ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Development and assessment of
quantitative oxygen-enhanced MRI in
patients with obstructive lung disease
Ninth meeting of the Strategic Alliance
ISBE, University of Manchester 29 September 2003
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Project objectives
• To implement methods for measuring oxygen-enhanced MRI (OEMRI) in the lung.
• To extend these methods to quantitative parametric mapping of
dynamic OE-MRI in the lung
• To apply these methods in a cohort of normal volunteers and chronic
obstructive pulmonary disease (COPD) patients to assess aspects
of lung function and technique reproducibility
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Imaging
•
•
•
•
IR HASTE sequence, 10mm thick coronal slice
6 normal volunteers
MR compatible Intersurgical Bain Breathing system with 9.5 m tube
volunteers commented that breathing was uncomfortable especially
on expiration
• Protocol (approx 10 minutes per slice)
air
T1
oxygen
dynamic
air
T1
time
dynamic
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Image registration
• attempts at registration using clamped plate spline had limited
success, partly due to the difficulty in defining corresponding points
around lung outline
• try something simpler as a first approximation:
– assume most variation is in vertical direction
– resample points along top edge of lung and diaphragm at
discrete x-locations and perform simple linear stretch
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Results: T1 maps
selecting images for which right
diaphragm position matches to <2 pixels
registering all images by 1D linear
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
T1 maps breathing air and oxygen
air
oxygen
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
T1 maps breathing air and oxygen
air
oxygen
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
1/T1(O2) – 1/T1(air)
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Results: dynamic sequence
ROI top third of right lung
blue: raw images red: registered images
ROI middle third of right lung
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Results: dynamic sequence
ROI bottom third of right lung
blue: raw images red: registered images
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Results: dynamic sequence
ROI top third of right lung
blue: raw images red: registered images
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Results: dynamic sequence
ROI middle third of right lung
blue: raw images red: registered images
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Results: dynamic sequence
blue: raw images red: registered images
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
sd(raw) – sd(registered)
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Oxygen uptake time
• very little literature on dynamic measurements
– Hatabu et al (2001) fit to exponential using ROI whole right or left
lung, found decay times of 27±10s (9 subjects)
– Muller et al (2002) pixel by pixel straight line fit, find mean slope
of 10±1% per min and total signal change of 15±6% (4
volunteers) i.e. total uptake time of about 90s
• fit whole of right lung to exponential function, find decay time 50±12s
(for 4 volunteers)
• fit 8 ROI in right lung to slope plus constant to find average total
uptake time of around 100s (1 volunteer)
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Summary
• pilot study on volunteers has demonstrated that we can measure
oxygen enhancement in the lung
• average T1 values while breathing air and O2 are in agreement with
published data
• using a simple registration we can obtain higher quality regional T1
maps than have previously been reported and this allows the
calculation of (1/T1(oxygen)-1/T1(air)) maps
• registration allows the calculation of uptake times without the need
for temporal smoothing- find longer times then previously reported,
possibly due to differences in breathing apparatus
• publication opportunities:
– ISMRM
– journal publication (on registration?)
ISBE-AstraZeneca Strategic Alliance Project 23
Progress Report
Future plans
• construct and test alternative breathing system
– exchange face mask for mouth piece
– replace anaesthetic trolley with simple solenoid valve for more
rapid switching between air and O2
– monitor oxygen concentration at the mouth piece
– test Bain system vs. non-rebreathing system
– test different flow rates
• COPD patients
– ethics application
– patient recruitment Wythenshaw
• MR protocol
– optimise inversion time
– investigate rapid T1 mapping e.g. Snapshot FLASH, TrueFISP