Hyperpolarized Nuclei for NMR Imaging and Spectroscopy - Lunds ...

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6 N m = exp( Em kBT) + I exp( Ei kBT) ∑ i=−I where N m is the number of nuclei in the state m, E m is given by Eq. [1], and T is the temperature. By combining Eqs. [4] and [6], it follows that P can be expressed as 2.2 Hyperpolarization P = 2.2.1 The “brute-force” approach [6] ⎛ B ⎞ ⎜ ⎟ . [7] ⎝ 2kT ⎠ tanh γ h 0 From Eq. [7], it follows that the thermal polarization increases with increasing magnetic field strength and decreasing temperature. A straightforward, “brute-force” approach to increase the polarization in a sample consists of subjecting it to a very strong magnetic field at a temperature close to absolute zero. The polarizations of selected nuclei at 1.5 T and 310 K, and at 20 T and 4 K (the temperature of liquid helium), are shown in Table 1. Table 1. The polarization of selected nuclei at 1.5 T and body temperature, and at 20 T and 4 K. Nucleus Polarization P 1 at 1.5 T, 310 K 1 H 4.9·10 –6 3 He 3.8·10 –6 13 C 1.2·10 –6 129 Xe 1.4·10 –6 Polarization P 2 at 20 T, 4 K 5.1·10 –3 3.9·10 –3 1.3·10 –3 1.4·10 –3 Ratio P 2/P1 1033 1033 1033 1033 The polarization, which is in the ppm range at 1.5 T and body temperature, can hence be increased by a factor of 1000 by cooling down the sample to liquid helium temperature at a field strength of 20 T. If the sample could be brought from 20 T, 4 K to 1.5 T, 310 K instantaneously and without loss of polarization, it could thus be regarded as “hyperpolarized.” Figure 1
illustrates the difference between thermal equilibrium and the hyperpolarized state. Energy Thermal equilibrium Hyperpolarized Figure 1. Pictorial description of the orientation of the nuclei at thermal equilibrium and in the hyperpolarized state. In the figure, the magnetic field (B 0) is directed vertically upwards. Eventually, the polarization level of the hyperpolarized imaging agent returns to its thermal equilibrium value at a rate governed by the longitudinal relaxation rate T 1: Pt () = exp( −tT1) ( P( 0 ) −Pthermal )+ Pthermal . [8] Here, P(0) and P thermal denote the initial and equilibrium polarization values, respectively. The relaxation rate T 1 depends on the chemical and physical environment of the hyperpolarized nucleus, and can range from less than one second to minutes, or even days, for some nuclei. The relaxation rate may differ significantly between in vitro and in vivo conditions. In general, 1 H has relaxation rates below 5 s in vivo, whereas the relaxation rates of the other nuclei in Table 1 can be more than one minute (see sections 2.4.1, 2.4.2, and 2.6.2). Whenever the hyperpolarization is created outside the body, the available signal will depend on the concentration of the imaging agent after administration. Because only a limited amount of the hyperpolarized imaging agent can be administered, its anticipated concentration is 3 to 6 orders of magnitude lower than the natural 1 H concentration in the body. The polarization increase of about 1000 in Table 1 will thus not be sufficient to compen- 7
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Page 4 and 5: DOKUMENTDATABLAD enl SIS 61 41 21 O
Page 6 and 7: Doctoral Dissertation Department of
Page 9 and 10: Abstract Based on the principle of
Page 11 and 12: Original papers This thesis is base
Page 13 and 14: Table of Contents 1 Introduction .
