European Journal of Radiology 84 (2015) 668–670

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Feasibility of intermittent pneumatic compression for venous thromboembolism prophylaxis during magnetic resonance imaging-guided interventions Majid Maybody a,∗ , Bedros Taslakian c , Jeremy C. Durack a , Elena A. Kaye b , Joseph P. Erinjeri a , Govindarajan Srimathveeravalli a , Stephen B. Solomon a a

Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, United States Department of Medical Physics, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, United States c Department of Diagnostic Radiology, American University of Beirut Medical Center, Riad El-Solh, 1107 2020 Beirut, Lebanon b

a r t i c l e

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Article history: Received 7 October 2014 Received in revised form 21 November 2014 Accepted 14 January 2015 Keywords: Sequential compression device Interventional radiology iMRI Venous thromboembolism prophylaxis

a b s t r a c t Purpose: Venous thromboembolism (VTE) is a common cause of morbidity and mortality in hospitalized and surgical patients. To reduce risk, perioperative VTE prophylaxis is recommended for cancer patients undergoing surgical or interventional procedures. Magnetic resonance imaging (MRI) is increasingly used in interventional oncology when alternative imaging modalities do not adequately delineate malignancies. Extended periods of immobilization during MRI-guided interventions necessitate an MR compatible sequential compression device (SCD) for intraprocedural mechanical VTE prophylaxis. Such devices are not commercially available. Materials and methods: A standard SCD routinely used at our institution for VTE prophylaxis during interventional procedures was used. To satisfy MR safety requirements, the SCD controller was placed in the MR control room and connected to the compression sleeves in the magnet room through the wave guide using tubing extensions. The controller pressure sensor was used to monitor adequate pressure delivery and detect ineffective low or abnormal high pressure delivery. VTE prophylaxis was provided using the above mentioned device for 38 patients undergoing MR-guided ablations. Results: There was no evidence of device failure due to loss of pressure in the extension tubing assembly. No interference with the anesthesia or interventional procedures was documented. Conclusion: Although the controller of a standard SCD is labeled as “MR-unsafe”, the SCD can be used in interventional MR settings by placing the device outside the MR scanner room. Using serial tubing extensions did not cause device failure. The described method can be used to provide perioperative mechanical VTE prophylaxis for high risk patients undergoing MR-guided procedures. © 2015 Elsevier Ireland Ltd. All rights reserved.

1. Introduction Interventional magnetic resonance imaging (iMRI) can improve visualization, medical device manipulation and intra-procedural

Abbreviations: VTE, venous thromboembolism; MRI, magnetic resonance imaging; SCD, sequential compression device; iMRI, interventional magnetic resonance imaging; CT, computed tomography; US, ultrasound; MRgFUS, MR-guided Focused Ultrasound Surgery; SIR, Society of Interventional Radiology. ∗ Corresponding author at: Interventional Radiology Service, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, M276C, New York, NY 10065, United States. Tel.: +1 212 639 2793; fax: +1 212 717 3325. E-mail addresses: [email protected] (M. Maybody), [email protected] (B. Taslakian), [email protected] (J.C. Durack), [email protected] (E.A. Kaye), [email protected] (J.P. Erinjeri), [email protected] (G. Srimathveeravalli), [email protected] (S.B. Solomon). http://dx.doi.org/10.1016/j.ejrad.2015.01.011 0720-048X/© 2015 Elsevier Ireland Ltd. All rights reserved.

monitoring for response to therapy, particularly when target lesions are inadequately imaged by other modalities such as computed tomography (CT) or ultrasound (US) [1]. In particular, superior tissue differentiation can be achieved without intravenous contrast administration or ionizing radiation, a clear benefit for iMRI guidance when serial imaging of target tissues is required (Fig. 1). In addition, some ablation protocols, such as MR-guided Focused Ultrasound Surgery (MRgFUS), are based on MRI guidance. The duration of iMRI procedures typically exceeds similar CT or US guided interventions mainly due to longer image acquisition time [2]. Additional procedure time is commonly required for interventions performed under general anesthesia. Prolonged procedure time on immobilized patients potentially increases the risk of venous thromboembolism (VTE). This risk becomes more significant in our patient population with active cancer.

