Diffusion-weighted MRI with deep learning for visualizing treatment results of MR-guided HIFU ablation of uterine fibroids.

Objectives: No method is available to determine the non-perfused volume (NPV) repeatedly during magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) ablations of uterine fibroids, as repeated acquisition of contrast-enhanced T1-weighted (CE-T1w) scans is inhibited by safety concerns. The objective of this study was to develop and test a deep learning-based method for translation of diffusion-weighted imaging (DWI) into synthetic CE-T1w scans, for monitoring MR-HIFU treatment progression.

Methods: The algorithm was retrospectively trained and validated on data from 33 and 20 patients respectively who underwent an MR-HIFU treatment of uterine fibroids between June 2017 and January 2019.

Hyperthermia-induced doxorubicin delivery from thermosensitive liposomes via MR-HIFU in a pig model.

Purpose: Encapsulation of cytotoxic drugs for a localized release is an effective way to increase the therapeutic window of such agents. In this article we present the localized release of doxorubicin (DOX) from phosphatidyldiglycerol (DPPG) based thermosensitive liposomes using MR-HIFU mediated hyperthermia in a swine model.

Materials And Methods: German landrace pigs of weights between 37.

Visualization of thermal washout due to spatiotemporally heterogenous perfusion in the application of a model-based control algorithm for MR-HIFU mediated hyperthermia.

Purpose: This article will report results from the application of a previously published model-predictive control algorithm for MR-HIFU hyperthermia. The purpose of the investigation was to test the controller's performance and behavior in the presence of heterogeneous perfusion.

Materials And Methods: Hyperthermia at 42°C was induced and maintained for up to 30 min in a circular section of a thermometry slice in the biceps femoris of German landrace pigs (=5) using a commercial MR-HIFU system and a recently developed MPC algorithm.

Feasibility study of MR-guided pancreas ablation using high-intensity focused ultrasound in a healthy swine model.

Pancreatic cancer is typically diagnosed in a late stage with limited therapeutic options. For those patients, ultrasound-guided high-intensity focused ultrasound (US-HIFU) can improve local control and alleviate pain. However, MRI-guided HIFU (MR-HIFU) has not yet been studied extensively in this context.

Use of multiparametric MRI to characterize uterine fibroid tissue types.

Background: Although the biological characteristics of uterine fibroids (UF) have implications for therapy choice and effectiveness, there is limited MRI data about these characteristics. Currently, the Funaki classification and Scaled Signal Intensity (SSI) are used to predict treatment outcome but both screening-tools appear to be suboptimal. Therefore, multiparametric and quantitative MRI was studied to evaluate various biological characteristics of UF.

Field drift correction of proton resonance frequency shift temperature mapping with multichannel fast alternating nonselective free induction decay readouts.

Purpose: To demonstrate that proton resonance frequency shift MR thermometry (PRFS-MRT) acquisition with nonselective free induction decay (FID), combined with coil sensitivity profiles, allows spatially resolved B drift-corrected thermometry.

Methods: Phantom experiments were performed at 1.5T and 3T.

Magnetic Resonance-Guided High-Intensity Focused Ultrasound (MR-HIFU): Technical Background and Overview of Current Clinical Applications (Part 1).

Background:  Extracorporeal high-intensity focused ultrasound (HIFU) is a promising method for the noninvasive thermal ablation of benign and malignant tissue. Current HIFU treatments are performed under ultrasound (US-HIFU) or magnetic resonance (MR-HIFU) image guidance offering integrated therapy planning, real-time control (spatial and temperature guidance) and evaluation.

Methods:  This review is based on publications in peer-reviewed journals addressing thermal ablation using HIFU and includes our own clinical results as well.

Magnetic Resonance-Guided High-Intensity Focused Ultrasound (MR-HIFU): Overview of Emerging Applications (Part 2).

Background:  High-intensity focused ultrasound (HIFU) allows noninvasive heating of deep-seated tissues. Guidance under magnetic resonance imaging (MR-HIFU) offers spatial targeting based on anatomical MR images as well as MR-based near-real-time temperature maps. Temperature feedback allows delivery of a well-defined thermal dose enabling new applications such as the ablation of malignant tissue.

Interleaved Mapping of Temperature and Longitudinal Relaxation Rate to Monitor Drug Delivery During Magnetic Resonance-Guided High-Intensity Focused Ultrasound-Induced Hyperthermia.

