Author's Accepted Manuscript
Management and Organization of PET/MR Patricia Devlin, Andrew Sher, Christian Rubbert, David Jordan, Peter Faulhaber, Norbert Avril, Pablo Ros
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S0037-198X(14)00016-9 http://dx.doi.org/10.1053/j.ro.2014.04.003 YSROE50470
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Seminar in Roentgenology
Cite this article as: Patricia Devlin, Andrew Sher, Christian Rubbert, David Jordan, Peter Faulhaber, Norbert Avril, Pablo Ros, Management and Organization of PET/MR, Seminar in Roentgenology, http://dx.doi.org/10.1053/j.ro.2014.04.003 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Management and Organization of PET/MR
Patricia Devlin, Andrew Sher, Christian Rubbert, David Jordan, Peter Faulhaber, Norbert Avril and Pablo Ros
Department of Radiology University Hospitals Case Medical Center Case Center for Imaging Research Case Western Reserve University Cleveland, OH 44106, USA
Address for correspondence: Pat Devlin, BS, ARRT (R), CNMT Manager of Nuclear Medicine, PET, MRI Department of Radiology University Hospitals Case Medical Center Phone: 216-844-4993 Email: [email protected]
Number of words:
Conflict of interest: none
Abstract PET/MR is a new imaging modality which is currently being evaluated for research and clinical purposes. The necessary space requirements, the implementation of MR safety zone restrictions and controls, and the benefits of the system for anatomical localization are discussed. Appropriate staffing is of critical importance, as Nuclear Medicine technologists supporting the PET/MR need to be trained in the MRI magnet environment and MR specific patient screening, while MRI technologists require training in radiation safety. A close collaboration between nuclear medicine and radiology physicians is critical to maximize the benefit from the PET/MR in the clinical setting. This collaboration must address protocols used for clinical cases as well as reporting. For research purposes, an appropriate funding infrastructure needs to be in place to operate and maintain the system.
Introduction The decision to install a PET/MR system within a health care organization requires an understanding of the mission and vision for using the PET/MR. A critical question to consider is if the PET/MR will be utilized for research, routine clinical imaging, or for both purposes. If the primary purpose of PET/MR is research then an appropriate funding infrastructure needs to be in place to operate and maintain the system. For clinical applications it is essential that adult and pediatric referring clinicians, including those from Medical Oncology, Radiation Oncology, Neurology and Cardiology, be engaged in discussions about potential use. Regardless of purpose, it is important to recognize that from a financial perspective, a facility should not expect ideal annual growth and increasing net revenue until PET/MR system development and deployment is more mature. Continued adoption of the PET/MR modality may take several years and additional peer-reviewed evidence in its support before it is clinically accepted in the United States. The physical location of the system within the Radiology department must simultaneously satisfy the requirements of patient workflow, radiation safety, radioactive materials security, and MRI safety. The Philips Ingenuity TF PET/MR was installed in the University Hospitals Seidman Cancer Center in Cleveland, OH, in December 2011. The installation was the first FDAapproved sequential system designed for use in a clinical environment in the United States. The decision to locate the PET/MR in the newly built Seidman Cancer Center provided the opportunity to plan for and achieve the required MRI safety zones in accordance with the American College of Radiology (ACR) guidelines1. The system is located within the Nuclear Medicine department on the same floor as additional imaging services including PET/CT, CT, and MRI. In this location, Radiology administrative and technical staff can easily share responsibilities between clinical PET/MR, research PET/MR, PET/CT, and diagnostic MR. In an existing Radiology department, the decision of where to locate the PET/MR may be dictated by available space. If the location is within the Nuclear Medicine department, a large amount of space may be required to implement MRI safety zone restrictions and controls. The 4-zone safety model1 requires that there be a distinct Zone II area (such as waiting rooms and dressing rooms), separate from the general public areas of the hospital, which is securely and physically separated from Zone III. Zone III is an area through which the PET/MR room itself (Zone IV) is accessed. Zone III must be fully secured against entry by anyone not under the control and surveillance of safety-trained personnel (the PET/MR technologists). Thus, site 3
planning must provide for the scan room itself, a Zone III region or area that includes the control console area and controls all access paths into the PET/MR scanner, and a method of restricting access into Zone III from the dressing and waiting areas. Zone II must provide sufficient space for patients to be privately screened for MR safety, change into MR-safe gowns or scrubs, and securely store their street clothes and personal belongings.
