Tecnologias mn

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Tecnologias mn

  1. 1. Tecnicas de Medicina Nuclear Bases y fundamentos
  2. 2. Procedimiento de obtención de imágenes médicasGammagrafíaTomografia Computarizada por Emision de Fotones Simples (SPECT)Tomografía por Emisión de Positrones . PET
  3. 3. Aprender conceptos básicos sobre cómo se generan las imágenes de Medicina Nuclear: gammagrafías, SPECT y PET
  4. 4. La Medicina Nuclear (MN) utiliza sustanciasradiactivas: isótopos (iso = igual; topos = lugar)Fines: diagnósticos, terapéuticos y deinvestigación.Estassustancias radiactivas (radionúclidos otrazadores) se introducen (in vivo) en la partedel cuerpo que se quiere estudiar y se hace laimagen detectando la radiación que emite.
  5. 5.  Es mínimamente invasiva (inyección). Es una técnica funcional: no estudia la anatomía sino su funcionamiento. Abarca en la practica, la totalidad del organismo. El nivel de radiación es similar al de otras técnicas radiológicas (ej. RX)
  6. 6. INTRODUCCIÓNAlgunos de los elementos más usados en MN:Radionúclido Energía T(1/2) Estudios (keV) 99m Tc 140 6 horas Cerebro, tiroides, riñón, pulmón 131 I 364 8´04 días Tiroides y riñon 67 Ga 39 3´25 días Tumores y abscesos 133 Xe 81 5´3 días Pulmón 201 Tl 30-140 72 horas Estudios cardíacos
  7. 7. Fines diagnósticos:Renograma isotópico de unpaciente con HTA Imágenes de Medicina nuclearsecundaria, que muestra una normales.atrofia renal derecha
  8. 8. INTRODUCCIÓNDiferencias (MN, rayos X): •MN usa radiación gamma (): Energías Frecuencias MN: [104 - 107 eV] [1019 - 1022 Hz] Rayos X: [10 - 104 eV] [1015 - 1019 Hz] •En MN la fuente de radiación es interna (en el interior del cuerpo del paciente), en rayos X es externa. •Trazador con radiofármaco: permite obtener una representación morfológica o información funcional o dinámica. (En rayos X contraste)
  9. 9. Esquema básico de un sistema de IMN Sustancia radiactiva Colimador Tubo Analizador Contador de órgano Cristal de fotomultiplicador centelleo de amplitud impulsosseleccionado Radiación  Gammagrafía
  10. 10. Imágenes en Medicina NuclearUso de Rx, radionucleidos y deradiofarmacos en obtención de imágenes
  11. 11. Con las imagnes de Medicina Nuclear pueden observarse procesos fisiologicos,como asimismo de Estructuras anatomicas.En estas tecnicas se inyectan en los pacientes por viaIntravenosa, drogas radiactivas (Radiofarmacos) que emiten rayos gammaUna vez que son captados por el tejido, organo o sistema de interes.La cantidad de radionucleidos inyectados, se encuentran en el orden deconcentracionesde nano a picomolar, de manera de disminuir los riesgos para los pacientesDurante el estudio de los procesos fisiologicos delos mismos.El semiperiodo fisico de estos materiales radiactivos es de solo unos pocosMinutos a semanas. The time course of theprocess being studied and the radiation dose to the target areconsidered. The nuclear camera then, in effect, takes a time-exposure"photograph" of the pharmaceutical as it enters and concentrates inthese tissues or organs. By tracing this blood flow activity, theresulting nuclear medicine image tells physicians about the biologicalactivity of the organ or the vascular system that nourishes it. NuclearMedicine has a wide variety of uses, including the diagnosis of cancer, studying heart disease, circulatory problems, detecting kidney malfunction, and other abnormalities in veins, tissues and organs.
  12. 12. Medicina Nuclear: camara gamma
  13. 13. RadiofarmacosEtOOC O COOEt N NH 99mTc S S Aplicacion: perfusion cerebral
  14. 14. Imagen nuclear deCuerpo completo
  15. 15. SPECT: single photon emission computerized tomographySPECT esta basada en una tecnica convencional de imagenes nuclearesY usando ademas la tecnica y metodos de reconstruccion tomografica.
