Molecular Imaging Technologies:
from Cells to Humans
Arion Chatziioannou Ph.D.
Crump Institute for Molecular Imaging
Department of Molecular & Medical Pharmacology
David Geffen School of Medicine at UCLA
Imaging Technologies
PET
SPECT
sp
pace
CT
MRI
ti
time
Information Content
Tag specific information, relevant to the state of the process
Imaging can not only visualize, but quantitate the relevant process
Molecular Imaging Targets/Probes
MAb, Fragments
Receptor Mapping
Hormones
Drugs and Ligands
Peptides
Accumulation via
Phosphorylation
[18F]FDG
glut 4
Enzyme Activity:
Inhibition, Conc.,
Synthesis
Internalization
Hexocinase
DNA
Accumulation via
AA Transport or
Protein Synthesis
AAT
Reporter Gene DNA
Accumulation via
DNA-Synthesis
mRNA
Oligonucleotides
mRNA Binding
mRNA
Reporter Probe
Molecular Imaging Probes
Bioluminescence Imaging
Luciferase (enzyme)
+
Luciferin (substrate)
+
energy
Light
Firefly
Fi
fl controls
l production
d i off
both luciferase and luciferin
Given an excess off substrate
Gi
b t t
thousands of photons can be
produced per enzyme
The Imaging
g g Chamber
CCD
Chip
Optical
Filter wheel
Shutter
Ω ~ 1%
QE ~90%
Lens and
Aperture
Illuminator
Heated
Sample
Stage
Electronics
Depth (mm)
Standard Images are composed of two datasets
Photographic
g p
+ Luminescent
Overlay
y
Optical
p
and PET Imaging
g g
Anterior view
Posterior view
• Human metastatic melanoma tumor model
• triple fusion protein (luminescence,
(luminescence fluorescence
fluorescence, PET)
PET Sensitivity
• No collimators necessary: 100% efficiency possible
•
Stopping power of 1cm LSO ~30%
P(A, B) = P(A)∩P(B) = P(A)*P(B)
•
•
•
Coincidence
C
i id
stopping
t
i iis ~10%
10%
Solid angle is ~50%
In practice 5-10% sensitivity
9
8
7
6
5
4
3
2
1
0
Sensitivity %
1997
2000 Year 2004
2007
Dynamic Range
The range of activities encompasses >10 log orders
e±/sec
1 pCi
•
•
100
103
106
1 nCi
High Sensitivity
Cell cultures have uptakes on
the order of pCi/cell (0.1 e±/sec)
Ph
Phosphorylation
h l ti – assays have
h
on the order of (0.1 e±/sec)
1 μCi
•
•
109
1 mCi
High
Hi
h Flexibility
Fl ibilit
Probe synthesis produces
>mCi of activity (~108 e±/sec)
In-vivo imaging >1nCi
Different technologies completely cover this large spectrum.
Microfluidics
Operation Mechanism of a Pressure-Driven Valve
Valve open
Valve close
Pressure
Flow
microfluidics:
Chemical Synthesis
Biological Assays
Cell cultures
M.A. Unger, H. P. Chou, T. Thorsen, A. Scherer, S.
R. Quake, Science 2000, 288, 113.
Direct Beta Detection
Detector Cross-section
Key Parameters:
1. Thin substrate allows detection of low energy betas
2. Thick detector will absorb more energy from incoming betas
PSAPD Detection Limits, Linearity
microfluidic chip
PSAPD
Cell Culture and FDG Uptake
~72 Cells
A549 cell line
microfluidic chip array
Loading of FDG solution into Cell Chambers
Movie plays x6 faster than real time
Cell Culture System: Sensitivity
~80 cells
3-5 cells
Activity per c
cell (pCi/Cell)
350
300
250
200
150
100
50
0
1 cell
2 cells
3-5 cells
N cells
Number of Cells
1 cell
Intracellular FDG concentration: 25nmol
• 20 minute acquisition, 1mCi/cc FDG
• System
S t
can quantify
tif the
th FDG uptake
t k off 1 cell
ll
Translational Molecular Imaging
Molecular
In vitro
Clinic
In vivo
Small Animal PET Systems
Si
Siemens
Phili
Philips
GE Medical
Mediso
Gamma Medica
Comecer
Oxford Positron
Results (volumetric projections)
Negative control
•
HSV-tk positive mouse
Time lapse movies of the tracer distribution
Results - Time Activity Curves
7000
Heart
6000
Kidney
Activity
Coronal slices through
individual framesBladder
of the time lapse movie for
5000
Liver
the HSV-tk positive
mouse
4000
3000
2000
1000
0
0
50
100
150
Time (sec)
200
250
300
Conclusions
• Molecular Imaging “Seeks to advance our
understanding of biology and medicine through
noninvasive
i
i in
i vivo
i investigation
i
ti ti off cellular
ll l molecular
l
l
events involved in normal and pathologic processes”
(Society of Molecular Imaging)
• Requires a mutually educating collaborative
environment that includes biologists, physicists,
chemists mathematicians,
chemists,
mathematicians physicians and clinicians
• Physicists and engineers provide expertise in the
development
p
and usage
g of state of the art imaging
g g
tools for biologists
• Devise and develop new tools that will answer
important biological questions
M Phelps
E Hoffman
S Cherry
S Gambhir
H Herschman
N Satyamurthy
T Ribas
J Czernin
O Witte
W Weber
P Michel
J Heath
L Wu
J Barrio
G Small
S Devos
D
I Mellinghoff
C Radu
T Graeber
H Tseng
A Wu
C Shen
M Van Dam
C Wu
H Huang
D Stout
R Silverman
R Sumida
J Edwards
W Lladno
A Liu
D Truong
V Dominguez
and
R Taschereau
G Alexandrakis
D Prout
F Rannou
YC Chun
Y Shao
P Ray
F Berger
V Kenanova
T Olafsen
PL Chow
Y Tai
N Vu
Z Tak For Yu
J Shu
J Cho
Q Bao
A Douraghy
N Karakatsanis
A Loening
L
i
B Bai
also
Siemens Preclinical Solutions
Radiation Monitoring Devices
NIH – NCI, NIBIB, DOE, JCCC