Download Correlation of Ocular Ultrasound and Spectralis Enhanced Depth

64
The Journal of Ophthalmic Photography
Volume 33, Number 2 • Fall 2011
ORIGINAL ARTICLE
Alexis Smith, BA, CRA, OCT-C
University of Michigan
Kellogg Eye Center
1000 Wall Street
Ann Arbor, MI 48105
734/232-8069
734/936-8623 Fax
[email protected]
Correlation of Ocular Ultrasound and
Spectralis Enhanced Depth Imaging (EDI) of Ocular Lesions
Abstract
Purpose: To determine whether Spectralis Enhanced
Depth Imaging (EDI) Spectral Domain OCT images provide enough resolution of the choroid to visualize and
measure lesions traditionally followed by ultrasound.
Design: Observational Case Series
Methods: EDI OCT scans were correlated with patients
who are traditionally followed with Ultrasound. EDI
OCT scans were obtained by positioning the Heidelberg
Spectralis SD-OCT closer to the eye than usual in order
to obtain an inverted image, which concentrates the
signal on the choroid. At the time of this article, we
had not received the update from Spectralis, which
employs an EDI button to replace the need to move
the camera closer to invert the image. Seven line scans
were obtained over the thickest portion of the lesion,
and measurements using the Spectralis software were
made, measuring from the end of the Retinal Pigment
Epithelium to the end of the Choroid.
Conclusions: For this observational case series, it
seems that EDI OCT could be useful for obtaining
measurements of choroidal lesions that are too small
to accurately measure or visualize with ultrasound. In
addition, ease of use of the OCT machine for patient
and operator is a benefit, while ophthalmic ultrasound is extremely operator dependent and requires
direct contact with the eye. However, currently EDI
OCT cannot image very peripheral lesions or lesions
too large to fit within the active scan screen, and
media opacification limits the signal strength of OCT.
Keywords
Enhanced Depth Imaging (EDI), Choroidal Lesions,
Ultrasound, Standardized Echography, Spectral Domain
Optical Coherence Tomography (SD-OCT), Heidelberg
Spectralis
U
ltrasound is the gold standard for measuring
intraocular tumors; however, a lesion must
be elevated by 0.75mm before it can be distinguished. Even if a lesion can be detected, accurate
measurement may require even more elevation.1 Since
most adult intraocular tumors begin in the choroid,
Optical Coherence Tomography (OCT) has been limited
in viewing these tumors.2 The technique of Enhanced
Depth Imaging (EDI) using the Heidelberg Spectralis
SD-OCT (Heidelberg Engineering, Heidelberg, Germany) first
appeared in the literature in 2008. It provides enhanced
resolution of the choroid, and thus, the ability to visualize
and follow choroidal lesions.2
There are a few tips for obtaining high quality EDI
scans of the choroid using the Spectralis. If the lesion
is small enough, try to get all margins in the frame and
capture a raster of lines over the lesion in order to scroll
a
b
Figure 1: (a) Standard OCT scan of the retina, scan signal concentration is on the anterior retina. (b) EDI image of the same retina;
we can now delineate the borders of the choroidal lesion.
Correlation of Ocular Ultrasound and Spectralis Enhanced Depth Imaging (EDI) of Ocular Lesions
65
a
Figure 3: Atypical, amelanotic choroidal nevus.
b
Figure 2: Measuring a lesion found on OCT using the Spectralis
software.
a
b
Figure 5: Caliper placement is more difficult with ultrasound.
a
b
Figure 4: (a) With ultrasound, the lesion measured approximately
0.7 mm. (b) With OCT, the lesion measures approximately 0.4 mm.
through to find maximum height and width. Maximum
height and width are important; if the ocular oncologist
decides intervention in the form of plaque therapy is
needed, the largest measurement is used to determine
the size of the plaque needed.1
In addition, use the Automatic Real Time (ART)
mode with the maximum frames possible, since the preset volume scan, which averages nine frames, usually
does not reveal enough detail to delineate borders of the
lesion. If you do not have the Spectralis update with the
EDI button, choosing “XL” as the size of the eye usually
results in higher resolution scans instead of only moving
the camera closer (Figure 1).
To measure a lesion found on OCT using the
Spectralis software, drag the caliper icon in the lower right
hand corner of the screen and resize it to measure the
lesion, (Figure 2a). To measure these choroidal lesions, the
measuring tool was placed at the edge of the hyper-reflective line indicative of the retinal pigment epithelium and
stretched to the outer edge of the choroid, where it meets
the inner sclera, (Figure 2b). In the normal population,
choroidal thickness measured by OCT is thickest under
the fovea and begins to thin further out from the fovea
nasally. Mean choroidal thickness is 287µ under the fovea
and 145µ when measuring 3 mm nasal to the fovea.3
For the purpose of this article, the inverted images
have been rotated 180 degrees in Photoshop to appear
the way we traditionally view OCT scans, with the anterior retina facing up.