  16. 16. a d b c CollimatorElectronics NaI(Ti) crystal PMT Y Counts/pixel X
  17. 17. Características de Rendimiento de los sistemas de imágenes de Medicina NuclearResolución Espacial – Es la medida del grado de detalles provistos por laimagen final reconstruida y por lo tanto del tamaño de lesiones quepotencialmente pueden ser detectadas. En otras palabras: cual es el gradode detalle en el cual puede ser Observada una imagen o cuanto puede serresuelta o separada.Sensibilidad, tiempo muerto – describe de que manera y con que eficienciase Detectan los decaimientos radiactivos y la distribucion del trazador, paraFormar finalmente la imagen.Una fuente isotropica irradia en forma igual hacia todas las direcciones delespacio. Los detectores, recolectan parte del total de los decaimientos,dentro de un angulo Solido limitado por los colimadores.Algunos de estos eventos se pierden debido a que el sistema necesita deun tiempo de procesamiento entre la deteccion de un evento y el siguiente.(dead time o Tiempo Muerto).
  18. 18. Signal to Noise ratio (SNR) - The relative strength of the informationand the noise. If the lesion is small compared with the spatial resolutionthe contrast is reduced because the high lesion activity blurred into theneighborhood by the detector response.Uniformity, Linearity - The image of an object should be independentof its position in the field of view. This is not true in real systems.This can be assessed in calibration measurements to derive correctionfactors. This reduces non-uniformity from 10% to 3%.
  19. 19. The conventional nuclear medicine imaging process.Typical radionuclides used are 140 KeV Tc-99m and 70 KeV photonsfrom Tl-201.The gamma ray photons emitted from the radiopharmaceuticalpenetrate through the patient body and are detected by a set ofcollimated radiation detectors. The emitted photon experienceinteraction within the body by the photoelectric effect which stopstheir emergence from the body or compton scattering whichtransfers part of the energy to free electrons and the photon isscattered into a new direction. These photons are also detectedby the camera and cause blurring of the image if un-treated withimage reconstruction and processing tools.
  20. 20. q Pixel I Activity ai Intersected area fi r P(r,q)
  21. 21. In 2-D tomographic imaging, the 1D detector array rotates aroundthe object distribution f(x,y) and collects projection data from various projection angles q. The integral transform of the object distributionto its projections is given by: Ç p (t ,q )  ct I 0 exp[  z   ( x , y )ds]Which is called the Radon transform. The goal of imagereconstruction is to solve the inverse Radon transform. The solutionis the constructed image estimate f(x,y) of the object distributionf(x,y).The measured projection data can be written as the integral ofradioactivity along the projection rays.
  22. 22. The measured projection data can be written as the integral ofradioactivity along the projection rays. z  p(t ,q )  ce  ( x , y )ds In SPECT attenuation coefficient is not so important, so it canbe considered as constant in the body region under inspection. z  p(t ,q )  ce  ( x , y ) exp[  l ( x, y )]ds l(x,y) is the pathlength between the point (x,y) and the edge of theattenuator (or patient’s body) along the direction of the projectionray.The image reconstruction problem is further complicated by the nonstationary properties of the collimator detector and scatter responsefunctions and their dependence on the size and composition of thepatient’s body.
  23. 23. PROCEDIMIENTO DE OBTENCIÓN DE IMÁGENES MÉDICAS Cristal de centelleo (Yoduro de sodio con talio-C INa(Ta)) Transductor de energía  en energía luminosa. El cristal está acoplado a un conjunto de fotomultiplicadores de sección exagonal. Transductor de energía luminosa en electrones. Salida del fotomultiplicador: impulsos eléctricos amplitud proporcional a la energía de la radiación  y número proporcional a la actividad del elemento radiactivo en el punto analizado. Llevando estas señales a un circuito de posicionamiento, obtenemos las coordenadas X e Y, que indican la posición donde se ha detectado el fotón.
  24. 24. PROCEDIMIENTO DE OBTENCIÓN DE IMÁGENES MÉDICASColimador tipo pinhole. Colimadores de múltiplesLa imagen es invertida y el orificios paralelos,tamaño dependiente dela convergentes y divergentesdistancia al plano objeto.