Objectives: Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) is a method to heat lesions noninvasively to a stable, elevated temperature and a well-suited method to induce local hyperthermia (41°C-43°C) in deep-seated tissues. Magnetic Resonance (MR) imaging provides therapy planning on anatomical images and offers temperature feedback based on near-real-time MR thermometry. Although constant acquisition of MR thermometry data is crucial to ensure prolonged hyperthermia, it limits the freedom to perform measurements of other MR parameters, which are of interest during hyperthermia treatments.

Thermal combination therapies for local drug delivery by magnetic resonance-guided high-intensity focused ultrasound.

Several thermal-therapy strategies such as thermal ablation, hyperthermia-triggered drug delivery from temperature-sensitive liposomes (TSLs), and combinations of the above were investigated in a rhabdomyosarcoma rat tumor model ( = 113). Magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) was used as a noninvasive heating device with precise temperature control for image-guided drug delivery. For the latter, TSLs were prepared, coencapsulating doxorubicin (dox) and [Gd(HPDO3A)(HO)], and injected in tumor-bearing rats before MR-HIFU treatment.

Multiparametric MRI analysis for the evaluation of MR-guided high intensity focused ultrasound tumor treatment.

For the clinical application of high intensity focused ultrasound (HIFU) for thermal ablation of malignant tumors, accurate treatment evaluation is of key importance. In this study, we have employed a multiparametric MRI protocol, consisting of quantitative T1, T2, ADC, amide proton transfer (APT), T1ρ and DCE-MRI measurements, to evaluate MR-guided HIFU treatment of subcutaneous tumors in rats. K-means clustering using all different combinations of the endogenous contrast MRI parameters (feature vectors) was performed to segment the multiparametric data into tissue populations with similar MR parameter values.

A Digital Preclinical PET/MRI Insert and Initial Results.

Combining Positron Emission Tomography (PET) with Magnetic Resonance Imaging (MRI) results in a promising hybrid molecular imaging modality as it unifies the high sensitivity of PET for molecular and cellular processes with the functional and anatomical information from MRI. Digital Silicon Photomultipliers (dSiPMs) are the digital evolution in scintillation light detector technology and promise high PET SNR. DSiPMs from Philips Digital Photon Counting (PDPC) were used to develop a preclinical PET/RF gantry with 1-mm scintillation crystal pitch as an insert for clinical MRI scanners.

SPECT/CT imaging of temperature-sensitive liposomes for MR-image guided drug delivery with high intensity focused ultrasound.

The goal of this study was to investigate the blood kinetics and biodistribution of temperature-sensitive liposomes (TSLs) for MR image-guided drug delivery. The co-encapsulated doxorubicin and [Gd(HPDO3A)(H₂O)] as well as the ¹¹¹In-labeled liposomal carrier were quantified in blood and organs of tumor bearing rats. After TSL injection, mild hyperthermia (T=42 °C) was induced in the tumor using high intensity focused ultrasound under MR image-guidance (MR-HIFU).

Magnetic resonance guided high-intensity focused ultrasound mediated hyperthermia improves the intratumoral distribution of temperature-sensitive liposomal doxorubicin.

Objectives: The aim of this study was to investigate the intratumoral distribution of a temperature-sensitive liposomal carrier and its encapsulated compounds, doxorubicin, and a magnetic resonance (MR) imaging contrast agent after high-intensity focused ultrasound (HIFU)-mediated hyperthermia-induced local drug release.

Materials And Methods: (111)In-labeled temperature-sensitive liposomes encapsulating doxorubicin and [Gd(HPDO3A) (H(2)O)] were injected intravenously in the tail vein of rats (n = 12) bearing a subcutaneous rhabdomyosarcoma tumor on the hind leg. Immediately after the injection, local tumor hyperthermia (2 × 15 minutes) was applied using a clinical 3 T MR-HIFU system.

Tumour hyperthermia and ablation in rats using a clinical MR-HIFU system equipped with a dedicated small animal set-up.

Purpose: We report on the design, performance, and specifications of a dedicated set-up for the treatment of rats on a clinical magnetic resonance high intensity focused ultrasound (MR-HIFU) system.

