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ARRT Board Instrumentation
Terms in this set (56)
Explain the procedure for preforming an I-131 MIBG study
-Iv injection of 3-10 mCi of I-131 MIBG
-administer over 15 seconds
-static images should be obtained @ 4,24,and 48 hours after the injection
-Take static images of the skull, chest, abdomen, and pelvis in the Anterior and Posterior positions.
-Images of the femurs should also preformed if evaluating for mets from and existing pheochromocytoma.
-All static images should be obtained for 100k counts or minimum of 20 minutes.
-SPECT images may be obtained if requested
List all quality control procedures that are required on a weekly basis
- Department wipes
- Department surveys
Discuss the function of the parathyroid gland
- The parathyroid glands control and regulate the level of calcium in the body by producing and releasing parathyroid hormone (PTH)
- Low calcium levels in the body simulate production of parathyroid hormone from the parathyroid glands and stimulate calcium release from the skeletal system, gastrointestinal tract, and kidneys.
-PTH is not stored within the parathyroid glands, but it is produced and released when simulated by low calcium.
Discuss the procedure for detection of parathyroid adenomas with nuclear medicine imaging.
2 different methods are:
*a dual isotope method using both Thallium-201 and Tech-99m pertechnetate
*serial static imaging method using Tech-99m mibi
Explain the RB-82 cardiac PET protocol.
-Rb-82 is used in conjunction with a rest/stress cardiac protocol.
-iv administration of 40-60 mCi Rb-82 is required before both rest and stress image acquisitions.
-For PET/CT a scout image should be preformed before each acquisition to ensure proper patient positioning.
-It is critical to allow clearance of the blood pool before beginning either acquisition
-For patients with normal left ventricular function, imaging may be initiated withing 70 to 90 seconds .
-For patients with diminished left ventricular function, imaging may be delayed to 110 to 130 minutes.
Explain the FDG (F-18) cardiac viability PET protocol
-Used to assess myocardial viability
-Myocardial perfusion must be assessed first
-Perfusion can be assessed using Rb-82 or N-13
-the patient must fast for a minimum of 6 hours
-Patient must get a blood sugar test (should be between 100 and 140 mg/dl for best imaging
-patient is given 10 to 15 mCi of FDG iv
-Patient should wait for 45 minutes for adequate blood pool clearance
-Scan time is 10 -30 minutes and attenuation correction should be preformed.
-Gating should be preformed because wall motion is useful when determining myocardial viability.
Explain the procedure for parathyroid imaging using Tc-99m- sestamibi
- Iv injection of 20-30 mCi of Tc-99m mibi
-Allow 10 minutes for proper circulation
-use high resolution collimator to image the parathyroid glands.
- Static image should be obtained for 600 seconds on a 256x256x16 matrix.
-position images with the thyroid at the top and the heart at the bottom of the FOV
- Take static image without marker
- Take static image with marker on sternal notch
- Wait 2 hours to allow MIBI to washout of the thyroid gland.
-Obtain a second set of images
- On delayed images any residual activity around the poles of the thyroid gland will indicate the presence of a parathyroid adenoma.
Explain the indications for an I-131 MIBG procedure
- Used to localize pheochromocytoma in patients who present with classic symptoms of the tumor or abnormal blood work indicating the presence of such a tumor.
-I-131 MIBG studies are also obtained to eval for Mets from a previously diagnosed pheochromocytoma.
-other neuroendocrine tumors such as neiroblastoma, medullary thyroid carcinoma, and merkel cell tumors can also be diagnosed or evaluated with this procedure.
Discuss the indications for preforming thyroid imaging
-Helps differentiate between benign and malignant thyroid nodules
- assesses the function of an individual nodule compared with the other parts of the thyroid gland
-for conditions such as toxic nodular goiter, imaging may be performed to assess the homogeneity of the thyroid gland
-images are also obtained to assess the residual thyroid tissue after thyroidectomy and to assess for metastasis from thyroid cancer
Discuss the procedure for iodine- 131 whole body imaging.
-Whole body imaging with iodine 131 is used to evaluate metastasis from thyroid cancer
-I 131 whole body scan can be obtained by itself or with high dose iodine ablation of thyroid cancer
-I 131 whole body scan is performed following oral administration of 1 to 4 mCi of I 131
-images are required at 48 hours and 72 hours after administration of I 131
-views acquired should include a whole body scan was static images of the neck chest abdomen and pelvis
-all static images should be acquired for no less than 600 seconds when used in conjunction with high dose steroid ablation
-identical views should be obtained 7 days after ablation was performed
Discuss the role of FDG (F-18) as cardiac PET radiotracer.
