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Medical imaging, using various radiological and nuclear medicine studies, plays an important role in the detection, diagnosis and treatment of hematologic diseases and solid tumors of all types. Nuclear Medicine studies include Bone Scanning, Gallium Scanning, Multiple Gated Radionuclide Cardiac Study (MUGA) and Postiron Emission Tomography (PET). Radiological Sciences studies include Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Mammography, Ultrasound Imaging and X-ray.

Following diagnosis, imaging studies are used to follow the course of the disease—monitoring progression or regression and thus aid physicians in prescribing treatment.

This page presents information on Nuclear Medicine imaging studies: Why studies may be ordered, how the imaging process works, and what the patient can expect during the imaging process. A companion booklet presents similar information about Radiological Sciences imaging studies.

It is hoped that this information will be useful to patients. Please remember, however, that the best source of information about tests and studies used in your treatment is your doctor.

RADIOLOGICAL SCIENCES STUDIES

NUCLEAR MEDICINE STUDIES

COMMONLY ORDERED STUDIES FOR ONCOLOGY PATIENTS

Computed Tomography

CT technology permits direct imaging and differentiation of soft tissue (eg. liver, lung tissue, and fat). CT imaging is especially useful in locating large, space occupying lesions, tumors and metastases. The images produced reveal not only the presence of tumor, but also its size, spatial location and extent.

CT works on the same principle as x-rays: X-rays pass through the body and are absorbed or weakened (attenuated) by body tissues. This creates a profile (matrix) of x-ray beams of differing strengths. The profile is registered on film, creating an image. In CT, the film used in x-ray studies is replaced by a detector that measures the x-ray profile.

The typical CT scanner resembles a large doughnut surrounded by a box. The patient opening (aperture) is 24" to 28" diameter. Within the ring of the "doughnut" is a rotating frame with an x-ray tube mounted to the frame and the detector mounted on the opposite arc of the frame. A fan shaped beam of x-ray is created as the frame rotates the x-ray tube and detector around the patient. Each time the frame makes a 360 degree rotation, an image ("slice" or "cut") is acquired. The image is focused to a thickness of between 1 mm and 10 mm using lead shutters in front of the x-ray tube and detector.

As the frame rotates the detector take numerous "snapshots" (profiles) of the weakened x-ray beam. Typically, each rotation will produce about 1,000 profiles. Each profile is then divided into partitions by the detector and fed into about 700 separated channels. In turn each profile is then backwards reconstructed (back projected) by a dedicated computer into a two-dimensional reproduction of the image that was scanned.

New technological advancements have made possible the development of spiral or helical CT scanners that rotate continuously and make possible imaging of entire anatomic regions with a single 20 to 30 second breath hold. Rather than a series of individual cuts which may be misaligned due to slight patient motion or breathing, spiral CT acquires a volume of data from the patient’s anatomy in a single position. This data set can then be computer reconstructed to provide a 3 dimensional picture.
Even newer developments include multiple slice, high resolution scanners that collect up to eight times as much data as earlier spiral technology, making possible imaging and diagnosis with greater patient comfort.

Preparation. All patients referred for CT are required to have current laboratory tests on file, to include Blood Urea Nitrogen (BUN) and Creatinine—as a precaution against the presence of renal disorders which could impede elimination of the contrast solution. (At UCLA, "current" is within the past 14 days for patients age 65 and older; 4 weeks for all others. Other facilities may use a different standard.)

A liquid solution known as a contrast is frequently used in CT. The contrast is a solution of pharmaceutical agents used to make specific organ, blood vessels and tissues "stand out" in greater contrast, permitting better imaging of disease or injury.

Contrast may be administered orally, by injection, or, more rarely, rectally.

