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Objective: The perceived burden of diagnostic tests by patients during the assessment of esophageal cancer warrants attention with the current increase in repeated imaging for purposes of disease monitoring during and after treatment. The purpose of this prospective study was to evaluate the experienced burden associated with repeated MRI and positron emission tomography with integrated CT (PET/CT) examinations during neoadjuvant treatment for esophageal cancer from the perspective of the patient., Methods: In 27 patients receiving neoadjuvant chemoradiotherapy (nCRT) for esophageal cancer MRI and PET/CT examinations were performed before nCRT, during nCRT and before surgery. The experienced burden during repeated MRI and PET/CT examinations was evaluated with a self-report questionnaire addressing discomfort, pain, anxiety and embarrassment, each measured on a 5-point Likert scale (1 = none; up to 5 = very much). In addition, a comparative assessment was used to rank MRI, PET/CT and baseline endoscopy., Results: All scans were performed without the occurrence of an adverse event. Few patients experienced discomfort (mean score ±SD: 1.9 ± 1.0 for MRI vs 2.0 ± 1.0 for PET/CT, p = 0.586), pain (1.1 ± 0.4 for MRI vs 1.3 ± 0.7 for PET/CT, p = 0.059), anxiety (1.0 ± 0.2 for MRI vs 1.0 ± 0.2 for PET/CT, p = 1.000) and embarrassment (1.0 ± 0 for MRI vs 1.0 ± 0.2 for PET/CT, p = 0.317) during both MRI and PET/CT. Patients preferred MRI over PET/CT (67% vs 22%, respectively, p = 0.023), and MRI over endoscopy (59% vs 19%, respectively, p = 0.027). In the comparison between PET/CT and endoscopy, 59% of patients preferred PET/CT and 26% preferred endoscopy (p = 0.093)., Conclusion: Repeated imaging with both MRI and PET/CT is generally well-tolerated for the assessment of response to treatment in esophageal cancer patients. Shorter acquisition times and altered body positioning during scanning will likely improve patient experience. Advances in knowledge: This paper demonstrates that MRI and PET/CT are generally well-tolerated imaging procedures for the assessment of response to treatment in esophageal cancer patients. When asked to rank different tests, patients preferred MRI over PET/CT and endoscopy.

An organized layer of connective tissue coursing from aorta to esophagus was recently discovered in the mediastinum. The relations with other peri-esophageal fascias have not been described and it is unclear whether this layer can be visualized by non-invasive imaging. This study aimed to provide a comprehensive description of the peri-esophageal fascias and determine whether the connective tissue layer between aorta and esophagus can be visualized by magnetic resonance imaging (MRI). First, T2-weighted MRI scanning of the thoracic region of a human cadaver was performed, followed by histological examination of transverse sections of the peri-esophageal tissue between the thyroid gland and the diaphragm. Secondly, pretreatment motion-triggered MRI scans were prospectively obtained from 34 patients with esophageal cancer and independently assessed by two radiologists for the presence and location of the connective tissue layer coursing from aorta to esophagus. A layer of connective tissue coursing from the anterior aspect of the descending aorta to the left lateral aspect of the esophagus, with a thin extension coursing to the right pleural reflection, was visualized ex vivo in the cadaver on MR images, macroscopic tissue sections, and after histologic staining, as well as on in vivo MR images. The layer connecting esophagus and aorta was named 'aorto-esophageal ligament' and the layer connecting aorta to the right pleural reflection 'aorto-pleural ligament'. These connective tissue layers divides the posterior mediastinum in an anterior compartment containing the esophagus, (carinal) lymph nodes and vagus nerve, and a posterior compartment, containing the azygos vein, thoracic duct and occasionally lymph nodes. The anterior compartment was named 'peri-esophageal compartment' and the posterior compartment 'para-aortic compartment'. The connective tissue layers superior to the aortic arch and at the diaphragm corresponded with the currently available anatomic descriptions. This study confirms the existence of the previously described connective tissue layer coursing from aorta to esophagus, challenging the long-standing paradigm that no such structure exists. A comprehensive, detailed description of the peri-esophageal fascias is provided and, furthermore, it is shown that the connective tissue layer coursing from aorta to esophagus can be visualized in vivo by MRI., (© 2016 Anatomical Society.)