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Fig. 1. Example of a typical iMRI ablation case. An 82-year old female with stage IV bladder cancer and borderline renal function with a growing solitary liver metastasis. The liver is the only site of disease progression. (a) Axial T2-weighted fat-saturated MR image of the liver showing a small hyperintense hepatic lesion in segment VII–VIII (arrow). (b) Non-enhanced CT scan at the same level showing difficulty in differentiating the hepatic lesion from the adjacent vessels rendering CT-guided ablation less desirable.

Hospital-acquired VTE causes considerable patient morbidity and mortality [3]. Prolonged surgeries and interventions predispose patients to VTE through venous stasis and sometimes venous injury. Underlying hypercoagulable disease states, prolonged surgical interventions, immobilization or often a combination of these factors increase patients risk for developing VTE. The risk of VTE is high in patients with active cancer [4,5]. Perioperative VTE prophylaxis has been recommended by the American Society of Clinical Oncology (ASCO) and the American College of Chest Physicians (ACCP) in patients undergoing surgical and interventional procedures [6–8]. Perioperative VTE prophylaxis measures include the use of pharmacological and/or mechanical noninvasive methods such as sequential compression therapy [6,7]. Mechanical VTE prophylaxis using a lower extremity sequential compressive device (SCD), rather than pharmacological therapy, is preferred for intraprocedural VTE prevention to reduce the risk of bleeding until such risk diminishes and pharmacologic prophylaxis is safe to be initiated [8]. In addition, anticoagulation should be withheld 12–24 h (low molecular weight heparin) and up to 5 days (aspirin and clopidogrel) prior to certain image-guided interventions, thus contraindicated as per the Society of Interventional Radiology (SIR) guidelines [9]. Sequential compression therapy massages the legs in a wavelike, milking motion that promotes blood flow in the lower extremities which has been shown effective in VTE prevention in surgical and medical patients with high risk of bleeding [10,11]. SCD systems used in the hospital setting typically consist of an air compression controller, extension tubing assembly and disposable single-use lower extremity compression sleeves. Air is intermittently pumped into the leg sleeves to a set pressure, augmenting antegrade venous blood flow via mechanical compression below the knees. The controller is often capable of determining time to venous blood return after reaching a preset pressure of 45 mmHg in the compression cycle, before initiating the next compression. To comply with American College of Radiology (ACR) Guidelines on MR Safe Practices [12] all equipments used in iMRI environment should be clearly labeled to indicate their level of MRI safety, designated as “MR Safe” (green label), “MR Conditional” (yellow label) or “MR Unsafe” (red label). The classification “MR Safe” refers to objects that are completely nonmagnetic, non-electrically conductive and non-radiofrequency reactive. “MR Conditional” includes the objects that contain metallic materials but have no ferromagnetic components and therefore under particular conditions are allowed into MRI magnet room (zone IV). Any object for which manufacturer’s description of components and materials is lacking needs to be tested according to MR Safe Practice guidelines [12]. If

