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Biomedical physics

Biomedical physics
Biomedical  physics   Erika  Garu4   Florian  Grüner   1  The  course  structure   Friday    8:30  –  10:00      Lecture     Friday    10:15  –  11:45  Journal  club  /  exercise     Web  page:   hIp://­‐15.htm     Journal  Club:   ­‐  Begin  24.10.14   ­‐  One  paper  /  week     ­‐  Everybody  read  /  understand  /  prepare  a  quesXon  /  discuss   ­‐  During  exercise  hours  one  person  introduces  the  paper  ON  THE  BOARD  /   all  discuss  (no  slides  required)       2/29  66­‐278  Seminar  on  biomedical  physics   3LP   •  AddiXonal    not  mandatory  for  biomedical  physics   •  Does  not  require  to  follow  the  course  on  biomedical  physics   •  Start  on  31/10,    Wed.  12:00  –  13:30,  sem.  room  3     Part  1  6  invited  seminars  from  medical  doctors  and  medical  industry     •  RadiaXon  physics/biology       •  Image­‐guided    therapy     •  Radio­‐oncology     •  magneXc  parXcle  imaging   •  intervenXonal  imaging   •  ultrasound     Part  2  seminars  from  students  on  topics  related  to  the  invited  seminars   The  seminars  are  prepared  in  presentaXon  format  (slides  required)  of  about   15­‐20  minutes  /  student.       3/29  Biomedical  physics     •  Fundamentals  of  RadiaXon  Physics       •  Medical  DiagnosXc  Techniques            medical  imaging   •  Imaging  technics  (basic)   •  RadiaXon  Therapy       Not  covered  in  the  course  (but  belonging  to  biomedical  physics):     •  Advanced  Imaging       •  RadiaXon  ProtecXon  and  Dosimetry       •  Radiobiology       •  Anatomy  and  Physiology     •  Molecular  and  cellular  oncology       Some  of  the  missing  topics  will  be  covered  in:   66­‐278  Seminar  on  Biomedical  Physics   4/29  Medical  imaging     Structure  of  the  course   1)  IntroducXon   2)  DetecXon  of  photons  (physics  and  detectors)    principles  /  tools   3)  Therapy  with  proton  and  ion  beams     4)  X­‐  ray  sources                sources   5)  Sources  for  nuclear  medicine     6)  Image  quality                  objec5ve   7)  X­‐ray  imaging   8)  Computed  tomography   9)  Planar  scinXgraphy              imaging  modali5es   10)  Emission  tomography   11)  MagneXc  Resonance  Imaging     12)  MulXmodal  systems     The  course  will  not  cover  ultrasound  and  opXcal  imaging   5/29  Literature    Based  on  Prince  and  Links,  Medical  Imaging  Signals  and  Systems  and    Lecture  Notes  by  Prince.  Figures  are  from  the  book.    and  lectures  from  Yao  Wang  (NYU­‐Poly)     AddiXonal  suggested  literature:     •  C.Grupen  and  I.Buvat:  Handbook  of  ParXcle  DetecXon  and  Imaging;   •  W.R.Leo:  Techniques  for  Nuclear  and  ParXcle  Physics  Experiments,   Springer;     6/29  What  is  the  added  value  of     physics  for  medicine   ….or  why  should  YOU  study  biomedical  physics   …or  why  should  senior  physicists  care  about  medical  research   …and  why  care  medical  researchers/industry  about  physics  First  answer….synergy   X­‐ray  source   image   physics   reconstrucXon   accelerator  physics   detector  physics   medical  doctors  Second  answer….overcoming  limits   single  molecule  imaging   imaging  of  diagnosXc  agents  not   possible  in­‐vivo   CERN­‐sized  detector  reduced  to  paXent­‐size   3D  protein  structure  Biomedical  Physics  =   joint  research   Physicists  don‘t  know  the  limits  of  current  medical  technologies   medical  doctors  don‘t  