be told to drink only clear liquids starting at midnight the night before your examination and instructed to not eat or drink anything for at least four hours prior to your scan. However, for scans of some parts of the body, there will not be restrictions on eating prior to the examination.

Ask whether you can bring your own music; some facilities allow patients to listen to music during their examinations.

You will be asked to sign a consent form that states you understand the benefits and risks of the CT scan and agree to undergo the test. Talk with your doctor about any concerns you have about the CT scan.

During the procedure

When you arrive for your CT scan, you may need to change into a hospital gown or remove clothing or jewelry that could interfere with the scan. This includes belts, earrings, shirts with snaps or zippers, bras, and glasses.

Depending on which part of your body is targeted, you may receive a contrast agent (a special dye). It may be given orally (as a drink) or through an intravenous (IV) injection. The dye travels through your bloodstream and helps to create a clearer picture of specific parts of your body.

If you are given an injection, you may feel heat or itching at the injection site or have a metallic taste in your mouth; both sensations should disappear after a few minutes. If you experience a more serious reaction, tell the technologist immediately.

The technologist will help position you on an exam table. The table may have straps, pillows, or a special cradle for your head to hold you in place. You will probably lie on your back, although you may be asked to lie on your side or your stomach, depending on which part of your body is being scanned, especially if you are undergoing a biopsy.

During the examination, the technologist who monitors the procedure will be in an adjoining control room, but he or she will be able to observe you through a window or by means of a video camera, and you will be able to communicate through an intercom system.

The CT scanner resembles a large donut. The exam table will slide back and forth through the large hole in the center of the machine as the scanner rotates around you. For the first scans, the table will move rapidly through the scanner, which helps the technologist confirm that your body is properly positioned. For the remaining scans, the table will move more slowly.

CT scans are not painful. However, you will need to lie still for the entire scan, which may become uncomfortable. Since the scanner is shaped like a donut, you will not be enclosed in the scanner at any time. You can also expect to hear whirring or clicking sounds from the machine; some machines are noisier than others.

You may be asked to hold your breath during part of the scan because the motion created by breathing can blur the images. The exam table may be raised, lowered, or tilted to create the correct angle for the x-rays; ask the technologist performing the scan to tell you when the table will move.

The examination will generally last up to an hour, although the scanning itself takes only 10 to 15 minutes or less. Newer scanners, including spiral or helical CT scanners, are even faster. If a larger part of your body is being scanned, the procedure may last longer. The technologist should be able to give you a time estimate before you begin.

When the scan is finished, you may be asked to remain on the exam table while a radiologist reviews the images to determine whether additional images are needed.

After the procedure

You can expect to resume your normal activities immediately after your CT scan, including driving. If you received a contrast agent for the scan, you may be told to drink a lot of water to flush it out of your body.

Integrated PET-CT Scan—What to Expect

An integrated PET-CT scan combines the images from a positron emission tomography (PET) scan and a computed tomography (CT) scan, performed at the same time on the same machine. Together, the two scans create a more complete image than either test can offer alone.

Like the individual tests that it combines, an integrated PET-CT scan is a diagnostic examination used to detect cancer and find out the cancer’s stage (a way of describing a cancer, such as where it is located, whether or where it has spread, and whether it is affecting the functions of other organs in the body). Staging helps the doctor decide what kind of treatment is best and predict a patient’s prognosis (chance of recovery). The scan can also be used to locate an area for a biopsy (the removal of a small amount of tissue for examination under a microscope to determine whether cancer is present) or to evaluate the effectiveness of cancer treatments, such as chemotherapy or radiation therapy.

About PET and CT scans

A PET scan creates pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into a patient’s body. This substance is absorbed mainly by organs and tissues that use the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. A scanner then detects this substance to produce images of the inside of the body. The risks associated with exposure to such a small dose of radiation through a PET scan are minimal and are outweighed by the benefits of the test.

Meanwhile, a CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a patient’s vein to provide better detail in the images.

One risk of this test is radiation exposure. It is minimal for the PET scan portion of the test, and the radioactive substance remains in your body only for a short time. However, there is more radiation exposure associated with the CT scan part of the procedure. Usually, these risks outweigh the potential benefit; however, if you are receiving multiple CT scans and x-rays, talk with your doctor about whether another type of test that involves less exposure to radiation can be done.

The medical team

An integrated PET-CT scan is given at the radiology or nuclear medicine department of a hospital or at an imaging center. It is performed by a radiologist (a doctor who performs and interprets imaging tests to identify problems in the body) or radiologic technologist (a health care professional who is specially trained and certified to operate PET-CT scanners, among other types of nuclear medicine).

