Technical High-Resolution

Short

with

Developments

MR Imaging Short TE, and

TR,

ofthe

Wrist

and

Instrumentation

and

Eye

Partial-Echo

Acquisition’ allows

Thomas K. F. Foo, PhD Frank C. Shellock, PhD Cecil E. Hayes, PhD John F. Schenck, MD, PhD Beth E. Slayman, BSc

better

such

images,

Index terms: Eye, MR. 224.1214 ‘ Magnetic resonance (MR), high-resolution #{149} Magnetic resonance (MR), technology #{149} Magnetic resonance (MR), three-dimensional #{149} Wrist, MR, 43.1214

M

1992:

resonance

AGNETIC

with

important

high

the wrist and Carpal tunnel triangular crosis

sources

(MR)

spatial

in the

some

of

of chronic

3). Higher-resolution field of view (FOV)

pain

of

of eye disease. tears in the and

the

are

of injuries

fibrocartilage, are

tions

of about

structures sualized

more

of the

100

avenue

rosis

and

m,

bone

into

vi-

osteopo-

disorders.

The small size of the eye requires MR images of high resolution for adequate visualization of the optic nerve, retina, lens, and other anatomic structures. Because the eye is a 2-3-cm-diameter spheroid, the use of FOVs greater than 6 cm results in pixel averaging and poor

definition of fine structures. lution imaging techniques imaging studies,

times because

are

High-resowith tong

inappropriate for eye of possible image deg-

radation from patient eye motion. Motion is especially a problem in high-resotution

MR

images

with

pixel

sizes

of

between 100-500 p.m. At this resolution, even small displacements during data acquisition wilt result in unacceptable motion artifacts on the image. Hence, a combination of high-resolution image acquisition with relatively short imaging times allows for better visualization of the eye and minimizes motion-reimage

artifacts.

osteonecommon

in the wrist

(1-

MR images with a between 4 and 6 cm

studies.

Although

tioning

may

optimal

reduce

patient

patient

patients are often

with musculosketetal unable to tolerate

imaging

study

posi-

discomfort, long

injuries MR

gradient-recalled steady state (GRASS;

imaging

of

acGE

Medical Systems, Milwaukee) and radio-frequency (RF)-phase spoiled GRASS MR imaging have been demonstrated to be useful for evaluating inju-

MR

images

have previously been obtained with whole-body MR imaging systems. Spatial resolution of between 100 and 200 im per pixel has been attained by using small gradient coil sets producing gradient fields in excess of 4 G/cm (0.0004 T/cm) (7-9). If standard 1-G/cm (0.0001T/cm) gradient fields available in commercial MR imaging systems are used, however, the minimum image FOV is limited to 8 cm when a ± 16-kHz receiver bandwidth is used. This is because receiver bandwidth and FOV are related by = ‘yG, D, where zf is the receiver bandwidth, y is the magnetogyric ratio, G, is the maximum readout gradient amplitude, and D is the image FOV. Notice that the image FOV is a product of the number of data samples and pixel size. To attain spatial resolution of between 100 and 200 p.m per pixel with the same number of data samples (in this case, 256) and with a fixed maximum gradient amplitude, the receiver bandwidth must be reduced. At a bandwidth of ±8 kHz, the minimum possible FOV is 4 cm. At this lower bandwidth, the data acquisition time is increased from 8.192 msec to 16.384 msec, increasing the minimum TE. In a previous article, a minimum TE of 28 msec was reported for a 4-cm-FOV image obtained with standard gradient coils (10). Because structures in the wrist and eye have short T2 values (11), shorter TEs are desirable for maintenance of high signal-to-noise

times.

Fast acquisition quisition in the

MR

eye.