Specific absorption rate (SAR) assessment is essential for safety purposes during MR acquisition. Online SAR assessment is not trivial and requires, in addition, knowledge of the electric tissue properties and the electric fields in the human anatomy. In this study, the potential of the recently developed CSI-EPT method to reconstruct SAR distributions is investigated. This method is based on integral representations for the electromagnetic field and attempts to reconstruct the tissue parameters and the electric field strength based on [Formula: see text] field data only. Full three-dimensional FDTD simulations using a female pelvis model are used to validate two-dimensional CSI reconstruction results in the central transverse plane of a 3T body coil. Numerical experiments demonstrate that the reconstructed SAR distributions are in good agreement with the SAR distributions as determined via 3D FDTD simulations and show that these distributions can be computed very efficiently in the central transverse plane of a body coil with the two-dimensional approach of CSI-EPT.

Magnetic resonance imaging (MRI) provides excellent soft-tissue contrast and allows for specific scanning sequences to optimize differentiation between various tissue types and properties. Moreover, it offers the potential for real-time motion imaging. This makes magnetic resonance imaging an ideal candidate imaging modality for radiation treatment planning in lung cancer. Although the number of clinical research protocols for the application of magnetic resonance imaging for lung cancer treatment is increasing (www.clinicaltrials.gov) and the magnetic resonance imaging sequences are becoming faster, there are still some technical challenges. This review describes the opportunities and challenges of magnetic resonance imaging for radiation treatment planning in lung cancer., (© The Author(s) 2015.)

Purpose: Knowledge on low frequency (LF) tissue conductivity is relevant for various biomedical purposes. To obtain this information, LF phase maps arising from time-varying imaging gradients have been demonstrated to create a LF conductivity contrast. Essential in this methodology is the subtraction of phase images acquired with opposite gradient polarities to separate LF and RF phase effects. Here we demonstrate how sensitive these subtractions are with respect to geometrical distortions., Theory and Methods: The effect of geometrical distortions on LF phase maps is mathematically defined. After quantifying typical geometrical distortions, their effects on LF phase maps are evaluated using conductive phantoms. For validation, electromagnetic simulations of LF phase maps were performed., Results: Even sub-voxel distortions of 10% of the voxel size, measured for a typical LF MR sequence, cause leakage of RF phase into LF phase of several milli-radians, leading to a misleading pattern of LF phase maps. This leakage is mathematically confirmed, while simulations indicate that the expected LF phase should be in order of micro-radians., Conclusion: The conductivity scaling of LF phase maps is attributable to the RF phase leakage, thus dependent on the RF conductivity. In fact, simulations show that the LF phase is not measurable. Magn Reson Med 76:905-912, 2016. © 2015 Wiley Periodicals, Inc., (© 2015 Wiley Periodicals, Inc.)

Introduction The reliability of hyperthermia treatment planning (HTP) is strongly dependent on the accuracy of the electric properties of each tissue. The values currently used are mostly based on ex vivo measurements. In this study, in vivo conductivity of human muscle, bladder content and cervical tumours, acquired with magnetic resonance-based electric properties tomography (MR-EPT), are exploited to investigate the effect on HTP for cervical cancer patients. Methods Temperature-based optimisation of five different patients was performed using literature-based conductivity values yielding certain antenna settings, which are then used to compute the temperature distribution of the patient models with EPT-based conductivity values. Furthermore, the effects of altered bladder and muscle conductivity were studied separately. Finally, the temperature-based optimisation was performed with patient models based on EPT conductivity values. Results The tumour temperatures for all EPT-based dielectric patient models were lower compared to the optimal tumour temperatures based on literature values. The largest deviation was observed for patient 1 with ΔT90 = -1.37 °C. A negative impact was also observed when the treatment was optimised based on the EPT values. For four patients ΔT90 was less than 0.6 °C; for one patient it was 1.5 °C. Conclusions Electric conductivity values acquired by EPT are higher than commonly used from literature. This difference has a substantial impact on cervical tumour temperatures achieved during hyperthermia. A higher conductivity in the bladder and in the muscle tissue surrounding the tumour leads to higher power dissipation in the bladder and muscle, and therefore to lower tumour temperatures.

