Name:
Second window ICG predicts postoperative MRI gadolinium enhancement in high grade gliomas and brain metastases
Description:
Second window ICG predicts postoperative MRI gadolinium enhancement in high grade gliomas and brain metastases
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Duration:
T00H08M51S
Embed URL:
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https://cadmoreoriginalmedia.blob.core.windows.net/9fb798e5-cdb5-45fd-99e2-6b44affaf9b5/21-204.mp4?sv=2019-02-02&sr=c&sig=4gtPsOne5yI3Fwa%2BG8JgJzan8WZLwqLHkne4p9MPa6o%3D&st=2024-05-07T21%3A33%3A26Z&se=2024-05-07T23%3A38%3A26Z&sp=r
Upload Date:
2021-12-08T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
[MUSIC PLAYING]
SPEAKER: In this video presentation, we discuss the application of second window indocyanine green in predicting postoperative MRI gadolinium enhancement in both high-grade gliomas and brain metastases. What makes indocyanine green unique in the context of intraoperative visualization is that it is a near-infrared fluorophore, which confers ICG with some unique benefits in the surgical setting. ICG is excited around 805 nm, and its emission is detected around 835 nm.
SPEAKER: ICG is thought to accumulate due to the enhanced permeability and retention effect in the tumor microenvironment due to angiogenesis and the disruption of blood- brain barrier integrity, and it may be endocytosed directly by tumor cells. The supposed mechanism of ICG distribution closely mimics that of gadolinium in contrast-enhanced imaging studies, potentially allowing us to utilize its near-infrared fluorescence as a proxy for postoperative MRI enhancement.
SPEAKER: This property would allow for the use of ICG as an adjunct or alternative to current neuronavigation and intraoperative MRI techniques, which are not always reliable or easily accessible. Our study took place between 2014 and 2019 and included over 350 patients with a variety of CNS tumors. The technique we used is named "second window ICG" because we administered the dye in high doses up to 5 mg/kg up to 24 hours before surgery.
SPEAKER: Intraoperative near-infrared imaging was performed using an exoscope, and the residual fluorescence postresection was compared to gadolinium enhancement on postoperative MRI. Importantly, near-infrared imaging did not guide the extent of surgical resection actually performed by the surgeon.
SPEAKER: ICG is more traditionally used in the context of video angiography in typical doses between 0.2 and 0.5 mg/kg, with imaging performed within minutes of administration. Our technique and application of ICG is termed "second window ICG" because we administer high doses of ICG between 2.5 and 5 mg/kg 24 hours before surgery. We are able to take advantage of the enhanced permeability and retention effect in the tumor microenvironment to detect the fluorescence of ICG in this second window, as seen on the diagram.
SPEAKER: For the high-grade glioma group, we had 34 patients with near-infrared imaging of the final surgical cavity view postresection. Of the 25 patients who had positive near-infrared imaging signal in the final view, 23 of these patients had correlating residual neoplasm on postoperative MRI. Of the 9 patients with no residual near-infrared fluorescence in the final view, 8 had a complete resection of enhancing tumor on postoperative MRI.
SPEAKER: When compared to white light alone, ICG imaging had a higher sensitivity at 96%, negative predictive value at 89%, and accuracy at 91% in predicting residual neoplasm on MRI. Here we have a case highlighting the utility of the second window ICG in predicting postoperative MRI. This patient was a 71-year-old man presenting with progressive confusion over a 3-week period, having specific difficulties with speech.
SPEAKER: His primary care provider thought he had a stroke and referred the patient for an MRI. Preoperative imaging reveals a 38-mm mass in the left parietal lobe, presumably glioblastoma. Here's a still of the contrast- enhanced MRI further showing the tumor. The patient was started on dexamethasone three times per day.
SPEAKER: Here, we are performing the craniotomy for this patient. The fluorescence that's seen in this video is a pseudocolor overlay on top of the white light. One of the unique advantages of ICG is its ability to penetrate through the dura mater given that it has a longer wavelength than visible light dyes. This transdermal fluorescence allows us to center over the tumor prior to incising the dura.
SPEAKER: Once the dura has been opened, we can see the dye permeating the hypervascular tumor environment allowing the surgeon to identify the neoplastic tissue.
SPEAKER: Once the majority of the tumor has been removed, we can see some residual fluorescence in this final view. As previously mentioned, fluorescence was not used to guide the extent of resection in the study. Here, the surgeon removes a sample, which is clearly visualized by ICG from the margin of the cavity to send to pathology for further evaluation.
SPEAKER: Postoperative MRI shows some residual enhancement around the resection cavity, deep and close to the lateral ventricle. These enhancements are highlighted by the white arrows. This is a comparison highlighting the correlation between ICG fluorescence and gadolinium enhancement.
SPEAKER: Prior to the recession on the left, we can see the fluorescence in the bulk of a tumor correlating to the enhancement seen on MRI. Postresection, on the right, we can see the location of residual fluorescence near the lateral ventricle correlating to the rim of enhancement also seen on postop MRI. Ultimately, this patient underwent combined chemoradiation following surgery due to this residual tumor.
SPEAKER: For the brain metastases group, we have 44 patients with near-infrared imaging on the final surgical cavity postresection. This group highlights that a lack of near-infrared fluorescence in the final view correlates with a lack of gadolinium enhancement on postop MRI, emphasizing the sensitivity and negative predictive values seen with second window ICG. Of the 16 patients in our study with no residual ICG fluorescence upon resection, all 16 had a complete resection of enhancing tumor on postop MRI.
SPEAKER: Though compared to the high-grade glioma groups, second window ICG has a lower specificity for predicting MRI enhancement in brain metastases. Near-infrared imaging clinically predicted the tumor recurrence better than postop MRI. Of the patients with recurrent tumors, a greater number had positive findings on final view near-infrared imaging compared to postoperative MRI.
SPEAKER: This figure shows the correlation between final view ICG and postoperative gadolinium enhancement in a gross-total resection and a non–gross-total resection. The top row depicts a metastasis in the right temporal lobe. Upon resection, there is no visible near-infrared fluorescence in the surgical cavity seen in box E on the top right.
SPEAKER: This correlates with the lack of significant enhancement seen in the postoperative MRI, box B. In contrast, the bottom row shows a non–gross-total resection for a right occipital mass. Box J on the bottom right highlights the residual enhancement seen anteriorly in the resection cavity in the final view, which correlates to the anterior we located enhancement seen in the postoperative MRI.
SPEAKER: In conclusion, second window ICG extravasates into the tumor microenvironment of high-grade gliomas and brain metastases via the enhanced permeability and retention effect with gadolinium-like distribution properties. ICG provides intraoperatively useful means of predicting postoperative gadolinium enhancement with the high sensitivity and negative predictive value. In this context, second window ICG serves as a valuable tool to improve overall sensitivity and achieve a greater extent of resection, which may have positive implications related to survival in adjuvant therapy.
SPEAKER: These are our references. Thank you for your attention.