Dear browsers,

Perhaps, many of you never heard about "Nuclear Medicine" a relatively new and fast emerging medical specialty worldwide.  In India, more and more medical colleges have started teaching this specialty at the postgraduate level.  This facility is available in some of the best hospitals too, though the cost of the state-of-the art machinery is very prohibitive.  I have compiled this article (courtesy: Department of Nuclear Medicine, Kuwait Medical School, where I am working) to the benefit of our fellow Barkurians.  Your comments are most welcome.

What is Nuclear Medicine?

Nuclear medicine is a medical specialty that uses safe, painless, and cost-effective techniques both to image the body and treat disease. Nuclear medicine imaging is unique in that it documents organ function and structure, in contrast to diagnostic radiology, which is based upon anatomy. It is a way to gather medical information that may otherwise be unavailable, require surgery, or necessitate more expensive diagnostic tests.

As an integral part of patient care, nuclear medicine is used in the diagnosis, management, treatment, and prevention of serious disease. Nuclear medicine imaging procedures often identify abnormalities very early in the progression of a disease -long before some medical problems are apparent with other diagnostic tests. This early detection allows a disease to be treated early in its course when there may be a more successful prognosis.

Nuclear medicine uses very small amounts of radioactive materials or radiopharmaceuticals to diagnose and treat disease. Radiopharmaceuticals are substances that are attracted to specific organs, bones, or tissues. The radiopharmaceuticals used in nuclear medicine emit gamma rays that can be detected externally by special types of cameras: gamma or PET cameras. These cameras work in conjunction with computers used to form images that provide data and information about the area of body being imaged. The amount of radiation from a nuclear medicine procedure is comparable to that received during a diagnostic x-ray.

Today, nuclear medicine offers procedures that are helpful to a broad span of medical specialties, from pediatrics to cardiology to psychiatry. There are nearly one hundred different nuclear medicine imaging procedures available and not a major organ system which is not imaged by nuclear medicine.

Fast Facts about Nuclear Medicine

• Nuclear medicine procedures are cost-effective.
• There are nearly 100 different nuclear medicine imaging procedures available today.
• Nuclear medicine uniquely provides information about the function of virtually every major organ system within the body.
• Nuclear medicine procedures are among the safest diagnostic imaging tests available.
• The amount of radiation in a nuclear medicine procedure is comparable to that received during a diagnostic x-ray.
• Nuclear medicine procedures are painless and do not require anesthesia.
• Children commonly undergo nuclear medicine procedures to evaluate bone pain, injuries, infection, or kidney and bladder function.
• Common nuclear medicine applications include diagnosis and treatment of hyperthyroidism (Graves' Disease), cardiac stress tests to analyze heart function, bone scans for orthopedic injuries, lung scans for blood clots, and liver and gall bladder procedures to diagnose abnormal function or blockages.
• Nuclear medicine is an integral part of patient care and contributes to the well being of patients worldwide.

Benefits of Nuclear Medicine

Nuclear medicine is a safe, painless, and cost-effective way of gathering information that may otherwise be unavailable or require more expensive and risky diagnostic test. A unique aspect of a nuclear medicine test is its extreme sensitivity to abnormalities in an organ's structure or function. As an integral part of patient care, nuclear medicine is used in the diagnosis, management, treatment and prevention of serious disease. Nuclear medicine imaging procedures often identify abnormalities very early in the progression of a disease --long before some medical problems are apparent with other diagnostic test. This early detection allows a disease to be treated early in its course when there may be a more successful prognosis.

Although nuclear medicine is commonly used for diagnostic purposes, it also has valuable therapeutic applications such as treatment of hyperthyroidism, thyroid cancer, blood imbalances, and pain relief from certain types of bone cancer.

Safety of Nuclear Medicine

Nuclear medicine procedures are among the safest diagnostic imaging exams available. A patient only receives an extremely small amount of a radiopharmaceutical, just enough to provide sufficient diagnostic information. In fact, the amount of radiation from a nuclear medicine procedure is comparable to, or often times less than, that of a diagnostic x-ray.

Although we don't think much about it, everyone is continually exposed to radiation from natural and manmade sources. For most people, natural background radiation from space, rocks, soil, and even carbon and potassium atoms in his or her own body, accounts for 85 percent of their annual exposure. Additional exposure is received from consumer products such as household smoke detectors, color television sets, and luminous dial clocks. The remainder is from x-rays and radioactive materials used for medical diagnosis and therapy. With most nuclear medicine procedures, the patient receives about the same amount of radiation as that acquired in a few months of normal living.