High-spatial-resolution

this

to be better a possible

and

Theory

sevas-

at pixel resoluthe trabecular

for research other

in

in high-resolution

the wrist

articu-

over precise

sustained

in bone begin (5). This presents

new

tions

Reduced imaging time also minimizes patient fatigue resulting from the difficult positioning schemes used in wrist

images

resolution

diagnosis

in studies syndrome,

of injuries

(4). Furthermore,

tated

183:277-281

thickness

can be measured allowing a more

sessment

area

of the carpal

cartilage and fibrocartiand median nerves. On the

tar cartilage eral pixels,

High-resolution spin-echo and twoand three-dimensional gradient-recalled acquisition in the steady state (GRASS) and spoiled GRASS images of the wrist and eye were obtained with a whole-body magnetic resonance imager by using trapezoidal phase-encoding gradient waveforms and by lowering receiver bandwidth to ± 8 kHz, which results in a minimum field of view (FOV) of 4 cm and pixel resolution of 156 jm for a 256 x 256 matrix. Short echo times were achieved by using partial-echo acquisition. Poor signal-to-noise ratio resulting from smaller voxel sizes was overcome by using prototype receive-only eye and wrist coils. Images were obtained in reduced time and were superior to those obtained in studies performed with an 8-12-cm FOV and commercially available coils.

Radiology

visualization

bones, articular lage, and radial

ratio

(S/N).

In addition,

high magnetic susceptibility of bone makes short TEs desirable with gradient echoes, to reduce T2* effects. Materials

and

Methods

From the Applied Science Laboratory, GE Medical Systems, W-875, Box 414, Milwaukee, WI 53201 (T.K.F.F., C.E.H., B.E.S.); Division of Magnetic Resonance Imaging, Department of Radiology, Cedars-Sinai Medical Center, Los Angeles, and UCLA School of Medicine, Los Angeles (F.G.S.); and GE Corporate Research and

the techniques described, FOVs between 16 and 24 cm were used, with resolution of approximately 0.6-1.9 mm per pixel. In this article, we present methods for attaining short echo times (TEs) and repetition times (TRs) for

All experiments were performed by using a commercial 1.5-T (64-MHz) MR imaging system (GE Medical Systems) with standard 1-G/cm (0.0001-T/cm) gradients. A quadrature receive-only wrist coil was used in the wrist studies, and a single-loop 4-cm-diameter coil was used for the eye studies. In all

Development,

GRASS

cases,

ries 1

Schenectady,

NY (IFS.).

Re-

ceived August 29, 1991; revision requested October 21; revision received November 1; accepted November 12. Address reprint requests to T.K.F.F. © RSNA, 1992

Volume

183

Number

#{149}

1

to the

patellofeinoral

and

spoiled

echo

(SE) sequences

high

(100-200

olution and

im

joint

GRASS

while per

and

spin-

preserving

pixel)

in two-dimensional

three-dimensional

(6), but

spatial

res-

muttisection volume

acquisi-

in

a receiver

bandwidth

of ±8 kHz

and trapezoidal phase-encoding gradient waveforms were used. Trapezoidal gradient waveforms were used to attain maximum gradient area (zeroth moRadiolo2v

#{149} 777

ment) while minimizing gradient waveform pulse widths. A linear receive-only wrist

coil, the precursor

short

TRs

in some studies. pulse sequences,

reduced

the

total

zGRAO’ENT

imaging

time to several minutes (depending on the imaging prescription). In addition, RF-phase spoiling was also used for the gradient-echo pulse sequences to improve Ti-weighted image contrast in studies

of the

eye.

With

short

TRs,

section

acquisition

order

increased.

The

effective

YGRACENT

NMRsaeeA.