have  insight  into  possibiliXes  of  physics  What  can  HEP  do  for  medical  physics   From  HEP  we  are  used  to:   •  Work  on  large  complex  systems     •  Challenging  integraXon  condiXons   •  Technology  fronXer  soluXon  for:  materials,   electronics,  data  acquisiXon,  data  volume,   processing/analysis  techniques,  simulaXon     11  A  calorimeter  for  HEP  /  PET   PET  calorimeter  system   (a  laying  human  fits  into  the  detector  bore)   CMS  calorimeter  system   (the  humans  are  not  part  of  the  experiment)  A  calorimeter  for  HEP   calorimeter   Huge  detector  volume:   •  segmented  in  single  ch.  O(10M)   •  Inside  4T  magneXc  coil     Single  channel:     •  PlasXc  scinXllator     •  Analog  silicon­‐photomulXplier  (SiPM)     Readout  electronics:   Single  channel   •  MulX­‐channel  r/o  chip     •  Energy    Xme  measurement       Number  of  sellable  apparatus:  1   SiPM   3  cm   13  A  calorimeter  for  PET     Medium  detector  volume:   •  segmented  in  single  ch.  O(100­‐1000)   •  For  PET/MRI  next  to  1T  coil  +  7T                gradient  field       1m   Single  channel:     •  Inorganic  scinXllator  (crystal)     •  Currently  photomulXplier  tubes  or                Avalanche  PhotoDiode       GE  Discovery  VCT   Single  channel   Readout  electronics:   •  MulX­‐channel  r/o  chip     •  Energy    Xme  measurement       3 4 Number  of  sellable  apparatus:  10 ­‐10       APD   14   Siemens  ConvenXonal  X­‐ray  sources   convenXonal/industrial  X­‐ray  tubes   •  broad  energy  spectrum   •  large  divergence  („  2  pi“)   •  not  tunable   •  large  spot  size,  lower  spaXal  resoluXon    Brilliant  X­‐ray  sources…way  too  large  for  clinical   applicaXon   Synchrotron   XFEL  Laser­‐driven  X­‐ray  sources   Ø  advantages:   §   quasi­‐monochroma5c  (few  )  →  high  CNR/dose   high   §   laminar  beam  geometry  →  scaRer  reduc5on   brilliance   §    low  divergence  →  high  spa5al  resolu5on   §   tunable  energy  Diagnosis     Main  applicaXon  of  medical  imaging  techniques  in  disease  diagnosis,  e.g.:   •  cancer     •  cardiovascular  disease     •  neurological  disorders  (e.g.,  Alzheimer’s  disease)     and  in  drug  development  (small  animal  imaging  with  microPET  or   microSPECT,  microCT,  microMRI,  bioluminescence  and  fluorescence  imaging   systems)   Next  three  slides  are  from:  Nuclear  Medicine  Imaging  in  Diagnosis  and  Treatment   Advancing  Nuclear  Medicine  Through  InnovaXon.   NaXonal  Research  Council  (US)  and  InsXtute  of  Medicine  (US)  CommiIee  on  State  of  the  Science  of  Nuclear   Medicine.   Washington  (DC):  NaXonal  Academies  Press  (US);  2007.   18/29   Copyright  ©  2007,  NaXonal  Academy  of  Sciences.  Staging  of  lung  cancer  with  FDG  and  PET/CT.  The  whole­‐body  image  (Panel  A)  shows  normal  FDG   uptake  in  the  brain  and  the  urinary  bladder.  In  addiXon,  several  regions  of  intensely  increased  FDG   uptake  are  seen  in  the  chest.  On  the  cross­‐secXonal  images  of  chest  (Panels  B  through  E),  the   primary  tumor  (PT,  Panel  B)  is  seen  in  the  right  lung  (Ln)  (arrow)  with  several  malignant  lymph   nodes  on  the  same  side.  There  are  addiXonal  malignant  lymph  nodes  on  the  opposite  side  of  the   paXent’s  chest  (Panel  E,  arrows).     19/29   SOURCE:  Courtesy  of  Wolfgang  Weber,  University  of  California  at  Los  Angeles  (UCLA).  