Purpose: To explore and evaluate the potential value of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) for the prediction of pathologic response to neoadjuvant chemoradiotherapy (nCRT) in oesophageal cancer., Material and Methods: Twenty-six patients underwent DCE-MRI before, during (week 2-3) and after nCRT, but before surgery (pre/per/post, respectively). Histopathologic tumour regression grade (TRG) was assessed after oesophagectomy. Tumour area-under-the-concentration time curve (AUC), time-to-peak (TTP) and slope were calculated. The ability of these DCE-parameters to distinguish good responders (GR, TRG 1-2) from poor responders (noGR, TRG⩾3), and pathologic complete responders (pCR) from no-pCR was assessed., Results: Twelve patients (48%) showed GR of which 8 patients (32%) pCR. Analysis of AUC change throughout treatment, AUCper-pre, was most predictive for GR, at a threshold of 22.7% resulting in a sensitivity of 92%, specificity of 77%, PPV of 79%, and a NPV of 91%. AUCpost-pre was most predictive for pCR, at a threshold of -24.6% resulting in a sensitivity of 83%, specificity of 88%, PPV of 71%, and a NPV of 93%. TTP and slope were not associated with pathologic response., Conclusions: This study demonstrates that changes in AUC throughout treatment are promising for prediction of histopathologic response to nCRT for oesophageal cancer., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

The in vivo electric conductivity (σ) values of tissue are essential for accurate electromagnetic simulations and specific absorption rate (SAR) assessment for applications such as thermal dose computations in hyperthermia. Currently used σ-values are mostly based on ex vivo measurements. In this study the conductivity of human muscle, bladder content and cervical tumors is acquired non-invasively in vivo using MRI. The conductivity of 20 cervical cancer patients was measured with the MR-based electric properties tomography method on a standard 3T MRI system. The average in vivo σ-value of muscle is 14% higher than currently used in human simulation models. The σ-value of bladder content is an order of magnitude higher than the value for bladder wall tissue that is used for the complete bladder in many models. Our findings are confirmed by various in vivo animal studies from the literature. In cervical tumors, the observed average conductivity was 13% higher than the literature value reported for cervical tissue. Considerable deviations were found for the electrical conductivity observed in this study and the commonly used values for SAR assessment, emphasizing the importance of acquiring in vivo conductivity for more accurate SAR assessment in various applications.

Purpose: MR safety at 7 Tesla relies on accurate numerical simulations of transmit electromagnetic fields to fully assess local specific absorption rate (SAR) safety. Numerical simulations for SAR safety are currently performed using models of healthy patients. These simulations might not be useful for estimating SAR in patients who have large lesions with potentially abnormal dielectric properties, e.g., brain tumors., Theory and Methods: In this study, brain tumor patient models are constructed based on scans of four patients with high grade brain tumors. Dielectric properties for the modeled tumors are assigned based on electrical properties tomography data for the same patients. Simulations were performed to determine SAR., Results: Local SAR increases in the tumors by as much as 30%. However, the location of the maximum 10-gram averaged SAR typically occurs outside of the tumor, and thus does not increase. In the worst case, if the tumor model is moved to the location of maximum electric field intensity, then we do observe an increase in the estimated peak 10-gram SAR directly related to the tumor., Conclusion: Peak local SAR estimation made on the results of a healthy patient model simulation may underestimate the true peak local SAR in a brain tumor patient., (© 2015 Wiley Periodicals, Inc.)

