What is scintigraphy? The process of obtaining an image or series of sequential images of the distribution of a radionuclide in tissues, organs, or

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Barrie Dean
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2 Let's remind... What is nuclear medicine? Nuclear medicine can be broadly divided into two branches "in vitro" and "in vivo" procedures. There are numerous radioisotopic "in vitro" procedures for genotyping and molecular profiling applicable to clinical molecular biology.

3 The majority of nuclear medicine procedures are "in vivo" non-invasive procedures. After administration of the radiopharmaceutical typically by intravenous route (sometimes locally) to a patient, its distribution and localization provides functional or metabolic information. This helps doctors to make critical decisions based on objective information about the status and function of a particular organ or disease. The data is depicted with the aide of imaging systems called gamma-cameras (be they planar or SPECT systems) and transformed into images which allow visual determination and staging of the disease. One of the fastest growing techniques is positron emission tomography (PET) that requires special instrumentations called PET tomographs. This technique allows clinicians to track organ function at a molecular level, therefore revealing intricate health changes earlier in individual patients than other diagnostic methods.

4 What is scintigraphy? The process of obtaining an image or series of sequential images of the distribution of a radionuclide in tissues, organs, or body systems using a scintillation gamma camera,e.g. hepatic scintigraphy, renal scintigraphy etc. Also known as radionuclide scintigraphy.

5 Departments of Nuclear Medicine major equipment: activity meters, monitoring equipment, probes, scanners, gamma cameras, SPECT(Single photon emission computed tomography ) and PET (Positron emission tomography).

6 RADIATION DETECTORS As a detector of ionizing radiation any substance may be used that produces a measurable signal as a result of energy deposition in the material. The signal can be electrical charge, light, chemically changed molecules, etc. Some materials will emit the signal during the exposure to ionizing radiation, others can retain the changes and be measured a long time after the exposure. According to their uses detectors for ionizing radiation are divided into counters, dosimeters and spectrometers.

7 DETECTORS USED FOR RADIOACTIVITY MEASUREMENT

8 Gas-filled detectors Activity meter Radioactive sample (placed inside the meter) emits radiation. It can ionize some of the gas molecules in the tube. In the ionization process an ion-pair will be produced consisting of a negative electron and a positive atom (ion). If an electric field is applied between two electrodes then the electrons will move towards the positive electrode and the positive ions towards the negative electrode. A current will appear in the outer circuit which is proportional to the number of ion pairs produced per second. A scheme of the meter Photo

Depending on the strength of the electric field (high voltage) and the design of the detector the properties of the gas detector will be different. Usually a distinction is made between the: 1.

9 Depending on the strength of the electric field (high voltage) and the design of the detector the properties of the gas detector will be different. Usually a distinction is made between the: 1. ionization chamber 2. proportional counter 3. Geiger-Müller counter (GM-counter). The ionization chamber can be used as a activity meter. The proportional counter can be used as a spectrometer while the GM-counter is used as a survey meter.

10 ACTIVITY METER DOSE CALIBRATOR

11 ACTIVITY METER Well-shaped ionization chamber Proportionality between the number of photons emitted and the ionization current SC97

12 ACTIVITY METER The response of the detector will depend on: Radionuclide (energy and abundance of photons). Geometry of the detector. Geometry of the source. The condition of the instrument (QC).

13 GEOMETRIC EFFICIENCY The quotient: number of photons reaching the detector over the number of photons emitted from the sample Increasing geometric efficiency

14 QUALITY CONTROL OF ACTIVITY METER (WHAT SHOULD BE DONE AND WHO SHOULD DO IT) This is a suggestion of who is going to do what and when. It depends on the instrument and the people available. Daily Monthly Yearly Zero adjust T T P Background T T P Precision T P Linearity P Electrical safety P P: physicist T: technician

15 SEALED SOURCES FOR CALIBRATION OF ACTIVITY METERS Long half-life Range of photon energies Range of activities Calibrated within 5% Co57 (cobalt), Ba133 (barium) Cs137 (caesium),

16 Sealed sources for calibration of activity meters Radionuclide Photon energy (kev) Half-life Activity (MBq) Co d 185 Ba , y 9.3 Cs y 7.4 Other...

17 GM-counter A counter is a device that will only count the number of particles and photons interacting with the detector. It will not provide information about the type and energy of the radiation. This type of detector is generally used as a survey meter to determine if radiation is present or not and to check for contamination of radionuclides.

18 DIFFERENT TYPES OF G-M counters Purpose: 1. determine if radiation is present or not (survey meter ) 2. check for contamination of radionuclides 3. measurement of radiation dose rate

19 What is a gamma camera? An imaging apparatus used to visualize the distribution of radionuclides within the body. Siemens Used to measure the spatial and temporal distribution of a radiopharmaceutical

20 GAMMA CAMERA Position X Position Y Energy Z PM-tubes Detector Collimator

This property is used in scintillations detectors which are commonly used in medical applications.