requirements are not necessarily provided in existing nuclear medicine department designs. Alternatively, locating the system in Radiology may require additional space provisions due to the use of radiopharmaceuticals for PET/MR. If the area is not close to an existing nuclear medicine department, a hot lab is needed for storage, handling, and assay of radiopharmaceuticals. A proper waiting area is also needed for patients to be held between injection of radiotracer and imaging. Hot labs and especially patient uptake rooms often require substantial radiation shielding for PET operations, given the high energy (511 keV) photon emissions2. Additional attention needs to be given to the use of unsealed radiopharmaceuticals outside
radiopharmaceutical and perform radiation surveys of the area following patient studies and any other quality control activities (such as phantom scans using unsealed radioactivity). If the examination is not designed to acquire MRI images during the tracer uptake time, it may be possible to inject the patient and hold them for uptake in the Nuclear Medicine department. The patient can then be moved to the PET/MR in Radiology following the uptake period and immediately prior to scanning.
Physical Preparation for PET/MR Installation The requirements for the PET/MR scanner room size vary by vendor. The Philips Ingenuity TF PET/MR system requires a room measuring approximately 6.1 meters by 12.2 meters (20 feet x 40 feet) to accommodate the scanner and associated in-room equipment. The weight bearing floor must support approximately 8000 kg (according to the vendor site planning documents). The scan room must meet both radiation (lead) and RF (copper) shielding requirements. The room must be access-controlled for MR safety by having locks on all outside doors; in turn, the spaces beyond these doors must be configured as securely locked Zone III spaces. A separate room is required for the PET/MR system electronics, including access to a chiller or cooling water supply for the system electronics. A control room is required for technologists to operate the scanner and maintain visual and audible surveillance of the patient. Environmental 4
considerations also apply; proper climate and humidity controls must be provided to maintain the environmental conditions specified by the vendor for proper functioning of the PET/MR. Operation of PET/MR As Nuclear Medicine technologists had to adapt to CT technology when PET/CT began, the use of MRI in PET/MR drives significant educational and staffing requirements3. Nuclear Medicine technologists supporting the PET/MR who are not MR certified must receive thorough MRI safety training encompassing safe work practices in the MR environment and patient screening for MR safety. Similarly, if PET/MR staffing includes MRI technologists, radiation safety training is required to familiarize them with the hazards and procedures attendant to the use of unsealed radionuclides and the potential for high radiation exposure from the use of PET tracers. The PET/MR system at University Hospitals is staffed primarily by an experienced MRI technologist and an experienced NM/PET technologist registered in both NM and MRI. Plans for training were developed to comply with both radiation safety and MRI safety requirements with each technologist closely monitoring the safety requirements of their primary modality. Each modality expert technologist works with the radiologists to optimize image quality for each exam component, and they then work together to optimize the combined PET/MR multi-modality exam. Technologists inject patients based on their ARRT credentials and competency. Those who are certified in nuclear medicine inject radiopharmaceuticals, but not gadolinium; those who are certified in MR inject gadolinium, but not radiopharmaceuticals; those with dual certification and dual competency inject both agents. There is a need to develop technologist training and certification or registry programs to qualify an individual to perform all of the technologist functions in PET/MR3. Optimizing a modality in its infancy requires a great deal of technical and physician participation. In the early cases, it was common for patient exams to last a significant amount of time and for radiologists to remain at the console to define MR sequences.