  25. 25.  Gammagrafía SPECT PET
  26. 26.  Es la técnica mas simple. Su funcionamiento es similar al de las radiografías, una sola imagen por volumen. Varios tipos dependiendo de la zona: › Osea (tumores de hueso) › Pulmonar (trombos en las arterias pulmonares) › Tiroidea (nódulos en la tiroides) › Renal (función de los riñones)
  27. 27. Renograma isotópico de unGammagrafía de un paciente con HTA secundaria,adenoma suprarrenal que muestra una clara atrofiacausante de hipertensión renal derecha. La pequeñaarterial secundaria cantidad de contraste isotópico que se observa ha llegado por vía del pedículo suprarrenal.
  28. 28.  Gammacámara que puede realizar movimientos de rotación alrededor del cuerpo del paciente o anillo. Imagen de la distribución del trazador en 3D utilizando la combinación de imágenes obtenidas desde diversas orientaciones. Pueden obtenerse imágenes de cortes axiales, sagitales, coronales. Mediante los algoritmos de retroproyección, similares a los TC, se puede reconstruir la imagen.
  29. 29. Ejemplo de un escáner de SPECT
  30. 30. fotón  Positrón fotón  Detectores de radiación Detección de positrones mediante dos gammacámaras
  31. 31. Tipos de cámaras PET: a) un par b) un anillo hexagonal giratorio alrededor del paciente c) Anillo circular que rodea al paciente
  32. 32.  PET generates images depicting the distributions of positron-emitting nuclides in patients In the typical scanner, several rings of detectors surround the patient PET scanners use annihilation coincidence detection (ACD) instead of collimation to obtain projections of the activity distribution in the subject
  33. 33.  Positrons emitted in matter lose most of their kinetic energy by causing ionization and excitation When a positron has lost most of its kinetic energy, it interacts with an electron by annihilation The entire mass of the electron-positron pair is converted into two 511-keV photons, which are emitted in nearly opposite directions
  34. 34.  If both annihilation photons interact with detectors, the annihilation occurred close to the line connecting the two interactions Circuitry within the scanner identifies interactions occurring at nearly the same time, a process called annihilation coincidence detection Circuitry of the scanner then determines the line in space connecting the locations of the two detector interactions
  35. 35.  ACD establishes the trajectories of the detected photons, a function performed by collimation in SPECT systems Much less wasteful of photons than collimation Avoids degradation of spatial resolution with distance from the detector that occurs when collimation is used to form projection images
  36. 36.  A true coincidence is the simultaneous interaction of emissions resulting from a single nuclear transformation A random coincidence, which mimics a true coincidence, occurs when emissions from different nuclear transformations interact simultaneously with the detectors A scatter coincidence occurs when one or both of the photons from a single annihilation are scattered, but both are detected
  37. 37.  Scintillation crystals coupled to PMTs are used as detectors in PET Signals from PMTs are processed in pulse mode to create signals identifying the position, deposited energy, and time of each interaction Energy signal is used for energy discrimination to reduce mispositioned events due to scatter and the time signal is used for coincidence detection
  38. 38.  Early PET scanners coupled each scintillation crystal to a single PMT › Size of individual crystal largely determined spatial resolution of the system Modern designs couple larger crystals to more than one PMT Relative magnitudes of the signals from the PMTs coupled to a single crystal used to determine the position of the interaction in the crystal
  39. 39.  Material must emit light very promptly to permit true coincident interactions to be distinguished from random coincidences and to minimize dead-time count losses at high interaction rates Must have high linear attenuation coefficient for 511-keV photons in order to maximize counting efficiency
  40. 40.  Most PET systems use crystals of bismuth germanate (Bi4Ge3O12, abbreviated BGO) › Light output 12% to 14% that of NaI(Tl), but greater density and average atomic number give it higher efficiency at detecting 511-keV photons Other inorganic scintillators being investigated: lutetium oxyorthosilicate and gadolinium oxyorthosilicate – faster light emission than BGO produces better performance at high interaction rates
  41. 41.  Energy signals sent to energy discrimination circuits which can reject events in which the deposited energy differs significantly from 511 keV to reduce effect of photon scatter in patient Energy window may be adjusted to include part of the Compton continuum, increasing sensitivity but also increasing the number of scattered photons detected
  42. 42.  Time signals of interactions not rejected by the energy discrimination circuits are used for coincidence detection When a coincidence is detected, the circuitry or computer of the scanner determines a line in space connecting the two interactions › PET system collects data for all projections simultaneously Projection data used to produce transverse images of the radionuclide distribution as in x-ray CT or SPECT
