AJR 2000; 175:469-473
© American Roentgen Ray Society
Dynamic MR Dacryocystography
A New Method for Evaluating Nasolacrimal Duct Obstructions
Yasuo Takehara1,
Haruo Isoda1,
Katsuaki Kurihashi2,
Satoshi Isogai1,
Nami Kodaira1,
Hatsuko Masunaga1,
Masahiro Sugiyama1,
Fukujirou Ozawa1,
Hiroyasu Takeda1,
Atsushi Nozaki3 and
Harumi Sakahara1
1
Department of Radiology, Hamamatsu University School of Medicine, 3600 Handa,
431-3192 Hamamatsu, Japan.
2
Kurihashi Eye Clinic, 1366-1 Hatsuoi, 433-8112 Hamamatsu, Japan.
3
GE-Yokogawa Medical Systems, 4-7-127 Asahigaoka, Hino-shi, 191 Tokyo,
Japan.
Received July 12, 1999;
accepted after revision January 21, 2000.
Address correspondence to Y. Takehara.
Abstract
OBJECTIVE. The purpose of this study was to evaluate the clinical
performance of newly implemented dynamic MR dacryocystography.
CONCLUSION. Dynamic MR dacryocystography, which requires neither
ionizing radiation nor chemical contrast media with high viscosity, may be a
useful tool for depicting nasolacrimal obstructions.
Introduction
Epiphora describes an overflow of tears caused by imperfect drainage of the
tear-conducting passages (Fig.
1) and is a common ophthalmic problem, accounting for 3% of
ambulatory clinic visits [1].
When tear shedding is extreme, it causes considerable annoyance for patients
by degrading visual acuity. The cause of the epiphora is usually benign;
however, in some cases malignant nasolacrimal duct obstruction occurs.
Therefore, the complaint of epiphora should not be underestimated or ignored.
Since Ewing [2] implemented
conventional radiographic dacryocystography in 1909, the imaging techniques
for evaluation of lacrimal tract abnormalities have used chemical contrast
media such as iodinated contrast media for radiography or gadolinium chelates
for MR imaging [3].
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Fig. 1. —Diagram shows normal nasolacrimal drainage system from frontal view
of left eye. SC = superior canaliculus, IC = inferior canaliculus, LS =
lacrimal sac, ND = nasolacrimal duct, VR = valve of
Rosenmüller, VK = valve of Krause, VH = valve of
Hasner.
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Before the advent of MR imaging, all techniques for nasolacrimal duct
imaging used X-rays or gamma rays that inevitably focused ionizing radiation
on the lens of both eyes [4].
Some investigators have tested MR imaging for dacryocystography, with or
without chemical contrast media such as gadolinium chelates
[5]; however, they failed to
depict the dynamic behavior of the fluid in the lacrimal pathways. The MR
dacryocystography evaluated in our study requires neither ionizing radiation
nor viscous chemical contrast media. The viscosity of the water and lidocaine
contrast material we used is less than that of chemical contrast media,
thereby filling any narrowed lacrimal channels. MR dacryocystography can also
be useful for tracking injected fluid in a dynamic fashion.
Subjects and Methods
Patients
The patient population included two men and six women (age range, 54-82
years; mean, 64.8 years). The study was conducted on eight consecutive
patients who visited the ambulatory clinic complaining of epiphora. All eight
underwent both MR dacryocystography and radiographic dacryocystography, either
by radiographic dynamic digital subtraction dacryocystography (3/8 patients)
or radiographic distention dacryocystography (5/8 patients). The patients
subsequently underwent surgery within 1-2 weeks after the examinations.
