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