Quality Control Procedures for a Dose Calibrator

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• Quality Control Procedures for a Dose Calibrator

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(No Transcript)
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• The quality control program for a Dose Calibrator
  consists of a series of procedures that measures
  its
• Constancy
• Linearity
• Geometry Dependence
• Accuracy

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• CONSTANCY TEST
• Constancy means reproducibility in measuring a
  constant source over a long period of time.
• Assay at least one relatively long-lived source
  such as Cs-137, Co-60, or Co-57 using a
  reproducible geometry each day before using the
  calibrator.
• Use the following procedure
• Assay each reference source, using the
  appropriate dose calibrator (i.e., use the Cs-137
  setting to assay Cs-137)
• Measure background at the same setting, and
  subtract or confirm the proper operation of the
  automatic background subtract circuit if it is
  used.

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• For each source used, either plot on graph paper
  or log in a book the background level for each
  setting checked and the net activity of each
  constancy source.
• Using one of the sources, repeat the above
  procedure for all commonly used radioisotope
  settings. Plot or log in the results.
• Establish an action level or tolerance for each
  recorded measurements at which the individual
  performing the test will automatically notify the
  chief technician or authorized user of a
  suspected malfunction of the calibrator. These
  action levels will be written in the log book or
  posted on the calibrator. The regulation requires
  repair or replacement if the error exceeds 10
  percent.

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LINEARITY TEST

• Linearity means that the calibrator is able to
  indicate the correct activity over the entire
  range of use of that calibrator.
• This test will be done using a vial or syringe of
  Tc-99m whose initial activity is at least as
  large as the maximum activity normally assayed in
  a prepared radiopharmaceutical kit, in a unit
  dosage syringe, or in a radiopharmaceutical
  therapy dose, whichever is largest.
• The test shall continue until the activity
  contained in the vial or syringe is smallest
  activity assayed, but greater than 10
  microcuries.
• Linearity test is done at installation and at
  least every three months. Repair, replace or a
  correction factor is done if the result is
  outside plus or minus 10 percent.

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• Decay Method
• Assay the Tc-99m syringe or vial in the dose
  calibrator, and subtract background to obtain the
  net activity in millicuries. Record the date,
  time to the nearest minute, and net activity.
  This first assay should be done in the morning at
  a regular time, for example, 800 a.m.
• If starting at 800a.m., repeat the assay at 200
  p.m. Continue on subsequent days until the
  assayed activity is less than the minimum
  activity normally assayed. For dose calibrators
  with a range switch, select the range normally
  used for the measurement.
• Convert the time and date information recorded
  for each assay to hours elapsed since the first
  assay.

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• On a sheet of semi-log graph paper, label the
  logarithmic vertical axis in millicuries and
  label the linear horizontal axis in hours
  elapsed. At the top graph, note the date and the
  manufacturer, model number, and serial number of
  the dose calibrator. Plot the data.
• Draw a best fit straight line through the data
  points. For the point farthest from the line,
  calculate its deviation from the value on the
  line.
• A observed A line deviation
• A line
• If the worst deviation is more than plus or minus
  0.10, the dose calibrator should be repaired or
  adjusted. If this cannot be done, it will be
  necessary to make a correction table or graph
  that will allow you to convert from activity
  indicated by the dose calibrator to true
  activity
• Put a sticker on the dose calibrator that says
  when the next linearity test is due.

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• Shield Method
• For initial calibration or reinstallation of the
  dose calibrator the decay method will be used to
  determine linearity and to establish calibration
  factors for shield methods.
• The Calicheck device will be used for doing
  linearity test of the dose calibrator. These
  procedures must be in writing and available for
  review by the department.
• The Lineator device will be used for doing
  linearity test of the dose calibrator. These
  procedures must be in writing and available for
  review by the department.
• A set of sleeves of various thickness will be
  used to test for linearity other that the
  Calicheck or Lineator device. The sleeves will
  be calibrated using the following procedure.

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• Calibration of the Sleeves
• Begin the linearity test as described in the
  above decay method. After making the first assay,
  the sleeves will be calibrated as follows. Steps
  B D below must be completed within six minutes.
• Put the base and sleeve one in the dose
  calibrator with the vial. Record the sleeve
  number and indicated activity.
• Remove the sleeve one and put in sleeve two.
  Record the sleeve number and indicated activity.
• Continue for all sleeves.
• Complete the decay method linearity test steps B
  G above.
• From the graph made in step D of the decay
  method, find the decay time associated with
  activity indicated with sleeve one in place. This
  is the equivalent decay time for sleeve 1.
  Record that time with the data recorded in step
  B.
• Find the decay time associated with the activity
  indicated with sleeve 2 in place. This is the
  equivalent decay time for sleeve 2. Record that
  time with the data recorded in step C.