Oral contrast may be one of two types in general use, barium sulfate and Gastrografin®. Gastrografin is a water-based drink mixed with iodine and may have a slightly bitter taste. The iodine content of Gastrografin is the reason patients who are having CT with contrast are asked about allergic reaction to iodine and shellfish. Barium sulfate has a consistency similar to milkshake and is mixed with water. Patients are usually directed to drink 1,000 to 1,500 cc (= about 3 to 4 12 oz drinks) in order to sufficiently fill the stomach and intestines with contrast.

The oral contrast solution acts to attenuate (weaken) the x-ray beam as it passes through the organs containing the solution. The organs filled with contrast are then enhanced and appear as highlighted white areas on the CT film.

Prior to administration of oral contrast solution, patients are asked to be "NPO" (Latin: nil per os, literally, "nothing by mouth") for some hours before the CT scan. The purpose of this requirement is to eliminate as much food as possible from the gastro-intestinal tract, since food and food remains can mimic the presence of disease when oral contrast is present.

After the scan is concluded, the contrast solution is eliminated through the intestinal tract and kidneys in the same manner as food and drink. Occasional minor side effects, such has constipation, may occur.

At UCLA patients whose CT is to include oral contrast are asked to be NPO three hours prior to arrival for the scan and to arrive one hour prior to the time of their scan to drink the contrast solution. Other facilities may have other NPO time frames and follow different procedures, including asking the patient to pick up the contrast solution the evening before the scan.

Intravenous (IV) contrast solution, a clear liquid containing iodine that is injected into a vein, may be used singly or in conjunction with oral contrast. Typically, 75 to 150 cc (about 2.5 to 5 oz) is injected depending upon the patient’s age, weight, cardiovascular status, and area being scanned. Since IV contrast is usually injected at a specific point in the progress of the scan, the needle is inserted into a vein, and held in place by a strap or tape. The vein is then flushed with saline solution. The contrast solution is loaded into a power-assisted injector, which will inject the contrast into the vein through a tube connected to the needle. The injection is at all times controlled by the technologist or radiologist performing the scan.

Upon injection into the vein, the contrast circulates through the heart and passes into the arteries, through the capillaries and then into the veins and back to the heart. As images are acquired, the x-ray beam is attenuated (weakened) as it passes through blood vessels and organs containing contrast. The vessels and organs are thus enhanced as appear on the CT film as whitened areas.

IV contrast is eliminated from the blood through action of the kidneys and liver.

While iodine contrast is generally safe, patients with a history of allergies, especially to iodine or shellfish, history of diabetes, asthma, heart disease, kidney problems or thyroid condition should make these conditions known when referred for CT with contrast. The most commonly reported side effect of iodine contrast injection is a warm or hot "flushed" sensation during the actual injection and a metallic taste in the mouth, lasting a few minutes. Some iodine sensitive patients experience itching with hives (bumps on the skin), a reaction that can last from several minutes to more than an hour after the injection. Should this reaction occur it will be treated with medication as soon as it manifests itself.
New forms of "non-ionic" contrast (contrast solution with a different chemical structure) further lessen the risk of allergic reaction.

Patients with concerns about the use of contrast should discuss those concerns with their physician at the time the scan is ordered and with the imaging technologist at the time of the appointment.

Rectal contrast may be used to enhance images of the large intestine and other organs located in the pelvis. The substances used for rectal contrast are barium and Gastrografin, the same as are used for oral contrast, but with different levels of concentration. Certain medical conditions may dictate the use of one contrast solution rather than the other. In scans of the pelvis, all three types of contrast, oral, IV and rectal may be administered.

Rectal contrast is given as an enema. With the patient lying on her or his side, a small tip is inserted into the rectum. The tip is at the end of a length of tubing, connected at the opposite end to a bag filled with contrast, and suspended above the patient. The patient then lies flat and the contrast fills the lower intestine. While the contrast is entering the intestine, the patient may feel mild discomfort, coolness, and a generalized "fullness."

