Imaging in Biological Research Part B

496 Pages·2004·6.915 MB·English

by  P. Michael Conn

METHODS IN ENZYMOLOGY
EDITORS-IN-CHIEF
John N. Abelson Melvin I. Simon
DIVISIONOFBIOLOGY
CALIFORNIAINSTITUTEOFTECHNOLOGY
PASADENA,CALIFORNIA
FOUNDINGEDITORS
Sidney P. Colowick and Nathan O. Kaplan
Preface
As these volumes were being completed, American Paul C. Lauterbur and
Briton Sir Peter Mansfield won the 2003 Nobel Prize for medicine for
discoveriesleadingtothedevelopmentofMRI.
The Washington Post story on October 6, 2003 announced the accolade,
noting: ‘‘Magnetic resonance imaging, or MRI, has become a routine method
for medical diagnosis and treatment. It is used to examine almost all organs
withoutneedforsurgery,butisespeciallyvaluablefordetailedexaminationof
thebrain and spinal cord.’’ Unfortunately,the articleoverlooked thegrowing
usefulnessofthistechniqueinbasicresearch.
MRI, along with other imaging methods, has made it possible to glance
inside the living system. For patients, this may obviate the need for surgery;
for researchers, it becomes a noninvasive method that enables the model
systemstocontinue‘‘doingwhattheydo’’withoutbeingdisturbed.Thevalue
and potential of these techniques is enormous, and that is why these once
clinicalmethodsarefindingtheirwaytothelaboratory.
Authors have been selected based on research contributions in the area
about which they have written and based on their ability to describe their
methodologicalcontributionsinaclearandreproducibleway.Theyhavebeen
encouragedtomakeuseofgraphicsandcomparisonstoothermethods,andto
providetricksandapproachesthatmakeitpossibletoadaptmethodstoother
systems.
The editor wants to express appreciation to the contributors for providing
theircontributionsinatimelyfashion,tothesenioreditorsforguidance,andto
thestaffatAcademicPressforhelpfulinput.
P. Michael Conn
xi
Contributors to Volume 386
Articlenumbersareinparenthesesandfollowingthenamesofcontributors.
Affiliationslistedarecurrent.
Ellen Ackerstaff (1), Department of Kishore K. Bhakoo (14), Stem Cell Ima-
Radiology, The Johns Hopkins Univer- ging Group, MRC Clinical Sciences
sity School of Medicine, Baltimore, Centre, Faculty of Medicine, Imperial
Maryland21205 College London, Hammersmith Hospi-
tal,LondonW120HS,UnitedKingdom
Shivani Agarwal (2), Department of
NeurologicalSurgery,ColumbiaUniver- ZaverM.Bhujwalla(1),Departmentof
sity,NewYork,NewYork10032 Radiology, The Johns Hopkins Univer-
sity School of Medicine, Baltimore,
Noam Alperin (16), Physiologic Imaging
Maryland21205
andModelingLab,DepartmentofRadi-
ology, The University of Illinois at David A. Bluemke (5), Department of
Chicago,Chicago,Illinois60612 Radiology, Johns Hopkins Hospital,
The Johns Hopkins University School
CarolynJ.Anderson(11),Mallinckrodt ofMedicine,Baltimore,Maryland21287
InstituteofRadiology,WashingtonUni-
versity School of Medicine, St. Louis, Jeff W. M. Bulte (13), Department of
Missouri63110 Radiology and Institute for Cell Engi-
neering, The Johns Hopkins University
Ali S. Arbab (13), Laboratory of Diag- SchoolofMedicine,Baltimore,Maryland
nostic Radiology Research, Experimen- 21205-2195
tal Neuroimaging Section, National
E.SanderConnolly,Jr.(2),Department
InstitutesofHealth,Bethesda,Maryland
ofNeurologicalSurgery,ColumbiaUni-
20892
versity,NewYork,NewYork10032
DmitriArtemov(1),DepartmentofRadi- I. Jane Cox (14), Imaging Sciences De-
ology, The Johns Hopkins University
partment,MRCClinicalSciencesCentre,
SchoolofMedicine,Baltimore,Maryland
Imperial College London, Hammer-
21205
smith Hospital, London W12 0HS,
MarkD.Bednarski(10),LucasMRIRe- UnitedKingdom
