monitoring-blood-brain-barrier-opening-rats-with-preclinical-focused

Monitoring Blood-Brain Barrier Opening in Rats with a Preclinical Focused Ultrasound System

The brain has a highly selective semipermeable blood barrier, termed the blood-brain barrier (BBB), which prevents the delivery of therapeutic ...

University of California, San Francisco

To develop a technique for optimizing coverage of brain 3D (1) H magnetic resonance spectroscopic imaging (MRSI) by automatic placement of outer-volume suppression (OVS) saturation bands (sat bands) and to compare the performance for point-resolved spectroscopic sequence (PRESS) MRSI protocols with manual and automatic placement of sat bands.

Improved spatial coverage for brain 3D PRESS MRSI by automatic placement of outer-volume suppression saturation bands.

Two major difficulties encountered in implementing Magnetic Resonance Spectroscopic Imaging (MRSI) in a clinical setting are limited coverage and difficulty in prescription. The goal of this project was to automate completely the process of 3D PRESS MRSI prescription, including placement of the selection box, saturation bands and shim volume, while maximizing the coverage of the brain. The automated prescription technique included acquisition of an anatomical MRI image, optimization of the oblique selection box parameters, optimization of the placement of outer-volume suppression saturation bands, and loading of the calculated parameters into a customized 3D MRSI pulse sequence. To validate the technique and compare its performance with existing protocols, 3D MRSI data were acquired from six exams from three healthy volunteers. To assess the performance of the automated 3D MRSI prescription for patients with brain tumors, the data were collected from 16 exams from 8 subjects with gliomas. This technique demonstrated robust coverage of the tumor, high consistency of prescription and very good data quality within the T2 lesion.

Automated prescription of oblique brain 3D magnetic resonance spectroscopic imaging.

Feasibility of targeted and volumetric hyperthermia (40-45 °C) delivery to the prostate with a commercial MR-guided endorectal ultrasound phased array system, designed specifically for thermal ablation and approved for ablation trials (ExAblate 2100, Insightec Ltd.), was assessed through computer simulations and tissue-equivalent phantom experiments with the intention of fast clinical translation for targeted hyperthermia in conjunction with radiotherapy and chemotherapy.

Model-based feasibility assessment and evaluation of prostate hyperthermia with a commercial MR-guided endorectal HIFU ablation array.

Near-field heating is a potential problem in focused ultrasound treatments, as it can result in thermal injury to skin, subcutaneous fat, and other tissues. Our goals were to determine if T2-based temperature mapping could be used reliably to measure near-field heating in adipose tissue and whether it is practical to perform such mapping during focused ultrasound treatments.

T2-based temperature monitoring in abdominal fat during MR-guided focused ultrasound treatment of patients with uterine fibroids.

To demonstrate the feasibility of using ultrashort echo-time MRI to quantify T1 changes in cortical bone due to heating.

Quantifying temperature-dependent T1 changes in cortical bone using ultrashort echo-time MRI.

Current clinical protocols for MR-guided focused ultrasound (MRgFUS) treatment of osseous lesions, including painful bone metastases and osteoid osteomas, rely on measurement of the temperature change in adjacent muscle to estimate the temperature of the bone. The goal of this study was to determine if T2-based thermometry could be used to monitor the temperature change in bone marrow during focused ultrasound ablation of bone lesions.

T2-based temperature monitoring in bone marrow for MR-guided focused ultrasound.

To evaluate the effect of differences in sonication duration and power on the size of postcontrast ablation zone following magnetic resonance-guided focused ultrasound (MRgFUS) of bone in a swine femoral bone model.

Effect of Sonication Duration and Power on Ablation Depth During MR-Guided Focused Ultrasound of Bone.

Hyperthermia therapy (HT) has shown to be an effective adjuvant to radiation, chemotherapy, and immunotherapy. In order to be safe and effective, delivery of HT requires maintenance of target tissue temperature within a narrow range (40-44 °C) for 30-60 min, which necessitates conformal heat delivery and accurate temperature monitoring. The goal of this project was to develop an MR thermometry-guided hyperthermia delivery platform based upon the ExAblate prostate array that would achieve uniform stable heating over large volumes within the prostate, while allowing the user to precisely control the power deposition patterns and shape of the region of treatment (ROT).

MR thermometry-guided ultrasound hyperthermia of user-defined regions using the ExAblate prostate ablation array.

Accurate interpretation of hip MRI is time-intensive and difficult, prone to inter- and intrareviewer variability, and lacks a universally accepted grading scale to evaluate morphological abnormalities.

Computer-Aided Detection AI Reduces Interreader Variability in Grading Hip Abnormalities With MRI.

In magnetic resonance (MR)-guided thermal therapy, respiratory motion can cause a significant temperature error in MR thermometry and reduce the efficiency of the treatment. A respiratory motion simulator is necessary for the development of new MR imaging (MRI) and motion compensation techniques.

Technical note: Low-cost MR-compatible pneumatic respiratory organ motion simulator for the development of MR-guided thermal therapy.