  43. 43.  In 2D (slice) data acquisition, coincidences are detected and recorded within each detector ring or small groups of adjacent detector rings PET scanners designed for 2D data acquisition have thin annular collimators (typically tungsten) to prevent most radiation emitted by activity outside a transaxial slice from reaching the detector ring for that slice Fraction of scatter coincidences reduced because of the geometry
  44. 44.  Coincidences within one or more pairs of adjacent detector rings may be added to improve sensitivity Data from each pair of detector rings are added to that of the slice midway between the two rings Increasing the number of adjacent rings used in 2D acquisition reduces the axial spatial resolution
  45. 45.  In 3D (volume) data acquisition, axial collimators are not used and coincidences are detected between many or all detector rings Greatly increases the number of true coincidences detected; may permit smaller activities to be administered to patients
  46. 46.  For the same administered activity, the increased interaction rate increases random coincidence fraction and dead- time count losses › 3D acquisition may require less activity to be administered Scatter coincidence fraction is much larger and number of interactions from activity outside the FOV is increased › Activity outside the FOV causes few true coincidences, but increases rate of random coincidences and dead-time count losses
  47. 47.  3D acquisition may be most useful in low- scatter studies, such as pediatric and brain studies Some PET systems are equipped with retractable axial collimators, permitting them to perform 2D or 3D acquisition
  48. 48.  For 2D data acquisition, image reconstruction methods are similar to SPECT For 3D data acquisition, special 3D analytic or iterative reconstruction techniques are required In PET, the correction for nonuniform attenuation can be applied to the projection data before reconstruction; in SPECT, the correction for nonuniform attenuation is intertwined with and complicates the reconstruction process
  49. 49.  Whole-body PET systems achieve a spatial resolution slightly better than 5 mm FWHM in the center of the detector ring Spatial resolution limited by: a) intrinsic spatial resolution of detectors b) distance traveled by positrons before annihilation c) the fact that annihilation photons are not emitted in exactly opposite directions from each other Intrinsic resolution of detectors most significant
  50. 50.  Spatial resolution of PET is best in the center of the detector ring and decreases slightly with distance from the center This occurs because of detector thickness and inability to determine the depth in the crystal where an interaction occurs Uncertainty in depth of interaction causes uncertainty in the line of response for annihilation photons that strike the detectors obliquely
  51. 51.  Distance traveled by positron before annihilation also degrades the spatial resolution Distance is determined by maximal positron energy of the radionuclide and density of the tissue Radionuclide that emits lower energy positrons yields superior resolution Activity in denser tissue yields higher resolution than activity in less dense tissue
  52. 52.  Although positrons lose nearly all of their momentum before annihilation, the positron and electron possess some residual momentum when they annihilate Conservation of momentum predicts that the resultant photons will not be emitted in exactly opposite directions This causes a small loss of resolution, which increases with the diameter of the detector ring
  53. 53.  Point source of positron-emitting radionuclide in air midway between two identical detectors True coincidence rate is RT  2 AG 2 where A is the activity of the source, G is the geometric efficiency of either detector, and  is the intrinsic efficiency of either detector Because the rate of true coincidences detected is proportional to the square of the intrinsic efficiency, maximizing the intrinsic efficiency is very important
  54. 54.  Differs in PET from SPECT, because both annihilation photons must escape the patient to cause a coincidence event to be registered Probability of both photons escaping the patient without interaction is the product of the probabilities of each escaping: e ) e  x   d  x ) ) e  d
  55. 55.  For a 20-cm path in soft tissue, the chance of both annihilation photons of a pair escaping the tissue without interacting is about 15% Attenuation causes a loss of information and, because the loss is not the same for all lines of response, causes artifacts in the reconstructed transverse images Loss of information also contributes to statistical noise in the images
  56. 56.  Some PET systems provide one or more retractable positron-emitting sources to measure the transmission of annihilation photons through the patient › Gamma-ray emitting source (Cs-137) may be used Sources revolve around the patient so attenuation is measured along all lines of response through the patient Attenuation correction cannot compensate for increased statistical noise; increases imaging time