Preparing for the test

When you schedule the test, you will receive detailed instructions about how to prepare. For example, you may be told to drink only clear liquids beginning at midnight the night before your examination and instructed to not eat or drink anything during the four hours before your scan.

You will be asked to sign a consent form that states you understand the benefits and risks of the PET-CT scan and agree to undergo the test. Talk with your doctor about any concerns you may have about the scan.

In addition, tell your doctor about all medications you are taking, and ask whether you should take them on the day of the test. Also discuss any drug allergies or other medical conditions you have, especially any allergic reactions to iodine that you may have experienced. Women should tell their doctors if they are breast-feeding or if there is any chance that they may be pregnant because a PET-CT scan could put the baby at risk.

Some facilities allow patients to listen to music during the scan, so you may want to ask whether you can bring your own music to make you more comfortable.

During the test

When you arrive for the PET-CT scan, you may need to change into a hospital gown or remove clothing or jewelry that could interfere with the scan.

A radiation technologist or nurse will then deliver radioactive substance needed for the PET scan into your vein through an intravenous (IV) injection. The IV line will feel like a pinprick when it is inserted, but the radioactive material will not create any sensation in your body.

After the injection, the radioactive substance will take 30 to 90 minutes to reach the tissues that will be scanned. During that time, you will need to lie quietly without moving or talking; too much motion can affect the sites where the radioactive substance accumulates.

Depending on which part of your body is targeted, you may also be given a contrast agent (a special dye) for the CT scan. It may be given orally (as a drink), through an IV line, or through an injection. The dye travels through your bloodstream and helps to create a clearer picture of specific parts of your body.

If you are given the dye through an injection, you may feel heat or itching at the injection site or have a metallic taste in your mouth; both sensations should disappear after a few minutes. If you have a severe reaction, tell the radiation technologist immediately.

When it is time for the test to begin, a technologist will help position you on a padded exam table outside of the PET-CT scanner. The table may have straps, pillows, or a special cradle for your head to help hold you in place. You will probably lie on your back, although you may be asked to lie on your side or your stomach, depending on which part of your body is being scanned.

During the examination, a technologist will monitor the test through a window or a video screen in a nearby control room, and you will be able to communicate through an intercom system.

The PET-CT scanner resembles a large donut. The exam table will slide back and forth through the large hole in the center of the machine as the scanner rotates around you. For the first scans, the table will move rapidly through the scanner, which helps the technologist confirm that your body is properly positioned. For the remaining scans, the table will move more slowly. The scans are done sequentially—first the CT scans, then the PET scans.

A PET-CT scan is not painful. However, you will need to lie still for the entire scan, and you may need to keep your arms raised above your head, which could become uncomfortable. In addition, you may be asked to hold your breath during part of the scan because the motion created by breathing can blur the images. The exam table may be raised, lowered, or tilted to create the correct angle for the scan; ask the technologist performing the scan to tell you when the table will move. You can also expect to hear whirring or clicking sounds from the machine; some machines are noisier than others.

The appointment typically lasts up to an hour, although the scan itself takes only about 30 minutes. If a larger part of your body is being scanned, the procedure may last longer. The technologist should be able to give you a time estimate before you begin.

When the scan is finished, you may be asked to remain on the exam table while a radiologist reviews the images. If the images are blurred or otherwise unreadable, you may need to have an additional scan.

Internet Overuse May Cause Depression

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Study: Teens Who Pathologically Use Internet May Be About 2.5 Times More Likely to Become Depressed

Aug. 2, 2010 — Teenagers who are addicted to the Internet are more likely to develop depression or other psychiatric problems than teens who are classified as normal Internet users, a new study says.

Researchers in Australia and China studied pathological or uncontrolled Internet use and later mental health problems in 1,041 teenage students in China. The students were free of depression and anxiety at the start of the study.

Sixty-two of the teenagers were classified at the start of the study as being moderately pathological users of the Internet, and two were found to be severely at risk for uncontrollable urges to go online.

Nine months later, the youngsters were evaluated again for anxiety and depression and 87 were judged as having developed depression. Eight reported significant anxiety symptoms.

Researchers say that their work suggests that teens who use the Internet pathologically may be about 2.5 times more likely to develop depression than  teens who are not addicted to the Internet.

“This result suggests that young people who are initially free of mental health problems but use the Internet pathologically could develop depression as a consequence,” the authors write. “As we understand that mental health problems among adolescents bear a significant personal cost as well as costs to the community, early intervention and prevention that targets at-risk groups with identified risk factors is effective in reducing the burden of depression among young people.”

The study is published online in advance of the October print issue of Archives of Pediatrics & Adolescent Medicine.