RATA WWADOW

b.

a. Figure

1.

such

Table

allowed

Minimum

used

and

tissue

afforded

contrast

angles

better

while

to be

image

S/N

maintaining

TE times

using

partial-echo

fast

GRASS

aging symmetric

partial

been

was

partial-echo

samples

were

For

acquisition,

Parameter

points

are

im-

the

for the

echo

were acIn contrast,

same

image

Partial

Pixel

Full

TE (msec) TR (msec) Imaging time (sec)

11.4 31.1 8.5

TE (msec) TR (msec) Imaging time (mm)

10.6 35.8 8.9

Note.-2D S Imaging t Imaging

the tional

by approximately

S/N

by about

benefit

30%

25%.

of shorter

and

The addi-

TE times,

how-

ever, established an acceptable trade-off. For example, the minimum possible TE at an FOV of 4 cm with a full gradient echo is 22.5 msec; with a 60% partial (gradient)-echo acquisition, a minimum TE of 8.0 msec can be achieved for a 256 x 256 matrix. The longer readout time for a full echo (16.384 msec) also results in significant T2* decay data acquisition. Consequently,

images image

exhibited resolution

during these

marked blurring, and was degraded. The

For SE imaging, partial-echo acquisition resulted in reduction of the minimum TE to 21.4 msec, from a 42.2-msec

homodyne

278

Radiology

#{149}

gradient

180#{176} refocusing msec at the minisimilar trapezoi-

detection

Echo

full-echo

Partial

and/or

Spoiled

Pixel

Resolution Full

Echo GRASS* 24.9 62.1 16.9

GRASS

and/or

Echo

Spoiled

43.1 109.7 29.9 GRASSt

10.6 51.3 14.0

42.7 111.3 30.9

= two-dimensional, 3D = three-dimensional. parameters: 3-mm section thickness, 4-cm FOV, one image, one signal average. parameters: 0.5-mm section thickness, 4-cm FOV, 64 partitions, one signal average.

image

reduced

78 x i56-m

22.1 59.3 16.2

k-space

the

sequence.

and Full-Echo

22.5 55.8 15.2

acquisition parameters for partialand full-echo acquisition in two-dimensional multisection and three-dimensional volume acquisitions can be found in Table 1.

data,

SE pulse

the phase-encoding

for Partial-

Resolution

Echo

FOV. Similarly, an effective resolution of 512 was obtained from an acquisition of 286 data samples. In the synthesis of the missing algorithm (using a 60% echo) resulted in the introduction of correlated noise in the image. This increased the noise in

Times

Imaging

Total

3D Volume

acquired

acquisition,

and

a 160-

minimum TE becomes longer. With acquisition of a partial echo, the TE can be reduced as the echo peak is shifted closer to the RF excitation pulse and the zeroth moment of the dephasing lobe of the readout gradient is reduced. Images with an effective resolution greater than the number of data samples acquired were obtained by synthesizing the missing k-space data, through use of a homodyne detection algorithm (13,14). This allowed an image with an effective resolution in the readout direction of 256 pixels to be recovered from a 160point

for the

by splitting

2D GRASS

before and after the echo peak in a full symmetric echo acquisition, for a total of 256 data samples. With greater numbers of data samptes acquired before the echo peak, 128

TR

156 x 156-m

28 data

before

peak, and 132 data samples quired after the echo peak.

and

by

GRASS

acquired.

TE

in ultra-

spoiled

acquired

28 msec

Acquisitions

(2-3

achieved

acquisition

and/or

and

(12). Instead of acquisition of full, echo data, an asymmetric or echo

point

have

to less than

waveforms

1

short

imaging times. Reduction of TE and TR.-Short msec)

TE was reduced

gradient

TR was

This

flip

phase-encoding

lobe into equal halves and placing each lobe on either side of the selective pulse. A partial-echo acquisition further reduced the minimum TE, to 21.4 mum FOV of 4 cm. (b) In the GRASS and/or spoiled GRASS pulse sequences, dal gradient waveforms were used to minimize TE and TR.

then a product of the sequence TR and the number of sections in an acquisition. larger

(a) Trapezoidal

The minimum

that data from different physical tocations were acquired during each TR interval, the effective TR for each section was