Materials And Methods: The small animal HIFU-compatible 4-channel MR receiver volume coil and animal support were designed as add-on to a clinical 3T Philips Sonalleve MR-HIFU system. Prolonged hyperthermia (T ≈ 42°C, 15 min) and thermal ablation (T = 65°C) was performed in vivo on subcutaneous rat tumours using 1.

A novel approach to identify non-palpable breast lesions combining fluorescent liposomes and magnetic resonance-guided high intensity focused ultrasound-triggered release.

The combination of fluorescein-containing liposomes (FCL) and magnetic resonance-guided high intensity focused ultrasound (MR-HIFU)-triggered release is a promising approach for lesion demarcation and more efficient removal of non-palpable breast lesions. Exposure of FCL to ablation temperatures (60 °C) using MR-HIFU would result in palpable, stained tumors, which are more easy to identify during surgical resection. In this study, proof-of-concept concerning fluorescent FCL for MR-HIFU-triggered release and tumor demarcation of non-palpable breast lesions is presented.

Magnetic resonance imaging of high intensity focused ultrasound mediated drug delivery from temperature-sensitive liposomes: an in vivo proof-of-concept study.

Temperature-sensitive liposomes (TSLs) co-encapsulating doxorubicin and 250 mM [Gd(HPDO3A)(H₂O)] were evaluated for HIFU-mediated drug delivery under MR image guidance. In vitro studies showed simultaneous and quantitative release of the drug and the MRI contrast agent from the lumen of the TSLs at 42°C, while no leakage was observed over 1 h at 37°C. In a proof-of-concept study, local hyperthermia has been applied for 30 min in 9L rat tumors using a clinical MR-HIFU system.

On the use of steady-state signal equations for 2D TrueFISP imaging.

To explain the signal behavior in 2D-TrueFISP imaging, a slice excitation profile should be considered that describes a variation of effective flip angles and magnetization phases after excitation. These parameters can be incorporated into steady-state equations to predict the final signal within a pixel. The use of steady-state equations assumes that excitation occurs instantaneously, although in reality this is a nonlinear process.

Quantification of left ventricular volumes and ejection fraction in mice using PET, compared with MRI.

Unlabelled: PET has become an important noninvasive imaging technique in cardiovascular research for the characterization of mouse models in vivo. This modality offers unique insight into biochemical changes on a molecular level, with excellent sensitivity. However, morphologic and functional changes may be of equal importance for a thorough assessment of left ventricular (LV) pathophysiology.

Diffusion tensor imaging of left ventricular remodeling in response to myocardial infarction in the mouse.

The cardiac muscle architecture lies at the basis of the mechanical and electrical properties of the heart, and dynamic alterations in fiber structure are known to be of prime importance in healing and remodeling after myocardial infarction. In this study, left ventricular remodeling was characterized using diffusion tensor imaging (DTI) in a mouse model of myocardial infarction. Myocardial infarction was induced in mice by permanent ligation of the left anterior descending coronary artery.

Smoothelin-B deficiency results in reduced arterial contractility, hypertension, and cardiac hypertrophy in mice.

Background: Smoothelins are actin-binding proteins that are abundantly expressed in healthy visceral (smoothelin-A) and vascular (smoothelin-B) smooth muscle. Their expression is strongly associated with the contractile phenotype of smooth muscle cells. Analysis of mice lacking both smoothelins (Smtn-A/B(-/-) mice) previously revealed a critical role for smoothelin-A in intestinal smooth muscle contraction.

Evaluation of manual and automatic segmentation of the mouse heart from CINE MR images.

Purpose: To compare global functional parameters determined from a stack of cinematographic MR images of mouse heart by a manual segmentation and an automatic segmentation algorithm.

Materials And Methods: The manual and automatic segmentation results of 22 mouse hearts were compared. The automatic segmentation was based on propagation of a minimum cost algorithm in polar space starting from manually drawn contours in one heart phase.

Comparison between prospective and retrospective triggering for mouse cardiac MRI.

High-resolution magnetic resonance imaging (MRI) has evolved into one of the major non-invasive tools to study the healthy and diseased mouse heart. This study presents a Cartesian CINE MRI protocol based on a fast low-angle shot sequence with a navigator echo to generate cardiac triggering and respiratory gating signals retrospectively, making the use of ECG leads and respiratory motion sensors obsolete. MRI of the in vivo mouse heart using this sequence resulted in CINE images with no detectable cardiac and respiratory motion artefacts.