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• Continue for all sleeves.
• The table of sleeve numbers and equivalent decay
  times constitutes the calibration of the sleeve
  set. The sleeve set may now be used to test dose
  calibrators for linearity.
• Calibration of the Dose Calibrator
• Assay the Tc-99m syringe or vial in the dose
  calibrator, and subtract background to obtain the
  new activity in millicuries. Record the net
  activity.
• Steps C E below must be completed within six
  minutes.
• Put the base and sleeve 1 in the dose calibrator
  with the vial. Record the sleeve number and
  indicated activity.
• Remove sleeve one and put it in sleeve two.
  Record the sleeves number and indicated activity.
• Continue for all sleeves.

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• On a sheet of semi-log graph paper, label the
  logarithmic vertical axis in millicuries, and
  label the linear horizontal axis in hours
  elapsed. At the top of the graph, note the date
  and the model number and serial number of the
  dose calibrator.
• Plot the data using the equivalent decay time
  associated with each sleeve.
• Draw a best fit straight line through the data
  points. For the point farthest from the line,
  calculate its deviation from the value on the
  line.
• A observed A line deviation
• A line
• If the worst deviation is more than plus or minus
  0.10, the dose calibrator should be repaired or
  adjusted. If this cannot be done, it will be
  necessary to make a correction table or graph
  that will allow a conversion from activity
  indicated by the dose calibrator to true
  activity.
• Place a sticker on the dose calibrator that says
  when the next linearity test is due.

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• GEOMETRY DEPENDENCE TEST
• Geometry dependence means that the indicated
  activity does not change with volume or
  configuration.
• This test will be done using a syringe that is
  normally used for injection.
• The following test assumes injections are done
  with 3-cc plastic syringes and that
  radiopharmaceutical kits are made in 30-cc glass
  vials.
• If volumes of syringes and vials differ from
  above, then the procedures will be changed so
  that the syringes and vials are tested throughout
  the range of volumes commonly used.
• Geometry dependence is done at installation.
  Repair, replace or correction factor is done if
  outside plus or minus 10 percent.

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• In a small beaker or vial, mix 2 cc of a solution
  of Tc-99m with an activity concentration between
  1 and 10 mCi/ml. Set out a second small beaker or
  vial with non-radioactive saline or tap water.
• Draw 0.5 cc of the Tc-99m solution into the
  syringe and assay it. Document the volume,
  millicuries and record instrument setting.
• Remove the syringe from the calibrator, draw an
  additional 0.5 cc of non-radioactive saline or
  tap water, and assay again. Record the volume and
  millicuries indicated.

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• Repeat the process until a 2.0-cc volume has been
  assayed.
• Select as a standard the volume closest to that
  normally used for injections. For all the other
  volumes, divide the standard millicuries by the
  millicuries indicated for each volume. The
  quotient is a volume correction factor. The data
  will be graphed with horizontal 10 percent error
  lines drawn above and below the chose standard
  volume.
• If any correction factor are greater than 1.10 or
  less than 0.90, or if any data points lie outside
  the 10 percent error lines, it will be necessary
  to make a correction table or graph that will
  allow conversion from indicated activity to
  true activity. If it is necessary, label the
  table or graph syringe geometry dependence, and
  note the date of the test and the model number
  and serial number of the calibrator.

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ACCURACY TEST

• Accuracy means that, for a given calibrated
  reference source, the indicated millicuries value
  is equal to the millicuries value determined by
  the National Institute of Standards and
  Technology (NIST) or by the supplier who has
  compared that source to a source that was
  calibrated by the NIST.
• At least two sources with different principal
  photon energies (such as Co-57, Co-60, or Cs-137)
  will be used.
• One source will have principal photon energy
  between 100 keV and 500 keV.
• If a Ra-226 source is used, it will be at least
  10 microcuries other sources will be at least 50
  microcuries.
• Use at least one reference source with an
  activity in the range of activities normally
  assayed.
• Accuracy test is done at installation and
  annually thereafter. Repair or replace if outside
  plus or minus 10 percent.

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• Assay a calibrated reference source at the
  appropriate setting (i.e., use the Co-57 setting
  to assay Co-57), and then remove the source and
  measure background. Subtract background from the
  indicated activity to obtain the net activity.
  Record this measurement. Repeat for a total of
  three determinations.
• Average the three determinations. The average
  value should be within 10 percent of the
  certified activity of the reference source,
  mathematically corrected for decay.
• Repeat the procedure for other calibrated
  reference sources.
• If the average value does not agree, within 10
  percent, with the certified value of the
  reference source, the dose calibrator must be
  repaired or replaced.

