2012 Proceedings - International Tissue Elasticity Conference

Session CAA–3: Clinical and Animal Applications – III
Friday, October 5 3:00P – 3:45P
022 SHEAR WAVE ELASTOGRAPHY OF PEDIATRIC EPILEPTOGENIC TUMORS: PRELIMINARY
RESULTS.
HW Chan 1,3 , A Chakraborty 2 , NL Dorward 1 , JC Bamber 3 , W Harkness 2 .
1 Neurosurgery Department, Royal Free Hospital, Pond St, London, NW3 2QG, England, UK;
2 Neurosurgery Department, Great Ormond Street Hospital, Great Ormond St, London, WC1N 3JH,
England, UK; 3 Joint Department of Physics, Institute of Cancer Research and Royal Marsden
Hospital, Sutton, Surrey, SM2 5PT, England, UK.
Background: Almost half of all children with brain tumors have medically intractable epilepsy and
therefore are invariably offered surgical therapy with outcomes dependent on the extent of resection.
Previous evaluation of adult brain tumor stiffness contrast using preoperative magnetic resonance
elastography [1] and intraoperative ultrasound vibrography [2] demonstrated good correlation with the
surgeon’s opinion of relative stiffness from palpation. We present here our results with shear wave
elastography (SWE) of pediatric epileptogenic tumors during resective brain surgery.
Aims: To measure the Young’s modulus (YM) of pediatric epileptogenic tumors in vivo, to compare tumor
YM with surgeon’s palpation and to differentiate tumor from normal surrounding brain.
Methods: 11 patients with epileptogenic cerebral tumors were scanned during resective brain surgery.
The scans were performed using an Aixplorer ® (SuperSonic Imagine, France) scanner equipped with a
sector transducer (SE12–3) with a bandwidth of 3–12MHz, using the ShearWaveTM Elastography (SWE)
mode. YM measurements were made in a region–of–interest (ROI) identified as tumor on the B–mode
ultrasound scan using the built–in Q–BoxTM function (Figures 1 and 2). The surgeon’s opinion of tumor
stiffness relative to surrounding brain was scored by palpation during surgery, and tumor diagnosis was
obtained from sectional histology. Both were recorded in a manner that was blind to the SWE result.
Results: The patients’ ages ranged from 10 months to 15 years and included 8 females and 3 males. One female
patient was operated on twice for residual supratentorial primitive neuroectodermal tumor (sPNET). According to
the surgeon’s opinion, 7 tumors were softer than brain (3 dysembryoplastic neuroepithelial tumor (DNT),
2 astrocytoma grade II, 1 choroid plexus papilloma, 1 sPNET), and 5 were firmer than brain (1 epidermoid cyst,
1 subependymal giant cell astrocytoma (SEGA), 1 sPNET (second operation after radiotherapy), 1 DNT,
1 ganglioglioma). The mean YM ranged from 6.6 to 35.6kPa (mean 19.98kPa; SD 11.5kPa) and 117.2 to 300kPa
(mean 186.9kPa; SD 67.9kPa) for tumors that were scored by the surgeon as softer and firmer than brain,
respectively. The mean YM for the normal grey and white matter in these patients were 28.5kPa (SD 5.1kPa) and
18.2kPa (SD 5.5kPa), respectively. The tumor that had a mean YM of 300kPa was a SEGA, which was located 5cm
from the brain surface (beneath the fluid–filled lateral ventricle), thereby possibly giving inaccurate YM data.
Conclusions: Our preliminary results showed good correlation between YM measurements made with
SWE and surgeon’s opinion by palpation. Although the YM for tumors that scored softer than brain by
the surgeon overlapped with the YM range for normal brain, there was always a YM difference at the
tumor–brain boundary (e.g. Figure 1). The YM contrast between tumor and normal brain was much better
for tumors that were stiffer than brain (Figure 3), than for tumors that were softer than brain. This is the
first intraoperative evaluation of pediatric epileptogenic tumors with shear wave elastography, which
seems to show promise for use as an intraoperative adjunct in tumor resection.
Acknowledgements: This work was supported by Engineering and Physical Sciences Research Council, UK. Ethical approval was
obtained from the National Research Ethics Service (NRES) Committee London – Queen Square Research Ethics Committee (Ref:
08/H0716/92).
References:
[1] Xu, L., et al.: Magnetic Resonance Elastography of Brain Tumors: Preliminary Results. Acta. Radiol., 48(3), pp. 327–330 2007.
[2] Scholz, M., et al.: Vibrography during Tumor Neurosurgery. J. Ultrasound Med., 24(7), pp. 985–992, 2005.
Figure 1: SWE scan of dysembryoplastic
neuroepithelial tumor (DNT) outlined by
dotted line. The Q–Box TM function was used
to measure YM within the tumor ( ) and
at the peripheries ( , , ).
Figure 2: B–mode scan of the
corresponding SWE
scan in Figure 1.
Figure 3: SWE scan of left mesial
temporal epidermoid cyst
showing a good YM contrast
between tumor and brain.
indicates Presenter 113