-FDG which is a glucose analog is the gold standard for assessing myocardial viability
-FDG has a half-life of 110 minutes so a cyclotron is not required on site
-FDG has the highest spatial resolution of all positron emitters due to low kinetic energy of the positron
-FDG is taken up in the myocardium via active transport and it competes with other forms of glucose in the body for transport in the myocardium
- In a fasting patient the myocardium would likely use more fatty acids than glucose
-by injecting another form of glucose the natural insulin response is for the myocardium to primarily use glucose instead of fatty acids
Explain the N-13 cardiac PET protocol
-N 13 is usually used in conjunction with a rest/ stress cardiac protocol
-IV administration of 10 to 15 mCi of N 13 is required before both rest and stress images
- N 13 should be administered slowly over 20 to 30 seconds
- it is rapidly take it up in the myocardium usually within 90 seconds -imaging should be started within 2 to 3 minutes of administration
- total scan time should ideally be from 5 to 15 minutes
-a waiting period of 90 minutes should be allowed between rest and stress to allow six half-lives of tracer decay for optimal stress imaging
- lung uptake is common in patients who smoke or have congestive heart failure there
-there may be intense liver uptake which can make the inferior wall difficult to interpret the time between injection and scan it may need to be increased
Explain the indications for preforming a parathyroid scan
-Routinely performed to identify single parathyroid adenomas multiple parathyroid adenomas or a glandular hyperplasia in patients who have a new diagnosis of hypocalcemia and elevated parathyroid hormone levels
- parathyroid scans can be helpful in shortening surgical time by accurately localizing parathyroid adenoma's before surgery
-imaging is also useful and localizing parathyroid tissue and patience with reoccurrence hyper parathyroidism after surgical intervention
Explain the dual isotope procedure for parathyroid imaging
-Begins with an IV injection of 2 to 3 MCI of thallium-201
-within 2 to 3 minutes of injection images should begin
- if using a high resolution collimator obtain static image for 600 seconds. -detector should be positioned with the thyroid gland at the top and the heart at the bottom of the field of view
-if using a pinhole collimator two views may be needed to accurately evaluate for parathyroid adenoma's
one should be obtained with the field of view centered on the upper mediation between the thyroid and the heart and the other with the thyroid In the center of the field of view
-once the thallium images have been obtained 5 to 10 mCi of tech 99M pertechnetate should be administered intravenously
-after a five minute waiting period to allow for proper circulation of tech 99M obtain identical views with identical parameters used with thallium 201
-process the images by serial subtraction of the tech 99 images from the thallium-201 images until the entire thyroid gland has been removed
List contradictions for thyroid imaging
- Iodine dye
- High iodine foods
- thyroid medications
Explain the procedure for preforming a thyroid uptake
-Evaluate the function of the thyroid gland.
-An uptake is commonly used in conjunction with thyroid imaging, but can be preformed alone if simply assessing hyperthyroidism or hypothyroidism.
-Preformed using 200 to 600 uCi of Iodine- 123 or Iodine-131.
- The iodine capsule must be counted using either an uptake probe or a pinhole collimator.
-The counts of the capsule and room BG must be recorded prior to administration of the capsules.
-Patient must also be questioned to check for contradictions before the capsules are given.
-Uptakes are usually completed at 6 and 24 hrs after administration.
-These uptakes are preformedby obtaining counts of the thyroid for 1 to 2 min and then recording the number of coutns
-A standard usually the thigh should also be counted for 1 to 2 min and the number of counts should also be recorded.
The formula is:
Thyroid counts- patient BG (Thigh)
_________________________________________ X 100% = thyroid uptake
Capsule counts- Room BG
Explain the purpose of a photomultiplier tube
-Is a light-sensitive device that usually contains one photo Kathwood in a series of 10 dynodes
-The purpose is to convert the light energy from the crystal to electrical energy and amplify the resulting pulse of electricity
-The resulting pulse height is equally proportional to the energy of the GammaRay coming into contact with the sodium Iodide Crystal
Define the CT number
-Air equals -100
-water equals 0
-soft tissue equals 30 to 60
-dense bone equals 1000
-CT number over 100 equals calcification
-Stands for a picture archiving and communication systems
- PACS illuminates the need for films thus reducing cost in space requirement for Storage of medical images
-allows for rapid retrieval of all medical images performed on a patient
-access to images that are required with multiple modalities simultaneous access to image performed at multiple sites
-PACS and RIS work simultaneously to support the entire function of the radiology department
Discuss the coincidence timing calibration preformed on PET scanners.
