Transcranial magnetic stimulation (TMS) applied to a left dorsolateral prefrontal cortex (DLPFC) area with a specific connectivity profile to the subgenual anterior cingulate cortex (sgACC) has emerged as a highly effective non-invasive treatment option for depression. However, antidepressant outcomes demonstrate significant variability among therapy plans and individuals. One overlooked contributing factor is the individual brain state at the time of treatment. In this study we used interleaved TMS-fMRI to investigate the influence of brain state on acute TMS effects, both locally and remotely. TMS was performed during rest and during different phases of cognitive task processing. Twenty healthy participants were included in this study. In the first session, imaging data for TMS targeting were acquired, allowing for identification of individualized targets in the left DLPFC based on highest anti-correlation with the sgACC. The second session involved chronometric interleaved TMS-fMRI measurements, with 10 Hz triplets of TMS administered during rest and at distinct timings during an N-back task. Consistent with prior findings, interleaved TMS-fMRI revealed significant BOLD activation changes in the targeted network. The precise timing of TMS relative to the cognitive states during the task demonstrated distinct BOLD response in clinically relevant brain regions, including the sgACC. Employing a standardized timing approach for TMS using a task revealed more consistent modulation of the sgACC at the group level compared to stimulation during rest. In conclusion, our findings strongly suggest that acute local and remote effects of TMS are influenced by brain state during stimulation. This study establishes a basis for considering brain state as a significant factor in designing treatment protocols, possibly improving TMS treatment outcomes.

Magnetic resonance has become a backbone of medical imaging but suffers from inherently low sensitivity. This can be alleviated by improved radio frequency (RF) coils. Multi-turn multi-gap coaxial coils (MTMG-CCs) introduced in this work are flexible, form-fitting RF coils extending the concept of the single-turn single-gap CC by introducing multiple cable turns and/or gaps. It is demonstrated that this enables free choice of the coil diameter, and thus, optimizing it for the application to a certain anatomical site, while operating at the self-resonance frequency. An equivalent circuit for MTMG-CCs is modeled to predict their resonance frequency. Possible configurations regarding size, number of turns and gaps, and cable types for different B ₀ field strengths are calculated. Standard copper wire loop coils (SCs) and flexible CCs made from commercial coaxial cable were fabricated as receive-only coils for 3 T and transmit/receive coils at 7 T with diameters between 4 and 15 cm. Electromagnetic simulations are used to investigate the currents on MTMG-CCs, and demonstrate comparable specific absorption rate of 7 T CCs and SCs. Signal-to-noise ratio (SNR), transmit efficiency, and active detuning performance of CCs were compared in bench tests and MR experiments. For the form-fitted receive-only CCs at 3 T no significant SNR degradation was found as compared to flat SCs on a balloon phantom. Form-fitted transmit/receive CCs at 7 T showed higher transmit efficiency and SNR. MTMG-CCs can be sized to optimize sensitivity, are flexible and lightweight, and could therefore enable the fabrication of wearable coils with improved patient comfort.

Background: Breast cancer, the most common malignant cancer in women worldwide, is typically diagnosed by x-ray mammography, which is an unpleasant procedure, has low sensitivity in women with dense breasts, and involves ionizing radiation. Breast magnetic resonance imaging (MRI) is the most sensitive imaging modality and works without ionizing radiation, but is currently constrained to the prone imaging position due to suboptimal hardware, therefore hampering the clinical workflow. Objectives: The aim of this work is to improve image quality in breast MRI, to simplify the clinical workflow, shorten measurement time, and achieve consistency in breast shape with other procedures such as ultrasound, surgery, and radiation therapy. Materials and Methods: To this end, we propose “panoramic breast MRI”—an approach combining a wearable radiofrequency coil for 3 T breast MRI (the “BraCoil”), acquisition in the supine position, and a panoramic visualization of the images. We demonstrate the potential of panoramic breast MRI in a pilot study on 12 healthy volunteers and 1 patient, and compare it to the state of the art. Results: With the BraCoil, we demonstrate up to 3-fold signal-to-noise ratio compared with clinical standard coils and acceleration factors up to 6 × 4. Panoramic visualization of supine breast images reduces the number of slices to be viewed by a factor of 2–4. Conclusions: Panoramic breast MRI allows for high-quality diagnostic imaging and facilitated correlation to other diagnostic and interventional procedures. The developed wearable radiofrequency coil in combination with dedicated image processing has the potential to improve patient comfort while enabling more time-efficient breast MRI compared with clinical coils.