_n__

XcaSAD’ENT

flip

angles of less than 40#{176} were used to avoid saturation of the spin ensemble. In normal (sequential) two-dimensional acquisition, all data from the same imaging location were acquired during each TR interval, before data acquisition at the next imaging location was begun. By interleaving the twodimensional GRASS and/or spoiled GRASS

180’

EXOTATION

to the quadrature

wrist coil, was used In the gradient-echo

9o SF

minimum

TE. In addition,

sep-

aration of the phase-encoding gradient lobe into two halves contributed to a reduction of minimum TE. The highresolution SE pulse sequence is shown in Figure 1. Notice that if a single phaseencoding lobe had been used, the pulse width of this phase-encoding gradient waveform

would

be doubled,

substan-

tially increasing the minimum TE. The minimum TR also was reduced as a result of fewer data samples being acquired. Since the minimum TR is also determined by means of system hardware heating considerations in the gradient amplifiers and gradient coils, a shorter readout period allowed use of higher duty cycles and provided additional time savings through lowering of the gradient root-mean-squared power output. Although the minimum possible FOV was

4 cm,

our studies.

FOVs

of 5-6

Because

cm

were

the larger

used

in

FOVs

April 1992

a resolution is 234 x 234 aging parameters were msec TR, 60#{176} flip angle, and two signal averages. time for 16 images was

m (6-cm FOV). Im8.7-msec TE, 204.83-mm-thick sections, Total acquisition 3.6 minutes.

Table 2 Imaging Parameters Modes Available

for Acquisition Pulse

Parameter

SE

TE (msec) TR (msec) Imaging time (mm) Section thickness (mm)

tess

2D GRASS and/or Spoiled GRASS*

3D GRASS and/or Spoiled GRASS*

8.6 25.6

8.0 25.7

21.4 300.0 6.0

3.6

3.5

3

3

1

the minimum ingly reduced. 256

effective

gradient

field

moments,

matrix

at a 5-cm

FOV allowed images with 98 x 195-p.m pixel resolution to be obtained in only a marginally increased total imaging time. Surface coils-To overcome the poor image S/N resulting from smaller voxet sizes,

prototype

receive-only

wrist

and

eye coils with high sensitivity were constructed and used in all experiments. For the wrist studies, an elliptical receive-onty quadrature bird-cage RF coil was constructed (15). This coil was capacitively coupled to a hybrid phase

Volume

183

Number

#{149}

(a) Axial three-dimensional volume GRASS image of the left wrist, proximal to the epiphysis, of a healthy 31-year-old man. Imaging parameters were 5-cm FOV, 1.0-mm section thickness, 512 x 256 effective image matrix, 9.0-msec TE, 35.8-msec TR, and one signal average. The flip angle was 30#{176}. Notice the increased detail of the trabecular bone and clear definilion of the tendons and the median nerve. The in-plane resolution of this image was 98 x 195 p.m. Total imaging time for this 32-image volume acquisition was 4.9 minutes. (b) A similar axial-plane image of the left wrist of a healthy 24-year-old woman. The imaging parameters were identical to those used to obtain the image in a, except that 0.5-mm section thickness and two signal averages were used. Total imaging time was 9.8 minutes. The image was obtained with the volunteer supine, with her left wrist at her side. Notice the differences in the trabecular structure depicted in a and b.

1

splitter (16), which combined the two input signals in quadrature, and was constructed from eight segments and measured 6.5 cm long. The major and minor axes of the effiptical cylindrical coil were 11.4 and 5.7 cm, respectively. Diode blocking circuits ensured that the receiver coil was decoupled from the body coil during RF excitation. When this coil was used, imaging was per-

TEs and TRs were accordAlso, the use of a 512 x image

b. 3.