the test determines the object’s classification as “MR unsafe”, the object cannot be introduced into the magnet room [12]. We describe a simple modification to adapt a standard SCD system for safe application during MRI-guided interventions. To our best knowledge, no such method has been described in the literature. 2. Materials and methods The Kendall Express 700 series SCD (Covidien, Mansfield, MA, USA), routinely used at our institution for intra-procedural VTE prophylaxis, was modified for MRI compatibility. Metal and ferromagnetic detectors were used to inspect the SCD system. While the sleeve (Kendall SCD Express Sleeve – Knee Length. Covidien, Mansfield, MA, USA) and the tubing (Kendall SCD Controller Tubing Assembly – size: 7’. Covidien, Mansfield, MA, USA) contained no metallic components and were determined “MRI Safe”, the SCD controller was found to contain both metallic and ferrous materials, which classifies it as “MRI unsafe” and was not allowed into MRI magnet room (zone IV). To satisfy MRI safety requirements, the SCD controller was installed in the MRI control room (zone III), and the rest of the system parts considered “MRI safe” were brought into the magnet room (zone IV). The SCD controller was connected to each of the two compression sleeves through the wave guide using three serial tubing extensions (Fig. 2). This provided enough length so the tubing assembly was not under any tension as the patient was brought in and out of the magnet during the intervention. It also ensured sufficient length of the tubing assembly that allowed connection to the patient from the “back end” of the magnet opposite the “front end” where interventional radiology and anesthesialogy staff are usually stationed. This configuration lowered the chance of any physical interference with the intervention. The SCD controller pressure sensor, a standard device feature, was adapted to monitor adequate pressure delivery and detect ineffective low or abnormally high pressure delivery due to the potentially introduced dead space. Audible high pressure alarms, a standard device setting, was set to alert users to system pressure levels exceeding 90 mmHg, leg sleeve pressures greater than 47 mmHg for 10 consecutive cycles or greater than 65 mmHg for 5 consecutive cycles. A low pressure alarm indicated leg sleeve pressures less than 43 mmHg for 10 consecutive cycles. The anesthesialogy staff or sedation nurse monitored SCD function during procedures. As per our institutional guidelines, SCD was indicated for VTE prophylaxis during all ablation procedures. Using this device setting VTE prophylaxis was provided for 38 MRI-guided cryoablation interventions performed under general anesthesia at our institution between March 2011 and December 2013. MRI-compatible

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Fig. 2. Provision of SCD during an MR-guided renal mass ablation. The patient is in prone position and all interventional radiology and anesthesia procedures are performed from the “front side” of the magnet. (a) Photograph of the “back side” of the magnet showing the serial extension tubing assembly (open arrows) which connects the compression sleeves, applied routinely on the patient’s legs inside the magnet, to the controller via the wave guide in the wall (double thin arrows). The position and length of extension tubing is checked at the start of each intervention to make sure the patient can easily go in and out of the magnet repeatedly without interference with the interventional radiology or anesthesia staff. (b) The SCD controller (curved arrow) sits in the control room (zone III), where the sedation nurse or anesthesia staff can monitor its function during the procedure.

applicators (Galil Medical, Inc., Arden Hills, MN, USA) were used for cryoablation of the following malignancies: bone (n = 6), breast (n = 10), kidney (n = 5), liver (n = 8) and soft tissue (n = 9). The institutional review board (IRB) approved this study and a waiver of informed consent from the involved subjects was granted. 3. Results There were no device failures or malfunctions in any of the 38 MRI-guided cryoablation interventions. No pressure changes outside of the described alert parameters were detected by the SCD controller system. No interference or disruption of anesthesia, MR imaging or the interventional procedure were reported due to the SCD components. The use of wave guide did not introduce any noticeable changes to MR image quality. 4. Discussion This work demonstrates how a standard SCD system, not formally marketed as “MRI Safe”, can be adapted for safe use in iMRI environment at low cost. Device adaptation required additional extension tubing to connect the controller, placed outside the magnet room in zone III, and the compression sleeves attached to the patient in the magnet room (zone IV). Using serial extension tubing assembly did not affect the performance of the SCD device and did not interfere with performance of imaging, interventional or anesthesialogy staff. While the system described in this work was applied during MRI-guided cryoablations only, it can be used to provide perioperative mechanical VTE prophylaxis for high risk patients undergoing any MR-guided intervention or surgery as well as prolonged diagnostic MRI examinations.

5. Conclusion We implemented a simple modification to a standard SCD system for safe use in iMRI. This setting is functional and is currently the standard way of mechanical VTE prophylaxis during long MRI guided interventions and surgeries at our institution.

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