Two Years of PET/MR Imaging at NYU

Setting a Date

After months of meetings and hours of planning, the date was set. On July 25th, 2012, the Center for Biomedical Imaging (CBI) at NYU Department of Radiology would conduct its first simultaneous PET/MR scan. Even before the traffic-halting arrival of the PET/MR scanner (Siemens Biograph mMR) in May of 2012, research scientists from the center gathered with their administrative team to iron out logistics such as developing protocols, training the appropriate staff, and recruiting physicians for project collaborations and patient referrals. It wasn't until a referral from oncologist, Dr. Amy Tiersten, could the center schedule a day and start planning for their first patient scan in the PET/MR.

 

  

 

The Big Day

 As July 25th grew near, more and more CBI personnel become involved to ensure that the day would run as smoothly as possible. Assistant Professor, Eric Sigmund, described the day as ‘hectic’ and ‘a blur’. He explained how the patient was getting a PET/CT scan at the NYU Cancer Institute (now the Perlmutter Cancer Center) before her PET/MR scan and how they had to coordinate her arrival at CBI. The reason for this protocol was not only to have the PET/CT image to compare those from the PET/MR, but also to reduce the patient’s radiation exposure by having only one dose of the radioactive tracer.

When the patient finally arrived through the doors of 660 First Avenue, the real action started. As the patient changed into her gown, the MRI technicians, research scientists, and Siemen’s representatives quickly set up for the scan. Once the patient was positioned in the bore of the machine, body coil in place, the door was sealed and the scan begun. With the scanner’s dual modalities, as the first set of full body scans were coming through, so did the PET images. After obtaining the Dynamic Contrast Enhanced (DCE), diffusion, and anatomic MR images simultaneously with the PET data, the team went back in to the room to switch out the body coil for a breast coil.

The team then ran a series of sequences that Sigmund refers to as the “greatest hits of MRI”. They acquired T1, T2, (with and without fat saturation), DCE, and diffusion (IVIM) images. Just like the first set of scans, the PET images were also taken during the MRI acquisitions. After the scan was over, the patient got up to change her clothes and the team disassembled their set up. As the moment finally settled in, breaths began to calm and smiles started to appear. Of course, after such an eventful day, there was cake.

Where We Are Today

Since that very first scan 2 years ago, the researchers at CBI have gone on to complete over 750 more. These scans have translated into 44 conference presentations and 10 published journal articles. While the research cores at CBI have continued to utilize the PET/MR scanner for clinical studies and to compare PET/CT and PET/MR images, the center assembled a ‘PET group’ to develop new methods and tools to take advantage of the simultaneous acquisition of PET and MR data. There is more to the scanner than the convenience of being able to use two modalities at the same time. One theme that continues to resonate is the synergy of the machine or, as Sigmund says simply “what can this machine do that the two modalities can’t [do] separately?”

For one thing, the two modalities can provide supplemental information to each other. Post-Doctoral Fellow, Florian Knoll, has taken advantage of the shared spatial and temporal information of the two modalities and developed an algorithm that incorporates both data sets. The application of joint PET/MR reconstruction algorithm has greatly improved the resolution of the PET images.

Thomas Koesters, another Post-Doctoral fellow, has also relied on the MR data to improve the reconstruction of the PET image. He developed an MR-based motion correction algorithm for PET reconstruction. By extracting the respiration signal from the MR data and incorporating it to the Expectation Maximization (EM) algorithm for PET reconstruction, Koesters has been able to produce motion-free PET images.

Another realm of PET research that the center was interested in is in the development of new PET tracers. Tracers can provide signification information and bind with specific tissue and receptors. In 2012, Yu-shin Ding was recruited to be the Director of PET Radiochemistry at NYU School of Medicine. Ding had over 20 years of experience developing and applying novel ligands for PET. Her work has spanned from the early stages of preclinical animal studies to clinical studies in humans. While at NYU, Ding has already developed several F-18 labeled PET ligands including FPEB, a tracer that binds to the mGluR5 receptor that can be used for various central nervous system disorders. Ding has been working closely with Senior Research Scientist, Jean Logan. Logan is know for her work in tracer kinetics and is also the creator of the Logan Plot.

Days to Come

While the CBI PET group has achieved much success in this short period of 2 years, there is more to come. This fall, the center will be breaking ground in preparations for the addition of a cyclotron and radiochemical lab. The new cyclotron and lab enables tracers to be made on-site and used in a scan immediately after being synthesized. These two additions to the center will also benefit the initiative of the Center of Advanced Imaging Innovation and Research. CAI2R is a new research core within NYU radiology research that focuses on a new imaging paradigm along with a highly collaborative environment for rapid translation of new technology. Many of the collaborative research projects that the center has taken part in requires custom-made tracers. With the capability to synthesizing tracers that are not commercially available, the cyclotron and radiochemistry lab will be an essential part of the novel tracer development and will also facilitate its translation from preclinical studies to human studies. Both the cyclotron and the radiochemistry lab will be up and running by September 2015.

In addition to Ding’s work on radiotracers, she has also developed several PET/MR protocols and pilot studies for neurologic disorders. She is currently in the preliminary stages of PET/MR studies for chronic back pain and obesity. Another clinical study that is on the verge of starting is on “Simultaneous PET/MRI using Advance MR Metrics for Characterization of Bladder Cancer Aggressiveness and Treatment Response”. Radiologist, Dr. Andrew Rosenkrantz, has recently received the Howard S. Stern Research Grant from the Society of Abdominal Radiology for this study.

While the number of PET/MR studies and publications continue to increase, the center also predicts an increase in the number of clinical PET/MR scans. As of today, there have been over 125 PET/MR scans ordered by doctors for the purpose of making clinical decisions. These numbers will grow as the center develops and refines their PET/MR techniques for clinical use. 

Sponsors

Philanthropic Support

We gratefully acknowledge generous support for radiology research at NYU Langone Health from:
 
• The Big George Foundation
• Raymond and Beverly Sackler
• Bernard and Irene Schwartz

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