Management of patients suffering from low back pain (LBP) is challenging and requires development of diagnostic techniques to identify specific patient subgroups and phenotypes in order to customize treatment and predict clinical outcome. The Back Pain Consortium (BACPAC) Research Program Spine Imaging Working Group has developed standard operating procedures (SOPs) for spinal imaging protocols to be used in all BACPAC studies. These SOPs include procedures to conduct spinal imaging assessments with guidelines for standardizing the collection, reading/grading (using structured reporting with semi-quantitative evaluation using ordinal rating scales), and storage of images. This article presents the approach to image acquisition and evaluation recommended by the BACPAC Spine Imaging Working Group. While the approach is specific to BACPAC studies, it is general enough to be applied at other centers performing magnetic resonance imaging (MRI) acquisitions in patients with LBP. The herein presented SOPs are meant to improve understanding of pain mechanisms and facilitate patient phenotyping by codifying MRI-based methods that provide standardized, non-invasive assessments of spinal pathologies. Finally, these recommended procedures may facilitate the integration of better harmonized MRI data of the lumbar spine across studies and sites within and outside of BACPAC studies.

Magnetic Resonance Imaging of the Lumbar Spine: Recommendations for Acquisition and Image Evaluation from the BACPAC Spine Imaging Working Group.

T2-weighted Single Shot Fast Spin Echo (SSFSE) scans at 3 Tesla (3T) are increasingly used to image fetal pathology due to their excellent tissue contrast resolution and signal-to-noise ratio (SNR). Temperature changes that may occur in response to radio frequency (RF) pulses used for these sequences at 3T have not been studied in human fetal brains. To evaluate the safety of T2-weighted SSFSE for fetal brains at 3T, magnetic resonance (MR) thermometry was used to measure relative temperature changes in a typical clinical fetal brain MR exam.

Estimate of fetal brain temperature using proton resonance frequency thermometry during 3 Tesla fetal magnetic resonance imaging.

Interest in transcranial MR imaging-guided focused ultrasound procedures has recently grown. These incisionless procedures enable precise focal ablation of brain tissue using real-time monitoring by MR thermometry. This article will provide an updated review on clinically applicable technical underpinnings and considerations of proton resonance frequency MR thermometry, the most common clinically used MR thermometry sequence.

MR Thermometry during Transcranial MR Imaging-Guided Focused Ultrasound Procedures: A Review.

High quality scan prescription that optimally covers the area of interest with scan planes aligned to relevant anatomical structures is crucial for error-free radiologic interpretation. The goal of this project was to develop a machine learning pipeline for oblique scan prescription that could be trained on localizer images and metadata from previously acquired MR exams.

Article	Year
Improved spatial coverage for brain 3D PRESS MRSI by automatic placement of outer-volume suppression saturation bands. Journal of magnetic resonance imaging : JMRI\| PubMed ID: 21448942	2011
Automated prescription of oblique brain 3D magnetic resonance spectroscopic imaging. Magnetic resonance in medicine\| PubMed ID: 22692829	2013
Model-based feasibility assessment and evaluation of prostate hyperthermia with a commercial MR-guided endorectal HIFU ablation array. Medical physics\| PubMed ID: 24593742	2014
T2-based temperature monitoring in abdominal fat during MR-guided focused ultrasound treatment of patients with uterine fibroids. Journal of therapeutic ultrasound\| PubMed ID: 26366288	2015
Quantifying temperature-dependent T1 changes in cortical bone using ultrashort echo-time MRI. Magnetic resonance in medicine\| PubMed ID: 26390357	2015
T2-based temperature monitoring in bone marrow for MR-guided focused ultrasound. Journal of therapeutic ultrasound\| PubMed ID: 27882240	2016
Effect of Sonication Duration and Power on Ablation Depth During MR-Guided Focused Ultrasound of Bone. Journal of magnetic resonance imaging : JMRI\| PubMed ID: 28225581	2017
MR thermometry-guided ultrasound hyperthermia of user-defined regions using the ExAblate prostate ablation array. Journal of therapeutic ultrasound\| PubMed ID: 30123506	2018
Computer-Aided Detection AI Reduces Interreader Variability in Grading Hip Abnormalities With MRI. Journal of magnetic resonance imaging : JMRI\| PubMed ID: 32293775	2020
Technical note: Low-cost MR-compatible pneumatic respiratory organ motion simulator for the development of MR-guided thermal therapy. Medical physics\| PubMed ID: 35635215	2022
Magnetic Resonance Imaging of the Lumbar Spine: Recommendations for Acquisition and Image Evaluation from the BACPAC Spine Imaging Working Group. Pain medicine (Malden, Mass.)\| PubMed ID: 36069660	2023
Estimate of fetal brain temperature using proton resonance frequency thermometry during 3 Tesla fetal magnetic resonance imaging. Quantitative imaging in medicine and surgery\| PubMed ID: 38106288	2023
MR Thermometry during Transcranial MR Imaging-Guided Focused Ultrasound Procedures: A Review. AJNR. American journal of neuroradiology\| PubMed ID: 38123912	2023
Machine learning-based automated scan prescription of lumbar spine MRI acquisitions. Magnetic resonance imaging\| PubMed ID: 38574982	2024

Eugene Ozhinsky

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