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• QUESTIONS
• List the series of Quality Control Procedures for
  a Dose Calibrator.
• Answer Accuracy, Linearity, Geometric
  Dependence, Constancy
• When would an Accuracy Test Procedure be done ?
• Answer At installation and annually thereafter.
• When would a Linearity Test Procedure be done ?
• Answer At installation and at least every three
  months.
• When would a Geometric Dependence Test Procedure
  be done ?
• Answer At installation and after it is
  repaired.
• When would a Constancy Test Procedure be done ?
• Answer Every day

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Quality Control

• Quality control is the term used to refer to the
  routine assessment of instrument performance in
  nuclear medicine
• Quality control procedures should be used to
  establish a baseline level of performance
• Action levels are required by the Society of
  Nuclear Medicine

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Scintillation Camera Quality Control

• The performance of a scintillation camera system
  must be assessed each day to assure the
  acquisition of diagnostically reliable images
• The most useful data to determine acceptability
  of camera performance reflect the parameters of
  field uniformity, spatial resolution, and
  linearity

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Quality Control Tests

• Uniformity
• The ability of a camera to depict a uniform
  distribution of activity as uniform
• Spatial resolution
• A transmission phantom consists of some pattern
  in lead, the alternating patterns produce closely
  spaced areas of differing activity levels
• Linearity
• The ability to reproduce a linear activity source
  as linear in the image

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Approaches to Camera Quality Control

• Three major factors that are essential to a good
  quality control program
• Which radionuclides to use
• Whether to test intrinsically, extrinsically, or
  a combination of the two
• Which phantoms to use

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Intrinsic versus Extrinsic testing

• Intrinsic testing, measuring the performance of
  the system without the collimator
• The advantage is that a uniform radiation field
  is obtained using a small source, the
  disadvantage is that the person performing the
  test will receive radiation

• Extrinsic testing, evaluation of the entire
  system including the collimator
• A uniform radionuclide distribution is placed on
  the collimator, a sheet source or a flood phantom

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Routine Camera Quality Control Procedures

• Photopeak settings, the correct energy window for
  the radionuclide being used must be selected
• Orientation controls, must remain constant to
  ensure the same detector area is always recorded
• Intensity and image size, have a significant
  impact on interpretation, so the same parameters
  should be used

• Uniformity, using either an extrinsic or
  intrinsic method
• Linearity and resolution should be checked weekly
• Collimators should be checked for faults of
  damage

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Signalto Noise Ratio

• By
• Chinyere Millington

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Signal -to- Noise Ratio

• In general, the quality of an image can be
  described by its signal-to-noise ratio (SNR).
• The SNR directly affects the diagnostic and
  quantitative accuracy.
• It describes the relative strength of the desired
  information and the noise in an image.

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Signal -to- Noise Ratio

• For example, the only was lesions can be detected
  is if their activity is sufficiently different
  from that of the surrounding tissue.
• The greater the contrast between the lesions and
  the surrounding tissue, the greater the signal.

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Signal -to- Noise Ratio

• The noise in an image is as a result of
  statistical fluctuation within lesion and
  surrounding tissue.
• If there are few counts in a image, the
  fluctuation will be large.
• In this case, someone viewing this image would
  not be able to recognize the lesions as being
  different from the rest of the tissue.

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Signal -to- Noise Ratio

• To achieve a high SNR, high resolution and high
  sensitivity are required.
• The ratio can be increased by either increasing
  contrast or decreasing noise.
• A technologist will find the concept of SNR very
  helpful in optimizing acquisitions and processing
  protocols.

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Signal -to- Noise Ratio

• Since the goal is to maximize an images SNR, an
  optimum choice of collimator should be used which
  can preserve contrast, while providing
  sufficiently sensitivity to keep image noise to
  an acceptable low level.
• An optimum reconstruction filter may also be used
  in order to improve the SNR.

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Signal -to- Noise Ratio

• Speaker Notes
• A major goal of nuclear medicine imaging
  equipment is to maximize the SNR in an image.
• The response of the imaging system to a point
  source of activity can indicate the ability of
  the system to perceive signal.
• The ability to perceive hot spots from background
  can be used to convey if there is good image
  quality.
• By increasing either the contrast (through
  improved spatial resolution) or decreasing noise
  (through increased sensitivity), the SNR can be
  increased.
• Usually the choice that maximizes SNR falls
  between the highest resolution choice and the
  highest sensitivity choice.