Teens and Internet Addiction

The researchers say screening young people who may be at risk of Internet addiction may be a good idea in all high schools to identify those who may need counseling or treatment.

The youths in the study were between 13 and 18 and attended high schools in Guangzhou, China.

Researchers say the findings “have direct implications for the prevention of mental illness in young people, particularly in developing countries.”

They write that although previous research has found that pathological Internet users are mostly young men with introverted personalities, the rates of psychiatric symptoms among girls are rising.

The researchers say that most of the youths in the study, 93.6%, were classified as normal users.

The study reports that:

  • 45.5% said the most common use of the Internet was for entertainment.
  • 28.1% said they used the Internet to search for information.
  • 26.4% said they used the Internet to avoid boredom, make friends, or communicate with school chums.

“Young people who used the Internet pathologically were more likely to use it for entertainment and less likely to use it for information,” the authors say.

Incidence of Thrombosis in Lymphoma Patients

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Anticoagulation therapy probably benefits those with advanced disease who are undergoing cancer treatments.

Thrombosis is a common complication of cancer and is thought to occur most commonly in patients with solid tumors, such as those of the lung and gastrointestinal tract. Hematologic malignancies also are associated with thrombus formation, but the magnitude of this risk is unclear.

To address this uncertainty, investigators from Argentina and Italy performed a meta-analysis of published studies in which researchers reported thrombotic events in cancer patients, including those with lymphomas. Among 1149 recorded thromboses in 18,018 lymphoma patients, 83.5% were venous (80% deep venous thromboses, 13% pulmonary emboli, 7% both), and 16.5% were arterial (56% myocardial infarctions, 34% strokes, 10% not described). Overall, the incidence rate (IR) for thrombosis was 6.4%. Thrombotic events almost always occurred during treatment. The researchers analyzed the specific types of lymphoma that were associated with thrombosis: The IR for non-Hodgkin lymphoma (NHL) patients was higher than that for HL patients (6.5% vs. 4.7%; P<0.001). Furthermore, NHL patients with high-grade disease had the highest rate of thrombosis (8.3%). In general, IRs increased progressively with increasing stage of disease, from 5% among patients with stage I disease to 11.5% among those with stage IV disease. In the few patients (54) with central nervous system (CNS) lymphomas, thromboses occurred frequently (IR, 48%).

Comment: This meta-analysis yielded a 6% incidence of thrombosis among lymphoma patients, with even higher incidences in those with NHL or high-grade or advanced-stage disease and especially among those with CNS involvement. These thrombosis incidence rates for lymphoma are similar to those that occur with other cancers, and they indicate that thromboprophylaxis is appropriate for these patients. Because thromboses usually occur during cancer treatment and are more common in patients with advanced disease, anticoagulant prophylaxis might be most beneficial under these circumstances.

— David Green, MD, PhD

Published in Journal Watch Oncology and Hematology August 3, 2010

Is there any benefit to taking fish oil supplements for depression?

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Fish oil supplements may help ease symptoms of depression in some people. As with prescription antidepressants, fish oil appears most helpful for severe symptoms — but it may not be as effective for mild to moderate depression.

Fish oil is a good source of omega-3 fatty acids, which play an important role in brain function. People with depression may have low blood levels of brain chemicals called eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These chemicals are found in fish oil. The best dose of fish oil isn’t clear, but it appears that supplements containing 100 to 300 milligrams of either EPA or a combination of EPA and DHA may be helpful in relieving depression.

Supplements aren’t the only way to get more omega-3s. Eating fish a few times a week may be the best way to provide your body with enough of these healthy oils. Fish high in omega-3s include sardines, mackerel, salmon, snapper, trout, and canned white tuna. Shellfish, including mussels and oysters, also contain omega-3s.

Fish oil isn’t considered a replacement for treatment of depression, but it may be helpful as an addition to prescribed medications or other treatment. Although more studies are needed to determine exactly what role omega-3 fatty acids play in depression, it’s still a good idea to get enough of these healthy oils. Omega-3s help protect heart health and appear to have other health benefits.

source: mayo clinic

A solar salamander

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Photosynthetic algae have been found inside the cells of a vertebrate for the first time.

salamander embryosSpotted salamander embryos have an unexpectedly close relationship with a single-celled alga.TED LEVIN/photolibrary.com

Occasionally, researchers stumble across something extraordinary in a system that has been studied for decades.

Ryan Kerney of Dalhousie University in Halifax, Nova Scotia, Canada, did just that while looking closely at a clutch of emerald-green balls — embryos of the spotted salamander (Ambystoma maculatum). He noticed that their bright green colour comes from within the embryos themselves, as well as from the jelly capsule that encases them.