Sequence

Note.-For all sequences, imaging parameters included 6-cm FOV, 234 x 234-pm pixel resolution, one signal average, and 32 images obtamed. 2D = two-dimensional, 3D = three-dimensional. * For the interleaved GRASS and/or spoiled GRASS sequences, the effective TR is the product of the sequence TR and the number of sections per acquisition. Imaging time was shorter for the three-dimensional volume acquisition because fewer RF excitations without data acquisition were employed than in the multisection acquisition.

required

Figure

formed with the patient in the prone position, with the arm extended over the head. A simple single-loop receive-only surface coil with similar decoupling circuitry was used in the eye studies. The 2.5-cm-diameter circular loop provided adequate penetration for visualization of the eye but limited signal from externat structures. The receiver coil was used to limit the so oversampling k space to avoid aliasing was not necessary. This allowed a further reduction in imaging time. Subjects-Four male and three female volunteers were examined in the wrist studies. For the eye studies, two patients (one male and one female) with known

retinal

melanomas

were

were

used

in evaluation

sition

of

the wrist and eye. Although higher image resolution was possible with these techniques, the optimal FOV for wrist studies was 5-6 cm. Smaller FOVs can be used if disease or disorder is known

exto Acqui-

parameters

attainable for twoGRASS and/or spoiled SE sequences and for three-

dimensional

GRASS

and

dimensional volume pulse sequences are listed in Table 2. In imaging of the eye, a 16 x 160 x 128 partial-echo volume acquisition was used, which generated 16 images with section thicknesses of 1.0-1.5 mm with a 6-cm FOV in 42 seconds. In all eye studies, the patient was instructed to main-

tam a fixed stare, tated artifacts.

Results

and

with

conventionally

FOV)

to reduce

studies

of images acquired with methods surpassed that obtained (8-12-cm of the wrist and eye (ie,

with

commercially

only

or transmit-receive

The

thinner

available (0.3-1.0

for

better

brocartilage.

The in

much

of the

acquisitions

definition

articular

coils).

mm)

volume

between

shown

receive-

surface

sections

three-dimensional allowed

motion-re-

Discussion

The quality the described

trast

studied.

Imaging protocols.-Muttisection twodimensional and volume three-dimensionat pulse sequences with the characteristics we have described (tower receiver bandwidth and partial-echo acquisition)

to exist, but for general diagnostic aminations, we found it preferable have the entire wrist in the FOV.

and

con-

cartilage

trabecutae greater

fi-

and were

detail

also

in

the

vot-

ume acquisitions. It was fortuitous that the minimum TE achieved in studies of the wrist was in the range of 8-10 msec. In this range, fat and water contributions do

to the not

lation. especially

MR

result

signal

are

in

in intravoxel

This further in the

three-dimensional

increased bone

phase

signal marrow.

volume

and cancel-

S/N, The

acquisition

Radiology

279

#{149}

afforded

greater

imaging

image

S/N

per section

time

for the

used

in the

a.ei

I

same

:

two-

dimensional multisection acquisition. High-resolution images obtained in the axial plane also depicted the median nerve and the tendons forming the carpat tunnel. The median nerve in the right wrist of a normal volunteer was clearly visible (Fig 2). The individual

nerve

bundles

could

also

in the median

nerve

.

Although

‘A

the maximum possible resoa 256 x 256 image matrix

lution with was 156 p.m per further increase

possible to to 78 p.m per pixel by using a 286 x 256 partialecho acquisition. This resulted in an effective image resolution equivalent to that attained with a 512 x 256 matrix, but S/N decreased due to the smaller

voxet

sizes,

increased. proved

pixel

and

image the

with

by

the imx 256-

a 5-cm

imaging

volume 1.4

this

for

achieving

(a 31-year-old

a 24-year-old lutions

woman).

of 98

p.m,

this

imaging

technique

cle may

have

an

such

assessment

as

The images tinct

for an image was

62.5

The

is 203 Hz

the image. same

the

resolution,

receiver

shift

pixels

in

512-pixel

res-

resolution

bandwidth

at the

is reduced

to

shift artifact equivalent to a 6-8-pixel shift in the image. The impact of the chemical shift artifact on the diagnostic quality of 31.25

Hz.