Cannulation
The cannulation was performed by an ophthalmologist. With the patient under
topical anesthesia and using 2% lidocaine solution (Xylocaine jelly; Fujisawa,
Osaka, Japan), the ophthalmologist inserted a pair of thin plastic cannulas
into the lower lacrimal canaliculi of both eyes. A catheter with a short taper
ending in a very small opening was made from polyethylene microcannulas with
an outer diameter of 0.8 mm (No. 5 Microcatheter; Igarashi, Tokyo, Japan) so
that the outer diameter of the tip segment became 0.2-0.3 mm. The narrowed
tips were made by heating a catheter using a disposable lighter, then drawing
out the softened segment. After the polyethylene tubing cooled, the taper was
cut at the desired diameter. The proximal end of the catheter was threaded
over a 23-gauge butterfly-shaped hypodermic needle (23-gauge winged needle;
Terumo, Tokyo, Japan). The finished catheter length was approximately 20-30
cm. The microcannulas were connected with a Y-shaped tube system so that the
patients could inject contrast media in both lacrimal pathways simultaneously
by manually compressing the piston of a single syringe. After all air bubbles
were cleared from the system, the tips of the catheters were inserted 5 mm
into the punctum. The catheters were securely taped to the patient's face. All
patients were irrigated at the ambulatory clinic a few hours before MR
dacryocystography.
MR Imaging Techniques
Before MR dacryocystography, conventional T1- and T2-weighted images with
soft-tissue contrast were acquired to rule out tumors. After conventional
T1-weighted sagittal localizers, axial and coronal T2-weighted images were
obtained using fast spin-echo or half-Fourier single-shot fast spin-echo
sequences with a medium TE of 100 msec without a fat saturation pulse. Then MR
dacryocystography was performed. Repeated acquisitions of thick-slice (20-30
mm) heavily T2-weighted images were obtained while an admixture of
saline-lidocaine hydrochloride solution was injected. The section included the
lacrimal apparatus and the nasolacrimal pathways. The admixture of
saline-lidocaine was composed of 7 mL of saline and 3 mL of 0.5% lidocaine
hydrochloride solution. The imaging was performed using a 1.5-T imager (Signa
Horizon; General Electric Medical Systems, Milwaukee, WI) with a standard head
coil. MR dacryocystography used half-Fourier single-shot fast spin-echo
sequences with parameters including TR/TE range, 4000/600-1000; number of
excitations, 0.5; field of view, 14 cm; slice thickness, 2-4 cm; matrix, 256
x 256; and receiver bandwidth, 62.5 kHz. Acquisition time for each image
was less than 2 sec. During the fluid injection, imaging was repeated for 3
min with intervals of 4-5 sec. Overall MR imaging time, including MR
dacryocystography and conventional T1- and T2-weighted imaging, was less than
20 min.
Radiologists viewed up to 45 frames on the monitor. The review process took
them no longer than 15 min.
Image Evaluation
Two radiologists who were unaware of clinical data or information from
other imaging techniques evaluated MR dacryocystography and radiographic
dacryocystography separately for the detection of obstructed points and the
presence or absence of lacrimal sac dilatation. Surgery was performed by an
experienced ophthalmologist using a surgical microscope, and the
intraoperative findings were carefully recorded. A computer workstation was
available to display all the dynamic MR dacryocystography images in a
"cineloop" mode for interpretation.
Results
No complications were encountered in the study. In all eight patients, MR
dacryocystography was successfully performed and diagnostic images were
obtained. The findings concerning lacrimal sac dilatation and the obstructed
level in the lacrimal pathway were, as a whole, supported by radiographic
dacryocystography and confirmed by intraoperative findings (Figs.
2A,2B
and
3A,3B,3C,3D,3E).
Regarding duct obstructions, all seven lesions in six patients were correctly
diagnosed with MR dacryocystography. As for sac obstructions, MR
dacryocystography allowed correct diagnosis of one complete obstruction and
one partial obstruction (Figs.
4A,4B,4C).
On radiographic dacryocystography, however, there was a passage of contrast
media on both sides (Fig. 4D).
Subsequent surgery confirmed a stenosed segment at the lacrimal sac probably
caused by fibrosis. With this evidence and the patient's chief complaint,
lacrimal stenting was selected rather than canaliculorhinostomy, and the
outcome was favorable. For eight other lesions in seven patients,
dacryocystorhinostomy was performed on seven lacrimal pathways and
canaliculorhinostomy was performed on one lacrimal pathway. The outcome of
surgical intervention was favorable in all patients.