Because of his or her special training, the nuclear medicine physician is able to select the most appropriate examination for the patient's particular medical problem, and thereby avoid any unnecessary radiation exposure.

Nuclear Medicine Procedures

A Partial List of Why Physicians Order Nuclear Medicine Studies

Neurological Applications:

• Diagnose Stroke
• Diagnose Alzheimer's Disease
• Demonstrate Changes in AIDS Dementia
• Evaluate Patients for Carotid Surgery
• Localize Seizure Foci
• Evaluate Post Concussion Syndrome
• Diagnose Multi-Infarct Dementia

Oncologic Applications:

• Tumor Localization
• Tumor Staging
• Identify Metastatic Sites
• Judge Response to Therapy
• Relieve Bone Pain Caused by Cancer

Orthopedic Applications:

• Identify Occult Bone Trauma (Sports Injuries)
• Diagnose Osteomyelitis
• Evaluate Arthritic Changes and Extent
• Localize Sites for Biopsy in Tumor Patients
• Measure Extent of Certain Tumors
• Identify Bone Infarcts in Sickle Cell Disease

Renal Applications:

• Detect Urinary Tract Obstruction
• Diagnose Renovascular Hypertension
• Measure Differential Renal Function
• Detect Renal Transplant Rejection
• Detect Pyelonephritis
• Detect Renal Scars

Cardiac Applications:

• Diagnose Coronary Artery Disease
• Measure Effectiveness of Bypass Surgery
• Measure Effectiveness of Therapy for Heart Failure
• Detect Heart Transplant Rejection
• Select Patients for Bypass or Angioplasty
• Identify Patients at High Risk of Heart Attacks going to Surgery for Other Reasons
• Identify Right Heart Failure
• Measure Chemotherapy Cardiac Toxicity
• Evaluate Valvular Heart Disease
• Identify Shunts and Quantify Them
• Diagnose and Localize Acute Heart Attacks Before Enzyme Changes

Pulmonary Applications:

• Diagnose Pulmonary Emboli
• Detect Pulmonary Complications of AIDS
• Quantify Lung Ventilation and Perfusion
• Detect Lung Transplant Rejection
• Detect Inhalation Injury in Burn Patients

Other Applications:

• Diagnose and Treat Hyperthyroidism (Grave's Disease)
• Detect Acute Cholecystitis
• Detect Acute Gastrointestinal Bleeding
• Detect Testicular Torsion
• Detect Occult Infections
• Diagnose and Treat Blood Cell Disorders

What Is PET

Positron Emission Tomography (PET) is rapidly becoming a major diagnostic imaging modality used predominantly in determining the presence and severity of cancers, neurological conditions, and cardiovascular disease. It is currently the most effective way to check for cancer recurrences. Studies demonstrate that PET offers significant advantages over other forms of imaging such as CT or MRI scans in diagnosing disease. PET images demonstrate the chemistry of organs and other tissues such as tumors. A radiopharmaceutical, such as FDG (fluorodeoxyglucose), which includes both sugar (glucose) and a radionuclide (a radioactive element) that gives off signals, is injected into the patient and its emissions are measured by a PET scanner.

A PET scanner consists of an array of detectors that surround the patient. Using the gamma ray signals given off by the injected radionuclide, PET measures the amount of metabolic activity at a site in the body and a computer reassembles the signals into images. Cancer cells have higher metabolic rates than normal cells, and show up as denser areas on a PET scan. PET is useful in diagnosing certain cardiovascular and neurological diseases because it highlights areas with increased, diminished or no metabolic activity, thereby pinpointing problems.

Cancer & PET

PET is considered particularly effective in identifying whether cancer is present or not, if it has spread, if it is responding to treatment, and if a person is cancer free after treatment. Cancers for which PET is considered particularly effective include lung, head and neck, colorectal, esophageal, lymphoma, melanoma, breast, thyroid, cervical, pancreatic, and brain as well as other less-frequently-occurring cancers.