This

results

in

the high-resolution be

a chemical

images

remains

to

determined.

In studies

lution

of the

SE images

catty

useful

due

times

and

severe

facts.

High-resolution

eyes,

were to

the

the

high-reso-

contrast

were

obtained

spoiling

was

employed.

280

Radiology

#{149}

time of 5.4 seconds.

4b,

a mass

due

to retinal

eye in a patient

with

retinal

mela-

Tissue

contrast

in this image

is in-

mela-

and

S/N

(42 seconds)

allowed

(Fig

with

acquisition with

5).

The

A

short

this procedure

of high-resolution

minimal

motion-related

artifacts. Before use of high-resolution pulse sequences, the usual imaging protocol was a nineto 10-image Tiweighted SE study with 300-msec TR, i6-msec TE, 3-mm section thickness, and 12-cm FOV; acquisition time for this protocol was 2.7 minutes.

these

preliminary

re-

suits demonstrate that high-resolution images with a pixel resolution approaching that with MR microscopy can be obtained by using a standard wholebody MR imaging system without the addition of extra gradient amplifiers or special gradient coils. Although this technique has been demonstrated in the wrist and eye, it can also be used for other clinical applications that require high-resolution imaging, provided that

tong

allow the use of small, high-sensitivity surface coils. Short TE and TR also allow the acquisition of high-resolution images in less than 5 minutes, depending

GRASS

S/N

acquisition

the structures

imaging

motion-related

acceptable

an image

of the right

with a 5.9-msec TE and a 20.0-msec TR. Other imaging acquisition (234 x 468-p.m pixel resolution), two sig-

not diagnostiartiimages

(with shorter TRs) had less motion-related artifacts because of the 5-second total imaging time per image, but tissue contrast was insufficient for differentiation among the retina, vitreous humor, aqueous humor, or tens (Fig 4a). Furthermore, in this study, the malignant retinal melanoma could not be detected on the GRASS images.

More

MR image

noma could be clearly distinguished. three-dimensional volume spoiled GRASS acquisition with section thicknesses of 1.5 mm improved the image

In conclusion,

is equiv-

of 3-4

with

pixel for fat in

which

shift

frequency

At and

of each 30,

±

In images

olution,

8 kHz

chemical

to a chemical

a dis-

artifact.

256-pixel

resolution

Hz.

the body alent

±

Figure

images

showed

of

with

the frequency

in this arti-

shift

bandwidth

GRASS

thickness was 3 mm, 160 x 128 partial-echo

and

resolution

osteoporosis.

chemical

a receiver

reso-

applications,

of the wrist

section were

to identify the melanoma. (b) The same imaging parameters as in a were used to acquire this image, but RF phase spoiling (spoiled GRASS imaging) was employed. Ti contrast was adequate for identification of the mass due to retinal melanoma (arrow).

time

described of

fat-water

and

pixel

high-resolution

potential

(a) A 6-cm-FOV

was

man

With

the

4.

noma. The parameters

in-

in-plane resolution of 98 x 195 p.m. The images of the wrist in Figure 3 show differing trabecular structure in

two volunteers

Figure

sufficient

for

minutes,

trade-off

b.

a.

nal averages,

FOV.

time

acquisition

about

acceptable

TR was

3 illustrates in a 512

total

32-partition an

the minimum

obtained

Although

F.,,

pixel, it was the resolution

Figure visualization

creased

.

be identified.

and

Ti tissue

when

RF-phase

As shown

in

are superficial

enough

to

on the imaging protocol. Because the MR signal is proportional to voxel size, the small voxel sizes (100-250 p.m) require the face coils

though

use of specially designed to improve image S/N.

initial

results

with

Figure 5. Spoiled GRASS volume image obtained with the same FOV and acquisition matrix used in Figure 4, but with 1.5-mm seclion thickness. Imaging parameters were a 5.3-msec TE, 20.1-msec TR, and one signal average. Total imaging time for obtaining 16 images was 42 seconds. With improved S/N and smaller section thickness, the mass due to retinal melanoma (arrow) is more clearly defined.

