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

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3.4 Animals The in vivo experiments in Paper II, III, and IV were performed on naïve animals (Paper II: four male Wistar rats, Paper III: four male Albino guinea pigs, Paper IV: six male Sprague-Dawley rats). Both naïve (ten male Wistar rats) and diseased (ten male Wistar rats instilled with lipopolysaccaride (LPS)) animals were investigated in Paper V. The animal experiments were approved by the local ethical committee (Malmö/Lunds djurförsöksetiska nämnd). 3.5 Investigation of dissolved 129 Xe for MRA applications In Paper I, the potential for angiographic use of hyperpolarized imaging agents was investigated. Ethanol was chosen as a carrier agent for hyperpolarized 129 Xe, due to the high solubility (Ostwald solubility coefficient 1.47) of Xe in this carrier (Himm 1986). 3.5.1 Properties of hyperpolarized 129 Xe dissolved in ethanol Plastic syringes were filled with 25 ml ethanol and connected to a Tedlar bag containing hyperpolarized 129 Xe (isotopically enriched to 75%). After filling the syringe with 35 ml of gas, the syringe was shaken intensively to dissolve the 129 Xe. The dissolved concentration of 129 Xe was measured by 129 Xe NMR spectra by comparing the area of the dissolved spectral peak (163 ppm) with the area of the gas peak (0 ppm). The relaxation times of dissolved 129 Xe were measured by NMR spectroscopy applied to syringes without any gaseous content. The T 1 relaxation was measured by applying a train of 16 excitation pulses with a small flip angle (3°) and 12 s repetition time (TR). The T 2 relaxation was measured using a Carr-Purcell-Meiboom-Gill (CPMG) multi-echo sequence (128 echoes, inter-echo time 100 ms). The T 1 relaxation was additionally measured in syringes where the ethanol had been pre-bubbled with helium to expel any dissolved oxygen. 3.5.2 Imaging of flowing 129 Xe and image analysis A flow phantom was constructed that consisted of two tubes with 6-mm diameter. With a constant, gravity driven, flow of ethanol through the phantom (mean velocity 15 cm s –1 ), dissolved hyperpolarized 129 Xe was injected upstream of the phantom and rapid SE-EPI images (scan time 44 ms) were acquired repeatedly with 1.5-s intervals during the passage of the Xe bolus. 30
The images were evaluated with respect to artifacts and SNR, by means of region of interest (ROI) measurements. To investigate potential losses of hyperpolarization during the dissolving procedure, a syringe filled with thermally polarized 129 Xe was imaged for 5 h using an SE-EPI sequence. The SNR of the thermally polarized Xe was compared with the SNR of the hyperpolarized EPI images after normalization with respect to polarization, concentration, and differences in imaging parameters. 3.6 Vascular imaging of a 13 C-based imaging agent In Paper II, the trueFISP pulse sequence was optimized to match the properties of the hyperpolarized 13 C imaging agent, in order to obtain in vivo angiograms. To describe the signal evolution of a hyperpolarized substance, when imaged with the trueFISP sequence (including a preparation RF pulse, see section 3.3.1), the following expression was derived: θ ⎛ 2 2 θ 2 2 θ⎞ S( θ, n)∝ sin ⎜ E1cos + E2sin ⎟ 2⎝2 2⎠ n 2 [23] where E1 = exp( −TR T1) , E2 = exp( −TR T2) , θ is the flip angle, and n the number of applied RF excitations. 3.6.1 In vitro investigations — sequence optimization In a first experiment, the image SNR was measured as a function of the flip angle. Syringes were filled with the hyperpolarized agent and imaged sequentially at different flip angles. The first and last syringe were imaged with the same flip angle, and the difference in signal intensity was used for calculation of the T 1 relaxation value, which subsequently was used to normalize all the image intensities as regards the signal decay between polarization and imaging. For comparison, the corresponding experiment was also performed using a FLASH pulse sequence. In a second experiment, 15 rapid trueFISP images were acquired with 180° flip angle and no time gap between images. The signal decrease in these images was taken as a measure of the T 2 relaxation, since the magnetization should ideally be present entirely in the transverse plane during the experiment. 31
Page 1: ��
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 and 20: vector addition of all the magnetic
Page 21 and 22: illustrates the difference between
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: Table 5. Parameters of the imaging
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
Page 84 and 85: formance of the gradient system, si
Page 86 and 87: S. MÅNSSON ET AL. Fig. 2. a-h) EPI
Page 88 and 89: 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
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also to several other sources such
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low γ of 13 C reduces the sensitiv
Page 105 and 106:
9. Chawla MS, Chen XJ, Möller HE,
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My 1 0.8 0.6 0.4 0.2 0 0 50 100 150
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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
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230 Deninger et al. FIG. 9. Monte C
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232 Deninger et al. 5. Gur D, Draye
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3 He MRI-based measurement of posit
Page 129 and 130:
Introduction It is well known that
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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
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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
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Paper V
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Abstract The ability to quantify pu
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lation and perfusion information by
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Applying the conditions at the inne
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where L is obtained from Eq. [8]. V
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After tracheal intubation, the anim
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Parametric analysis The fit of the
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in the LPS-treated group is consist
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3. Worsley DF, Palevsky HI, Alavi A
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enin activity in rats chronically e
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V-20 blood without Xe C a V a (t) L
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V-22 Error in estimated diffusion l
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V-24 NMR Ventilator repetition loop
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Figure 7. The peak amplitudes (circ
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