This viridescence is caused by the single-celled alga Oophila amblystomatis. This has long been understood to enjoy a symbiotic relationship with the spotted salamander, which lays its eggs in bodies of water. However, the symbiosis was thought to occur between the salamander embryo and algae living outside it — with the embryo producing nitrogen-rich waste that is useful to algae, and the algae increasing the oxygen content of the water in the immediate vicinity of the respiring embryos.

At a presentation on 28 July at the Ninth International Congress of Vertebrate Morphology in Punta del Este, Uruguay, Kerney reported that these algae are, in fact, commonly located inside cells all over the spotted salamander’s body. Moreover, there are signs that intracellular algae may be directly providing the products of photosynthesis — oxygen and carbohydrate — to the salamander cells that encapsulate them.

Breaking the rules

Such a close co-existence with a photosynthetic organism has previously been found in invertebrates, such as corals, but never in a vertebrate.

Because vertebrate cells have what is known as an adaptive immune system — which destroys biological material not considered ‘self’ — it was thought to be impossible for a symbiont to live stably inside them. But, in this case, the salamander cells have either turned their internal immune system off, or the algae have somehow bypassed it.

“On a lark, I decided to take a long-exposure fluorescent image of a pre-hatchling salamander embryo,” says Kerney. When this revealed widely scattered dots of unstained cells fluorescing in the background — an indicator that those cells might contain chlorophyll — Kerney switched to transmission electron microscopy (TEM) to take a closer look.

“The surrounding salamander cells that contain the algae often have several mitochrondria bordering the algal symbiont,” Kerney says, pointing to a TEM image.

Mitochondria are the powerhouses of animal cells, converting oxygen and a metabolic product of glucose into ATP, a molecule that cells use to store chemical energy. So salamander mitochondria gathered around an algal cell might be there to take advantage of the oxygen and carbohydrate generated by photosynthesis in that particular cell.

Green flash

How the relationship between the two species originated is unknown. But Kerney is probing how algae enter salamander cells, and some earlier findings are proving helpful.

Lynda Goff, a molecular marine biologist at the University of California, Santa Cruz, worked on this pair of organisms about 30 years ago and demonstrated, among other things, that embryos lacking algae in their surrounding jelly are slow to hatch. “We saw a logarithmic increase in algal cells as the embryo developed,” she says. And in those that did contain algae, the community was not static.

This logarithmic increase suggests that algae associated with the salamander embryos either divide rapidly as the embryo develops, or quickly enter the jelly or the embryo from outside as it grows.

So how might the algae enter the embryos? A likely moment occurs as the embryos’ nervous systems begin to form. A time-lapse video made by Roger Hangarter at Indiana University in Bloomington, and presented by Kerney at the meeting, reveals a fluorescent green flash next to each embryo at that point in its development.

The flare is a bloom of algae, which is probably drawn to a release of nitrogen-rich waste from the embryo, says Kerney. If waste is released, then there must also be a way in — and the large number of algae in the bloom increases the chances that some will make it in.

adult salamanderAlgae in the salamanders’ cells could be providing them with photosynthetic products, including oxygen.John Cancalosi/naturepl.com

This might explain why so many researchers have failed to find algae inside spotted salamander embryos before: most of them studied embryos that had not yet reached the phase coinciding with these algal blooms, so algae inside the animals would have been scant.

However, that doesn’t necessarily mean that embryos at an earlier stage contain no algae.

One of Kerney’s most curious discoveries is of the presence of algae in the oviducts of adult female spotted salamanders, where the embryo-encompassing jelly sacs form — a finding that points to the possibility that symbiotic algae are passed from mother to the offspring’s jelly sacs during reproduction.

“I wonder if algae could be getting into the germ [sex] cells,” says David Wake, an emeritus professor at the University of California, Berkeley, who watched Kerney’s presentation. “That would really challenge the dogma [of vertebrate cells disposing of foreign biological material]. But why not?”

source: nature

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Both Wake and David Buckley, a researcher specializing in salamander
development at the National Museum of Natural Sciences in Madrid, agree
that the work might tell us more about how self-recognition is learned
by vertebrate cells during development. Because salamanders can regrow
limbs, almost all the cells in a grown adult retain a degree of
pluripotency — that is, the specialized cells can continue to divide and
change into other cell types throughout the salamander’s life.

It may be that specialized cells in these adult salamanders are able
to accommodate algae inside them because the process by which they
learn self-recognition is different from that of other vertebrates.
“It makes me wonder if other species of salamander that have known
symbiotic relationships with algae also harbour algae inside their
cells,” said audience member Daniel Buchholz, a developmental biologist
at the University of Cincinnati in Ohio. “I think that if people start
looking we may see many more examples.”
// ]]>