Accuracy of MRI with an endorectal coil for staging endometrial cancer

Alt, Céline D.; Brocker, Kerstin A.; Eichbaum, Michael; Sohn, Christof; Kopp‐Schneider, Annette; Kauczor, Hans Ulrich; Hallscheidt, Peter

doi:10.1258/ar.2012.110617

Cited by 4 publications

(1 citation statement)

References 33 publications

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“…In this preclinical study, we showed that a relatively large FOV could be covered by an endovaginal array that included both forward-looking and sideways-looking elements, and that approximately four times SNR enhancement was obtained in-vivo at distances of 40 mm from the array. The main technological difference between this endovaginal array and other endovaginal, cervix, 20,21,41 endourethral, 24 or endorectal coil arrays, 42,43 is the novel coil structure used in the forward-looking coil at the tip of the array, which enables acquiring high SNR images above the tip (i.e., in the forward-looking direction). The metallic-backed forward-looking coil was specifically optimized to allow high-sensitivity imaging of the cervix and posterior parametrium, which are regions that cannot be accessed with most coil designs, due to the narrow diameter of the cervical canal, which prohibits advancement of large (>10 mm) diameter coils upwards into the cervix and parametrium.…”

Section: Discussionmentioning

confidence: 99%

An endovaginal MRI array with a forward‐looking coil for advanced gynecological cancer brachytherapy procedures: Design and initial results

et al. 2021

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Purpose To develop an endovaginal MRI array that provides signal enhancement forward into the posterior parametrium and sideways into the vaginal wall, accelerating multiple‐contrast detection of residual tumors that survive external beam radiation. The array's enclosure should form an obturator for cervical cancer brachytherapy, allowing integration with MRI‐guided catheter placement, CT, and interstitial radiation dose delivery. Methods The endovaginal array consisted of forward‐looking and sideways‐looking components. The forward‐looking element imaged the cervix and posterior endometrium, and the sideways‐looking elements imaged the vaginal wall. Electromagnetic simulation was performed to optimize the geometry of a forward‐looking coil placed on a conductive‐metallic substrate, extending the forward penetration above the coil's tip. Thereafter, an endovaginal array with one forward‐looking coil and four sideways‐looking elements was constructed and tested at 1.5 Tesla in saline and gel phantoms, and three sexually mature swine. Each coil's tuning, matching, and decoupling were optimized theoretically, implemented with electronic circuits, and validated with network‐analyzer measurements. The array enclosure emulates a conventional brachytherapy obturator, allowing use of the internal imaging array together with tandem coils and interstitial catheters, as well as use of the enclosure alone during CT and radiation delivery. To evaluate the receive magnetic field (B1−) spatial profile, the endovaginal array's specific absorption‐rate (SAR) distribution was simulated inside a gel ASTM phantom to determine extreme heating locations in advance of a heating test. Heating tests were then performed during high SAR imaging in a gel phantom at the predetermined locations, testing compliance with MRI safety standards. To assess array imaging performance, signal‐to‐noise‐ratios (SNR) were calculated in a saline phantom and in vivo. Swine images were acquired with the endovaginal array combined with the scanner's body and spine arrays. Results Simulated B1− profiles for the forward‐looking lobe pattern, obtained while varying several geometric parameters, disclosed that a forward‐looking coil placed on a metal‐backed substrate could double the effective forward penetration from approximately 25 to ∼40 mm. An endovaginal array, enclosed in an obturator enclosure was then constructed, with all coils tuned, matched, and decoupled. The ASTM gel‐phantom SAR test showed that peak local SAR was 1.2 W/kg in the forward‐looking coil and 0.3 W/kg in the sideways‐looking elements, well within ASTM/FDA/IEC guidelines. A 15‐min 4 W/kg average SAR imaging experiment resulted in less than 2oC temperature increase, also within ASTM/FDA/IEC heating limits. In a saline phantom, the forward‐looking coil and sideways‐looking array's SNR was four to eight times, over a 20–30 mm field‐of‐view (FOV), and five to eight times, over a 15–25 mm FOV, relative to the spine array's SNR, respectively. In three sexually mature swine, the forwar...

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