-Coincidence timing calibration is a critical evaluation of pet scanners that detects and corrects timing differences in the detectors of the scanner
-this is performed by placing a positron source between the Detector rings and recording the Time differences between the signals
-they should hit the detectors simultaneously if not it means there's a malfunction of the detector
Explain the procedure for evaluating gamma camera resolution
-Should be evaluated on a weekly basis in an intrinsic or extrinsic manner -a four quadrant bar phantom is required for the evaluation
- for intrinsic resolution evaluation remove the collimator and placed the bar facing directly on the Crystal
for extrinsic evaluation place the bar phantom directly on the collimator
- the acquisition parameters are the same for both acquire a static image for approximately 5000 counts on a 64 X 64 matrix
Discuss what occurs in the localization region of the characteristic curve of gas detector responses to pulse height versus voltage.
-In the ionization region the proportional increase in ion pair collection with increase voltage no longer exists
-Instead the curve flattens out and creates an area called a plateau
-there is no increase in pulse height because the applied voltage is adequate to collect all ion pairs that are produced and there is no longer a chance of recombination in the ionization region
Explain the procedure for evaluating intrinsic flood field uniformity
-Intrinsic uniformity involves the evaluation of flow field uniformly with a collimator removed from the detector
-intrinsic uniformity is obtained by using approximately 800 µCi of tech 99 pertechnatate point source in a syringe
-remove the collimator from the detector hood
-position the tech 99M point source in front of the detector at a distance approximately 6 feet from the detector
-acquire an image for approximately 15,000 counts using a 64 x 64 x 16 matrix
-The image should be in allies to ensure proper uniformity throughout the field of view
Define dead time
-dead time also known as resolving time is the interval immediately after ionizing event
-Dead time in many GM tubes can be as high as 200 µsec
Discuss how the daily sinogram check is analyzed
-The daily Sinogram should be compared to the sinogram that was performed during acceptance testing of the PET camera
-The difference between the two sinograms is expressed by a value known as the average variance which is an indicator of various detector problems
-if the average variance exceeds 2.5 then effort should be made to re-calibrate the pet camera
-If the average variance exceeds 5.0 then the manufacturer should be called the service the machine immediately
List and discuss the function of the cells continued within the myocardium
-Contractile cells cause the heart to pump
-Electrical cells=conduction of impulses throughout the heart
-Contractile cells make up the bulk of the myocardium
-Electrical cells are made of specific Excitatory and conductive fibers
Discuss the advantages of PET over SPECT in cardiac imaging
-Pet scanning of the heart provides greater spatial and Temporel resolution
-Pet imaging also exhibits greater attenuation and scatter correction Which enables better quantitative measuring
-PET allows for imaging during actual physical stress which could identify stress induced changes
Discuss the role of Quadramet (Sm-153 EDTMP) in clinical nuclear medicine
-Used to treat the pain associated with widespread metastatic lesions in the bone
-is commonly used in patients that have osteoblastic Matastatic bone lesions confirmed with the whole body bones scan
-The activity of Quadramet is 1 mCi per KG
-QuadraMet therapy does not instantly relieve the pain but may take up to seven days to do so
-In fact pain may even get worse or flare up a day or two post injection
Discuss what occurs in the continuous discharge region of the characteristic curve of gas detector responses to pulse height versus voltage.
-Voltage is once again increased in this once again causes a number of ion pairs collected to rise
- This effect may be deceptive because it is primarily due to free electrons producing avalanches on the collecting electrode not two ion pairs being collected
Continued operation in this region could cause the collecting electrodes to be damaged or destroyed
Define scatter radiation
-Is radiation that is diverted from its path due to some kind of collision
-scatter radiation may also make its way to the detector and be counted even though it is lower in energy and should be differentiated from full energy photons
-scatter radiation if excepted will increase the country and degrade image quality
Explain the uniformity procedure preformed on PET scanners daily for quality control
-Uniformity is evaluated using either a GE-68 or CS-137 source
-The radioactive source is mounted in brackets on the gantry of the pack camera and rotate around the skin field so each detector is equally exposed to the radioactive source
-if functioning properly there will be a homogeneous response from all detectors in a uniform sinogram will result
Discuss what occurs in the Geiger mueller region of the characteristic curve of gas detector responses to pulse height versus voltage.
