isbe-astrazeneca strategic alliance project 23 progress report development and assessment of...

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


Progress Report

Project objectives

• To implement methods for measuring oxygen-enhanced MRI (OE-MRI) 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


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)

T1 T1 dynamic dynamic

air oxygen air

time


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


Progress Report

Results: T1 maps

selecting images for which right diaphragm position matches to <2 pixelsselecting images for which right diaphragm position matches to <2 pixels

registering all images by 1D linear


Progress Report

T1 maps breathing air and oxygen

air oxygen


Progress Report

1/T1(O2) – 1/T1(air)


Progress Report

Results: dynamic sequence

ROI top third of right lung ROI middle third of right lung

blue: raw images red: registered images


Progress Report


ROI bottom third of right lung



Progress Report


ROI top third of right lung



Progress Report


ROI middle third of right lung



Progress Report




Progress Report

sd(raw) – sd(registered)


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)


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?)


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

isbe-astrazeneca strategic alliance project 23 progress report development and assessment of...

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