searchCenter,DepartmentofRadiology, AnthonyL.D’Ambrosio(2),Department
StanfordUniversity,Stanford,California, ofNeurologicalSurgery,ColumbiaUni-
94305-5488 versity, New York, New York 10032-
2699
Jimmy D. Bell (14), Molecular Imaging
Group, MRC Clinical Sciences Centre, MilindY.Desai(5),DivisionofCardiol-
ImperialCollegeLondon,Hammersmith ogy, Department of Internal Medicine,
Hospital, London W12 0HS, United The Johns Hopkins University School
Kingdom ofMedicine,Baltimore,Maryland21287
vii
viii contributors to volume 386
T. Douglas (13), Department of Chemis- Joa˜oA.Lima(5),DivisionofCardiology,
try and Biochemistry, Montana State Department of Internal Medicine, The
University,Bozeman,Montana59717 Johns Hopkins University School of
Medicine,Baltimore,Maryland21287
J.A.Frank(13),LaboratoryofDiagnos-
tic Radiology Research, Experimental Pengnian Charles Lin (4), Department
Neuroimaging Section, National Insti- of Radiation Oncology, Vanderbilt
tutes of Health, Bethesda, Maryland University Medical Center, Nashville,
20892 Tennessee37232
BarjorGimi(1),DepartmentofRadiology, Hanli Liu (17), Biomedical Engineering
The Johns Hopkins University School Program, The University of Texas at
ofMedicine,Baltimore,Maryland21205 Arlington,Arlington,Texas76019
Kristine Glunde (1), Department of Jia Lu (8), Defence Medical Research
Institute,Singapore117510
Radiology, The Johns Hopkins Univer-
sity School of Medicine, Baltimore, Mark F. Lythgoe (6), RCS Unit of Bio-
Maryland21205
physics, Institute of Child Health, Uni-
versityCollegeLondon,LondonWC1N
Yueqing Gu (17), Biomedical Engineer-
1EH,UnitedKingdom
ing Program, The University of Texas
atArlington,Arlington,Texas76019 WilliamJ.Mack(2),DepartmentofNeu-
rological Surgery, Columbia University,
Samira Guccione (10), Lucas MRI Re- NewYork,NewYork10032
search Center, Department of Radiol-
ogy, Stanford University School of Pasquina Marzola (7), Anatomy and
Medicine, Stanford, California 94305- Histology Section, Department of Mor-
5488 phologicalandBiomedicalSciences,Uni-
versityofVerona,Verona37134 Italy
ChienHo(3),PittsburghNMRCenterfor
Biomedical Research, Department of Ralph P. Mason (17, 18), Department of
Radiology, The University of Texas
Biological Sciences, Carnegie Mellon
University, Pittsburgh, Pennsylvania Southwestern Medical Center at Dallas,
Dallas,Texas75390-9058
15213
J.Mocco(2),DepartmentofNeurological
Lan Jiang (18), The University of Texas
Surgery,ColumbiaUniversity,NewYork,
Southwestern Medical Center at Dallas,
NewYork10032
Dallas,Texas75390
ShabbirMoochhala(8),DefenceMedical
Jae G. Kim (17), Biomedical Engineering ResearchInstitute,Singapore117510
Program, The University of Texas at
Arlington,Arlington,Texas76019 Arvind P. Pathak (1), Department of
Radiology, The Johns Hopkins Univer-
RyanG.King(2),DepartmentofNeuro- sity School of Medicine, Baltimore,
logical Surgery, Columbia University, Maryland21205
NewYork,NewYork10032
Richard L. Roberts (4), Department of
KincC.P.Li(10),DepartmentofRadiol- Pathology, Vanderbilt-Ingram Cancer
ogy, Stanford University, Stanford, CA Center, Vanderbilt University Medical
94305-5488 Center,Nashville,Tennessee37232
contributors to volume386 ix
KazuyaSato(3),PittsburghNMRCenter John S. Thornton (6), Lysholm Depart-
for Biomedical Research, Department ment of Neuroradiology, National Hos-
ofBiologicalSciences,CarnegieMellon pital for Neurology and Neurosurgery,
University, Pittsburgh, Pennsylvania UCLH NHS Trust, London WC1N
15213 3BG,UnitedKingdom
Andrea Sbarbati (7), Anatomy and Louise van der Weerd (6), RCS Unit of