Case one is a patient who presented with an atypical, amelanotic choroidal nevus (Figure 3). For a nevus,
malignancy cannot be ruled out without continued
monitoring for change over a period of years. With
ultrasound, the lesion measured approximately 0.7 mm;
however on OCT the lesion measures approximately
0.4 mm, (Figure 4). Because this lesion is so small, the
limited resolution of ultrasound makes it difficult to
differentiate layers and thus caliper placement is more
difficult.3 (Figure 5) As there is a measurement variation,
it is important to serially follow a lesion on the same
equipment; however the improved resolution of the
OCT may provide more ease of comparison in the case
of such a small lesion.
66
The Journal of Ophthalmic Photography
Volume 33, Number 2 • Fall 2011
Case two is a twenty
year old male with a suspicious choroidal nevus
in the left eye. Indications
that this is a suspicious
nevus to be followed
carefully are orange pigmentation, subretinal
fluid and proximity to the
optic nerve, (Figure 6).
Even though this lesion is
only mildly elevated, the
appearance of these three
a
b
risk factors means this
Figure 6: Suspicious choroidal nevus OS.
lesion has a 50% chance
of growing, which is indicative of melanoma. The other two risk factors to be considered when observing choroidal lesions are if the lesion
is greater than 2.0 mm in height or if the patient presents
with visual symptoms.4 This lesion is under the 2.0 mm
mark, measuring 1.36 mm on ultrasound and 1.04 mm
on OCT, (Figure 7). This variance in measurement could
be deemed acceptable, when taking into account the
acceptable range in measurements for ultrasound from
A-scan to B-scan is considered 0.2 to 0.3 mm in height.1
The patient was asked to come back in 4-6 months in
order to observe for growth.
Case three provides evidence that EDI OCT can
resolve choroidal infiltrate where ultrasound may not be
sensitive enough. A 52 year old male recently diagnosed
a
with leukemia presented with complaints of a “yellowgreen dirty screen” in the center of vision of both eyes,
general blurry vision in both eyes and occasional flashes
in both eyes. Fundus photos show a few small dot blot
hemorrhages on the right eye and subretinal fluid in the
area of the macula in both eyes, (Figure 8). Ultrasound
identified thickening in the macula with no echographic
b
evidence of choroidal thickening, (Figure 9). However, EDI
Figure 7: (a) Ultrasound measured the lesion at 1.36 mm. (b) The
OCT reveals choroidal thickening of 513µ in the right eye
lesion measured 1.04 mm on OCT.
and 503µ in the left eye, which is markedly thicker
than the normal average of 287µ3 (Figure 10).
The choroidal thickening
along with the subretinal
fluid in conjunction with
the diagnosis of Leukemia
is indicative of Leukemic
Choroidopathy.5 Four
weeks after the start of
chemotherapy, the patient’s
visual symptoms completely resolved and the choroid
measured 337µ on the
right eye and 310µ on the
a
b
left eye, which is much
closer to the normal range
Figure 8: Fundus photographs show a few small dot and blot hemorrhages OD and subretinal fluid in
(Figure 11).
the macula OU.
Correlation of Ocular Ultrasound and Spectralis Enhanced Depth Imaging (EDI) of Ocular Lesions
67
a
b
Figure 10: EDI OCT revealed choroidal thickening of 513µ OD and
503 µ OS.
a
a
b
Figure 9: Ultrasound identified thickening in the macula but no
evidence of choroidal thickening.
Conclusion
While OCT cannot replace ultrasound, the newer OCT
technique of Enhanced Depth Imaging can be useful
for measuring very small lesions or thickening of the
choroid.2,3,6 SD-OCT has the ability to register scans to a
reference image, which helps for future correlation, while
ultrasound is extremely operator dependent and there
are fewer individuals well versed in its use. By continuing
to scan small lesions or other choroidal pathology using
both ultrasound and EDI OCT, more information may
be able to be gleaned than using ultrasound alone.
References
1. Byrne, S. F. and R. L. Green (2002). Ultrasound of the Eye and
Orbit. 2nd ed. Philadelphia, Mosby.
b
Figure 11: Four weeks after the start of chemotherapy, the
patient’s visual symptoms completely resolved and the choroids
measured 337µ OD and 310µ OS.
2. Spaide, R. F., H. Koizumi, et al. (2008). “Enhanced depth imaging
spectral-domain optical coherence tomography.” American Journal
of Ophthalmology 146(4): 496-500.
3. Margolis, R. and R. F. Spaide (2009). “A pilot study of enhanced
depth imaging optical coherence tomography of the choroid in
normal eyes.” American Journal of Ophthalmology 147(5): 811-815.
4. Shields, C., J. Cater, et al. (2000). “Combination of Clinical Factors
Predictive of Growth of Small Choroidal Melanocytic Tumors.”
Archives of Ophthalmology 118: 360-364.
5. Tang, R. A., A. A. Vila-Coro, et al. (1988). “Acute Leukemia
Presenting as a Retinal Pigment Epithelium Detachment.” Archives
of Ophthalmology 106(1): 21-22.
6. Stalmans, P. (2010). “Why Optical Coherence Tomography
(OCT) Cannot Replace Ultrasound.” Eye to Eye. (5):10-11.