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Questions

• True / False
• The SNR has little affect on diagnostic and
  quantitative accuracy.
• Answer false (directly affects
  accuracy)
• The ---------- the contrast between the lesions
  and the surrounding tissue, the greater the
  ---------.
• Answer greater, signal
• List two things which are required to achieve
  high SNR.
• Answer high resolution, high
  sensitivity
• True/ False
• The less counts in an image, the larger the
  fluctuation within body tissue, therefore the
  better the image quality.
• Answer false (if fluctuation is
  large, will not be able to recognize difference
  between lesions and surrounding tissue )
• State two ways in which a technologist can
  maximize an images SNR.
• Answer by choosing an optimum
  collimator and reconstruction filter.

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Survey Instruments

• The interpretation of the studies performed in
  nuclear medicine are done assuming that all the
  systems used are reliable and accurate

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Quality Control

• Quality control sometimes called QC, is the term
  used to refer to the routine assessment of
  instruments performance in nuclear medicine. It
  is very important.
• Once acceptance tests are completed and it is
  determined that the camera is satisfactorily
  operating and meets the vendors specifications.
• Quality control procedures should be used to
  establish a baseline level of performance
• Quality control procedures are then used each
  day to monitor the continued performance of the
  instrument

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Survey Meter

• Two types of survey instruments are commonly
  used
• The cutie-pie, it has an ionization chamber for
  areas of high levels of x-rays or gamma-rays
• The Geiger-Mueller counter is used for lower
  levels of radiation because of its higher
  sensitivity
• They both require an annual calibration and a
  daily constancy testing with long lived
  radionuclide standards

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Accuracy

• Survey instruments are calibrated before first
  use, annually and after repair
• Calibration is performed at two different
  operating points of the instruments scale, 1/3
  and 2/3 of the full scale
• The standard used must be traceable within 5
  accuracy to the NIST, (National Institute of
  Standards and Technology)
• Many departments send their instruments out for
  calibration because they do not wish to keep a
  standard source on hand.

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Accuracy

• Differences
• Ionization chambers respond in proportion to the
  total energy deposited in the detector, and it
  can be related to exposure rate, no matter what
  the energy of the incoming photon
• Geiger-Mueller detectors produces pulses with
  sizes that are independent of energy deposited.
  Count rate may only be related to exposure rate
  if the energy of the radiation is known. This can
  be done if the photon energy used to calibrate
  the detector is the same as the source measured

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Constancy

• A reference with a long half life must be used to
  check the constancy of the survey meter
  performance
• Initial measurement of the source (CPM) or
  exposure rate (mR/hr) is made at time of
  calibration and should be noted on the instrument
• The source is checked with the same source each
  day the instrument is used, after battery change
  and maintenance
• If the exposure rate or cpm is not within 10 of
  expected results, it should be recalibrated

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Dose Calibrator Quality Control

• The accuracy of the dose of radiopharmaceutical
  given to the patient depends on the performance
  of the dose calibrator
• Tests performed
• Accuracy
• Constancy
• Linearity
• Geometric calibration

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Accuracy

• The instrument accuracy test is performed after
  installation and annually after that.
• Accuracy is tested with at least two sealed
  reference standards whose activity is traceable
  to the NIST.
• Several radionuclide such as Co 57, Cs 137 and Ba
  133, may be used
• Activity should be between 50 µCi and 200 µCi or
  more
• At least one of the sources must have a principal
  photon energy between 100 keV and 500 keV

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Constancy

• Is checked each day the instrument is used
• After accuracy of the dose calibrator has been
  determined, the constancy of the performance is
  monitored by daily testing with a long lived
  standard, preferably Cs 137 and a control chart
  is established
• The activity level of the standard is calculated
  using the proper decay schedule and plotted in
  semi-logarithmic paper.
• Points are connected with a straight line which
  indicates the decay of the standard, to other
  lines are drown indicating the tolerance level
  that should not exceed 10

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Linearity

• Is measured at installation and quarterly there
  after.
• Dose calibrator must function linearly over the
  high range doses and 30 µCi
• Linearity can be tested by the use of Tc99m with
  a half life of 6.01 hrs. we measure its activity
  twice a day and plot the readings on a chart, it
  is a slow procedure.
• Other method that is faster uses a set of
  calibrated lead attenuation sleeves to asses
  changes in linearity

