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

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3.8.1 The alveolar diffusion model The calculations were based on the diffusion of 129 Xe gas from the alveolar space to the pulmonary capillaries in a single-alveolus model. The model defined three compartments: the alveolar gas space, the lung tissue, and the capillary blood surrounding the alveolus (Figure 9a). Fick’s laws of diffusion (Fick 1855, Dowse et al. 2000) were used to describe the transport of 129 Xe within the tissue and capillary. A simple relation was derived, from which the total thickness L (= L t + L b) of the respiratory membrane could be calculated from the measured uptake time constant τ 1: 34 L ≈ D π τ1 . [25] 2 Here, D is the diffusion constant for Xe (∼1·10 –9 m 2 s –1 in plasma (Wolber et al. 2000c)). From this model, it could be shown that the amplitudes of the spectral peaks corresponding to tissue and capillary compartments, respectively, were characterized by an exponential increase during the early phase, followed by a linear increase with time (Figure 9b). It was further demonstrated that the slope and intercept parameters could be used for calculating several physiological parameters (see section 3.8.2). a Lt Lc b blood without Xe r a gas tissue capillary F Signal Sa (0) Sa0 St0 Sb0 slope St1 slope Sb1 Alveolar gas signal Tissue signal Blood signal 0 0.1 0.2 0.3 0.4 0.5 Time (s) Figure 9. a) The single-alveolus diffusion model. The radius of the alveolar gas space is denoted by r a and the thickness of the tissue and capillary compartments by L t and L c, respectively. F is the blood flow passing the alveolar unit. b) Simulations of gas, tissue, and blood (RBC) 129 Xe signals during the diffusion from alveolus to pulmonary capillaries.
3.8.2 Measurement procedure The spectroscopic sequence shown in Figure 8 was repeated 12 times (n = 1, … , 12) with delays ∆(n) ranging from 15 to 500 ms. Between each repetition, the animal was breathing air for 15 inspirations to wash out remaining Xe gas from the lungs. The non-localized spectra of hyperpolarized 129 Xe were acquired with a volume coil. Measurements were performed on one group of 10 naïve rats, and on a second group of 10 rats with acute inflammatory lung injury caused by intratracheal instillation of LPS. The functions Sg( ∆) = S0, g exp( − ∆ τ g) + S1, g ( gas peak) S( ∆) = S0( 1−exp( −∆ τ1) )+ S1∆ ( tissue and blood peaks) [26] were fitted to the amplitudes of the gas, tissue, and blood signals as a function of the delay ∆, similar to the plot in Figure 9b. The resulting time constant τ 1 of the tissue peak was used for calculation of the total diffusion length L (Eq. [25]). The intercepts and slopes of the tissue and blood signals were used for calculation of the thickness of tissue and capillary compartments, respectively, of pulmonary perfusion, mean transit time, and relative blood volume. The alveolar radius was estimated from the initial amplitude of the gas signal and the intercept of the asymptote (see Figure 9b). 35
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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 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 and 44: Table 5. Parameters of the imaging
Page 45 and 46: The images were evaluated with resp
Page 47: partial pressure present within the
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
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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
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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
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a b Figure 5. Series of angiograms
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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
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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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