Histology Section, Department of Mor- Biophysics, Institute of Child Health,
phological and Biomedical Sciences, University College London, London
University of Verona, Verona, Italy WC1N1EH,UnitedKingdom
37134
HuaWu(9),DepartmentofNuclearMed-
Daniel M. Sforza (15), Department icine, Tongji Hospital, Tongji Medical
of Molecular and Medical Pharmaco- College,HuazhongUniversityofScience
logy, UCLA School of Medicine, Los andTechnology,Wuhan430030,China
Angeles,California90095-1735
Yi-JenL.Wu(3),PittsburghNMRCenter
Desmond J. Smith (15), Department forBiomedicalResearch,Departmentof
of Molecular and Medical Pharmaco- Biological Sciences, Carnegie Mellon
logy, UCLA School of Medicine, Los University, Pittsburgh, Pennsylvania
Angeles,California90095-1735 15213
PeterM.Smith-Jones(12),NuclearMed- Qing Ye (3), Pittsburgh NMR Center for
icineService,DepartmentofRadiology,
Biomedical Research, Department of
Memorial Sloan-Kettering Cancer Cen-
Biological Sciences, Carnegie Mellon
ter,NewYork,NewYork10021
University, Pittsburgh, Pennsylvania
DavidB.Solit(12),DepartmentofMed- 15213
icine, Memorial Sloan-Kettering Cancer
XuemeiZhang(9),DepartmentofNucle-
Center,NewYork,NewYork10021
ar Medicine, Tongji Hospital, Tongji
Michael E. Sughrue (2), Department of Medical College, Huazhong University
NeurologicalSurgery,ColumbiaUniver- of Science and Technology, Wuhan
sity,NewYork,NewYork10032 430030,China
Xiankai Sun (11), Mallinckrodt Institute Zhenwei Zhang (9), Department of Nu-
of Radiology, Washington University
clear Medicine, Tongji Hospital, Tongji
SchoolofMedicine,St.Louis,Missouri
Medical College, Huazhong University
63110
of Science and Technology, Wuhan
SimonD.Taylor-Robinson(14),Depart- 430030,China
ment of Medicine, Imperial College
London, Hammersmith Hospital, Dawen Zhao (18), The University of
LondonW120HS,UnitedKingdom Texas Southwestern Medical Center at
Dallas,Dallas,Texas75390
David L. Thomas (6), Wellcome Trust
High Field MR Research Laboratory, Ming Zhao (9), Department of Nuclear
Department of Medical Physics and Medicine,TongjiHospital,TongjiMed-
Bioengineering, University College ical College, Huazhong University of
London, London WC1E6JA, United Science and Technology, Wuhan
Kingdom 430030,China
[1] molecularand functional imagingof cancer 3
[1] Molecular and Functional Imaging of Cancer:
Advances in MRI and MRS
By Arvind P. Pathak, Barjor Gimi, Kristine Glunde,
Ellen Ackerstaff, Dmitri Artemov, and Zaver M. Bhujwalla
Introduction
Cancer is a disease that exhibits a degree of multiplicity and redun-
dancy of pathways almost protean in nature. To understand and exploit
molecular pathways in cancer for therapeutic strategies, it is essential not
onlytodetectandimagetheexpressionofthese pathways, butalso tode-
termine the impact of this expression on function at the cellular level, as
wellaswithinthecomplexsystem, whichis atumor.Multiparametricmo-
lecularandfunctionalimagingtechniqueshaveseveralkeyrolestoplayin
cancertreatment,suchasrevealingkeytargetsfortherapy,visualizingde-
livery of the therapy, and assessing the outcome of treatment. As a tech-
nique, magnetic resonance (MR) has a formidable array of capabilities to
characterize function. Noninvasive multinuclear magnetic resonance im-
aging (MRI) and MR spectroscopic imaging (MRSI) provide a wealth of
spatial and temporal information on tumor vasculature, metabolism, and
physiology.MRisthereforeparticularlyapplicabletoinvestigatingacom-
plex disease such as cancer. Several of the MRI techniques are also trans-
latable into the clinic, and are therefore compatible with ‘‘bench to
bedside’’applications.