  57. 57.  SPECT with high-energy collimators or multihead SPECT cameras with coincidence detection capability › Less acceptable for brain imaging or evaluation and staging of neoplasms Dedicated PET systems that are less expensive than those with full rings of BGO detectors, but which provide better coincidence detection sensitivity than double-head scintillation cameras
  58. 58.  PET scanner more efficient than scintillation camera due to use of annihilation coincidence detection instead of collimation; also yields superior spatial resolution Spatial resolution in SPECT deteriorates from edge toward center; PET is relatively constant across transaxial image, best at center Attenuation less severe in SPECT; accurate attenuation correction possible in PET (with transmission source) Cost: SPECT ~US$500,000; PET ~US$1M - $2M
  59. 59.  Main factors limiting availability of PET are the relatively high cost of a dedicated PET scanner and, in many areas, the lack of local sources of F-18 FDG Multihead SPECT cameras with coincidence circuitry and SPECT cameras with high- energy collimators provide less expensive, although less accurate, alternatives for imaging FDG
  60. 60. PET enables physicians to assess chemical or physiological changesrelated to metabolism. Since the origins of many diseases arebiochemical in nature, these functional changes often predate or exceed structural change in tissue or organs. PET imaging utilizes a variety ofradiopharmaceuticals, called "tracers," to obtain images. PET tracersmimic the natural sugars, water, proteins, and oxygen found in ourbodies. These tracers are injected into a patient and collect in varioustissues and organs. The PET system takes a time-exposure of the tracerand generates a "photo" of cellular biological activities. PET imagescan be used to measure many processes, including sugar metabolism,blood flow and perfusion, receptor-ligand binding rates, oxygenutilization and a long list of other vital physiological activities.
  61. 61. PET scanning uses artificialradioactive tracers andradionuclides. Their lifetime isusually rather short, thus theyneed to be produced on site.
  62. 62. Some examples of such materials are:Radionuclide Half life ApplicationCarbon-11 20.3 min Positron emitter for metabolism studiesCopper –64 12.8 hours clinical diagnostic agent for cancer and metabolic disorderIodine –122 3.76 min Positron emitter for blood flow studyIodine –131 8.1 days Diagnose thyroid disorders including cancerIron - 52 8.2 hours Iron tracer for PET bone marrow imagingNitrogen – 13 9.9 min Positron emitter used as 13NH for heart perfusion studiesStrontium – 85 64 days Study of bone formation metabolismOxygen – 15 123 sec Positron emitter used for blood flowTechnetium – 99m 6 hours The most widely used radiopharmaceutical In nuclear medicine
  63. 63. PET has a million fold sensitivity advantage over MRI in tracer studyand its chemical specificity, PET is used to study neuroreceptors inthe brain and other body tissues. It is efficient in the nanomolar rangewhere much of the receptor proteins in the body. Clinical studiesinclude tumors of the brain, breast, lung, lower GI tract. Additionalstudy of Alzheimer’s disease, Parkinson’s disease, epilepsy andcoronary artery disease affecting heart muscle metabolism and flow.
  64. 64. PET studies has immeasurably added to the understanding of oxygenutilization and metabolic changes that accompany disease.
  65. 65. PET imaging starts with the injection of metabolically active tracer – a biologicmolecule that carries with it a positron emitting isotope. Over a few minutes theisotope accumulates in an area of the body for which the molecule has an affinity.i.e. glucose labeled with 11C or glucose analogue labeled with 18F, accumulates in the brain or tumors, where glucose is used as the primary source of energy. Theradioactive nuclei then decay by positron emission. In positron (positive electron) , a nuclear proton changes into a positive electron and a neutron. The atom maintainsits atomic mass but decreases its atomic number by 1. The ejected positron combines with an electron almost instantaneously, and these 2 particles undergo the process ofannihilation. The energy associated with the masses of the positron and electronparticles is 12.022MeV in accordance with E=MC2 . This energy is divided equallybetween 2 photons which fly away from one another at 1800 angle. Each photon hasan energy of 511 keV. These high energy gamma rays emerge from the body inopposite directions and recorded simultaneously by pair of detectors.
  66. 66. The annihilation event that gave rise to them must have occurred somewherealong the line connecting the detectors. Of course if one of the photons is scattered,then the line of coincidence will be incorrect. After 100,000 or more annihilationevents are detected, the distribution of the positron-emitting tracer is calculated bytomographic reconstruction procedures. PET reconstructs a 2 dimensional imagefrom the one dimensional projections seen at different angles. 3-D reconstructions can be done using 2D projections from multiple angles.
