MR perfusion imaging of pulmonary parenchyma using pulsed arterial spin labeling techniques: FAIRER and FAIR

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Purpose: To investigate the optimal oxygen flow rate for oxygen-enhanced MR ventilation imaging. Materials and Methods:Using a cardiac-triggered nonselective inversion recovery (IR) half Fourier single-shot fast spin echo sequence, series of images were acquired with the subject alternately inhaling room air and 100% oxygen. Oxygen flow rates of 5 L/min, 10 L/min, 15 L/min, 20 L/min, and 25 L/min were studied, and signal intensity from the oxygen-enhanced ventilation images and T 1 of the lung were measured. OXYGEN-ENHANCED MAGNETIC RESONANCE IMAG-ING has been used to assess regional ventilation of the lung in patients with pulmonary diseases and in animal models (1-4). Although oxygen is weakly paramagnetic, its overall effect on the lung is considerable given the large surface area of the lung and the large difference in partial pressures between room air and 100% oxygen. ResultsRelative to breathing room air, inhaling 100% oxygen increases concentration of dissolved oxygen in blood and lung tissue as more oxygen diffuses across the lung parenchyma and dissolves into blood and lung tissues. Consequently, increased concentration of dissolved oxygen in the lung will shorten its longitudinal relaxation time (T 1 ), enabling the detection of signal change if T 1 -weighted sequences such as inversion recovery (IR) or multiple IR are used for image acquisition (1-8). Generally, the procedure of the oxygen-enhanced ventilation imaging technique involves the acquisition of series of images with the subject alternately inhaling room air and 100% oxygen. The difference between the average images of the two states yields the oxygenenhanced ventilation image.To date, oxygen-enhanced ventilation imaging has been performed using different flow rates (1-7,9,10), while no study thus far has been conducted to determine the influence of oxygen flow rate on the signal and T 1 changes in the lung. Logically, if more oxygen dissolves in blood plasma in the lung, a larger detected signal change will result. However, the solubility of oxygen in blood plasma is poor, and therefore a low saturation point would be quickly established. Thus, there should exist an optimal point for changes in signal intensity and T 1 of the lung. The purpose of this study was to investigate the effect of oxygen flow rate for ventilation imaging of the lung with inhalation of 100% oxygen. More specifically, we sought to determine the oxygen flow rate at which optimal changes in signal intensity and T 1 of the lung occur. MATERIALS AND METHODSAll imaging experiments were performed on a CV/i 1.5 T system (GE Medical Systems, Milwaukee, WI) equipped with 40 mT/m gradients and a slew rate of 150 T/m/second. A four-element, receiver phased-array coil was used. Six healthy human volunteers (three males and three females, 25-48 years old, average age 33.7 Ϯ 6.5 years) were imaged. Written informed consent was obtained from each volunteer before experimentation.A series of 60 images at TI of 1200 msec were acquired at each flow rate while the subjects alternately...

Section: Discussionmentioning

confidence: 99%

Influence of oxygen flow rate on signal and T₁ changes in oxygen‐enhanced ventilation imaging

Liu

et al. 2002

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“…During the TI, the blood flows out of the tag and into the lungs, where it is later read out using a 2D FSE (86) or 3D gradient-echo (87) sequence. The portal system has been studied using the tag-alternation method where both tag-on and tag-off images were acquired in a single breath-hold (88).…”

Section: Applicationsmentioning

confidence: 99%

Non‐contrast enhanced MR angiography: Physical principles

Wheaton

Miyazaki

2012

140

Noncontrast‐enhanced magnetic resonance angiography (NCE‐MRA) methods have been demonstrated in anatomies throughout the body. Previously established NCE‐MRA techniques suffered from long scan times or low sensitivity. Advances in hardware and software have made NCE‐MRA scan times clinically feasible. Recent concerns over the safety of gadolinium‐based contrast material combined with the expense of the material and its administration have generated a demand for NCE‐MRA. In response, several new NCE‐MRA methods have been developed. The physical mechanisms underlying five general classes of NCE‐MRA methods (inflow effect, flow‐dependency on cardiac phase, flow‐encoding, spin labeling, and relaxation) are explained. The original techniques of time‐of‐flight (TOF) and phase contrast MRA (PC‐MRA) are briefly introduced. New developments in NCE‐MRA, including hybrid of opposite‐contrast (HOP‐MRA), four dimensional PC‐MRA (4D Flow), cardiac‐gated 3D fast‐spin‐echo, flow‐sensitive dephasing (FSD), arterial spin labeling (ASL), and balanced steady‐state free‐precession (bSSFP) are highlighted. The primary applications, advantages, and limitations of established and emerging NCE‐MRA techniques are discussed. J. Magn. Reson. Imaging 2012;36:286–304. © 2012 Wiley Periodicals, Inc.

“…An arterial spin labeling technique called FAIRER was used (23,24). Inflowing blood was labeled by inverting its magnetization.…”

Section: Perfusion Imagingmentioning

confidence: 99%

“…Arterial spin labeling, originally proposed to measure cerebral blood flow (19 -21), uses blood water as an endogenous, freely diffusible tracer, and has been successfully demonstrated to image pulmonary perfusion (23)(24)(25). In this study, we present a V/Q imaging scheme by combining oxygen-enhanced and an arterial spin labeling technique called flow-sensitive alternating inversion recovery with an extra radiofrequency pulse (FAIRER), which has been previously described (23,24).…”

mentioning

confidence: 99%

MR ventilation‐perfusion imaging of human lung using oxygen‐enhanced and arterial spin labeling techniques

Bankier

Prasad

et al. 2001

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Magnetic resonance ventilation-perfusion (V/Q) imaging has been demonstrated using oxygen and arterial spin labeling techniques. Inhaled oxygen is used as a paramagnetic contrast agent in ventilation imaging using a multiple inversion recovery (MIR) approach. Pulmonary perfusion imaging is conducted using a flow-sensitive alternating inversion recovery with an extra radiofrequency pulse (FAIRER) technique. A half Fourier single-short turbo spin echo (HASTE) sequence is used for data acquisition in both techniques. V/Q imaging was performed in ten of the twenty volunteers, while either ventilation or perfusion was imaged in the other ten. This V/Q imaging scheme is completely noninvasive, does not involve ionized radiation, and shows promising potential for clinical use in the diagnosis of lung diseases such as pulmonary embolism. J. Magn. Reson. Imaging 2001;14: 574 -579.