As with other contrast solutions, the action of the rectal contrast serves to attenuate x-ray beams as they pass through organs containing the contrast, and such organs are enhanced and appear as highlighted areas on the CT film. Rectal contrast enhances not only the large intestine, but also the bladder, and other organs located in the pelvis, and also, in female patients, the uterus.

As noted, food and food remains can mimic disease when contrast is present, patients are asked to be NPO (nothing by mouth) for a number of hours prior to the scan. For a pelvic CT with rectal contrast, patients are asked to use a Fleet’s enema the night prior to the scan.

The rectal contrast solutions pass through the body and are eliminated in the same fashion as food and drink. Minor side effects such as constipation may occur.

CT examinations generally proceed with the patient positioned on the CT table, after removing any articles of clothing or jewelry that might degrade the CT images. The patient may be asked to wear a gown. The portion of the body to be scanned is then positioned inside the CT gantry opening, often with the aid of cross-hair positioning lights. Once the patient is positioned, the technologist will leave the patient room, going to a control room adjacent to the scanner. During the course of the scan, the technologist can communicate with the patient through an intercom..

Patients are requested to remain still and to relax during the course of the scan. In many CT studies the patient is asked to draw a breath and to hold it for up to 30 seconds while the data set is acquired. Patients may hear the scanner rotating, and depending on the part of the body being scanned and the make and model of the scanner the rotation noise may be quite noticeable, or it may be barely audible. The table on which the patient is lying will move through the portal in the scanner in increments as the study progresses. The technologist may direct the gantry of the scanner to tilt during some studies, in others, it remains upright.

At the completion of the scan, the images are reviewed, and unless further images are required, the patient is at liberty to leave. The images are transferred to film, which is read by a radiologist and report dictated. A printed copy of the report is usually available within 48 hours. In some instances the reviewing radiologist will telephone the requesting physician as soon as the scan is read.
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Imaging Guided Biopsy

Image guidance is frequently used in percutaneous (through the skin) biopsies.

CT imaging is used to guide biopsy of several anatomic locations, particularly the lungs and liver. Newer model spiral or helical CT scanners are equipped with interventional programming that allows real time imaging for biopsy guidance. This allows the radiologist to observe the biopsy needle as it approaches and reaches the lesion within the body, thus significantly shortening procedure time and increasing diagnostic accuracy.

Magnetic Resonance Imaging (MR) guided biopsies are not as commonly used as CT or ultrasound guidance, but the practice is increasing, made possible with the development of open and "short bore" MR systems that allow greater access to the patient during scanning. MR guidance has the advantage of MR imaging’s high contrast resolution, which allows greater differentiation between organ structures and abnormalities.

Stereotactic mammography is used in some breast biopsies. "Stereotactiic" means that the biopsy path is imaged from two, somewhat angled directions to guide the biopsy needle. Several stereotactic pairs of x-ray images are made. These images and computer coordinates guide the needle, and small samples of tissue are then removed.

Ultrasound guidance is used extensively to guide biopsies, particularly of the breast and of organs located in the abdomen. Ultrasound allows considerable flexibility in following the needle path, since it does not use x-rays and allows essentially unlimited imaging.

While imaging guided biopsy is only minimally invasive and is frequently performed on an outpatient basis, it is still an invasive procedure and is performed in a hospital-type environment. Patients who are taking blood-thinning drugs, including daily aspirin, will be asked to discontinue use of such medication for up to seven days before the biopsy. Prior to the biopsy, patients may require a blood test, to include partial prothrombin time (PTT) and prothrombin time (PT) which both measure blood clotting time, and creatinine and blood urea nitrogen (BUN), if the biopsy is to be under CT guidance.

Frequently, in preparation for the biopsy the patient is asked to fast from midnight of the night before the procedure. At the conclusion of the procedure the patient is observed in a recovery area until medically stable for discharge. The patient must be driven to and from the procedure by someone else.