21 For PET detectors LSO PbWO4 Luminescence detectors Upon deexcitation some organic molecules and inorganic crystals can emit visible light. This phenomenon is called radioluminescence. This property is used in scintillations detectors which are commonly used in medical applications. The gamma camera detector is a scintillation detector made of a crystal of sodium iodide activated with thallium (NaI(Tl)). The sodium iodide crystal is mostly used to detect gamma-radiation.

22 Crystal production process

Associated electronic circuitry determines the x, y coordinates of each scintillation event, the outputs of all the tubes being summed to provide a z

23 Radiation emanating from the patient is detected by a single, large, NaI (Tl) scintillation crystal. An array of (37, 61 or 91) photomultiplier tubes detects the light quanta emitted by the crystal and converts their energies into electrical pulses. Associated electronic circuitry determines the x, y coordinates of each scintillation event, the outputs of all the tubes being summed to provide a z pulse, the amplitude of which corresponds to the total energy of the scintillation event. The gamma camera is connected to a dedicated computer, radioactive distributions being displayed on a monitor.

24 PM-TUBES

25 PULSE HEIGHT ANALYZER UL Pulse height (V) For example: Tc99m ±10% window Peak energy140 Kev UL-154 kev LL- 126 kev LL Time The pulse height analyzer allows only pulses of a certain height (energy) to be counted. counted not counted

26 PULSE-HEIGHT DISTRIBUTION NAI(TL)

27 GAMMA CAMERA DATA ACQUISITION Static Dynamic ECG-gated Wholebody scanning Tomography ECG-gated tomography

28 PLANAR AND SPECT IMAGING

29 The ECG gated acquisition is a type of dynamic acquisition. The RR-interval is divided into a certain number of frames (16 to 32) where each frame then represents a certain phase (t) of the heart cycle. Each time the R-peak in the ECG is detected the collection of data starts in frame 1 during time t, then in frame 2 during time t and so on. The total acquisition time is generally about 10 min so the whole study represents several hundred heart cycles. ECG-GATED ACQUISITION R Interval n Image n

30 ECG-GATED BLOODPOOL SCINTIGRAPHY Why such a study? Example of 16 frames of an ECG gated acquisition in LAO projection. The first image (upper left) is the end diastolic image and the sixth image (2nd row) is the end systolic image. This is the method of ejection fraction measurement

31 LEFT VENTRICLE TIME-ACTIVITY CURVE EjectEjection Fraction ~58 %

32 WHOLE BODY SCANNING Either the camera or the examination table moves

35 TOMOGRAPHIC ACQUISITION

36 TOMOGRAPHIC PLANES Gamma camera tomography is imaging of a volume where slices can be displayed in any plane

FACTORS AFFECTING IMAGE FORMATION Distribution of radiopharmaceutical Collimator selection and sensitivity Spatial resolution Energy

37 FACTORS AFFECTING IMAGE FORMATION Distribution of radiopharmaceutical Collimator selection and sensitivity Spatial resolution Energy resolution Uniformity Count rate performance Spatial positioning at different energies Center of rotation Scattered radiation Attenuation Noise

38 SPATIAL RESOLUTION Sum of intrinsic resolution and the collimator resolution Intrinsic resolution depends on the positioning of the scintillation events (detector thickness, number of PM-tubes, photon energy) Collimator resolution depends on the collimator geometry (size, shape and length of the holes)

39 SPATIAL RESOLUTION Object point Image stain Intensity IMAGING WITH GAMMA CAMERA IS NOT PERFECT!

40 SPATIAL RESOLUTION - DISTANCE RESOLUTION DEPENDS ON THE DISTANCE Optimal Large distance

41 NON-UNIFORMITY The image to the right is aquired after cleaning of the collimator (Contamination of collimator)

42 NON UNIFORMITY RING ARTIFACTS The lower image is the absolute difference between the upper two images. It clearly shows the ring artifacts. Good uniformity Bad uniformity Difference

NON-UNIFORMITY The images in the lower row are acquired using a collimator with 50% lower sensitivity in an 1cm 3 area in the center of the field of view.

43 NON-UNIFORMITY The images in the lower row are acquired using a collimator with 50% lower sensitivity in an 1cm 3 area in the center of the field of view. The images in the upper row are from the same patient acquired with a good collimator. It is important to point out the risk of false positive results if the camera is not working perfectly, Defect collimator

44 SCATTERED RADIATION Remember that compton scattering is the dominating process in the attenuation of photons in soft tissue. Scattered photon photon electron

45 THE AMOUNT OF SCATTERED PHOTONS REGISTERED depends on: Patient size Energy resolution of the gammacamera Window setting

46 In the case of a big patient some of the full energy photons that should have reached the gamma camera will be scattered in the patient. The relation scattered/full energy photons will increase with the volume of the patient. PATIENT SIZE

47 ATTENUATION CORRECTION

48 ATTENUATION CORRECTION Transmission measurements CT

49 Count density NOISE

50 VARIETY OF GAMMA CAMERAS scanners Division with regard for number of 1. One head rotating gamma camera 2. One head gamma camera 3. Two head rotating gamma camera 4. Three head gamma camera P. Zorga

51 Two head gamma camera for cardio studies

53 SKYLight Above the Crowd & Beyond the Possible A revolution in HOW we do nuclear medicine. A revolution in WHAT we do in nuclear medicine.