-The increase in applied voltage causes a sharp rise in the curve
-The high voltage produces a high-quality or avalanche of ions making contact with the collecting electrode
-The high-voltage in this region causes ionized particles to ionized other particles in their parts causing the avalanche
-Radiology information systems which are computerized databases used primarily for storage manipulation and distribution of patient radiological data and images
-RIS systems commonly support patient scheduling and registration request and document scanning faxing and emailing a patient exam results and radiology workflow management
-RIS and PACS Work simultaneously
Discuss the normalization procedure preformed on PET scanners weekly for quality control.
-The procedure requires a 20 CM rod source containing 1 to 3 mCi if GE-68 Which is placed in the center of the field of view
-To ensure better accuracy in normalization long acquisitions such as 6 to 8 hours or even overnight or recommended
Explain teh procedure for evaluating center of rotation
-COR evaluation should be performed on a weekly basis always in an extruding manner using an 800 microcuries TC 99M pertechnetate point source in a syringe
-Place the points or slightly off center of the imaging table position in the detectors to the source is in the center of the field of view on both the anterior and lateral positions
-place the points source slightly off center of the imaging table position and the detectors so the source is in the center of the field of view on both the anterior and lateral positions
-acquire a 360° SPECT image for 32 frames at 10 to 15 seconds per frame on a 64 x 64 matrix
-if a dual head camera is being used this evaluation should be performed with the detectors in 90° in a 180° position
Define radiation absorption
-Is the total dissipation of radioactive energy into the absorbing material
-Is the total dissipation of radioactive energy into the absorbing material radiation that is absorbed never reaches the detector and it's not included in count rate statistics
-Radiation absorption can occur in three different sites the source itself, the media between the radioactive source of the detector, and the detector itself.
-Absorption affects the country in the same manner by reducing the number of radioactive photons reaching the detector
Describe the importance of flood field uniformity
-Refers to an imaging systems ability to produce a uniform diagnostic image
-Camera should be evaluated prior to the start of every workday a non-uniform area may show up as a hot or cold spot
-A hot spot could be read as a bone tumor where as a cold spot could be interpreted as a liver tumor
Discuss what occurs in the proportional region of the characteristic curve of gas detector responses to pulse height versus voltage .
-An increase in the number of ion pears is once again seen
-where as the voltage applied in the ionization region is sufficient to collect all ion pears the increased number of ion pears in the proportional region is due to the phenomenon called gas amplification
-The increased voltage applied through the proportional region adds energy to the ions that are being collected
-this added energy allows the ions to ionize Other particles in their path
other particles in their path
-Additional ions will also be collected
Discuss what occurs in the recombination region of the characteristic curve of gas detector responses to pulse height versus voltage .
-There is no voltage applied to the two electrodes which means there is no direction given to ion pears produced by the passing radiation
-Without applied voltage no ions are collected and no pulse is produced
-once voltage is applied some ion pears can be collected while others will recombine
-as voltage increases the collection of ion pears will increase
Discuss the Butterworth filter as it applies to image reconstruction
-It provides the best compromise between smoothness and sharpness
-The Butterworth filter is also the most versatile filter in that it allows an additional adjustment to ensure the highest quality image
-SPECT filters can be adjusted using a parameter called cut off frequency an additional parameter known as order is available with the Butterworth filter
Discuss the Parzen filter as it applies to image reconstruction
-Produces the exact opposite effect of the ramp filter
-It provides the lowest level of image resolution but also generates the least amount of noise
-If the filter is chosen for nuclear medicine image reconstruction the resulting images may appear extremely smooth even to the extent of masking lesions
-The use of this filter for SPECT reconstruction is generally counterproductive because it may mask lesions
Discuss the interactive technique for tomographic imaging reconstruction.