Flexible form-fitting radiofrequency coils provide high signal-to-noise ratio (SNR) for magnetic resonance imaging (MRI), and in array configuration large anatomical areas of interest can be covered. We propose a modular system - "ModFlex"- of flexible lightweight 4-channel coaxial coil arrays for 3 T MRI. We investigated the performance difference between commercial reference coils and 8- and 16-channel ModFlex receive-only array systems. In vivo, six anatomical targets in four regions of interest - the neck, the ankle, the spine and the hip - were imaged with the novel coil array system. The versatility of ModFlex and the robustness of the coil characteristics for different use cases is demonstrated. We measured an SNR gain for 4 out of 6 and similar SNR for 2 out of 6 anatomical target regions as compared to commercial reference coils. Parallel imaging capabilities are comparable to standard coils in hip and neck imaging, but ModFlex outperforms standard coils in ankle and spine imaging. High SNR combined with high acceleration possibilities enables faster imaging workflows and/or high-resolution MR acquisitions. The coil's versatility is beneficial for use cases with varying subject sizes and could improve patient comfort.

The design, fabrication, assembly and testing of a modular dynamic torso phantom for magnetic resonance imaging (MRI) is presented. The phantom is composed of fully MRI-compatible materials and consists of a saline-filled acrylic shell, with dimensions comparable to a human torso, and three distinct interior motion modules. Two linear piezo stages are used to mimic respiratory motion of the chest-wall (≤ 10 mm; cycle time ≥ 2 s) and the abdominal organs (≤ 45 mm; cycle time ≥ 2 s). A pneumatic system is used to move a heart mock-up to represent cardiac motion (≤ 19 mm, rate ≤ 3 Hz). The motion capabilities and MRI compatibility of the phantom are tested in 3 T MRI experiments. The closed-loop control of the phantom’s breathing modules allows for accurate positioning and timing with absolute differences between input and output values ≤ 0.61 mm and ≤ 0.06 s. The purpose of this phantom is to serve as a scientific instrument for the future development and evaluation of motion tracking and artifact compensation techniques.

The aim of this study is the evaluation of a wearable radiofrequency coil vest (BraCoil) for supine breast MRI, comparing lesion displacement and size with standard prone MRI and supine ultrasound, and assessing its potential impact on clinical workflows for targeted ultrasound and ultrasound-guided biopsy. MRI and ultrasound data were collected from 11 female patients with 18 breast lesions. Patients underwent two MRI exams: standard prone MRI using a commercial coil and supine MRI using the BraCoil. Lesion positions were compared between prone MRI, supine MRI, and supine ultrasound using anatomical landmarks (skin, pectoral muscle, nipple). Statistical analysis was performed on the mean absolute differences in lesion positions. With ultrasound lesion positions as a reference, supine MRI acquired with the BraCoil showed significantly less lesion displacement compared to prone MRI, with on average 7.3 mm less lesion-skin (p = 0.004) and 26.7 mm less lesion-pectoral muscle (p = 0.0001) displacement. Lesion-nipple distances in supine MRI showed strong deviations compared to prone MRI (p < 0.004). Lesion size in supine MRI was more comparable to ultrasound than prone MRI (p = 0.03) but changed insignificantly across modalities. 4 out of 18 lesions were only detectable in targeted ultrasound after supine BraCoil MRI. Supine MRI with the BraCoil offers a significant advantage over prone MRI by providing more accurate lesion positioning relative to ultrasound. This approach could improve lesion localization in radiotherapy planning, surgery, targeted ultrasound, and ultrasound-guided biopsy, potentially reducing the need for MR-guided biopsies.