Prior to the imaging guided biopsy the patient is gowned and positioned on the imaging table. The skin over the area to be biopsied in then prepped and draped in customary surgical fashion and a local anesthetic is administered. To increase patient comfort, a sedative may also be given.

Once anesthesia is effected, a fine gauge needle, connected to a syringe, is inserted through the skin and its progress followed on the imaging screen. If IV contrast is administered to enhance the image, it is given at an appropriate time during the scan. When the needle reaches the targeted tissue, tissue cells are drawn into the needle. The needle will be advanced to gather additional tissue samples and then withdrawn and the tissue sample discharged to a slide for laboratory analysis. To gather adequate tissue for analysis, the needle may be inserted two or three times.

Blood loss during imaging guided percutaneous biopsies is minimal. At the conclusion of the procedure, the entry point is covered with a gauze bandage. Patients may experience some soreness after the procedure and the entry point may take on a bruised appearance for several days afterward. Otherwise there are no side effects and most patients tolerate the procedure without difficulty.
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Magnetic Resonance Imaging

Magnetic Resonance (MR) imaging provides superior detailing and contrast in images of soft tissues such as the brain (it can distinguish the white versus grey matter) and liver, blood vessels such as the carotid, renal and peripheral leg arteries and of bony structures including the spinal column and major joints.

MR uses magnetic energy and radio waves rather than x-ray radiation to create cross sectional images of the human body. The principal component of MR is a large cylindrical magnet ("open" MR systems utilize a "C" shaped magnet.) The strength of the magnetic field is measured in metric units known as Tesla. Most cylindrical magnets have a magnetic strength of between 0.5 and 1.5 Tesla. Most "C" shaped magnets have a magnetic strength of between 0.01 and 0.35 Tesla. (A 1.5 Tesla system has a magnetic field 30,000 times stronger than the pull of gravity on the earth’s surface.)

A special radio antenna known as a surface coil is placed around the part of the body to be imaged. During the examination, a radio signal is turned on and off, subsequently the magnetic energy absorbed by different atoms in the patient’s body is echoed back out of the body. The echoes are continuously measured by the MR scanner and a digital computer reconstructs the echoes into body images. Most MR imaging does not require preparation, and no blood tests are required prior to the examination.
MR studies may be done with a contrast medium, Gadolinium, or Ferridex for studies of the liver, both administered by injection, or without contrast. Unlike CT scanning, there is no potential for allergic reaction, but metal implants within the body (eg. cardiac pacemaker, orthopaedic pins, plates, or screws) may prevent an MR examination since metal implants are susceptible to the MR system’s magnetic field.

The patient aperture or "bore" of an MR cylindrical magnet is between 55 cm and 65cm wide (about 21_" to 25_") and 160 cm to 260 cm (about 5' 3" to 8' 6") in length. A small percentage of patients (<10%) suffer claustrophobia and are unable to tolerate examination in a cylindrical MR without sedation. Other options, increasingly available include newer "short bore" MR systems with shorter magnets and wider and shorter apertures, and open MR systems with a "C" shape magnet. (The open MR may not always be an option because of its less powerful Telsa strength.)

After arrival at the imaging center, the patient is asked to remove any articles of clothing or jewelry that might interfere with (degrade) the MR images. This may require wearing a patient gown.

The patient is positioned on the specialized MR table and the surface coil (radio antenna) is placed around the body area to be examined. The table is then moved inside the MR gantry.

The technologist will leave the MR patient room for the control console, nearby. Intercom communication between patient and technologist is open throughout the examination. During the MR sequences the patient will hear a "knocking" sound from within the MR system, which is the sound of the gradient coils being turned on and off to measure the MR signal echoing back out of the patient’s body. Ear plugs or headphones are frequently provided. (An MR sequence is the acquisition of data that yields a specific image orientation and a specific type of contrast or image appearance.) An MR examination typically is comprised of a series of from 2 to 6 sequences, with each sequence lasting between 2 and 15 minutes. The entire examination may last between 10 and 90 minutes in total.