Tumor vasculature plays an important role in growth, treatment, and
metastatic dissemination. The first section in this chapter therefore de-
scribes the use of MRI techniques and the underlying assumptions and
mechanisms in characterizing tumor vasculature. Recent advances in the
development of targeted contrast agents have significantly increased the
versatilityofMRformolecularimaging.AlthoughMRtechniquesprovide
a wealth of structural and functional information, MR suffers from poor
sensitivity.Thesecondsectiondiscussestheuseoftargetedcontrastagents
and amplification strategies to increase the sensitivity of detection of mo-
lecular targets in MR molecular imaging of cancer. Technical strategies
to improve the signal to noise ratio (SNR) for applications of MR mi-
croscopyincancerarealsoincludedinthissection.BecauseMRspectros-
copy(MRS)andMRSIprovideinformationonmetabolismandpH,MRS
applications in cancer are reviewed in the third section. One of the most
exciting aspects of MR is the ability to perform multiparametric imaging.
Copyright2004,ElsevierInc.
Allrightsreserved.
METHODSINENZYMOLOGY,VOL.386 0076-6879/04$35.00
4 disease models [1]
In the fourth section, we present two examples of the use of multipara-
metricimaginginunderstandingcancercellinvasionandincharacterizing
the relationship between tumor vasculature and metabolism.
Vascular Imaging of Tumors with MRI
MRI techniques can be used to characterize several aspects of tumor
vasculature. Tumor vasculature is typified by structural and functional
anomalies that include alterations in hemodynamics, blood rheology,
permeability,anddrainage,andplaysacriticalroleincancergrowth,treat-
ment,andmetastasis.VascularMRmethodsarethereforeusefulincancer
treatment and management. An overview of the endogenous and exoge-
nousMRcontrastmechanismsutilizedincharacterizingtumorvasculature
is presented inthis section.
MR Relaxation Mechanisms and the Basis of Contrast
Everycontrastmechanismforprobingthetumorvasculature,including
the use of exogenous MR contrast agents, is in some way a result of
changes in the MR signal intensity brought about by changes in tissue re-
laxation times (T , T , or T *). Briefly, T , the spin–lattice or longitudinal
1 2 2 1
relaxationtime,isthetimeconstantthatcharacterizestheexponentialpro-
cessbywhichthemagnetizationreturnsor‘‘relaxes’’toitsequilibriumpo-
sition. It does so by exchanging energy with its surroundings, or lattice, at
theLarmorfrequency.T relaxationoccursatthemolecularlevelthrough
1
several pathways, including interactions between protons in tissue water
and those on macromolecules or proteins, and by interactions with para-
magneticsubstances(i.e.,substanceswithunpairedelectronsintheirouter-
most shells). T -based MR contrast results from differences in T
1 1
dominating the MR signal intensity. For example, tissues with short T s
1
(such as fat) appear bright in T -weighted MRI, since the transverse mag-
1
netizationrecoverstoequilibriumrapidlycomparedwithtissueswithlong
T s (such ascerebrospinal fluid).
1
Microscopic magnetic field heterogeneities inthe main field, aswell as
variations in local magnetic susceptibility due to the physiologic microen-
vironment,causespinscontributingtothetransversemagnetizationtolose
phase coherence. The process through which this occurs is known as T *
2
relaxation.Thelossintransversecoherenceattributabletostaticmagnetic
fieldheterogeneitiescanberecoveredusingaspin–echosequenceorare-
focusing pulse. However, as protons diffuse through the microscopic field
inhomogeneities, they also lose phase coherence due to their Brownian
random walks through the magnetic field gradients, which result in phase
[1] molecularand functional imagingof cancer 5
dispersionthatcannotbereversedbytheapplicationofarefocusingpulse.
ThisprocessisknownasT relaxation.InT -weightedMRimages,tissues
2 2
with short T s, such as the liver, appear dark due to the rapid decay of
2
transverse magnetization compared with those with long T s, such as fat.
2
Similarly, in T *-weighted images, regions with large susceptibility gradi-
2
ents, such as air–tissue interfaces of the inner ear or orbits of the eye, or
large veins carryingdeoxygenated blood, appear hypointense.