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Fig. 2A. —54-year-old woman with right epiphora. Coronal MR dacryocystogram
shows cystic dilatation of right lacrimal sac (large arrow) and no
fluid passage beyond level of lacrimal sac. Note normal fluid passage is
acquired on contralateral side (small arrows).
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Fig. 2B. —54-year-old woman with right epiphora. Digital subtraction
dacryocystogram reveals duct obstruction with cystic sac dilatation
(arrow) on affected side. Note normal drainage in contralateral side
(arrowheads).
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Fig. 3A. —58-year-old woman with left epiphora. Dynamic MR dacryocystogram (at
10 sec after commencement of injection of saline-lidocaine solution). Only
lacrimal sac dilatation (S) is apparent.
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Fig. 3B. —58-year-old woman with left epiphora. Dynamic MR dacryocystogram (at
30 sec after injection). As injection proceeded, distended nasolacrimal duct
gradually appeared (arrow) upstream of valve of Hasner. S = dilated
left lacrimal sac.
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Fig. 3C. —58-year-old woman with left epiphora. Dynamic MR dacryocystogram (at
40 sec after injection). Obstruction point (large curved arrow) is in
lower nasolacrimal duct above valve of Hasner. Pressure injection does not
overcome obstructed point, and injected fluid is spilling from conjunctival
sac on affected side (straight arrow). On right side, note normal
lacrimal drainage (small curved arrows).
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Fig. 3E. —58-year-old woman with left epiphora. Digital subtraction
dacryocystogram reveals dilated nasolacrimal duct (straight arrow)
above valve of Hasner as injection pressure is increased; however, obstruction
cannot be overcome. Normal contrast passage is seen on contralateral side
(curved arrows). S = dilated left lacrimal sac.
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Fig. 4B. —69-year-old woman complaining of left epiphora. Dynamic MR
dacryocystogram 15 sec after fluid injection. Normal drainage was seen in
right nasolacrimal duct (arrows) but not in left nasolacrimal duct.
At this moment, operator asked patient to increase her injection pressure.
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Fig. 4C. —69-year-old woman complaining of left epiphora. Dynamic MR
dacryocystogram after pressure injection, at 30 sec; left nasolacrimal
drainage is also confirmed (arrows). Intraoperative findings
disclosed fibrosis in left lacrimal sac, which might have caused incomplete
obstruction in left nasolacrimal passage.
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Fig. 4D. —69-year-old woman complaining of left epiphora. Radiographic
dacryocystogram shows apparently normal (but very thin on left side) drainage
(arrowheads) of contrast media in both sides.
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Discussion
The lacrimal drainage system consists of the upper and lower canaliculi,
common canaliculus, lacrimal sac, and nasolacrimal duct
[3]
(Fig. 1). The three normal
anatomic narrowings are as follows: at the junction between the common
canaliculus and lacrimal sac (Rosenmüller's
valve), the neck of the sac (Krause's valve), and the opening into the nasal
cavity (Hasner's valve). The valves are thought to be folds of mucosa.
Abnormal strictures and obstructions are commonly located at the levels of
these physiologic narrowings
[6].
Many radiographic techniques have been reported previously. They include
macrodacryocystography using magnification
[7]; distention
dacryocystography using radiography during pressure injection of the contrast
media [8]; kinematic
dacryocystography using cinematography to evaluate the function (flow) in the
nasolacrimal duct [9];
tomographic dacryocystography; and digital substraction dacryocystography with
videotape recording [10]. Our
method, MR dacryocystography, yields integrated information that has been
featured by previous innovations.
MR dacryocystography uses stationary or slowly flowing water injected into
the lacrimal draining system as a substitute for contrast media. The imaging
strategy of MR dacryocystography involves the acquisition of a series of
heavily T2-weighted images. Because fluidfilled nasolacrimal ducts have long
longitudinal and transverse relaxation times, they have high signal intensity
on T2-weighted images. In these hydrographic images, everything looks black
and white. Observers can evaluate the nasolacrimal abnormalities indirectly
using these "all or nothing" images. The fast spin-echo sequence
used in the current study is relatively immune to local magnetic field
inhomogeneity. Thus, the sequence is less affected by field inhomogeneity
created by air in the maxillary sinus or artificial teeth in the oral
cavity.
