The Society of Interventional Radiology (SIR) held its 2017 Annual Meeting in Washington, DC, March 4-9. Three focused ultrasound abstracts were selected for SIR 2017: two oral presentations and one poster. Topics covered include vascular malformations, pediatric osteoid osteoma, and introducing junior radiologists to the field of focused ultrasound. An NIH poster on prostate imaging prior to treatment also mentioned focused ultrasound.

SIR 2017 bStanford University, Rizzoli Institute, and Sapienza University combined to present a series of five patients who were successfully treated with focused ultrasound for technically challenging vascular malformations that were not amenable to standard therapy. The average treatment time was 124 minutes, and there were no complications. Overall, the patients experienced reduced pain and symptoms, and the lesions were reduced in size.

The Children's National Medical Center and Philips reported on their focused ultrasound pilot trial for treating pediatric osteoid osteoma. Nine patients (16 ± 6 years) received focused ultrasound ablation. Four weeks after treatment, 80% of patients had complete pain resolution and were able to stop all pain medication. Recovery times in this study were comparable to radio frequency ablation (RFA), which is the current standard of therapy. A pivotal trial is planned, and an additional study evaluating safety and feasibility of focused ultrasound ablation in children with recurrent or relapsed malignant soft tissue tumors is currently ongoing.

The poster, presented by interventional radiologists from the University of Iowa Hospitals & Clinics, the University of Chicago, and the University of Texas M.D. Anderson Cancer Center introduced junior radiologists to the field of focused ultrasound. Entitled “High intensity focused ultrasound (HIFU): What junior radiologists need to know!” covered the basic physics of focused ultrasound, its approved uses, and ongoing research applications.

Another poster submitted by the Brad Wood laboratory at NIH advocated for interventional radiologists to use MRI/transrectal ultrasound fusion biopsy for prostate cancer and mentions focused ultrasound treatment of the prostate. 

 

Read the abstracts below:

#114 Treatment of Vascular Malformations Using MR Guided High Intensity Focused Ultrasound: Preliminary Results after Five Patients
Original Scientific Research-Oral
L Chan1, S Kishore2, M Lungren3, D Mohler4, R Avedian4, D Hovsepian2, A Bazzocchi5, A Napoli6, P Ghanouni7
1Stanford Medical Center Department of Radiology, Stanford, CA, 2Stanford University, Palo Alto, CA, 3N/A, Stanford, CA, 4Stanford University, Redwood City, CA, 5Rizzoli Institute, Bologna, Bologna, 6Sapienza University, Rome, Rome, 7Stanford University Medical Center, Stanford, CA

Purpose
To assess the safety and efficacy of Magnetic Resonance Guided High Intensity Focused Ultrasound (MRgFUS) as a non-invasive treatment alternative for vascular malformations that are technically challenging to treat by conventional treatment modalities.

Materials
All lesions were diagnosed by MRI as low-flow vascular malformations and were difficult to localize by physical examination or sonographically, thus precluding percutaneous sclerosis/ethanol ablation or surgical resection. Ablations were performed on the ExAblate 2100 focused ultrasound MR table with sonication planning initiated by ExAblate software. Pre procedural, day of treatment, and up to 36 months post-procedural assessments were performed via MRI and clinical assessments of pain and functional status.

Results
Five patients were treated, three males and two females, with a median age of 36 (range 18 to 54). Four lesions were located in the thigh and one in the calf. The median maximal lesion dimension was 1.4 cm (range 1.1 to 5.7 cm) and the mean enhancing volume was 5.5 cc. The ExAblate 2100 transducer generated a median sonication energy per treatment ranging from 658 to 2600 J with an average of 1737 J. Mean number of sonications was 37 (range 14-56). Average sonication duration was 9.8 minutes (range 0.3-20 minutes). The average treatment time was 123.8 minutes (range 50-202 minutes). After treatment, the mean non-perfused volume (NPV) was 6.6 cc. No complications occurred. There was a significant reduction in average and maximum pain on a ten-point scale (Average: 4.8 ± 1.3 to 2 ± 2, p=0.05; Maximum: 8.4 ± 1.5 to 2.6 ± 2.4, p=0.018) with a mean reduction of 70% in average pain and 66% in maximal pain. There was a 70% reduction in average maximum lesion diameter. Three patients had complete resolution and two had 50-75% reduction of lesional enhancement. Three patients had resolution of symptoms, 2 of which had complete resolution of lesional enhancement, and two patients had partial resolution of symptoms.

Conclusions
This largest series of MR guided FUS for vascular malformations demonstrates the potential of this non-invasive treatment modality for vascular malformations not amenable to standard therapies.

#213 Changing Paradigm for Treatment of Osteoid Osteoma in Children
K Sharma1, P Yarmolenko1, H Celik1, E Avinash1, A Kim1, M Oetgen1, A Partanen2, A Smitthimedhin1, J Patel1, P Kim1
1Childrens National Medical Center, Washington, DC, 2Philips, Best, Netherlands

Purpose
Magnetic resonance imaging-guided high intensity focused ultrasound (MR-HIFU) is a new therapy that promises precise, incisionless, and radiation-free ablation. Children and adolescents may benefit most from such a non-invasive approach. We sought to determine safety, feasibility, and clinical response of MR-HIFU ablation of painful osteoid osteoma (OO) in a pediatric population and compare it to current standard of care treatment with RFA.