In general, the addition of a paramagnetic solute causes an increase
in the 1/T and 1/T of solvent nuclei. The diamagnetic and paramagnetic
1 2
contributions to the relaxation rates of such solutions are additive and
areexpressed as1:
(cid:1) (cid:2) (cid:1) (cid:2) (cid:1) (cid:2)
1 1 1
¼ þ i¼1;2 (1)
Ti Ti Ti
obs d p
where(1/Ti) istheobservedsolventrelaxationrateinthepresenceofa
obs
paramagnetic species (e.g., contrast agent), (1/Ti) is the (diamagnetic)
d
solvent relaxation rate in the absence of a paramagnetic species, and
(1/Ti) representstheadditionalparamagneticcontribution.Intheabsence
p
of any solute–solute interactions, the solvent relaxation rates (in solution)
are linearly dependent on the concentration of the paramagnetic species
[M], and if (1/Ti) or the relaxivity R, is defined as the slope of this
i
dependencein mM(cid:3)1 s(cid:3)1, we may write Eq. (1)as:
(cid:1) (cid:2) (cid:1) (cid:2)
1 1
¼ þR½M(cid:5) i¼1;2 (2)
i
Ti Ti
obs d
All molecules, large and small, are in a constant state of motion, tum-
bling and colliding with other molecules. Intramolecular motion, as well
as interaction with nearby molecules, produces fluctuations in the local
magnetic field experienced by a proton. It turns out that these magnetic
interactions can promote both T and T relaxation, but whether they do
1 2
so depends on the rate at which their magnetic fields fluctuate. For
example,asmallmoleculesuchaswatermovesquickly,sothatitproduces
rapid magnetic fluctuations. A large molecule such as a protein moves
moreslowlyandproducesmagneticfluctuationsatacorrespondinglylower
rate. From the relaxation theory described by Solomon–Bloembergen,2,3
three primary factors that regulate the dipole–dipole interactions respon-
sible for both T and T relaxation are: (1) the strength of the magnetic
1 2
1R.B.Lauffer,Chem.Rev.87,901(1987).
2I.Solomon,Phys.Rev.99,559(1955).
3N.Bloembergen,J.Chem.Phys.27,572(1957).
6 disease models [1]
moment, (2) the separation between the two dipoles, and (3) the relative
motion of the two dipoles.
Intrinsic or Endogenous Contrast
Probing tumor vasculature using intrinsic contrast produced by deoxy-
hemoglobinintumormicrovesselsisbasedonthebloodoxygenationlevel
dependent (BOLD) contrast mechanism first proposed by Ogawa.4 The
concentration of endogenous paramagnetic deoxyhemoglobin is one of
the primary determinants of the eventual image contrast observed. The
presence of deoxyhemoglobin in a blood vessel causes a susceptibility dif-
ferencebetweenthevesselanditssurroundingtissue,inducingmicroscopic
magnetic field gradients that cause dephasing of the MR proton signal,
leadingtoareductioninthevalueofT *(Fig.1).Becauseoxyhemoglobin
2
is diamagnetic and does not produce the same dephasing, changes in oxy-
genation of the blood can be observed as signal changes in T *-weighted
2
images. The functional dependence of T * on oxygenation in a tissue is
2
expressed as:
1
/ð1(cid:3)YÞb (3)
T *
2
where Y is the fraction of oxygenated blood and b the fractional blood
volume. In hypoxic tumors where 0 < Y < 0.2, the contrast produced by
themethodisprimarilydependentonb.Thismethodworksbestinpoorly
oxygenatedtumorssuchassubcutaneousmodels,andinhumanxenografts
withrandomorientationofsproutingcapillaries,anditprovidesafastand
noninvasive measurement of tumor fractional blood volume because ex-
ogenous contrast is not required. However, the method cannot provide
quantitativemeasurementsoftumorvascularvolume,vascularpermeabil-
ity, or blood flow. Nonetheless, this technique has been used to detect
changes in tumor oxygenation and vascularization following induction of
angiogenesis by external angiogenic agents,5 as well as to obtain maps
of the ‘‘functional’’ vasculature in genetically modified HIF-1 (þ/þ and
(cid:3)/(cid:3)) animal models.6 BOLD contrast is not solely related to the oxy-
genationstatusofblood,butisalsoaffectedbyfactorssuchasoxygensat-
uration, the hematocrit, blood flow, blood volume, vessel orientation, and
4S.Ogawa,Magn.Reson.Med.14,68(1990).
5R. Abramovitch, H. Dafni, E. Smouha, L. Benjamin, and M. Neeman, Cancer Res. 59,
5012(1999).
6P. Carmeliet, Y. Dor, J.-M. Herbert, D. Fukumura, K. Brusselmans, M. Dewerchin,
M.Neeman,F.Bono,R.Abramovitch,P.Maxwell,C.J.Koch,P.Ratcliffe,L.Moons,
R.K.Jain,D.Collen,andE.Keshet,Nature394,485(1998).