With experience, PET/MR
attenuation correction and limited MR diagnostic scans have been refined, and with more mature protocols a complete PET/MR study typically can be completed in 60-90 minutes. Our goal is to reduce the number of diagnostic MR sequences to 3 to 5 per study to reduce the total PET/MR scan time to 60 minutes.
An optimal workflow might be to perform
radiopharmaceutical administration first, then MRI diagnostic sequences, then PET acquisition to reduce exam duration and increase throughput. It is not practical to evaluate technologist productivity at this stage of clinical PET/MR deployment. 5
Clinical use of PET/MR Currently there are no established clinical indications for PET/MR. We began assessing the diagnostic capability of this new multimodality imaging system under an Institutional Review Board (IRB) approved research study. Following equipment performance validation, the first clinical research PET/MR images were acquired in February 2012. The enrollment of 100 patients to obtain a direct comparison of clinically ordered PET/CT versus PET/MR was then completed within eight months. Key to defining which disease states would benefit from PET/MR was to understand the diagnostic accuracy MR attenuation correction could provide while assessing interpreter confidence levels. This evaluation involved months of data analysis, multiple Radiologist and Nuclear Medicine physicians, intra-observer, blinded inter-observer comparisons of interpretations, and obtaining a consensus on whether the new findings had the potential to impact patient care4. Another key was determining if the MR images obtained as an attenuation map could be utilized for both attenuation and anatomic information in a manner similar to the low-dose CTAC in PET/CT; or, was it necessary to obtain standard diagnostic MR sequences in order to provide the highest level of confidence. There are several new artifacts and image quality issues that need to be accounted for when using PET/MR for clinical purposes. The mismatch of data field-of-view for PET and MR can cause truncation artifacts, although vendor established compensation mechanisms are in place. MR coil attenuation mapping is another challenge for PET/MR. There is little flexibility to apply non-factory approved coils to the system when operating in the multimodality mode. Once coil AC maps are completed, the exam cards must be updated prior to use. Furthermore, not all coils available on a stand-alone MRI system are currently available on the PET/MR system, which can lead to changes in established clinical MRI protocols. As a result of our increasing experience and confidence with PET/MR imaging, we began offering clinical FDG-PET/MR imaging to referring physicians and patients in August 2013. Medical necessity that qualified referrals for both PET/CT and diagnostic MR exams was the point of entry to clinical PET/MR at our institution. Based on the data analysis of the 100 patient research trial, indications that would be best suited for this new modality were emerging. Included were gynecologic, colorectal, pancreatic, neurologic, head and neck malignancies, as well as lymphoma, pediatric oncologic studies and epilepsy/dementia. Benefits over PET/CT included reduction in radiation dose, improved soft tissue characterization and the inherently improved diagnostic capability of MR over CT in specific tumors. 6
Feedback has been positive, as referring physicians appreciate the added diagnostic information that comes with acquiring an MRI along with the PET and the quick turn-around time of reporting the combined scan. Patients appreciate the overall time savings as they can avoid having to return to the hospital for further imaging studies. However, shortening the length of a single exam remains an important goal to improve the clinical experience. As expected, the decreased use of radiation compared to PET/CT has also been found to be an attractive point to both physicians and patients, particularly in our pediatric population.
Clinical PET/MR Screening and Reporting Currently, FDG is the most clinically utilized radiotracer for the PET/MR modality. Other potential non-FDG tracers include Amyvid for the evaluation of dementia, sodium fluoride for imaging bone metabolism to detect metastases, and rubidium or N-13 ammonia for cardiac perfusion studies. It is helpful to carefully screen requests for potential PET/MR indications. The patient should fulfill the standard requirements for MR imaging. In our institution nuclear medicine and radiology fellows review the requests and determine an individual protocol for both PET and MR in consultation with the attending radiologists. A fellow follows each patient procedure and makes decisions about additional MR sequences or additional PET views. This is generally done in close collaboration with the nuclear medicine and radiology attending physicians. For specific questions, such as neuro-oncology requests or pediatric requests, a neuroradiologist or pediatric radiologist is involved as well. It has been our experience that PET/MR multimodality imaging requires multimodality interpretation. PET/MR performed for gynecologic, colorectal, and prostate indications would result in the combined image evaluation by both body section radiologists and NM physicians. Likewise, neurologic, epilepsy/dementia, and brain tumors result in combined evaluation by both neuroradiologists and NM physicians.