-Is commonly used when reconstructing SPECT images that have been corrected for attenuation
-The iterative method for reconstruction ensures the true number of counts in each pixel
Discuss the Hamming filter as it applies to image reconstruction
-Is the best filter for reconstructing SPECT studies that have a generally low number of counts
-The hamming filter is the proper choice for reconstructing images acquired with TL-201, GA-67, or bone SPECT scans
-The hamming filter smoothed out any imperfections and reduces any noise caused by lack of data
-The hamming filter permits a diagnostic quality image even if the county is excessively low
Discuss the ramp filter as it applies to image reconstruction
-The ramp filter provides the highest level of image resolution but also generates the greatest amount of noise
-Images may contain sharp areas of contrast and possibly ring artifacts
-It should be used on images that I have extremely high count rates
-The ramp filter is generally Of no use in the clinical nuclear medicine setting
Discuss the role of N-13 as a cardiac PET radiotracer
-The half-life of N-13 is 10 minutes
and to be able to use N- 13 a cyclotron Has to be on site
-Image quality with N-13 is superior because 90% of the tracer localizes in the myocardium leaving very little background in the images
-n-13 is taken up in the myocardium in a fairly homogeneous manner
The lateral wall of the left ventricle may appear slightly less perfused. this is an artifact that occurs even in healthy patients
-Gated wall motion analysis should help differentiate artifact from a true perfusion defect
Discuss the role of Rb-82 as a cardiac PET radiotracer
-Rb-82 Is the most popular radiotracer for cardiac pet imaging
- Rb- 82 half-life is 75 seconds but an on-site cyclotron is not required like it it is with N-13
-Rb-82 Can be obtained from a generator similar to that of Tc-99m
-Rb-82 Is a potassium analog so it is taken up in the myocardium via active transport
Define Center of rotation
-A term associated with SPECT imaging
-A center of rotation evaluation is a quality control procedure to assess the mechanical alignment of the collimator which enable the system to reconstruct from a center point during a circular SPECT acquisition
-This evaluation is critical to SPECT imaging because the COR actually falls on a line that is fixed in space
-The line is parallel to the imaging table and perpendicular to the plane of the gantry
Define gamma camera resolution
-Is the ability of a piece of equipment to diagnose or resolve lesions on a clinical nuclear medicine image
-Resolution depends on the detector, the collimator, and all the camera electronics working as a unit to provide an accurate diagnostic clinical image
-In nuclear medicine as the distance of the patient from the detector increases resolution decreases
-The patient should be positioned as closest possible to the detector head
Explain the procedure for evaluating extrinsic flood field uniformity
-Flood field uniformity is most commonly evaluated in an extrinsic manner with the collimator attached to the detector
-A Co-57 sheet source is required to assess extrinsic uniformity
-Place the CO-57 sheet source directly onto a low energy collimator
-acquire an image for approximately 15,000 counts using a 64 x 64 x 16 matrix
-Once the image is obtained it should be analyzed to ensure proper uniformity throughout the field of view
Discuss what occurs in the non proportional region of the characteristic curve of gas detector responses to pulse height versus voltage
-Voltage is once again increased in the relationship between applied voltage and collected ion pears is no longer proportional
-Instead the pulse height is related more to the increase in applied voltage and less to the collected Ion pairs
Discuss filtered back projection and its role in image reconstruction
-Is the most commonly used technique for image reconstruction
-The use of filters is an easy and effective way to remove the star pattern around each photon
-Filtered back projection is the most effective technique to reconstruct tomographic acquisitions because the resulting images are enhanced
List and describe the layers of the heart
-Epicardium is the outer thin layer
-Myocardium is the muscular middle layer that causes the pumping action of ventricles
-Myocardium is the muscular middle layer that causes the pumping action of ventricles
-Endocardium is the inner most layer and responsible for overall cardiac function
describe the function of order as it applies to butterworth filters
-Is the only filter in nuclear medicine that can be further modified
-This is accomplished with the parameter of order which modify is the Butterworth filter by allowing the slope of filter function to be altered
-This type of alteration allows for the greatest compromise between the smoothness of an image in the sharpness of the edge of the image
-The perimeter of order allows the nuclear medicine tech to provide the highest quality images to ensure accurate diagnosis
Describe the cutoff frequency as it applies to SPECT processing filters
-Decreased cut off frequency=increase scatter
-Decreased cut off = decreased resolution which equals a smoother image
-Decreased cut off= decreased resolution which equals a smoother image
-Increased cut off= greater image resolution
Discuss clinical indications for a cardiac PET scan
-May be performed if a patient has previously had a suboptimal clinically inadequate cardiac SPECT study
-If a patient has a large body habitus that makes it difficult to obtain optimal SPECT images PET with attenuation correction can reduce the likelihood of a false positive study
-Evaluation of patients suspected of having multi vessel coronary disease is improved with PET scanning because myocardial perfusion can be precisely quantified in milliliters per minute per gram of tissue
Discuss the role of attenuation correction in cardiac PET imaging
-Attenuation correction is crucial in pet imaging
-The effects of attenuation are more than evident with pet then with SPECT because the 511 KEV positrons are constantly being attenuated during their path between the two detectors
-The attenuation path is variable
-Therefore the algorithms used for attenuation correction during PET imaging are much more accurate than those used with SPECT imaging
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