A saline-lidocaine solution is less viscous than iodinated contrast media
and flows readily through a thin catheter with a narrow lumen; thus patients
can easily self-inject an appropriate amount of the solution while lying on a
cradle in the small bore of the MR imager. This solution's lower viscosity
helps fill any narrowed lumen in the lacrimal pathways and enables the use of
thinner and softer cannulas for intubation of the lacrimal canaliculi, which
ensures maximum patient comfort. Concerning safety margins, a saline-lidocaine
solution is safe and minimally irritating.
In terms of radiation protection, exposure of the eye lens to ionizing
radiation should be avoided. The eye lens is one of the organs most
susceptible to ionizing radiation. Galloway et al.
[10] observed that radiation
exposure to the eye lens is approximately 2.7 mGy in conventional radiographic
dacryocystography.
MR dacryocystography features high temporal resolution that allows dynamic
evaluation of fluid flow in the nasolacrimal drainage system. Unlike
conventional radiographic distention dacryocystography, MR dacryocystography
does not miss the best frame that pinpoints the obstructive segment. The best
frame with optimal nasolacrimal filling can be selected from the series of
images acquired. MR dacryocystography can be used interactively; therefore,
the operator observing the cathode ray tube monitor can also ask the patient
to increase the injection rate when filling is incomplete or delayed (Figs.
4A,4B,4C).
With radiographic dacryocystography, ideal exposure timing is hard to predict
without fluoroscopic aid; however, the chance of exposure to ionizing
radiation increases. For the same reason, combined CT dacryocystography with
or without helical scanning capability may not be justified if an MR imager is
also available in the institution.
In this study, we chose bilateral injections even for patients with
unilateral symptoms. Bilateral simultaneous injections not only offer
comparative flow characteristics through the nasolacrimal drainage system, but
also rule out abnormalities of the contralateral asymptomatic nasolacrimal
duct. According to our experiences with radiographic dacryocystography,
abnormalities are frequently also found in the asymptomatic side. Previous
investigators have also observed this
[11].
Several methods are available to evaluate the nasolacrimal duct passage
using eye drops of contrast media
[5] or radiopharmaceuticals
[11]. The strategy of these
methods is to detect nasolacrimal drainage impairment including functional
obstruction. Previous investigators emphasized that the eye drop method is
advantageous because functional obstructions are detected
[11]. Epiphora already
reflects nasolacrimal duct obstruction; therefore, the next step is to
differentiate functional (incomplete or partial) from mechanical (complete)
obstructions. Injection of a fluid into the nasolacrimal duct, monitored by
real-time imaging, can disclose the extent of the stenosis causing impaired
drainage. If the stenosis is mild and pressure injection can overcome the
stenosis, a tube stent placement can be considered instead of
dacryocystorhinostomy or canaliculorhinostomy.
One drawback of MR dacryocystography may be that it does not reflect any
soft-tissue contrast. MR dacryocystography is a form of hydrographic imaging.
In a practical clinical setting, it is therefore important to use additional
T1- and T2-weighted images for delineation of the soft tissues. Half-Fourier
single-shot fast spin-echo or fast spin-echo imaging using multiple thin
slices with a medium TE can provide static but detailed information on the
presence of mucosal thickening, neoplasms, and other soft-tissue
abnormalities. To discriminate mucosal thickening from normal flow of the
saline, comparison of images before and after administration of contrast media
is important. It may also be feasible to perform image subtraction.
Regarding lacrimal stones, no patient in our series had dacryolithiasis.
Therefore, we cannot discuss the performance of MR dacryocystography in its
detection. However, considering the insensitivity of MR imaging in the
detection of calcium, it may be difficult to detect calculi in the lacrimal
pathway, especially with small stones.
Although further investigations are necessary to clarify true performance
of dynamic MR dacryocystography, current preliminary data showed its potential
in depicting nasolacrimal duct obstructions. Dynamic MR dacryocystography may
supersede radiographic dacryocystography by eliminating the chance of exposure
to ionizing radiation or to viscous chemical contrast media.
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Abstract
Introduction