At the conclusion of the examination, the images are reviewed to insure that no more sequences need to be taken, and if the images are satisfactory, the patient will be discharged. Results are usually communicated to the requesting physician within 24 hours. Occasionally, patients will report a mild headache from the "knocking" sound, there are no other reported side effects.
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Mammography

Mammography uses low dose x-ray to create detailed images of breast tissue. The advantage of screening mammography is that it can show changes in the breast prior to the time any such changes might be felt. by manual examination. Diagnostic mammography is a more complex and time-consuming procedure used to determine the precise size and location of any breast abnormality and to image surrounding tissue and lymph nodes.

In any mammography procedure each breast is imaged separately. Each breast is positioned on a film cassette and then gently compressed with a paddle, thus flattening the breast and allowing the maximum amount of tissue to be imaged and examined. In a screening mammogram, typically two views of each breast are taken: From above (the "cranial-caudal" view, or CC) and from an oblique, or angled view (the "mediolateral-oblique" view or MLO). In a diagnostic mammogram, in addition to the cranial-caudal and mediolateral-oblique view, supplemental views are often taken. These can include views from each side ("lateromedial" or LM) and views from the outside toward the center ("mediolateral" or ML). Other supplemental techniques include spot compression and magnification views.

Once the breast is positioned and compressed the x-ray source is activated and x-rays are radiated through the breast onto the film cassette beneath the breast. Inside the cassette is a phosphor coating, which "glows" in proportion to the intensity of the x-ray beaming hitting it. The film is thus exposed with an image of the internal structures of the breast. In passing through the breast tissues, the x-rays are "weakened" (attenuated) by the different tissue densities encountered. Fat is very dense and absorbs (attenuates) large amounts of the x-rays. Connective tissue surrounding the breast ducts and fatty tissue is less dense and absorbs far less x-ray energy.

These differences in x-ray absorption and the correspondingly varied exposure level of the film creates images clearly showing normal structures within the breast: Fat, fibroglandular tissue, breast ducts and nipples, as well as abnormalities including microcalcifications, masses and cysts. Breast masses (both benign and malignant lesions) appear white on a mammogram. Fatty tissue appears black. All other tissue, (connective tissue, ducts, glands, and abnormalities such as microcalcifications) appear as levels of white. In interpreting a mammogram, the radiologist looks for shadows and patterns of tissue density to detect abnormalities. In interpreting a mammogram it is important that prior films be available for comparison.

No preparation is required prior to a mammogram. Patients are asked not to wear deodorant, talcum, baby powder, lotions or cream under the arms or on the breast on the day of a mammogram. These may interfere with the quality of the mammogram images. For example, aluminal flecks in some powders and deodorants can mimic microcalcifications.

Women having sensitive breasts may find the procedure easier if the mammogram is scheduled at a time when the breasts are least sensitive, usually the week following a menstrual period.
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Ultrasound Imaging

Ultrasound imaging (sonography) is a rapid, radiation free method of imaging that is particularly effective in producing images of soft tissue organs and fluid filled spaces such as the heart, pelvis and genito-urinary organs, the liver, pancreas and gallbladder, the eye, thyroid, and blood vessels.

Ultrasound imaging is based upon principles initially discovered by the 19th century mathematician and physicist Christian Doppler, who observed the variation in frequency that occurs when the sound and the observer are in relative motion either away from or toward each other. These principles were applied to the development of sonar in World War II, and in the 1960’s to medical diagnostic imaging.

In ultrasound imaging a small device known as a "transducer" is placed against the skin near the region of interest. The transducer both transmits and receives sound. It produces a stream of inaudible high frequency sound waves that penetrate the body and bounce off the interior organs. Ultrasound waves do not penetrate air. As the sound waves echo back from the internal structures and contours of the organs, the transducer detects the sound waves. Different tissues reflect these sound waves differently, producing a "signature," which can be measured and transformed into an image. The image is turned into a picture using computers with reconstruction software.