Monitoring  the  effects  of  chemotherapy  on  tumor  volume  and  glucose  uptake  with  serial   mulXslice  computed  tomography  (MSCT)  and  PET  imaging  in  a  paXent  with  cancer  of  the   esophagus.  The  large  tumor  seen  on  the  MSCT  image  (yellow  arrow)  is  associated  with  intense   FDG  uptake  on  the  pre­‐treatment  PET  image  (red  arrow).  At  2  weeks,  the  tumor  volume   decreased  only  mildly  (decrease  in  diameter  from  21  mm  to  19  mm),  while  the  FDG  uptake   declined  by  about  50  percent  (reflected  by  the  decrease  in  the  standardized  uptake  value  of  FDG   from  16.8  to  8.5).  At  2  months,  the  tumor  volume  has  strikingly  decreased  and  the  FDG  uptake  is   only  faintly  visible.     20/29   SOURCE:  Reprinted  by  permission  of  the  Society  of  Nuclear  Medicine  from  Wieder  et  al.  2005.  DFG­‐  PET  brain  images  in  a  normal  volunteer  (lez  panel)  and  in  a  paXent  with  Alzheimer’s  disease   (right  panel).  Tomographic  slices  through  the  brain  at  the  level  of  inferior  parietal/superior  temporal   cortex  are  shown.  The  color  displayed  in  each  part  of  the  brain  reflects  the  concentraXon  of  FDG   corresponding  to  the  metabolic  acXvity  of  the  neurons  in  that  region.  Red,  orange,  and  yellow  areas   are  (in  decreasing  order)  the  most  acXve,  while  green,  blue,  and  violet  areas  are  progressively  less   acXve.  Note  that  in  neurologically  healthy  individuals,  the  enXre  cerebral  cortex  has  a  moderately  high   level  of  metabolism.  In  the  paXent  with  Alzheimer’s  disease,  the  arrows  indicate  areas  of  diminished   metabolic  acXvity  in  the  paXent’s  parietotemporal  cortex,  a  region  important  for  processing  of   language  and  associaXve  memories.     SOURCE:  Courtesy  of  Daniel  Silverman,  UCLA.   21/29  Radiotherapy   Azer  diagnosis  some  diseases  like  hyperthyroidism,  cancer,  blood  disorders,   etc…    can  be  treated  using  radiotherapy.     Three  main  methods:   •  Unsealed  source  radiotherapy     •  Brachytherapy  (sealed  source  therapy)    è     •  External  beam:  x­‐rays,  electrons,  p,  n,  heavy  ions     •   Stages  in  the  radiotherapy  process:   QA,  imaging,  planning,  simulaXon,     treatment,  verificaXon,  modelling  outcome     "seeds"  ­‐  small  radioacXve   rods  implanted  directly   Physics,  engineering,  imaging,  technology  based   into  the  tumor.       22/29    Benefits  of  Radiotherapy   •  Breast  Cancer   •  Mastectomy   •  Compare  surgery  and   chemotherapy  (CMF)  with  and   without  radiotherapy   •  10  year  survival  improved  by  10   23/29  What  is  medical  imaging   Every  non­‐invasive  technique  that  allows  to  look  inside  the  human  body.     Invasive  techniques    surgery,  endoscopy     Non­‐invasive        magneXc  resonance  imaging,  ultrasound   techniques        projecXon  radiography,  computed  tomography,              nuclear  medicine      but  exposure  to  radia5on     In  addiXon  see  things  that  are  not  visible  to  the  eye  (blood  flow,  organ   metabolism,  receptor  binding)       Different  techniques  (modaliXes)  allow  to  look  inside  the  human  body  in   different  ways  (looking  at  different  signals)                   24/29  Signals  and  ModaliXes   Signal     Modality   Property  imaged   X­‐ray  transmission   projecXon  radiography   aIenuaXon  coefficient   through  the  body     or  CT   to  X­‐ray   Gamma­‐ray  emission   Planar  scinXgraphy  or   DistribuXon  of  induced   from  within  the  body     emission  tomography   radio  sources   Nuclear  magneXc   MagneXc  resonance   Hydrogen  proton   resonance  inducXon     imaging   density,  spin  precession   in  large  magneXc  field   Ultrasound  echoes   Ultrasound  imaging   Sound  reflecXvity   25/29  ProjecXon  vs.  