54 Skylight Gamma Camera Philips Skylight gamma camera showing pre-program motion From Park to Patient Loading

55 Skylight Gamma Camera Philips Skylight gamma camera showing pre-program motion From Park to Patient Loading

INTRODUCING THE MOST COMPLETE VARIABLE ANGLE

Gantry infinite flexibility advanced imaging

56 INTRODUCING THE MOST COMPLETE VARIABLE ANGLE FAMILY IN NUCLEAR MEDICINE... Ring Gantry economical solution advanced imaging small footprint Vertex V60 Forte No Gantry infinite flexibility advanced imaging expansion beyond NM Open Gantry SKYLight true openness advanced imaging bed imaging

smallest & largest detector radius minimum: 0, maximum: room width unlimited upright imaging extreme

57 GANTRY IS FASTENED INTO THE CEILING SKYLIGHT HOW IS THIS SYSTEM UNIQUE? Infinite Flexibility Free-Dimensional positioning image in any position- trauma image on any bed smallest & largest detector radius minimum: 0, maximum: room width unlimited upright imaging extreme high & low detector heights no limits on patient size excellent access & openness lymphoscintigraphy localization, pediatrics, claustrophobic patients

to imaging table stage next patient with second

58 High Throughput improved efficiency bed imaging flexibility faster set-up without patient transfer to imaging table stage next patient with second table automatic collimator exchange one-touch gantry robotics

59 BEYOND THE POSSIBLE RADIOLOGY CT ROOM

60 ADAC Forte FAST, EASY COLLIMATOR EXCHANGE ADAC Forte Integrated design Fast & easy, 4 min per pair No carts to store or move No table removal Customer Benefit: Reduced floor space requirement Greater throughput Easier for technologist Efficiency

61 HIGH QUALITY CARDIAC SPECT ADAC Forte No dead space Superior depth resolution No effect on acquisition time Consistent set-up with AC Customer Benefit: Higher resolution Better deep lesion image quality High throughput No learning curve for techs

62 POSITRON EMISSION TOMOGRAPHY PET

63 Positron emission tomography (PET) One of the fastest growing techniques is, positron emission tomography (PET) that requires special instrumentations called PET tomographs. This technique allows clinicians to track organ function at a molecular level, therefore revealing intricate health changes earlier in individual patients than other diagnostic method.

64 PET POSITRON EMISSION TOMOGRAPHY PET is an imaging technique that uses radioactive substances (positrons emitters) injected into patients to provide images of the body using specialized scanners.

65 RADIONUCLIDES POSITRON EMITTERS Radionuclide Halftime Particle energy (mean) C min 0.39 MeV N min 0.50 MeV O min 0.72 MeV F min 0.25 MeV Cu min 1.3 MeV Ga min 0.83 MeV Rb min 1.5 MeV

66 ANNIHILATION THE POSITIVE ELECTRON TRAVELS A CERTAIN DISTANCE (1-3 MM) BEFORE IT UNDERGOES ANIHILATIONS WITH A NEGATIVE ELECTRON, CREATING A PAIR OF COLLINEAR GAMMA RAYS. (511 kev) + + e - (511 kev) + (1-3 mm) Radionuclide

67 PET-SCANNER PRINCIPLE Detector Detector

68 M Dahlbom, UCLA PET-SCANNER

70 TUMOUR STAGING WITH PET (F18-FDG) CLINICAL USE

73 CLINICAL BENEFITS OF PET IMAGING Impact on patient management Reduced patient risk/improved patient outcome Increased revenue for diagnostic services Aid to defining appropriate care pathways Decreased overall healthcare costs

74 Reliable Performance ECAT EXACT

75 Case Study 1 ECAT EXACT

76 Highest Performance ECAT EXACT HR+

77 ECAT EXACT HR+ Case Study 1

78 RDS SOLUTIONS RDS Eclipse * RDS 111 *Works-in-progress

79 PET-MRI

80 PET-MRI

81 PET-MRI

Radionuclide Imaging MII Positron Emission Tomography (PET)

Radionuclide Imaging MII Positron Emission Tomography (PET) Radionuclide Imaging MII 3073 Positron Emission Tomography (PET) Positron (β + ) emission Positron is an electron with positive charge. Positron-emitting radionuclides are most commonly produced in cyclotron