Prior to an ultrasound examinations of abdominal organs the patient may be asked to take no food or drink after midnight of the night before the examination, and examination of pelvic organs may require ingestion of specified amounts of water beforehand. There are no reported side effects following ultrasound imaging.

Immediately before the examination, the patient is asked to remove any clothing or jewelry covering the area to be examined. Frequently, the patient will be asked to wear a gown. After the patient is positioned on the examining table, a clear gel is applied to the skin over the area to be imaged. The purpose of the gel is to help "connect" the ultrasound transducer to the skin.

The transducer is brought into contact with the skin. The transducer is then passed back and forth across the area being imaged. The patient needs to remain still as the images are produced. The images may be viewed as they are produced, and will be transposed to film for a permanent record. Results are communicated to the requesting physician within 24 hours.
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X-Ray Imaging

X-ray remains among the fastest and easiest means of viewing the body’s internal organs and skeletal structures.

X-ray imaging includes a range of techniques and applications. In general, x-ray imaging consists of two principal categories—radiographic imaging in which a still image is made of a bone or organ and shown on a film or computer screen, and fluoroscopic imaging in which an image is projected onto a monitor or computer screen and viewed in real time.

Multiple applications of radiography and fluoroscopy are used to image the anatomy:
Angiography: Imaging of the blood vessels.
Arthrography: Imaging of the joints.
Barium x-ray: Imaging of the gastro-intestinal tract.
Chest films: Imaging of the thoracic cavity and the heart.
Cholangiography: Imaging of the bile ducts.
Cholecystography: Imaging of the gallbladder.
Dental x-rays Imaging of the teeth and jaw.
Lymphangiography: Imaging of the lymphatic system.
Mammography: Imaging of the breasts.
Myelography: Imaging of the spinal cord.
Pyelography: Imaging of the urinary tract.
Skeletal x-rays: Imaging of bones and the skull.
Urography: Imaging of the bladder and kidneys.

X-ray is based upon principles first discovered by the 19th century physicist Wilhelm Roentgen. X-rays are generated through the bombardment of a tungsten target with electrons inside a device known as the x-ray tube. To generate this stream of electrons within the tube, a generator transforms AC (alternating current) electricity of 120 to 480 volts to power at 35 to 150 kV (kilo volts or thousands of volts). When this high voltage potential is applied to the x-ray tube, a tight beam of electrons is fired out of a wire (the "cathode") and strikes a disc (the "anode") made of tungsten or tungsten alloy, causing x-ray energy to be released from the metal’s atomic structure. The x-rays created are filtered and focused (collimated) as they leave the tube. The rays then pass through the anatomic part being studied in a straight line and are then recorded onto a film cassette placed behind or beneath the body part being studied. As the x-rays pass through the body, they are weakened (attenuated) by the differing densities of the tissues encountered. For example, bony tissue is very dense and attenuates a large amount of x-rays, while the soft tissue around bones is much less dense and attenuates far less x-ray energy. The differences in x-ray energy passed to the film cassette is expressed in the varying exposure levels on the film and creates the images seen on the film or captured by an image intensifier and TV system for real time viewing.

X-rays are a type of electromagnetic radiation. They are invisible to the naked eye and create no sensation when passed through the body. Though modern x-ray techniques use only a fraction of the x-ray dose required in the past, special care is taken to ensure patient safety. For example, patients may be given a lead apron to wear, which shield other body parts not being imaged from radiation. (Lead is highly dense and will absorb all x-rays passing into it.) Women patients should always inform their physician and the x-ray technician if there exists any possibility of pregnancy.

Many x-ray studies (eg. musculo-skeletal and thoracic imaging) require no preparation. Others (eg. gastro-intestinal studies) may require a period of fasting, and the use of a barium contrast to better define internal structures.

