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HEAPHY 1 & 2DIAGNOSTIC
Delia DEPHOFF
Fri 30th Aug 2013Session 2 / Talk 3
11:22 – 11:33
ABSTRACTEarlier this year Lakes Radiology was approached by Scion in Rotorua about using MRI and CT as part of a research project to assess the amount of water in wood. This paper reviews the process of setting up scan protocols, problems encountered and how they were solved, the significance of using MRI and CT, how the information obtained from the scans has assisted the researchers and what has been learned from this experience.
AS WET AS FOUR SHORT PLANKSDelia DephoffNZIMRT Conference 2013 Hamilton
Using MRI and CT for scientific research – one MRT’s experience
INTRODUCTION
Background – who, what and whyTrials scans – setting things up Research series – modifications along the way Review – was it of value, and what I learned
BACKGROUND - WHO Scion - Crown Research Institute
dedicated to improving the international competitiveness of the New Zealand forest industry and building a stronger biobased economy.
Lakes Radiology - TRG Group – private medical imaging facility
WHO
Slobodan the researcher Delia the MRT
BACKGROUND - DISCUSSION Research on different wood drying
processes
Why CT and MRI? Non-destructive measurement of the
moisture content of wood
What was different about this research? 1st time MR &CT used in same research
BACKGROUND - WOOD DRYING PROCESSES
Kiln dried wood (KD) – dries from the outside –resulting in cracking and warping
Dewatered wood (DW) – basically replaces water in wood with alcohol which is then extracted – wood dried quickly from the inside – minimise cracking and warping
TRIAL SCANS
TRIAL SCANS - AIM
To scan the wood to set scan parameters
To assess the data obtained and determine if the information would be useful for the research.
THE WOOD Pinus Radiata 100x50x600mm (2 foot 4x2)
TRIAL SCANS
Matching their expectations to the capability of the
scanners
TRIAL SCANS – POSITIONING
TRIAL SCANS - TECHNICAL FACTORS?
CT PROTOCOL Based on extremity scan Dropped to 80 kVp , eff 50mAs (32mAs) Kernals – soft tissue (B41s) and Bone (B70s) 2mm slices and 0.75mm slices Pitch 1.5 16x0.6m Rotation time 1.5 Scan time 44.75s CTD I Vol 1.43 mGy
TRIAL SCANS - CT
TRIAL SCANS - CT - ISSUES
Images - Streaking artefact ?partial volume averagingbeam hardening (Seeram, 2001)
TRIAL SCANS - CT SCANS - SOLUTIONS
TRIAL SCANS - MRI - ISSUES
Length of wood vs FOV Coils – spine coil and body matrix x
2 T1, PD, T2 Scanned a small block 5mm slices
TRIAL SCANS - MRI - COILS
TRIAL SCANS - DATA
HUGE amount of data esp CT Raw data – 2.5GB Siemens technical help Transferred data onto external hard
drive
RESEARCH SERIES
RESEARCH SERIES1st series – comparing kiln dried wood to de-watered wood
2nd series – de-watered wood, Green, 3xDW, 5xDW, 10xDW
3rd series – unexpected results therefore re-scan after 2xDW and 10xDW
1ST SERIES – CT KD PRE & POST
1ST SERIES – CT DW PRE & POST
1ST SERIES - MRI - ISSUES Wanted whole length of wood scanned Change parameters slightly Scan in two blocks, with overlap Slice 7mm Scan time approx 5mins each - 6 scans
– 30mins to scan each set of woodT1 PD T2
TR 768 3580 4660TE 22 37 92
1ST SERIES – MRI KD – PRE ONLYT1 PD T2
1ST SERIES – MRI DW PRE & POSTT1 PD T2
1st
2nd
2ND SERIES – MRI PRE & POSTT1 PD T2
Talked and asked questions – resulted in some minor adjustments to the research
Wood processing Basics of CT and MRI
Hounsfield Units Kernals – AKA Convolution filters B41s high frequency filter B70s low frequency filter (Bushong 2000) B90s
WHAT DO YOU DO WHILE SCANS ARE RUNNING?
3RD SERIES Results from 2nd series not quite as
expected Water content was down after 3 DW,
but increased after 5 DW, down again after 10DW
2x DW to 10 x DW Use alcohol as a reference
3RD SERIES WITH TUBE OF ALCOHOL - CT
3RD SERIES - CT
3RD SERIES MRI
3RD SERIES - MRIT1 PD T2
Green
2DW
10DW
REVIEW
WAS THE SCAN DATA OF HELPFUL FOR THEIR RESEARCH?
Yes and no PD most useful MR scan Amount of data, especially CT –
time to analyse Unexpected results
WHAT HAVE I LEARNED? To get everything set on the trial
scans, minimise errors, variables – check all parameters match
If there are options (e.g. kernals) give all for analysis
Revise CT and MR physics
WHAT HAVE I LEARNED? Water content of wood, free water and
bound water Wood drying processes – kiln, dewatering
and oven drying
You cannot measure the water content of a wet piece of wood, but you can measure how much water it used to contain once it has been dried.
WOULD I DO IT AGAIN?
YES!
THANKS TO Scion Research Lakes Radiology – TRG Group Slobodan Bradic
REFERENCES Bushong, S.C. (2000) Computed tomography. Mc
Graw-Hill: New York Seeram, E. (2001) Computed tomography. Physical
principles, clinical applications, and quality control (2nd ed). Saunders: Philadelphia