Materials
Patients with symptomatic, radiologically confirmed OO were treated with MR-HIFU ablation through an IRB-approved clinical trial. Treatment feasibility, patient safety, and clinical response were evaluated. Clinical response was measured in terms of pain relief, cessation of medication use, and improved sleep quality using three validated patient reported outcomes tools including VAS, SDS, and PROMIS.

Results
Nine patients were treated (7M, 2F; 16±6 years). MR-HIFU ablation of OO was feasible and safe, with no associated serious adverse events. Complete response with total pain resolution and cessation of all medication use was achieved in 89% (8/9 patients) and partial response was achieved 11% (1/9 patients) within four weeks. All treatments were performed on an outpatient basis and the anesthesia, procedure, and recovery times were comparable to radiofrequency ablation (RFA) treatments.

Conclusions
MR-HIFU ablation of painful OO in pediatric patients is safe and feasible with clinical response rate similar to the current standard of care treatment and may represent a completely non-invasive and radiation-free alternative to the current treatment approach. Given this safety data, a pivotal trial to determine efficacy with direct comparison to RFA is planned. In addition, a second clinical trial evaluating safety and feasibility of MR-HIFU ablation in children with recurrent or relapsed malignant soft tissue tumors is currently ongoing.

#710 High intensity focused ultrasound (HIFU): What junior radiologists need to know!
Educational Exhibit-Poster Only
I Elhelf1, S Wang2, E Cressman3, A Oto2
1University of Iowa Hospitals & Clinics, Iowa City, IA, USA, 2University of Chicago, Chicago, IL, 3University of Texas M.D. Anderson Cancer Center, Houston, TX

Learning Objectives
To educate junior radiologists about the basics of High Intensity Focused Ultrasound (HIFU) as well as its current applications and promising research trends.

Background
HIFU is a non-invasive technology with many applications including ablation of tumors. Advantages of HIFU include its completely non-invasive nature as well as the ability to monitor the treatment process either by real time ultrasound or MRI. Currently, HIFU is FDA approved for treatment of uterine fibroids, bone metastasis, and prostate cancer. Ablation of other tumors, like liver and pancreatic tumors, is widely available in Europe and Asia but not yet approved in the US. Active research is currently conducted in different fields, especially in interventional neurology. Despite the advantages of HIFU, it still has its limitations that need to be addressed and further investigated.

Clinical Findings/Procedure Details
HIFU entails focusing of high energy ultrasound beams into one focal point. This is achieved using special ultrasound generators and focusing techniques. Once ultrasound waves get focused at one spot, different biological effects take place that contribute to tissue damage at the focus. Interestingly, temperature at the focal point can reach 70 °C or more within milliseconds. Also, changes at the focal point can be monitored using MRI or ultrasound imaging. Typically, damage occurs at the focus without significant tissue damage before or after the focal point, making HIFU a completely non-invasive technology and adding more to the safety profile of this ablation technique. Different ablation techniques are applied to increase the ablation volume and reduce the ablation time.

Conclusion and/or Teaching Points
1. To understand the physical principles, modes of action and mechanisms of HIFU ablation through a simplified illustrated approach.
2. To highlight the main limitations, advantages, and disadvantages of HIFU in contrast to current ablation technologies in practice e.g.: RF ablation.
3. To be updated about the current FDA approved applications of HIFU.
4. To be oriented about selected non FDA approved applications showing success in clinical trials.


#750 Implementation of Prostate Cancer Diagnosis and Management Techniques in Interventional Radiology Practice
Type: Educational Exhibit-Poster Only
S Gaur1, V Anderson1, C Garcia1, J Peretti1, P Choyke1, P Pinto1, B Turkbey1, B Wood1
1National Institutes of Health, Bethesda, MD

Learning Objectives
Prostate cancer (PCa) diagnosis and management increasingly depends on imaging with the advent of prostate multi-parametric MRI (mpMRI) and guided biopsies. The purpose of this exhibit is to provide the IR community with an update on the relevance of imaging in guided biopsies and in therapies for the diagnosis and management of PCa.

Background
Traditionally, PCa has been diagnosed by systematic biopsy under transrectal ultrasound (TRUS) guidance. However, research has shown that these systematic biopsies result in under-diagnosis of aggressive and over-diagnosis of indolent PCa. MRI/TRUS fusion biopsy increases the detection rate of high-risk tumors. Its use in diagnosis has led to more treatment options for localized disease. For the past 10 years, we have refined a multidisciplinary approach for better detection and management of PCa. A workflow utilizing the expertise of interventional radiologists in both MR/TRUS-guided biopsy and MR-guided focal PCa therapy is presented.

Clinical Findings/Procedure Details
Acquisition and interpretation of mpMRI and related potential challenges will be discussed in concordance with the recent PIRADSv2 guidelines. Preparation of mpMRI data for MRI/TRUS guided biopsies along with tips and tricks will be presented. Utilization of MRI/TRUS fusion guided biopsies with common clinical scenarios (e.g. patients with inconclusive prior PCa workup, biopsy naïve status, undergoing active surveillance) will be explained and illustrated. MRI guided focal therapy techniques particularly useful for treatment of localized PCa, such as focal laser ablation, HIFU, and cryotherapy, will be reviewed. The applications and technical details of these procedures will be discussed. The real-time combination of imaging and intervention makes these ideal procedures for IR departments.

Conclusion and/or Teaching Points
Interventional radiologists have tremendous opportunity to employ their expertise in image-guided biopsy and therapy in PCa care. In a setting in which IR is connected to diagnostic radiologists, pathologists, urologists, radiation oncologists, and medical oncologists, an understanding of this potential is extremely useful.

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