Prior to the study, the patient is asked to remove any clothing or jewelry that might interfere with the creation of the x-ray image. The patient is then placed so that the anatomic portion to be imaged is in the correct field of view between the x-ray tube and the film cassette or image intensifier. In all studies the patient is asked to remain still for a few moments while the technician makes the x-ray film or image. In some studies, such as a chest x-ray the patient is asked to daw a breath and hold it while the chest is imaged.

The images are reviewed, and, unless additional studies are required, the patient is free to leave. Depending upon circumstances, the results will be communicated to the requesting physician immediately or within 24 to 48 hours.

The information contained in this publication is presented for education and information only. The information herein should not be used for the diagnosis or treatment of any disease or other health problem. This publication is not a substitute for professional care. If you have, or suspect that you might have, a health problem, you should consult a physician or other qualified health care provider.
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Nuclear Medicine

Radiological studies—x-rays and CT scans—send radiation from an exterior source through the body to be detected and recorded on film or by computer. Nuclear medicine studies are based on a reverse principle, a radioactive substance is introduced into the body (orally or intravenously by injection or by inhalation for some lung studies). The radioactive substance emits gamma rays (similar to x-rays, although with a shorter wavelength) as it travels through the body. A device known as a gamma camera detects the gamma rays, which are converted into a computer signal and reconstructed as an image.
The radioactive substances (called radionuclides) are formulated to be temporarily collected by the specific part of the body being studied. As the radionuclide is taken up by organs in the body ,faint radiation signals are emitted and detected by the gamma camera’s scintillation crystal. The scintillation crystal converts the radiation signal into faint light, which is in turn converted to an electric signal. The electric signal is then digitized (converted to a computer signal) and reconstructed as an image. The image can be viewed on a monitor and imaged on film or saved on a disk.

The images produced by nuclear medicine studies show not only the anatomy or structure of an organ or other body part, but also the functioning of the organ. The radionuclides introduced into the body for nuclear medicine studies are absorbed at varying rates or in different concentrations by different tissue types. (For example, the thyroid gland absorbs more radioactive iodine than other tissues.) The amount of radionuclide absorbed and then emitted by tissues is linked to the cellular function (metatbolic activity) of that tissue. Where cancer is present or suspected, cells which are dividing rapidly, like cancer tissue cells, will been seen as "hot spots" of metabolic activity since such cells will absorb more of the radionuclide. Also, diseased or poorly functioning tissue emits a signal different from that emitted by healthy tissue, thus giving an indication of pathology sooner than other forms of imaging. This early indication of pathology is the result of the propensity of disease to affect the function of the tissue before it affects the anatomy of that tissue.
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Nuclear Medicine Imaging

Nuclear medicine imaging is allows visualization of organs and portions within organs that cannot be visualized on conventional x-ray images. Space occupying lesions (an injury or abnormality) stand out on nuclear medicine images, being seen as "cold spots" or areas of reduced radioactivity and indicative of abnormal tissue function. By contrast, rapidly dividing cells, often indicative of cancerous tissue, appear as "hot spots" because of increased radioactivity.

Nuclear medicine imaging can show the function of a variety of organs and parts of the body:

  • Abdomen—to test for gastrointestinal bleeding or bowel obstruction.
  • Blood—to test for blood cell disorders.
  • Bone—to test for bony metastases or degenerative arthritis.
  • Brain—to image tumors or aneurysms and evaluate stroke.
  • Breast—to image breast tumors.
  • Heart—to check for coronary artery disease, myocardial infarction or valve disease.
  • Hepatobiliary system—to test gallbladder and bile duct function.
  • Kidneys—to test renal function, detect renal tumors.
  • Liver and spleen—to test for chirrhosis or metastatic disease.
  • Lung—to test for pulmonary embolism, lung tumors or metastatic disease.
  • Lymph system—to test for the spread of cancer to the lymph nodes (lymphadenopathy).
  • Stomach—to test stomach function or to confirm peptic ulcer or gastric cancer.
  • Thyroid and parathyroid—to test for abnormal function or tumor.

