Role of CT DCG in Lacrimal Surgery

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					                 69th AIOC Proceedings, Ahmedabad 2011

   This paper was conferred with the AIOS APOS SANTOSH

               DR. LAKSHMI MAHESH: M.B.B.S. (1990), Stanley Medical College, Chennai;
               DNB (1993), Sankara Nethralaya, Chennai. Performing         Oculoplastic
               and Orbital surgeries for the last 18 years. Formerly, HOD, Oculoplasty,
               Sankara Nethralaya and Consultant, Manipal Hospital, Bangalore.
               Contact: 9945206810; E-mail:

Role of CT DCG in Lacrimal Surgery
Dr. Lakshmi Mahesh
Purpose: To Study the Indications and Diagnostic utility of Computed Tomographic
Dacryocystography (CT DCG) in lacrimal surgery. Methods: Retrospective analysis of patients
who underwent CT DCG between January 2007 and May 2010 at our hospital. Results: 25
patients had the procedure. Other than the post traumatic cases and failed DCR with anatomical
variations, unusual cases of canalicular pouch, inclusion cyst of lacrimal sac etc., were
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diagnosed. Conclusion: CT DCG is a safe and useful diagnostic alternative for the lacrimal
surgeon. It helps in better delineation of the lacrimal pathology resulting in proper decision
making and appropriate surgical approach maximising the success rate of surgery in difficult
situations. Thin slice helical CT with 2D and 3D reformatting and shorter acquisition time offer
excellent resolution and patient compliance.

N     asolacrimal ductal system dysfunction or disease is a common
      ophthalmological problem associated with epiphora, lacrimal sac mass
or inflammation. The spectrum of disease varies from congenital absence or
aberrancy of ductal structures to acquired stenosis and obstructions of adult
onset. Primary acquired nasolacrimal duct obstruction with associated infection
is relatively common whereas certain other disorders like primary sac and duct
tumors are very rare. Radiologic evaluation of the lacrimal system has evolved
over the past decades to include a variety of studies ranging from plain films to
conventional x-ray dacryocystography (DCG), nuclear medicine isotope studies
(dacryoscintigraphy, DSG), computed tomography (CT), combined CT-DCG and
magnetic resonance imaging (MRI). Improvements in computational technology
and imaging processing have been combined with older CT methods to allow
development of techniques that provide three- dimensional visualization of the
nasolacrimal duct system. The aim of this study was to study the usefulness of
CT DCG as a diagnostic tool in certain cases of lacrimal duct obstructions before
the surgical planning.

A total of 25 patients underwent this procedure between January 2007 and May
2010. There were 13 male and 12 female patients. The age ranged from 6 to 74
years. All the cases were performed at a single center with the Ophthalmologist
to help out for the syringing of the dye into the system. There were 2 children
in the study who co-operated for the same under topical anesthesia. Serum
creatinine levels were done prior to the procedure. In majority of the cases a
plain scan was avoided with unnecessary exposure to radiation. The total
procedure time was about ten to fifteen minutes. The dye (water soluble Iodine
based dye-Omnipaque, Ioversol) containing 300 mg Iodine/ml was diluted either
in 1:1 or 1:5 concentration. This was loaded into a 2cc disposable syringe with a
lacrimal cannula (26 gauge) and after application of topical anesthetic syringing
was carried out to inject the dye into the system. Simultaneous evaluation of the
other side was also carried out for comparison.4 Patients had a partial or total
obstruction of the system on the other side. The rest of the patients had unilateral
problem. There was no untoward effect or allergy to the dye noted in all cases.
There were various indications such as inability to ascertain level of block or the
presence of the sac (4), failed prior lacrimal surgery (6), suspected foreign body
(2), mass of lacrimal sac with infection (5), chronic canaliculitis with swelling
(1) and traumatic obstructions (7). In many cases the sac had been displaced
               69th AIOC Proceedings, Ahmedabad 2011

and the exact position could be ascertained. Interesting features such as a
canalicular pouch and a sac diverticulum could also be picked up. In all patients
who underwent subsequent surgery the findings on CT DCG co-rellated with
the intra-operative findings. 13 patients had features of associated sinus disease
which could be picked up very well as imaging of the paranasal sinuses could be
done simultaneously. These patients were treated medically for the sinusitis. 15
patients underwent surgery after the imaging procedure.

CT DCG was first described by Frietag et al in 2002. Both dye installation (drop
method) and cannulation technique can be employed. The drop method is
particularly useful in children and patients unable to co-operate for syringing.
Serial coronal and axial images of the respected area of study should be requested.
When combined with DCG, CT scan is excellent at identifying bony structures
around the nasolacrimal system. By using modern spiral CT techniques with
contrast material, high resolution thin sections of the system are obtained.
Shorter acquisition time and three-dimensional (3D) reconstruction now offer
very good imaging and patient compliance.
It plays a useful role in the evaluation of the patient with tearing when an anatomic
abnormality is suspected and is particularly helpful for surgical planning. In
axial scans through the lower orbit, the lacrimal sac fossa appears as a depression
in the antero-medial wall. In successively lower sections,the duct appears as a
round to oval defect in the frontal process of the maxillary bone at the antero-
medial corner of the ant rum. The duct may be filled with air or fluid. As the duct
is traced inferiorly,it can be seen to open beneath the inferior turbinate. Cross-
sections of the system are seen in coronal reformatted images because the line of
section is oriented downward and obliquely backward. Parasagittal reformatted
images will reveal the entire length of the system in longitudinal section. This
view is indispensable in picking up the exact level of the obstruction.
This procedure is contra-indicated in pregnancy and in those with history of
Iodine allergy. Children and un-co-operative patients can have sedation for the
procedure and general anesthesia with intubation can also be done in required
cases. Scanning is undertaken soon after the dye is syringed through the
respective canaliculi.
In trauma cases, it offers additional benefits of more exact localization of the
lacrimal drainage system fractues, bone displacemants ,location of previously
placed miniplates, wires or sheets used in fracture repair etc., Improvements in
computational technology and imaging processing have been combined with older
CT methods to allow development of techniques that provide three- dimensional
visualization of the nasolacrimal duct system. MR DCG is also helpful and gives
very good soft tissue details: however the cost, inability to delineate bone details
and the longer acquisition time make its use more restricted.
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At the present time CT DCG is becoming an invaluable tool in the diagnosis and
management of certain lacrimal duct obstructions. Regardless of the radiologic
studies requested, good communication between the clinician and the radiologist
in reference to the patient’s symptoms, examination findings and possible
diagnosis is helpful to ensure that the maximum amount of useful information
is obtained in every study.

1.   Ashenhurst M, Jaffer N, Hurwitz JJ, et al. Combined computed tomography and
     dacryocystography for complex lacrimal problems. Can J Ophthalmol 1991;26:27-31.
2.   Frietag SK, Woog JJ, Kousoubris PD, et al. Helical computed tomographic
     dacryocystography with three-dimensional reconstruction: a new view of lacrimal
     drainage system. Ophthal Plast Reconstr Surg 2002;18:121-32.
3.   Udhay P,Noronha OV,Mohan RE.Helical computed tomographic dacryosystography
     and its role in the diagnosis and management of lacrimal drainage system blocks and
     medial canthal masses. Indian J Ophthalmol 2008;56:31-7.
4.   Hurwitz JJ, Edward Kassel EE, Jaffer N.Computed Tomography and Combined CT-
     Dacryocystography (CT-DCG) In: Hurwitz JJ, editors, The Lacrimal System. Raven
     Press: New York 1996:83-5.

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