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Geometric Calibration

• After installation, if a change is made in the
  type of vial or syringe used in
  radiopharmaceutical processing and after repair.
• To measure the effect of changing the volume of
  liquid within a vial a 30ml vial containing a
  1mCi of Tc99m in a volume of 1 ml is used
• This is assayed, and de volume is increased with
  water in steps of 1, 4, 8, 10, 15, 20, and 25 ml,
  The net activity of each volume is determined by
  subtracting the background
• One of the volumes should be selected as standard
  and the correction factor for each of the other
  volumes can be calculated
• One can calculate the true activity of the sample
  by taking the correction factor determined for
  that volume times the measured activity of the
  sample

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• Questions
• Quality control is sometimes called?
• QC
• At what level of the full scale is calibration
  performed?
• 1/3 and 2/3
• At what level of error should an instrument be
  sent for recalibration?
• 9.99 10.01 11 10
• How often should linearity test be performed?
• After installation and quarterly thereafter
• When should constancy check be performed?
• Everyday before use

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NEMA STANDARDS AND THEIR APPLICATION TO NUCLEAR
MEDICINE
Fernando Santiago
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What Is NEMA?

• NEMA, was born on Sept.1, 1926 by the merger of
  the
• Electric Power Club and the Associated
  Manufacturers of Electrical Supplies. It
  provides a forum for the standardization of
  electrical equipment, enabling consumers to
  select from a range of safe, effective, and
  compatible electrical products.
• NEMA publishes over 500 standards and offers them
  for sale through Global Engineering, along with
  certain standards originally developed as
  American National Standards Institute (ANSI) or
  International Electrotechnical Commission (IEC)
  standards.
• Click On This Picture To Learn More
• About the History of NEMA.

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What is a NEMA Standard?

• Each NEMA standard is identified by number and
  date and there are five basic steps to creating a
  new standard. They are
• 1) Project initiation
• 2) Developing the draft
• 3) Balloting (gathering comments)
• 4) Codes and Standards Committee approval
• 5) Editing and Publication

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An Example of a NEMA Standard?
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NEMA and NUCLEAR MEDICINE
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(No Transcript)
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Dicom tries to standarize images in the manner
in which they are taken, stored, converted
into other formats and how they are shared or
how they are transmitted between different
media.
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• The DICOM Standard facilitates interoperability
  of medical imaging equipment by specifying
• A set of protocols to be followed by devices
  claiming conformance to the Standard.
• The syntax and semantics of commands and
  associated information which can be exchanged
  using these protocols.
• The information that must be supplied with an
  implementation to which conformance to the
  Standard is claimed.

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• The DICOM Standard does not specify
• The implementation details of any features of
  the Standard on a device claiming conformance
• The overall set of features and functions to be
  expected from a system implemented by integrating
  a group of devices each claiming DICOM
  conformance.
• A testing validation type of procedure to assess
  an implementation's conformance to the Standard.

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THE END
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QUALITY CONTROL REQUIREMENTS FOR NON IMAGING
SCINTILLATION DETECTORS

• By Yasnhai Diaz

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Non imaging scintillation detectors

• are used for sample counting, their reliable
  performance is essential for accurate results in
  a variety of in vivo and in vitro studies.

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Calibration

• Quality control of detectors usually involves
  calibration in which the pulse height units and
  energy is determined by selection of a narrow
  width(10 pulse height units).
• The pulse height spectrum is obtain for a long-
  lived radionuclide( Cs 137).
• The QC test requires that the source be
  positioned in the center of the detector.

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Calibration (cont..)

• The voltage or gain setting the yields the
  maximum or peak count must be recorder in the
  daily calibration log.
• Background counts accumulated are recorded as
  well.
• This procedure must be perform at installation
  and annually thereafter.

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Reproducitibility

• The ability of the instrument to reproducibly and
  reliably record and display events detected can
  be assessed by performing standard statistical
  fits of repetitive sample counts obtained using a
  radioactive source.
• The most prevalent statistical models used are
  the chi-square test.

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Reproducitibility (cont..)

• It is sufficient to perform this test initially
  when the program begun or when a new instrument
  is placed in use.
• The data should be also recorded and used for
  comparison at least twice per year and whenever
  the instrument is suspected of malfunctioning.

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Questions

• T/F
• Scintillation detectors are used for sample
  counting, their reliable performance is essential
  for accurate results in a variety of in vivo and
  in vitro studies.
• TRUE
• 2. The QC test requires that the source be
  positioned in the center of the detector.
• TRUE

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Questions

• 3. Calibration must be perform at installation
  and annually thereafter.
• TRUE
• 4. Background counts does not accumulate and
  does not need to be recorded in a log book.
• FALSE
• 5.Reproducibility must to perform initially when
  the program begun or when a new instrument is
  placed in use.
• TRUE