Small-Animal RF Modules

Simple-tune Pre-Clinical and Research RF Imaging Modules

Small-Animal Litz or Litzcage Modules
MRI coils with best sensitivity, homogeneity, and convenience.

Module-wMouse

Standard products include 1H rf coils as well as dual-frequency coils.
Custom coils are also available.

Easy tuning                   

Mouse Coils – Rat Coils – Rabbit Coils – Primate Head Coils

A unique symmetrizing circuit ensures the coil is easily tuned and matched to the full range of samples with negligible loss in efficiency, channel separation, or symmetry.  The tuning range is much better than with conventional birdcages and tuning methods.

comp-coils-1

Robust Design

Versatile, Robust Design
In Doty Imaging Modules, the rf Litz or Litzcage coils are enclosed in the rf shield and packaged in an integrated aesthetic cover. Coil dimensions are customized to your specifications.

rabbit coil

Exceptional Sensitivity

The linear Litz or CP (circular polarization) Quadrature Litzcage coils have SNR 10-15% higher than with conventional linear or quadrature birdcages of similar dimensions  – and often much better. The B1 homogeneity is 10-30% better and the coils have improved B0 homogeneity.  Simple-tune Litz coils can be easily double-tuned.

Doty RF Litz  or Litzcage Coil Modules

You wouldn’t consider buying something like a computer or spectrum analyzer without reviewing and comparing detailed specifica­tions.  You owe it to yourself to apply the same critical standards when purchasing an rf coil.  With rf coils, the most important criteria usually are S/N, B1 homogeneity, and reliability.  For S/N, simply check the 90° pulse spec.  Regardless of whether it’s single or double resonance, shielded or unshielded, linear or circular polarization, short or long, surface or volume, one simple relationship always holds for a given voxel size and other conditions:

image003

where τ90 is the   90° pulse length (we specify for a hard pulse) and P is the transmitter power. Many of the smaller coils listed in the tables have S/N better by factors of 1.5 to 3 than published birdcages of similar size and tuning. Our 1H Litzcages have truly extraordinary robustnesss, ease-of-use with widely differing samples, homogeneity, and S/N.

Does your τ90 drop by less than a factor of two (at constant P ) when your sample diameter drops by a factor of 2?  Do you have difficulty matching and tuning with certain samples?  Are you tired of tweaking numerous adjustments to try to get acceptable B1 homogeneity with your samples? If you answered yes to any of the above, you should inquire whether a Doty Litz or Litzcage  coil could improve your results.

With all the improvements, customers are often surprised that there is also usually a substantial cost advantage in choosing Doty coils.

Check for coil specifications in the tables below. Custom coils are also available.

Small Animal Modules

Typical RF Litzcage
Coil Specifications

CP (Circular Polarization) Quadrature

image007_000

Clear

I.D.

mm

Coil

Rung

Length
mm

Shield
Diameter mm

1H

MHz

τ90,
μs

 

Square
pulse, Power, W

Light
Load

Heavy
Load

18

25

37

600

25

45

100

25

22

52

500

25

50

120

38

33

80

500

60

25

100

50

65

80

500

90

50

250

63

55

94

500

100

60

250

100

85

150

300

120

100

400

200

250

250

200

500

200

700

Light
Load
– Spherical 30 mM saline sample, 75% of ID.

Heavy
Load –
Cylindrical 100 mM saline sample, at 75% of
ID and full length.

Small Animal Modules

Typical Dual-Frequency
RF Litz Coil Specifications

Linear

Linear

Litz-small_017

RF
Litz
Coil

Clear

I.D.

mm

Shield

Dia.

mm

Tuning

1H

MHz

For
1H

For
X = 31P

t90

(μs)

LL

Power

(W)

 

HL

Power

(W)

t90

(μs)

LL

Power

(W)

HL

Power

(W)

15

50

1H/X

500

23

26
31
34
24
28

34

72

1H
19F

200

26
26
80

34

79

1H/X

500

38
68
170
65
50
110

62

94

1H
19F

80

17

300
550

100

150

1H
19F

128

65

150
760

100

150

1H/X

200

110

120
510
220
50
180

130

200

1H/X

170

150

120
700
310
50
240

140

210

1H/X

128

130

140
700
275
55
240

For the above coils, the length of the homogeneous region is 80% of the coil ID.  Coils with a multi-X channel normally tune 31P through 13simply by changing plug-in capacitors. A “Light Load (LL)” is a spherical 30 mM saline sample of diameter 75% of the coil ID.  A “Heavy Load (HL)” is a cylindrical 100 mM saline sample of diameter 75% of the coil ID and length extending well beyond the homogeneous region. All coils feature simple tuning, highest Bhomogeneity, an external rf shield, and susceptibility matching near the sample region. They are resistant to mechanical shock, over-power, and moisture.

Please note: The abbreviation LL refers to Light Load and HL refers to Heavy Load.

Downloadable Documents

Download a preprint of “RF Coil Technology for Small-Animal MRI”, by F. David Doty, George Entzminger, Jatin Kulkarni, Kranti Pamarthy and John P. Staab, published in [NMR Biomed. 2007; 20: 304-325, published online in Wiley Interscience, at www.interscience.wiley.com, DOI: 10.1002/nbm.1149].

Images

Mouse Brain Images

image005_000

This T2 spin-echo experiment on a live mouse brain using a 2 cm linear Litz coil in a 4.7 T horizontal magnet demonstrated substantially better B1 homogeneity and better S/N than a quadrature birdcage of similar dimensions. The Litz coil easily tuned and matched to any load in less than a minute.

Images courtesy of Dr. Joel R. Garbow, Washington University, St. Louis, MO.

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