Nuclear Medicine
Nuclear Medicine : DaTscan | Preparation Guidelines | Frequently Asked Questions
The Department of Nuclear Medicine performs diagnostic exams utilizing radiopharmaceuticals. Patients undergoing Nuclear Medicine procedures must be injected with or ingest some form of a radioactive tracer. The main difference between Nuclear Medicine (including PET) and all other diagnostic modalities is that Nuclear Medicine demonstrates function (physiology) as well as structure (anatomy) of organs or organ systems.
An example of this is the Nuclear Medicine Thyroid Uptake and Scan. Other modalities may image the thyroid, however, a RAI (radioactive iodine) uptake and scan is the only way to measure the gland’s overall function. This is a major factor in determining the patient’s course of treatment.
This procedure is safe, simple and effective. The patient comes into the Nuclear Medicine department and swallows a capsule containing a pre-measured amount of Na123I (radioactive 123I-sodium iodide). After a specified amount of time (usually 24 hours), the patient returns to Nuclear Medicine to be imaged. Using the gamma camera, measurements and images are obtained of the patient’s neck area. The technologist then calculates how much of the RAI is taken up by the thyroid gland, also called “percent uptake”. This will determine if the patient’s function is “hypothyroid” (under active), “hyperthyroid” (overactive), or “euthyroid” (normal). The images obtained will show thyroid size, position, pathology and other pertinent diagnostic information which helps the clinician treat the patient accurately.
A wide variety of tests may be done using radiopharmaceuticals.
Some of the most common are listed below with a brief outline of each procedure.
Whole Body Bone Scan (WBBS)
This exam is most commonly used for diagnosing metastatic disease or primary bone cancers. It may also be used to diagnose Paget’s disease, fractures (old vs. new or post trauma), unexplained bone pain, and other bony abnormalitites.
The WBBS is a great asset to the referring physician as it is non-invasive, easy to perform, and safely provides information to the clinician that may be otherwise unavailable. This exam has made a huge impact on cancer patients (Breast, Prostate and others) when it comes to diagnosis, staging, and treatment. Patients undergoing breast surgery for cancer may have a different procedure if they are know to have bone metastases prior to surgery. Chemo and radiation therapy outcomes can be altered greatly with the information obtained by a WBBS. Since blastic metastases and other pathologic states cause changes in bone function or “uptake” earlier than structural changes, abnormalities may show up sooner on radionuclide bone scans than anatomic imaging such as X-ray or CT.
The procedure itself is non-invasive and simple. The patient receives an intravenous injection of 99mTc-MDP (technetium methylene diphosphonate). There are virtually no side effects or allergic reactions to this or any other radiopharmaceutical. The patient may leave the departmentafter injection and return approximately 3 hours later for the scan. Patients are encouraged to stay well hydrated to improve the images. Otherwise they may resume their normal routine. The WBBS takes approximately 45 minutes to one hour for most patients.
Because the radiation dose comes from the injection not the camera, additional images may be obtained of any area of interest, sites of pain, etc. without additional exposure for the patient.
3 Phase Bone Scan
This exam is used for detecting stress fractures, osteomyelitis (bone infection), RSD (reflex sympathetic dystrophy) and other bone abnormalities. It is similar to the WBBS in that the injection is the same radiopharmaceutical. The main difference is that 3 sets of images at specific times are obtained, therefore, 3 phases. The area of interest is positioned under the camera prior to injection. We take rapid, sequential images immediately after injection. This is the blood flow phase. Following this, blood pool images are taken. Finally, the patient returns 3 hours later for the delayed images which show bone uptake rather than soft tissue as do the earlier phases. Having all 3 sets of data can help provide a differential diagnosis. Patients having a 3 phase bone scan should provide us with outside x-rays and/or other anatomical imaging exams and reports. Having these for comparison assists the radiologist in more accurately determining location of abnormalities demonstrated on the bone scan.
BONE SPECT
SPECT (single photon emission computed tomography), whether it is of the bones or other organs refers to the way the images are obtained. Generally, Nuclear Medicine scans are “planar” or 2 dimensional. The gamma camera is placed parallel to the patient to obtain an image. SPECT involves taking a series of images in steps while the camera rotates or orbits around the patient, similar to CT. The images are later reconstructed and reformatted to give “slices” of data from the patient. This may assist in diagnosing deep seated lesions, obtaining location of pathology and detecting things that might be covered up by overlying radionuclide uptake in adjacent areas.
Patients must be able to cooperate fully for SPECT imaging as they must lie completely still during the 15-30 minute acquisition in addition to the other scans being done in conjunction with the SPECT.
We currently perform 3 types of Nuclear Medicine Renal Scans:
Renal Scan and Flow, Renal with Lasix Washout and Captopril Renal Scan.