References 1.

2.

3.

surAl-

4.

the high-

resolution technique described in this paper are encouraging, further clinical trials are necessary to evaluate the imaging parameters required to optimize tissue contrast. #{149}

5.

6.

Mayfield JK. Patterns of injury to carpal ligaments: a spectrum. Clin Orthop 1984; 187:36-42. Palmer AK, Werner FW. The triangular fibrocartilage complex of the wrist: anatomy and function. J Hand Surg 1981; 6:153-162. Remus WR, Conway WF, Totty WG, et a!. Carpal avascular necrosis: MR imaging. Radiology 1986; 160:689-693. Koenig H, Lucas D, Meissner R. The wrist: a preliminary report on high-resolulion MR imaging. Radiology 1986; 160:463-. 467. Wehrli FW, Wehrli SL, Williams J. Highfield MR microscopy of trabecular bone. Radiology 1990; 177(P):187. Shellock FG, Foo TKF, Deutsch AL, Mink

April

1992

JH.

Patellofemoral

joint: evaluation

dur-

ing active flexion with ultrafast spoiled GRASS MR imaging. Radiology 1991; 180: 581-585. Johnson GA, Thompson MB, Gewalt SL, Hayes CE. Nuclear magnetic resonance imaging at microscopic resolution. J Magn Reson 1986; 68:129-137. Karis JP, Johnson GA, Glover GH. Signalto-noise improvements in three-dimensional NMR microscopy using limited-angle excitation. J Magn Reson 1987; 71:2433. Wong EC, Jesmanowicz A, Hyde JS. High

7.

8.

9.

10.

Jesmanowicz

Magnetic

Spiral Work James Suresh

11.

Damian

aging

terms:

Computed

tomography

Radiology

(CT), CT,

New Rd,

Boston, MA 02215 (J.N.S., D.E.D.,J.H.T., P.C.), and Brigham and Women’s Hospital, Boston (5KM.). From the 1991 RSNA scientific assembly. Received August 23, 1991; revision requested September 25; revision received November 15; accepted November 18. Address reprint C

requests RSNA, 1992

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183

to J.N.S.

12.

Number

1

Resonance 15.

N.

and ocular

al. Ultra-fast (SPGR) image

MR im-

disease.

AJNR

13.

Noll DC, Nishimura

Holsinger

AE, et

spoiled gradient recalled acquisition (abstr). In: Book

16.

ofHead

Neck

and

in Medicine,

1988;

DC, Macovski

A.

Ho-

modyne detection in magnetic resonance imaging. IEEE Trans Med Imaging 1991; Ml-10:154-163. Hayes CE, Edelstein WA, SchenckJF, Mueller OM, Eash M. An efficient, highly homogeneous radiofrequency coil for

whole-body MA,

MR imaging

at 1.5 T. J Magn

Reson 1985; 63:622-628. Mueller OM, Edelstein WA. RF components for rotating B-field generation in MR

whole-body imaging systems (abstr). In: Book of Abstracts: Society of Magnetic Resonance in Medicine 1986. Berkeley, Calif:

of abstracts: Society of Magnetic Resonance in Medicine 1990. Berkeley, Calif: Society of Magnetic Resonance in Medicine, 1990; 1308. Macovski A, Noll DC. Homodyne detection for improved SNR and partial k-space reconstructions (abstr). In: Book of abstracts: Society of Magnetic Resonance in Medicine 1988. Berkeley, Calif: Society of

Society of Magnetic cine, 1986; 453-454.

