Early Detection of Cancer Using High-End Technology
Most cancers are curable if detected early. In fact, early detection is the only option currently to reduce deaths from cancer substantially. Recognizing possible warning signs of cancer and taking prompt action leads to early diagnosis. Increased awareness of possible warning signs of cancer, among physicians, nurses and other health care providers as well as among the general public, can have a great impact on the disease. Often a doctor can find early cancer during a physical exam or with routine tests, even if a person has no symptoms. The doctor may suggest other exams for people who are at increased risk for cancer.
Cancer screening
Cancer screening aims to detect cancer before symptoms appear. This may involve blood tests, urine tests, other tests, or medical imaging. Screening tests must be effective, safe, well-tolerated with acceptably low rates of false positive and false negative results. If signs of cancer are detected, more definitive and invasive follow-up tests are performed to reach a diagnosis. Screening for cancer can lead to cancer prevention and earlier diagnosis. However, it may also falsely appear to increase the time to death through lead time bias or length time bias. Cancer screening is not indicated unless life expectancy is greater than five years and the benefit is uncertain over the age of 70.
When to use PET scans and how they work
Positron emission tomography (PET) is a medical imaging procedure that can provide information about how an organ or system in the body is working and it can reveal changes in metabolism. PET scans can detect cancer in its early stages, help to monitor cancer treatment and check if the cancer is coming back.
CT and MRI images provide information such as size, shape and location of physical structures in the body while PET monitors body functioning. PET scans are different than CT scans in that they detect the metabolic processes of cancer cells. Cancer cells tend to have a higher metabolism than normal cells, and therefore absorb sugar faster. During a PET scan, radioisotopes are attached to a sugar-like solution and the images produced by the PET scan capture the increased metabolic activity, representing areas of cancer.
A PET scan involves the painless injection of a small amount of a „positron-emitting” radioactive material (called a radiopharmaceutical). Images of the body are then taken using a PET scanner. The camera detects emissions coming from the injected radiopharmaceutical and the computer attached to the camera creates two and three-dimensional images of the area being examined. The injection of the radioactive material does not make you feel any different or drowsy. There are no sedative drugs or anaesthesia used during this procedure. The PET scan is considered to be a safe procedure that exposes you to around the same amount of radiation that you would receive from the general environment over about three years.
Alternatives to the PET scan depend on the condition under investigation and could include:
- nuclear medicine scan
- x-ray
- magnetic resonance imaging (MRI) scan
- computed tomography (CT) scan
- ultrasound
- blood test
- biopsy
CT Scans for Cancer Detection
The Computed Tomography (CT) scan is an x-ray procedure that produces detailed cross-sectional images of your body. Instead of taking one picture, like a conventional x-ray, a CT scanner takes many pictures as it rotates around you; it creates a three-dimensional picture of the inside of the body and a computer then combines these images into a detailed, cross-sectional view that shows any abnormalities. CT scans are not painful and the examination will generally last up to an hour, although the scanning itself takes only 10 to 15 minutes or less.
You will need to lie still on the table while the scan is being done. You might feel a bit confined by the ring while the pictures are being taken. You may be asked to drink 1 to 2 pints of a liquid before the CT scan and you might also receive an IV (intravenous) line through which a different kind of contrast dye is injected. Contrast dyes help better outline structures in your body.
CT scans can see larger tumors, and may be able to see if the tumor is growing into nearby structures. A CT scan may also find enlarged lymph nodes, signs of cancer spread to liver or other organs, or signs that an ovarian tumor is affecting your kidneys or bladder.
CT scans can also be used to guide some types of biopsies or to evaluate the effectiveness of cancer treatments, such as chemotherapy or radiation therapy. In addition, CT scans are often used for radiation therapy treatment planning. Areas that are commonly scanned include the head, neck, chest, abdomen, pelvis, or limbs.
What having a PET-CT scan involves
Almost all PET scanners today are combined with a CT scanner so that the PET images can be combined or fused with the CT images. This allows the nuclear medicine specialist to combine the structural information from the CT scan with the PET’s functional information and improve the accuracy of the test. In these scanners, the person passes through both scanners on the one bed and in the same position.
In some cases, your doctor may recommend an integrated PET-CT scan, which combine images from a PET scan and a CT scan that have been performed at the same time using the same machine. PET-CT scans are used for many types of cancer and in some cancers they can help to:
- Diagnose and stage cancer
- Make decisions about whether you can have surgery to remove your cancer
- Make decisions about which is the best treatment for your cancer
- Show how well the treatment is working
- Show the difference between scar tissue and active cancer tissue
- Check whether your cancer has come back
- Find the place in the body where your cancer first started to grow (primary cancer)
MRI scans can be used on most areas of the body
The Magnetic Resonance Imaging (MRI) scanner uses a magnetic field and radio waves to build up detailed pictures of various parts of the body by picking up signals sent out by water molecules. Computer systems help with this but no X-rays are used. MRI scans are investigations that can be used to help doctors make a diagnosis or assess the effects of treatment. Your doctor will recommend an MRI scan based on the type of disease you have and the reason for the scan. The scan isn’t painful. However, you will have to lie still for up to one hour on a table which is quite hard.
The scanner produces a variety of loud noises which are made by magnetic coils that switch on and off during the scan. These coils measure the signal coming from your body in order to create the images. Some people aren’t able to have this scan, for example thos who have a heart pacemaker, have had any of the heart valves replaced by metal ones, have aneurysm clips in the brain, have ever done any welding or metalwork without wearing goggles, have ever had metal fragments removed from the eyes.
MRI can be used on most areas of the body. It is particularly good for some types of brain tumour, primary bone tumours, soft tissue sarcomas and for tumours affecting the spinal cord. As well as being used to find or stage tumours, MRI can be used to measure blood flow. You may have an injection of a special dye before the scan to help make the pictures clearer. For some parts of the body and for some types of tissues, MRI can produce clearer results than a CT scan. For other situations, the CT scan is better. Your doctor will know which is the best type of scan for you.
What the future holds for early cancer detection
It may soon be possible to test a person for cancer with just a drop of their blood and a small machine. As part of a European research project, scientists have developed a device (Spedoc) for detecting the HSP70 protein, which is over-expressed in patients with many types of cancer. The objective is to make it possible to diagnose cancer extremely early in the disease process, thereby improving outcomes for patients. However, it will be a long time before it becomes a routine test, although this protein is in fact high in patients with many types of cancer. In particular, it still needs to be proven that early HSP70 detection can actually change the way patients are treated and lead to real improvements in outcomes for specific types of cancer.
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