Electric properties tomography (EPT) is an imaging modality to reconstruct the electric conductivity and permittivity inside the human body based on B1(+) maps acquired by a magnetic resonance imaging (MRI) system. Current implementations of EPT are based on the local Maxwell equations and assume piecewise constant media. The accuracy of the reconstructed maps may therefore be sensitive to noise and reconstruction errors occur near tissue boundaries. In this paper, we introduce a multiplicative regularized CSI-EPT method (contrast source inversion-electric properties tomography) where the electric tissue properties are retrieved in an iterative fashion based on a contrast source inversion approach. The method takes the integral representations for the electromagnetic field as a starting point and the tissue parameters are obtained by iteratively minimizing an objective function which measures the discrepancy between measured and modeled data and the discrepancy in satisfying a consistency equation known as the object equation. Furthermore, the objective function consists of a multiplicative Total Variation factor for noise suppression during the reconstruction process. Finally, the presented implementation is able to simultaneously include more than one B1(+) data set acquired by complementary RF excitation settings. We have performed in vivo simulations using a female pelvis model to compute the B1(+) fields. Three different RF excitation settings were used to acquire complementary B1(+) fields for an improved overall reconstruction. Numerical results illustrate the improved reconstruction near tissue boundaries and the ability of CSI-EPT to reconstruct small tissue structures.

Purpose: To explore the value of diffusion-weighted magnetic resonance imaging (DW-MRI) for the prediction of pathologic response to neoadjuvant chemoradiotherapy (nCRT) in esophageal cancer., Material and Methods: In 20 patients receiving nCRT for esophageal cancer DW-MRI scanning was performed before nCRT, after 8-13 fractions, and before surgery. The median tumor apparent diffusion coefficient (ADC) was determined at these three time points. The predictive potential of initial tumor ADC, and change in ADC (ΔADC) during and after treatment for pathologic complete response (pathCR) and good response were assessed. Good response was defined as pathCR or near-pathCR (tumor regression grade [TRG] 1 or 2)., Results: A pathCR after nCRT was found in 4 of 20 patients (20%), and 8 patients (40%) showed a good response to nCRT. The ΔADCduring was significantly higher in pathCR vs. non-pathCR patients (34.6%±10.7% [mean±SD] vs. 14.0%±13.1%, p=0.016), as well as in good vs. poor responders (30.5%±8.3% vs. 9.5%±12.5%, p=0.002). The ΔADCduring was predictive of residual cancer at a threshold of 29% (sensitivity of 100%, specificity of 75%, PPV of 94%, and NPV of 100%), and for poor pathologic response at a threshold of 21% (sensitivity of 82%, specificity of 100%, PPV of 100%, and NPV of 80%)., Conclusions: In this exploratory study, the treatment-induced change in ADC during the first 2-3weeks of nCRT for esophageal cancer seemed highly predictive of histopathologic response. Larger series are warranted to verify these results., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Purpose: Investigation of the validity of the "transceive phase assumption" for Electric Property Tomography of pelvic tumors at 3T. The acquired electric conductivities of pelvic tumors are beneficial for improved specific absorption rate determination in hyperthermia treatment planning., Methods: Electromagnetic simulations and magnetic resonance imaging measurements of a pelvic-sized phantom and the human pelvis of a volunteer and a cervix cancer patient., Results: The reconstructed conductivity values of the phantom tumor model are in good quantitative agreement (mean deviation: 1-10%) with the probe measurements. Furthermore, the average reconstructed conductivity of a pelvic tumor model was in close agreement with the input conductivity (0.86 S/m vs. 0.90 S/m). The reconstructed tumor conductivity of the presented patient (cervical carcinoma, Stage: IVA) was 1.16 ± 0.40 S/m., Conclusion: This study demonstrates the feasibility of electric property tomography to measure quantitatively the conductivity of centrally located tumors in a pelvic-sized phantom and human pelvis with a standard magnetic resonance (MR) system and MR sequences. A good quantitative agreement was found between the reconstructed σ-values and probe measurements for a wide range of σ-values and for off-axis located spherical compartment. As most pelvic tumors are located in the central region of the pelvis, these results can be exploited in hyperthermia treatment planning systems., (© 2014 Wiley Periodicals, Inc.)