RENAL SCAN
This is the most common of the Renal procedures. It is used for general renal function and blood flow. Renal scans are primarily used to asses renal function and gross blood flow for patients with hypertension, hematuria, flank pain, follow up to Sono or CT, prior to colon cancer surgery (MD wants to make sure kidneys are functioning properly before hand), and chronic urinary tract infections.
The patient gets an intravenous injection of 99mTc-DTPA (Technetium Diethyl-triamine-penta-acetic acid) while lying on the imaging table and scanning is begun immediately post injection. The patient lies completely still for approx 45 minutes while imaging is performed. Additional views and possibly delayed images are obtained. There are no side effects or allergic reactions to the injection and as with all Nuclear medicine exams, the exposure is limited to the injected dose. Multiple images do not increase the patient’s radiation exposure. After the exam is completed, the technologist uses the Nuclear Medicine computer to analyze the data for the radiologist. Split renal function (how each kidney is working) and other important information can be obtained from this exam.
RENAL WITH LASIX WASHOUT
The acquisition of this test is the same as the above scan to begin with, however, there is an additional part. Lasix Washout studies are only used to rule out obstruction (UPJ obstruction, other ureteral obstruction, or when patients have hydronephrosis on other exams).
The scan begins as a regular renal scan and flow with the following exceptions:
After the initial renal scan, the patient is given an I.V. injection of a non-radioactive drug called “Lasix”. It is a diuretic and causes the kidneys to empty rapidly. If the patient is obstructed, the post-lasix images will not change. If there is no obstruction, the kidneys will empty. This exam may help the patient avoid unnecessary invasive or surgical procedures.
RENAL WITH CAPTOPRIL
This is done the same way as a regular renal scan and flow except the patient gets a prescription for 50mg of Captopril (or generic equivalent) from their MD and brings the pill(s) with them. They take the medication here 55 minutes prior to the scan. We do this to ensure the timing of the study.
Captopril is used to rule out RAS (renal artery stenosis). If the scan is normal with Captopril, the patient does not do anything further here. If the blood flow part of the scan is abnormal by more than a certain percentage, the patient is thought to have Renal Artery Stenosis. This helps the referring physician pinpoint the cause of hypertension in some patients.
Tagged RBC Liver SPECT
This is done ONLY to diagnose or confirm the presence of hemangioma(s), a benign lesion. In many cases, a lesion is thought to be a hemangioma on another exam such as Sono or CT. By ordering this exam, a referrer may be able to eliminate or confirm the need for biopsy. The procedure is done by drawing a small amount of blood from the patient and then re-injecting it after the red blood cells are tagged to a radioactive material. This is done by a technologist in the Nuclear Medicine Department. Two sets of images are obtained including SPECT. An early scan, immediately post-injection demonstrates blood flow to the liver and abdominal organs. 3-4 hours later, the patient returns for delayed images. If the lesion(s) in question shows increased uptake (or a “hot” appearance), it is a hemangioma. If there is no radionuclide uptake in the lesion, further testing including biopsy may be required.
LIVER/SPLEEN SCAN (WITH OR WITHOUT SPECT)
This is done primarily for FNH (fibrous nodular hyperplasia). It can also be requested for: Cirrhosis, Hepatitis C (to estimate “colloid shift”), liver mass/space occupying lesion (non hemangioma) on CT, Sono or MR. Liver/Spleen scans may also be used to detect metastatic disease to the liver and spleen. In most cases, SPECT will be done in addition to planar imaging.
The patient gets injected with 99mTc-sulfur colloid (technetium sulfur colloid) and imaging is begun approximately 15 minutes later. This is a safe, simple way to evaluate the liver/spleen RES (reticuloendothelial system).
In recent years, the increased availability of high resolution CT and MRI scanners has decreased the use of Liver/Spleen scans for the evaluation of small masses. It still remains the best way to estimate extent of cirrhosis and altered RES activity.
HIDA-hepatobiliary iminodiacetic acid (with and without CCK/ejection fraction)
Hida (hepatobiliary scan) is different from Sono and CT in that it shows FUNCTION rather than structure (how the gb is working, not only what it looks like). We do not see stones or gb wall thickness on a HIDA scan, but rather the effect they may have on GB function. Hida scan (without cck) may also be done on patients that have had a cholecystectomy to assess common duct patency.
The patient must be fasting for 6-7 hours prior to a HIDA scan. When the exam is begun, the patient is injected with 99mTc-choletec (technetium iminodiacetic acid) and imaging starts almost immediately. The patient lies on the imaging table for 1 hour while sequential images are taken over the abdominal area.
In some patients, we see the gallbladder fill and empty within this time frame and the exam is complete. In some cases the patient must come back up to 2-4 hours later for delayed images. Either because the gallbladder doesn’t visualize or doesn’t empty properly. Depending on what is demonstrated on the early images, the patient may be asked to eat a fatty meal and return for delays.