Resonance

in Medi-

Lesions:

YNAMIC

from 36 to 55.5 g of iodine CT scanning of the upper

aerodigestive tract often requires suspension of respiration and swallowing as well

as contrast

enhancement,

faster

methods have been explored. Ultrafast CT has proved useful in the evaluation of the airway (5), and spiral CT with a commercially available CT scanner that permits rapid scanning of large volumes (up to 10 mm/sec for up to 24 seconds) has

been

used

breath-hold of pulmonary scanning

successfully,

with

technique, nodules times

have

the

for the detection (6,7). Shorter the

benefit

of at-

A Figure 1. Lateral topogram obtained in a 71-year-old female patient before a spiral CT study of the neck shows the upper (solid arrows) umes

and

lower

angled

(open

to avoid

arrows)

dental

scanning

vol-

fillings.

towing use of lower volumes of intravenous contrast medium in dynamic CT studies. tential

To determine benefits (shorter

whether scanning

and less contrast medium) of could be realized without an reduction in scan quality, we prospective spiral CT studies with lesions of the head and

the

potime

spiral CT attendant performed in patients neck.

Twenty-one

consecutive

were examined prospectively. ner with slip-ring technology dard, continuously rotating used

(Somatom

langen, Germany). From a lateral topogram, spiral scanning volumes were selected to cover the area from the skull base to the thoracic inlet in the axial plane. Scanning was performed at i20 kV and 165 mAs by using a standard image reconstruction algorithm. Generally,

and Methods nonselected

patients (11 men, average age, 55.4 years; 10 women, average age, 60.9 years) with suspected or diagnosed tesions of the upper aerodigestive tract

was

#{149}

14. Ber-

Resonance

computed tomography (CT) has been used successfully in the evaluation of head and neck lesions (1-4). Optimally, scanning times average 3-4 minutes and contrast medium

1992; 183:281-283

the Departments of Radiology, Deaconess Hospital, 185 Pilgrim

M, Norman

of orbital

Materials I From England

Magnetic 815.

1041.

1985; 6:259-264. Foo TKF, Bernstein

D

Spiral computed tomography (CT) was used in the evaluation of 21 patients with head and neck lesions. Scanning time ranged from 24 to 36 seconds, and high-quality diagnostic scans with excellent anatomic resolution and minimal motion artifact were produced. Vascular opacification was optimized with substantially less contrast medium than used in conventional studies. These preliminary results show spiral CT to be at least comparable with conventional CT in the evaluation of the head and neck.

experimental #{149} Head and neck neoplasms, 10.30, 20.30 #{149} Head and neck neoplasms, 10.1211, 20.1211

1988.

of Magnetic

1988;

Brandt-Zawadzki

doses range (4). Because

Index

JB.

Sobel DF, Kelly W, Kjos BO, CharD,

CT in Evaluation in Progress’

N. Suojanen, MD K. Mukherji, MD E. Dupuy, MD H. Takahashi, MD Costello, MD

Jeffrey Philip

JS, Kneeland

in Medicine

Calif: Society

in Medicine,

short TE MRI of the fingers and using a local gradient coil (abstr). In: of abstracts: Society of Magnetic Res1991. Berkeley, Calif: Resonance in Medi-

Resonance

keley,

resolution

wrist Book onance in Medicine Society ofMagnetic cine, 1991; 312.

A, Hyde

Pulse sequences for small fields of view (abstr). In: Book of abstracts: Society of

Plus;

A scan(a stanCT scanner) Siemens,

Er-

two

scanning

volumes

were

re-

quired; these were angled to avoid dentat amalgam when necessary (Fig 1). A table feed of 4 mm/sec was used for the upper volume, with a scanning time of 12-16 seconds. For the lower volume, the table feed was the same, and scanning time was 24 seconds. Contiguous axial 4-mm-thick sections were then reconstructed from the volumetric data. Scans

produced

by means

of this

Radiology

tech-

#{149} 281