Procedures for nuclear medicine imaging studies are broadly similar regardless of the type of study.

  • Some studies require preparation in advance of the study, such as fasting or ingesting pharmaceuticals prior to the study.
  • On arrival the patient will be asked to remove clothing or jewelry that might interfere with the imaging process. In some instances, the patient is asked to wear a gown.
  • Patients should tell the physician or technologist if any prosthetic implants are present in the body, of all current medications, of any allergies, of any chronic conditions such as diabetes.
  • Pregnant or nursing women should consult their physician prior to any imaging study.
  • A pharmaceutical radionuclide is administered either orally, by intravenous injection, or inhalation (for lung imaging). The type and dose of radionuclide administered is based upon the organ to be imaged and the patient's body weight.
  • In many studies, the patient is imaged shortly after the administration of the radionuclide. In some studies, such as a bone scan, there is a waiting period between administration of the radionuclide and the actual study. A few studies, such as a gallium scan, require that the radionuclide be administered the day before the study. Since different organs and systems absorb the pharmaceutical radionuclides differently, waiting times vary.
  • Immediately before imaging begins the patient is placed on an examination table or, for some studies seated in a chair, and the gamma camera is placed in position over the area to be imaged. In some studies such as PET, the examining table passes through a doughnut hole-like aperture similar to a CT scanner. The patient is asked to relax and remain still through the course of the study. The duration of nuclear medicine studies varies from 15 to 60 minutes.
  • At the conclusion of the study, the images are reviewed, and if no further images are needed, the patient is free to leave.
  • The low level radioactivity is retained for a relatively short period. The radioactive energy will dissipate on its own, and is eliminated from the body through excretion. There are no reported side effects to nuclear medicine imaging.

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Bone Scan

This study creates a "picture" of the complete skeletal system. The patient receives an injection of the radioactive tracer. Approximately two hours later, the scan is performed. When completed, abnormalities of the bony structure appear as "uptakes" or "hot spots," which may indicate the presence of tumor, or may be the result of other causes, such as arthritis. The bone scan is also useful for analysis of bony healing. No preparation is required. During the two hour interval between the injection and the scan the patient is free to do as desired. The scan itself lasts about 45 minutes.
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Gallium Scan

A study of the mediastinum (the cavity around the lungs) using radioactive Gallium 67, used for patients with an history of lung disease or lymphoma to rule out the presence of residual disease in the thoracic cavity. No preparation is required. The patient is injected on day one, and returns after 48 or 72 hours for imaging. The imaging time is less than 30 minutes.
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Muga Scan (Multiple Gated Radionuclide Cardiac Scan)

A study to assess cardiac function, particularly left ventricle ejection fraction. Requested prior to and following certain chemotherapy regimens with possible cardiac effects in some patients. No preparation is required. Imaging time is about 30 minutes.
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Pet Scan (Positron Emission Tomography)

Creates "pictures" showing the body’s metabolism and other biological functions. The patient is injected with a small amount of glucose tagged with a radioactive tracer. About one hour after injection, the patient is scanned. As the glucose compound is distributed and processed throughout the body, the scanner detects the radioactive tag and shows its metabolic activity within all organ systems. PET provides information for evidence of the location of malignancy, the effect of treatment, and recurrence of disease. Patients may drink small amounts of black coffee, clear tea, or water before the scan but may not eat solid food within six hours prior to the scan. Imaging time is less than one hour.
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The information contained in this publication is presented for information and education only. The information herein should not be used for the diagnosis or treatment of disease or other health problem.

Disclaimer
Cancer Alternatives–Sue Stiles Program in Intregrative Oncology
at UCLA's Jonsson Comprehensive Cancer Center ©2008

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