If the referring physican requests Hida with CCK (cholecystokinase) or Hida with EF (ejection fraction), CCK must be given I.V. after the patient’s initial hour of imaging.
It makes the gallbladder contract rapidly so we can measure the rate or percent ejected from the GB. CCK may be CONTRAINDICATED in patients with gallstones as they can become lodged in the bile ducts. There are some side effects from CCK such as nausea, vomiting and abdominal pain. Patients are informed of this prior to beginning the exam.
CCK Hida scans will demonstrate abnormal gallbladder contractility. As with other Nuclear Medicine exams, the functional abnormality that may be demonstrated on this exam is extremely helpful in determining the patient’s course of treatment.
GALLIUM SCANS
Gallium is the name of the radiopharmaceutical used in this study. It is helpful in diagnosing things such as Lymphoma, Bronchogenic Carcinoma, Sarcoidosis, PCP in HIV+ patients and other inflammatory processes.
After receiving an injection of 67Gallium Citrate, the patient may leave and returns for imaging at different intervals. Most Gallium scans are performed at 48 and/or 72 hourspost injection as needed. Since Gallium is absorbed by different tissues at different rates, the timing of the images depends on what we’re looking for as well as what the radiologist feels is diagnostically useful for each individual patient. Whole body images are generally obtained. In some patients, SPECT or additional views in different projections may be needed.
Nuclear Medicine- PREPARATION
NUCLEAR MEDICINE GLOSSARY
GAMMA CAMERA – THE HIGHLY SOPHISTICATED IMAGING DEVICE USED IN CONJUCNTION WITH COMPUTERS TO OBTAIN NUCLEAR MEDICINE SCANS.
HALF LIFE – THE AMOUNT OF TIME IT TAKES FOR A SAMPLE OF RADIOACTIVE MATERIAL TO LOSE HALF ITS RADIOACTIVITY.
HOT SPOT (OR COLD SPOT) – A TERM USED IN NUCLEAR MEDICINE TO INDICATE THE CONCENTRATION OF RADIOACTIVE UPTAKE ON AN IMAGE. A “HOT” SPOT IS AN AREA OF INCREASED UPTAKE WHEREAS A”COLD” SPOT INDICATES AN AREA OF DECREASED UPTAKE. BOTH MAY INDICATE ANABNORMALITY BUT THIS WILL VARY FOR EACH PROCEDURE. IN SOME CASES WE ONLY LOOK FOR “HOT” AREAS, IN OTHERS ONLY “COLD”.
NUCLEAR MEDICINE (DIAGNOSTIC) - THE BRANCH OF MEDICINE THAT UTILIZES RADIOACTIVE MATERIALS TO DIAGNOSE DISEASE OR ASSESS FUNCTION.
NUCLEAR MEDICINE TECHNOLOGIST- A HIGHLY TRAINED AND EDUCATED PROFESSIONAL THAT SPECIALIZES IN PERFORMING NUCLEAR MEDICINE EXAMINATIONS, INSTRUMENTATION QUALITY CONTROL AND PATIENT CARE.
NUCLEAR MEDICINE SCAN – AN IMAGING PROCEDURE PERFORMED BY A NUCLEAR MEDICINE TECHNOGOLIST. A RADIOPHARMACUETICAL OR TRACER IS ADMINISTERED FOR ALL SCANS UTILIZING A GAMMA CAMERA.
NUCLEAR MEDICINE (THERAPEUTIC) – THE BRANCH OF MEDICINE THAT UTILIZES RADIOACTIVE MATERIALS TO TREAT DISEASE.
RADIONUCLIDE-THE RADIOACTIVE PART OF THE RADIOPHARMACEUTICAL.
RADIOPHARMACEUTICAL-A RADIOACTIVE DRUG THAT IS COMPOUNDED BY THE RADIOPHARMACY TO BE USED AS A TRACER IN NUCLEAR MEDICINE STUDIES. EACH PATIENT WILL RECEIVE A “DOSE” OF A RADIOPHARMACEUTCAL THAT IS TAILORED ESPECIALLY FOR THEM, CALIBRATED OR MEASURED FOR A SPECIFIC TIME.
TECHNETIUM (99MTC) – THIS IS THE RADIONUCLIDE MOST COMMONLY USED IN NUCLEAR MEDICINE. IT IS EASILY COMPOUNDED INTO DIFFERENT RADIOPHARMACEUTICALS WHICH MAKES IT VALUABLE AS AN IMAGING AGENT. TECHNETIUM HAS A SHORT HALF-LIFE (6 HOURS) WHICH MEANS IT DECAYS QUICKLY PROVIDING A LOWER RADIATION DOSE TO THE PATIENT.