Tomography   ProjecXon:   A  single  2D  image  “shadow”  of  the  3D  body   (one  dimension  is  integrated  è  loss  of  informaXon)     Tomography:   A  series  of  images  are  generated,  one  from  each  slice   of    3D  body  in  a  parXcular  direcXon  (no  integraXon)   26/29   axial  or  transverse  /    coronal  or  frontal    /    sagiIal        Anatomical  vs.  FuncXonal  imaging   Some  modaliXes  are  very  good  at  depicXng  anatomical  structures  (bones):   ­‐  X­‐ray  and  CT   ­‐  MRI   Some  modaliXes  are  less  good  with  anatomical  structure  but  reflect  the   funcXonal  status  (blood  flow,  oxygenaXon,  etc…  )   ­‐  Ultrasound   ­‐  PET,  funcXonal  MRI     27/29  Common  imaging  modaliXes   •  ProjecXon  radiography  (X­‐ray)   •  Computed  tomography   •  Nuclear  medicine  (SPECT,  PET)   •  MagneXc  resonance  Imaging  (MRI)   •  Ultrasound  imaging     •  OpXcal  imaging     28/29  ProjecXon  radiography   ScinXllator  screen  and  detector  (film,  camera,  solid­‐state)   X­‐ray  tube     cone  beam   29/29  ProjecXon  radiography   30/29  Computed  tomography   X­‐ray  in  a  2­‐D  “fan  beam”  rotated  around  the  subject   The  image  of  one  cross­‐secXon  is  computed  from  all  projecXons  (digital)   Whole  body  scan  in  less  than  one  minute     Slice  of  the  liver   (1  sec  data  taking)   31/29  Computed  tomography   32/29  Nuclear  medicine   Emission  images:     •  RadioacXve  substances    (radio  tracers)  have  to  be  introduced  into  the   body  that  emit  gamma­‐rays  or  positrons.   •  Radiotracers  move  within  the  body  according  to  the  natural  uptake   •  InvesXgated  is  the  local  concentraXon  of  radio  tracer  within  the  body     è FuncXonal  imaging  as  oppose  to  structural/anatomical  imaging       Three  techniques:   ­‐  Radionuclide  imaging  or  scinXgraphy  (2D  projecXon   Detect  single  γ­‐rays     (rather  than  intensity                equivalent  to  projecXon  radiography)   as  in  CT)    with  a   ­‐  Single  photon  emission  tomography  (SPECT)   scinXllator  detector   ­‐  Positron  emission  tomography  (PET)   called  Anger  camera   33/29  SPECT   Anger  camera   Cardiac  scans:  the  blood  flows  through   the  heart  muscle     34/29  Nuclear  medicine   35/29  MagneXc  resonance  imaging   In  a  magneXc  field  protons  (H)  align  themselves  along  the  field  lines   An  addiXonal  gradient  field  can  locally  disturb  the  alignment     To  reestablish  the  alignment  protons  precess  and  generate  detectable  EM­‐waves         Human  knee     2  Tesla  super­‐ conducXve   magnet   36/29  MagneXc  resonance  imaging   37/29  Ultrasound  imaging   •  High  frequency  sound  are  emiIed  into  the  imaged  body,  Xme  and   strength  of  the  returned  sound  pulses  are  measured   •  ComparaXve  inexpensive  and  completely  non­‐invasive     •  Image  quality  is  relaXvely  poor   11­‐weeks­‐old   human  embryo     38/29  Ultrasound  imaging   39/29  ElectromagneXc  waves  used  in  medical  imaging     larger  than  1  Å  high  aIenuaXon  from  the  body,     ­‐2 shorter  than  10  Å    =  too  high  energy  (1MeV)  for  direct  detecXon   40/29  41/29  
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