  67. 67. Tagged Positronmetabolic annihilationactivity - photons (1800 + N 0.250) P11C nucleus  Lead shield Scintillator Tungsten septum
  68. 68.  Detector crystal width Anger logic Photon noncolinarity Positron range Reconstruction algorithm
  69. 69. AcquisitionCalibration data Sinogram Correction data Counts/ray Reconstruction Image
  70. 70. SA reconstructed slices
  71. 71. • Blood volumes• Oxygen consumption• Perfusion• Glucose consumption
  72. 72. CENTELLEADORFOTOMULTIPLICADOR RADIOISÓTOPOS β+ DE ELECTRÓNICA VIDA CORTA 2 RAYOS γ COLINEALES
  73. 73. CICLOTRÓN Radioisótopo Inyección Radioisótopos + al β+ Trazador PacienteReconstrucción Detección Decaimiento β+ de la de y Imagen Coincidencias Aniquilación (2γ)
  74. 74. IMAGEN FUNCIONAL:DISTRIBUCIÓN DEL TRAZADOR EN EL ORGANISMO APLICACIONES: -DETECCIÓN DE TUMORES - FUNCIÓN CEREBRAL
  75. 75. -EFICIENCIA DEL DETECTOR- SENSIBILIDAD DEL SISTEMA- RESOLUCIÓN TEMPORAL- RESOLUCIÓN ESPACIAL- RITMO DE RECUENTO
  76. 76. Punto Paralelepípedo Esfera ¿Dentro No de Esfera? Sí PROGRAMA DE Rayo Θ,φ SIMULACIÓNn veces Intersección Detectores-Rayo MÉTODO MONTECARLO Detector ¿Dentro de No Sí planos? Numeración Detectores Guardar datos
  77. 77. DETECTOR IDEAL LOR 2γ COLINEALESEJE Y Datos EJE X
  78. 78. EJE X EJE Y
  79. 79. π/3 π/3
  80. 80. υxr F1 y υy υxr EQUIVALENTES F2 f(x,y) φ υx x    2i xr xr    2i xr xr f ( x, y )     d xr e  xr W ( xr )  dxr e  p( xr , ) d  0    
  81. 81. φ φ 0 xr Transformada de Radon 0 xr P( xr ,  )    f ( x, y) ( x cos   ysen  x )dxdy  r
  82. 82. PROYECCIÓN RETROPROYECCIÓN
  83. 83. Sobremuestreo en el Tipos de Filtrosorigen de frecuencias υy Δφ Filtro rampa υx Δυxr Ventana Hamming 0 υ
  84. 84. p(xr,φ) p·cos xr xr cos(2 N xr )
  85. 85. 4 2 xr = x·cosφ +y·senφ    2i xr xr    2i xr xr f ( x, y )     d xr e  xr W ( xr )  dxr e  p( xr , ) d  0     1 3 5 φ (x, z) υxr 3 xr 1 4 2 5
  86. 86. 6 mm 4 mm 3 mm
  87. 87. FWHM ≈ 3 mm
  88. 88. xr (cm) φ (rad)
  89. 89. CORREGIDA PORNORMALIZACIÓN
  90. 90. xr (cm) φ (rad)
  91. 91. CORREGIDA PORNORMALIZACIÓN
  92. 92. CONCLUSIONES:- Simulación de la Emisión y Detección de Gammas en P.E.T.- Reconstrucción de Imágenes con FBP en Modo 2D.- Estudios Realizados: Resolución, Normalización, Filtros.
  93. 93. Imágenes PET de un cerebro activo en varios estados, tras inyección intravenosa de 18F, con deoxy-glucosa. (de Shung-92)
  94. 94. Low Pet Scan of Patient. The Positron Emission TomographyLab at Mount Sinai MedicalCenter is located in New York City.We are dedicated to the study ofAlzheimers, Schizophrenia andgeneral questions regarding howthe brain changes with age. Thisresearch is accomplished throughthe co-registration of PET and MRImodalities. We have developedsoftware in order to better aid inthis research
  95. 95. http://neurosurgery.mgh.harvard.edu/pet-hp.htm Parkinsons Disease
  96. 96. http://neurosurgery.mgh.harvard.edu/pet-hp.htm Huntingtons disease
  97. 97.  Sitio caliente: sala de preparación de radiofármacos Sala de pacientes Sala de exploraciones Sala de almacenamiento de residuos radiactivos Equipo humano: Especialista y técnico

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