NMR Microscopy

Stef VanGordenJoseph Hornak

Rochester Institute of Technology

Objective

• The main goal of this research was to create a NMR microscope capable of producing a 1 mm thick, approximately 112 micron in-plane resolution tomographic images.

• Bruker 300 DRX Spectrometer

Overview of my Presentation

• Background

• Experimental

• Applications

• Conclusions

BACKGROUND

E = hhB

(Hornak 1997)

Bz/T

Energy Level Diagram

Gy

Sample with a Uniform Field

(Hornak 1997)

Hydrogen Molecules

S

N

Sample with Increasing Gradient

Gy

(Hornak 1997) B = x Gx

Hydrogen Molecules

EXPERIMENTAL

Starting Point

• Reproduction of previous 1-D and 2-D imaging results.

• Slice Selective Sequence Evaluation

Slice Selective Sequence

Slice Selective Case (tomographic slice)

Gz

Gy

Gx

Timing Diagram for the Slice Selective NMR Microscope

Variables

Thick Slice (From ~1mm to ~10 mm)

Width of 90° pulse = 80 µstw (180°) =160 µs

Amplitude attenuation = 20 dB

Thin Slice(From ~.5 mm to ~1 mm)

Width of 90° pulse = 157 µstw (180°) = 314 µs

Amplitude attenuation = 26 dB

THK = 2/(Gztw)

Applying Gradients

THK = 2/(Gztw)

100% =50 G/cm Maximum

10% = 5 G/cm => 6 mm

60% = 30 G/cm => 1 mm

Feature Documentation

In-plane Resolution Phantoms

Slice Thickness Phantoms

In-plane Resolution

In-plane Resolution

Fishing line in capillary tubes Glass rods

112 m

284 m

In-plane Resolution

45 m -- 112 m

object --- image

Object Size vs. Image Size

0

1000

2000

3000

4000

5000

0 2000 4000 6000

Object Size [microns]

Ima

ge

Siz

e

[mic

ron

s] Ideal Values

Actual results

0

100

200

300

400

500

0 50 100 150

1 pixel = 23.7 m

Slice Thickness Phantom

Screw phantom in sample tube

Signal from the screw phantom.

THK = ( (1/32 in/threads)(25.4 mm/in)THK = .8 mm for an angle of 360°

Nylon Screw Phantom Images

z

y

x

y

x

y

x

y

x

y

One or more rotations

Less than one rotation

Cone Phantom Design

Illustration of Cone Phantom

Cone Phantom Images

Images with slice thickness of 1mm and .5 mm respectively.

.711 mm

4°

Portion of Sample Tube (profile of middle)

Analyzing Wedge Images

.55mm

4.25mm

APPLICATIONS

Celery Images

Day 1: Images Two Weeks Later

Thick slice Thinner slice Thinnest slice

House Fly Image

Conclusion

• Moved practical NMR microscopy at RIT closer to reality.

• Current Capabilities slice thickness ~.5 mm in-plane resolution ~ 100

microns

The Next Step ...

• Slice Selection Locator• SNR improvements• Further In-plane

Resolution Evaluation

x

y

Slice SelectionLocator