• Early Detection: Because PET images biochemical activity, it can accurately characterize a tumor as benign or malignant, thereby avoiding surgical biopsy when the PET scan is negative. Conversely, because a PET scan images the entire body, confirmation of distant metastasis can alter treatment plans in certain cases from surgical intervention to chemotherapy.
• Staging of Cancer: PET is extremely sensitive in determining the full extent of disease, especially in lymphoma, malignant melanoma, breast, lung, colon and cervical cancers. Confirmation of metastatic disease allows the physician and patient to more accurately decide how to proceed with the patient's management.
• Checking for recurrences: PET is currently considered to be the most accurate diagnostic procedure to differentiate tumor recurrences from radiation necrosis or post-surgical changes. Such an approach allows for the development of a more rational treatment plan for the patient.
• Assessing the Effectiveness of Chemotherapy: The level of tumor metabolism is compared on PET scans taken before and after a chemotherapy cycle. A successful response seen on a PET scan frequently precedes alterations in anatomy and would therefore be an earlier indicator of tumor response than that seen with other diagnostic modalities.

PET and CT or MRI

Because PET measures metabolism, as opposed to MRI or CT, which "see" structure, it can be superior to these modalities, particularly in separating tumor from benign lesions, and in differentiating malignant from non-malignant masses such as scar tissue formed from treatments like radiation therapy. PET is often used in conjunction with an MRI or CT scan through "fusion" to give a full three-dimensional view of an organ and the location of cancer within that organ. Newer PET scanners are being made that are a combination of PET/CT devices.

Neurological Disease

PET's ability to measure metabolism also has significant implications in diagnosing Alzheimer's disease, Parkinson's disease, epilepsy and other neurological conditions, because it can vividly illustrate areas where brain activity differs from the norm.

Alzheimer's Diagnosis: Until recently, autopsy has been considered the only definitive test for Alzheimer's disease (AD). Recent studies indicate that PET can supply important diagnostic information and confirm an Alzheimer's diagnosis (Journal of Nuclear Medicine, November 2000). When comparing a normal brain versus an AD-affected brain on a PET scan, a distinctive image appears in the area of the AD-affected brain. This pattern is seen very early in the AD course. Conventionally, the confirmation of AD is a long process of elimination that averages between two and three years of diagnostic and cognitive testing. Early diagnosis can provide the patient access to therapies, which are more effective earlier in the disease.

• PET also is useful in differentiating Alzheimer's disease from other forms of dementia disorders, such as vascular dementia, Parkinson's disease, Huntington's disease, etc.
• Epilepsy: PET is one of the most accurate methods available to localize areas of the brain causing epileptic seizures and to determine if surgery is a treatment option.

Cardiovascular Disease

By measuring both blood flow (perfusion) and metabolic rate within the heart, physicians using PET scans can pinpoint areas of decreased blood flow such as that caused by blockages, and differentiate muscle damage from living muscle, which has inadequate blood flow (myocardial viability). This information is particularly important in patients who have had previous myocardial infarction and who are being considered for a revascularization procedure.

History of PET

In the 1970's PET scanning was formally introduced to the medical community. At that time it was seen as an exciting new research modality that opened doors through which medical researchers could watch, study, and understand the biology of human disease.

In 1976, the radiopharmaceutical fluorine-18-2-fluoro-2-deoxyglucose (FDG), a marker of sugar metabolism with a half-life of 110 minutes, enabled tracer doses to be administered safely to the patient with low radiation exposure. The development of radiopharmaceuticals like FDG made it easier to study living beings, and set the groundwork for more in-depth research into using PET to diagnose and evaluate the effect of treatment on human disease. To perform PET studies in the late 1970's, a large staff was needed: physicists to run the cyclotron that produces the F-18 and to oversee the scanner, chemists to make the tracers such as FDG, and dedicated, specialist physicians.

During the 1980's the technology that underlies PET advanced greatly. Commercial PET scanners were developed with more precise resolution and images. As a result, many of the steps required for producing a PET scan became automated and able to be performed by a trained technician and experienced physician, thereby reducing the cost and complexity of the procedure. Smaller, self-shielded cyclotrons were developed, making it possible to install cyclotrons at more locations.

PET Today

Until recently a PET center required a cyclotron and a radiochemistry laboratory on site to produce the FDG. As a result there was a scarcity of centers. However, there are now multiple sites that make FDG and distribute it to the centers that only need to have a PET scanner to perform the imaging study.

-James D'Almeida, Kuwait