Positron emission tomography, also called PET imaging or a PET scan, is a diagnostic examination that involves the acquisition of physiologic images based on the detection of radiation from the emission of positrons. Positrons are tiny particles emitted from a radioactive substance administered to the patient. The subsequent images of the human body developed with this technique are used to evaluate a variety of diseases.
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 can give false results if a patient's chemical balances are not normal. Specifically, test results of diabetic patients or patients who have eaten within a few hours prior to the examination can be adversely affected because of blood sugar or blood insulin levels.
Also, because the radioactive substance decays quickly and is effective for a short period of time, it must be produced in a laboratory near the PET scanner. It is important to be on time for the appointment and to receive the radioactive substance at the scheduled time. PET must be done by a radiologist who has specialized in nuclear medicine and has substantial experience with PET. Most large medical centers now have PET services available to their patients. Medicare and insurance companies cover many of the applications of PET, and coverage continues to increase.
Finally, the value of a PET scan is enhanced when it is part of a larger diagnostic work-up. This often entails comparison of the PET scan with other imaging studies, such as CT or MRI.
Wednesday, November 14, 2007
Friday, April 6, 2007
About CT Angiograms
A new innovative noninvasive test is available to diagnose coronary artery diseases. Earlier, noninvasive functional tests of the heart were used, such as treadmill tests and nuclear studies, to indirectly assess if there were blockages in the coronary arteries. The only way to directly look at the coronary arteries was via a cardiac catheterization and coronary angiogram.
Just as taking a picture of a moving object with a camera results in a blurry picture, conventional CT scans of the heart are not helpful. A new generation of CT scanners which can take 64 pictures a minute is now available; with the use of a little medication to slow the heart rate to less than 64, CT images of the coronary arteries are now possible.
This procedure use intravenous dye which contains iodine and CT scanning to image the coronary arteries. . In people allergic to iodine, pretreatment with medications is necessary to prevent allergic reactions to the dye. In people with abnormal kidney function and/or diabetes, the dye may worsen kidney function. Finally, there is radiation exposure which is similar to, if not greater than, that received with a conventional coronary angiogram. Nonetheless, this is generally a very safe test for most people, but should only be undergone when ordered by a physician familiar with the patient and their underlying medical condition.
Who should get a CT coronary angiogram?
While CT angiography should not be used as a "screening" test in the general population, it is a major new tool in the diagnosis of coronary artery disease. In patients at high risk for developing coronary disease (cigarette smokers, those with genetic risk, high cholesterol levels, hypertension, or diabetes), who have unclear results with treadmill or other testing, or who have symptoms suspicious of coronary disease, CT angiography is an excellent next step in the diagnosis. If the CT scan is normal or only mildly abnormal, it makes the likelihood of a severe blockage of the coronary arteries extraordinarily small. Conversely, if the CT scan is significantly abnormal, cardiac catheterization and angiography are then indicated, to see if angioplasty, stenting, or coronary bypass surgery may be indicated.
In people who have had bypass surgery, CT angiography is very effective at evaluating the patency of the bypass grafts. In people who have had coronary stents , it is sometimes difficult to image the inside of the stent to see if it is narrowed. Due to these complexities, while CT coronary angiography is an exciting new modality, it is imperative to discuss with your physician if this is the correct test for you. As more experience is obtained, the indications for the test will become even clearer.
Just as taking a picture of a moving object with a camera results in a blurry picture, conventional CT scans of the heart are not helpful. A new generation of CT scanners which can take 64 pictures a minute is now available; with the use of a little medication to slow the heart rate to less than 64, CT images of the coronary arteries are now possible.
This procedure use intravenous dye which contains iodine and CT scanning to image the coronary arteries. . In people allergic to iodine, pretreatment with medications is necessary to prevent allergic reactions to the dye. In people with abnormal kidney function and/or diabetes, the dye may worsen kidney function. Finally, there is radiation exposure which is similar to, if not greater than, that received with a conventional coronary angiogram. Nonetheless, this is generally a very safe test for most people, but should only be undergone when ordered by a physician familiar with the patient and their underlying medical condition.
Who should get a CT coronary angiogram?
While CT angiography should not be used as a "screening" test in the general population, it is a major new tool in the diagnosis of coronary artery disease. In patients at high risk for developing coronary disease (cigarette smokers, those with genetic risk, high cholesterol levels, hypertension, or diabetes), who have unclear results with treadmill or other testing, or who have symptoms suspicious of coronary disease, CT angiography is an excellent next step in the diagnosis. If the CT scan is normal or only mildly abnormal, it makes the likelihood of a severe blockage of the coronary arteries extraordinarily small. Conversely, if the CT scan is significantly abnormal, cardiac catheterization and angiography are then indicated, to see if angioplasty, stenting, or coronary bypass surgery may be indicated.
In people who have had bypass surgery, CT angiography is very effective at evaluating the patency of the bypass grafts. In people who have had coronary stents , it is sometimes difficult to image the inside of the stent to see if it is narrowed. Due to these complexities, while CT coronary angiography is an exciting new modality, it is imperative to discuss with your physician if this is the correct test for you. As more experience is obtained, the indications for the test will become even clearer.
Sunday, April 1, 2007
Colon Question
Q1. Lynch Syndrome all are true except?
a) It is due to mutation in MMR gene
b) Associated with APC gene
c) It has Autosomal Dominant Inheritence
d) Adenomas in patients with Lynch syndrome display high grade dysplasia than
adenoma in patients with sporadic colorectal cancer
Answers
1)b
Hereditary Non Polyposis Colorectal cancer (HNPCC) is autosomal dominanat. It predisposes to Colorectal Cancer (CRC) at an early age.
It is predominantly on right side, has increased incidence of synchronous and metachronous disease. Polyps in HNPCC have high grade dysplasia
HNPCC is of two types Lynch I --- Colorectal cancer only, Lynch II - CRC + Extracolonic like endometrial, breast, urological etc
In HNPCC THERE is germ line mutation of mismatch repair gene (MMR). There are six MMR genes in humans. four are related to HNPCC.onchromosomes 2,3 , 7
APC is associated with FAP
REf. Schakelford 170
a) It is due to mutation in MMR gene
b) Associated with APC gene
c) It has Autosomal Dominant Inheritence
d) Adenomas in patients with Lynch syndrome display high grade dysplasia than
adenoma in patients with sporadic colorectal cancer
Answers
1)b
Hereditary Non Polyposis Colorectal cancer (HNPCC) is autosomal dominanat. It predisposes to Colorectal Cancer (CRC) at an early age.
It is predominantly on right side, has increased incidence of synchronous and metachronous disease. Polyps in HNPCC have high grade dysplasia
HNPCC is of two types Lynch I --- Colorectal cancer only, Lynch II - CRC + Extracolonic like endometrial, breast, urological etc
In HNPCC THERE is germ line mutation of mismatch repair gene (MMR). There are six MMR genes in humans. four are related to HNPCC.onchromosomes 2,3 , 7
APC is associated with FAP
REf. Schakelford 170
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