Page 15 and 16: 1 Introduction The phenomenon of nu
Page 17 and 18: By using hyperpolarized imaging age
Page 19: vector addition of all the magnetic
Page 23 and 24: pumping process (Colegrove and Fran
Page 25 and 26: thetic effects, and has been used a
Page 27 and 28: 1 T 1,O2 p = ξ O2 [11] where ξ Xe
Page 29 and 30: 1 2 2 −6 ∝ γC γHrτ c. [17] T
Page 31 and 32: and thus breaks down at very low fr
Page 33 and 34: 230 mT, e.g., Tseng et al. 1998, Du
Page 35 and 36: lation-perfusion ratio (V · A/Q ·
Page 37 and 38: after gas inhalation, due to the wa
Page 39 and 40: tion of an NMR signal from a small
Page 41 and 42: larized gas with air took place as
Page 43 and 44: Table 5. Parameters of the imaging
Page 45 and 46: The images were evaluated with resp
Page 47 and 48: partial pressure present within the
Page 49 and 50: 3.8.2 Measurement procedure The spe
Page 51 and 52: 4.2 Vascular imaging of a 13 C-base
Page 53 and 54: gions. In central lung areas, regio
Page 55 and 56: 4.5 Diffusion capacity and perfusio
Page 57 and 58: 5 Discussion In this thesis, three
Page 59 and 60: due to the increased demand on the
Page 61 and 62: 5.3 Hyperpolarized 3 He ventilation
Page 63 and 64: a theoretical T 1 of ∼38 min in t
Page 65 and 66: eath-holding periods during, e.g.,
Page 67 and 68: 6 Conclusions The phantom study in
Page 69 and 70: 8 References ABRAGAM A, GOLDMAN M.
Page 71 and 72:
CHEN XJ, MÖLLER HE, CHAWLA MS, COF
Page 73 and 74:
GIERADA DS, SAAM B, YABLONSKIY D, C
Page 75 and 76:
KAUCZOR HU, HANKE A, VAN BEEK EJ. A
Page 77 and 78:
OLSSON LE, MAGNUSSON P, DENINGER AJ
Page 79 and 80:
TILTON RF, JR., KUNTZ ID, JR. Nucle
Page 81:
Paper I
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formance of the gradient system, si
Page 86 and 87:
S. MÅNSSON ET AL. Fig. 2. a-h) EPI
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though several technical issues rem
Page 91 and 92:
Hyperpolarized 13 C MR angiography
Page 93 and 94:
Introduction The most widespread te
Page 95 and 96:
of the gradient moments prior to ea
Page 97 and 98:
Methods Polarization procedure The
Page 99 and 100:
secutive trueFISP images were acqui
Page 101 and 102:
also to several other sources such
Page 103 and 104:
low γ of 13 C reduces the sensitiv
Page 105 and 106:
9. Chawla MS, Chen XJ, Möller HE,
Page 107 and 108:
My 1 0.8 0.6 0.4 0.2 0 0 50 100 150
Page 109 and 110:
Signal [a.u] 100 90 80 70 60 50 40
Page 111 and 112:
a b Figure 5. Series of angiograms
Page 113:
Paper III
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224 Deninger et al. FIG. 1. Sketch
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226 Deninger et al. FIG. 2. Coronal
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228 Deninger et al. FIG. 6. Histogr
Page 122 and 123:
230 Deninger et al. FIG. 9. Monte C
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232 Deninger et al. 5. Gur D, Draye
Page 127 and 128:
3 He MRI-based measurement of posit
Page 129 and 130:
Introduction It is well known that
Page 131 and 132:
3 He imaging All experiments were p
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coefficients b 1 and b 2, respectiv
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Using VI data after subtraction of
Page 137 and 138:
To investigate whether the calculat
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14. Gur D, Drayer BP, Borovetz HS,
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Table 1. Gradient of VI [cm −1 ]
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Cycle 1 Cycle 2 Cycle 3 Cycle 4 2 s
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a Prone Ventilation index c Supine
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a Prone Supine 0 b 1 R 2 Prone Supi
Page 149:
Paper V
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Abstract The ability to quantify pu
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lation and perfusion information by
Page 156 and 157:
Applying the conditions at the inne
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where L is obtained from Eq. [8]. V
Page 160 and 161:
After tracheal intubation, the anim
Page 162 and 163:
Parametric analysis The fit of the
Page 164 and 165:
in the LPS-treated group is consist
Page 166 and 167:
3. Worsley DF, Palevsky HI, Alavi A
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enin activity in rats chronically e
Page 170 and 171:
V-20 blood without Xe C a V a (t) L
Page 172 and 173:
V-22 Error in estimated diffusion l
Page 174 and 175:
V-24 NMR Ventilator repetition loop
Page 176:
Figure 7. The peak amplitudes (circ
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