Reporting is done in a single combined report, with
PET/MR interpretation dictated following joint clinician review of images. This single report of the combined modality is duplicated to appear on both the diagnostic PET study and diagnostic MR study in our electronic health record.
In addition to site planning, staffing and optimizing the technology, there was a need to assess and validate the business model of performing PET/MR. Reimbursement must be secured from both commercial payers and CMS, commercial typically following CMS guidelines. In June of 2013, CMS provided a decision to expand the national coverage determination for FDG PET/CT 5
.. Although there was no dedicated CPT code for PET/MR, the CMS decision provided for the
use of PET CPT (78811-78813) codes with diagnostic MRI codes. It is recommended to initiate an institutional review from billing compliance and precertification staff. At our institution, billing audits have confirmed reimbursement from CMS and commercial payers at contracted price for technical and professional charges. Conclusion: The early adoption of PET/MR at University Hospitals of Cleveland has sparked great interest from referring physicians seeking to understand the potential clinical utility of the system. Furthermore, researchers are exploring how the combination of investigational new radiopharmaceuticals and PET/MR can be used as a future diagnostic tool.
manufacturers continue to move to a single integrated system that provides superior simultaneous PET and MR image capability, additional opportunities will evolve in functional imaging. Despite these benefits, clinical justification for the purchase of a PET/MR system as a diagnostic tool may be difficult in the current health care environment. Considerations such as the price to purchase, a costly service contract, and the extensive renovation cost incurred to modify an existing Radiology department makes this modality a cautious investment in today’s market.
Collaboration and communication between administrators, physicians, researchers,
and technicians is essential for a successful installation and subsequent operation of a PET/MR. With continued research and clinical utilization, it is conceivable that PET/MR will find an important place as a diagnostic resource in the future.
1. Expert Panel on MRS, Kanal E, Barkovich AJ, et al: ACR guidance document on MR safe practices: 2013. J Magn Reson Imaging 37:501-30, 2013 2. Madsen MT, Anderson JA, Halama JR, et al: AAPM Task Group 108: PET and PET/CT shielding requirements. Med Phys 33:4-15, 2006 3. Gilmore CD, Comeau CR, Alessi AM, et al: PET/MR imaging consensus paper: a joint paper by the Society of Nuclear Medicine and Molecular Imaging Technologist Section and the Section for Magnetic Resonance Technologists. J Nucl Med Technol 41:108-13, 2013 4. Kershah S, Partovi S, Traughber BJ, et al: Comparison of Standardized Uptake Values in Normal Structures Between PET/CT and PET/MRI in an Oncology Patient Population. Mol Imaging Biol 15:776-85, 2013 5. Jacques L, Syrek T, Rollins J, et al: Decision Memorandum for Positron Emission Tomography (FDG) for Solid Tumors 06-11-2013. http://www.cms.gov/medicare-coveragedatabase/details/nca-decision-memo.aspx?NCAId=263, Accessed 3/27/2014
Figure Legends: Figure 1: Installation of the PET/MR unit
Figure 2 A and B: Floorplan of the PET/MR at University Hospitals Seidman Cancer Center. The installation is on the second floor of the cancer center and is located adjacent to nuclear medicine and radiology facilities. The location allows sharing of resources with nuclear medicine (hot lab, changing room, injection room, etc.) and radiology (front desk/reception, patient waiting room, scheduling). Office space and reading rooms located adjacent to the PET/MR easily facilitate interpretation of studies and physician assistance when needed.