Clinical Magnetic Resonance Imaging of Pancreatic Islet Grafts After Iron Nanoparticle Labeling

There is a crucial need for noninvasive assessment tools after cell transplantation. This study investigates whether a magnetic resonance imaging (MRI) strategy could be clinically applied to islet transplantation. The purest fractions of seven human islet preparations were labeled with superparamagnetic iron oxide particles (SPIO, 280 μg/mL) and transplanted into four patients with type 1 diabetes. MRI studies (T2*) were performed prior to and at various time points after transplantation. Viability and in vitro and in vivo functions of labeled islets were similar to those of control islets. All patients could stop insulin after transplantation. The first patient had diffuse hypointense images on her baseline liver MRI, typical for spontaneous high iron content, and transplant-related modifications could not be observed. The other three patients had normal intensity on pretransplant images, and iron-loaded islets could be identified after transplantation as hypointense spots within the liver. In one of them, i.v. iron therapy prevented subsequent visualization of the spots because of diffuse hypointense liver background. Altogether, this study demonstrates the feasibility and safety of MRI-based islet graft monitoring in clinical practice. Iron overload (spontaneous or induced) represents the major obstacle to the technique.     

A Novel Method for Quantitative Monitoring of Transplanted Islets of Langerhans by Positive Contrast Magnetic Resonance Imaging

The Automatic Quantitative Ultrashort Echo Time imaging (AQUTE) protocol for serial MRI allows quantitative in vivo monitoring of iron labeled pancreatic islets of Langerhans transplanted into the liver, quantifying graft implantation and persistence in a rodent model. Rats (n = 14), transplanted with iron oxide loaded cells (0–4000 islet equivalents, IEQ), were imaged using a 3D radial ultrashort echo time difference technique (dUTE) on a Siemens MAGNETOM 3T clinical scanner up to 5 months postsurgery. In vivo 3D dUTE images gave positive contrast from labeled cells, suppressing liver signal and small vessels, allowing automatic quantification. Position of labeled islet clusters was consistent over time and quantification of hyperintense pixels correlated with the number of injected IEQs (R²= 0.898, p < 0.0001), and showed persistence over time (5 months posttransplantation). Automatic quantification was superior to standard imaging and manual counting methods, due to the uniform suppressed background and high contrast, resulting in significant timesavings, reproducibility and ease of quantification. Three‐dimensional coverage of the whole liver in the absence of cardiac/respiratory artifact provided further improvement over conventional imaging. This imaging protocol reliably quantifies transplanted islet mass and has high translational potential to clinical studies of transplanted pancreatic islets.     

Magnetic resonance imaging with magnetic resonance cholangiopancreatography accurately predicts resectability of pancreatic carcinoma

Accurate preoperative staging of pancreatic malignancy aids in directing appropriate therapy and avoids unnecessary invasive procedures. We evaluated the accuracy of magnetic resonance imaging (MRI) with magnetic resonance cholangiopancreatography (MRCP) in determining resectability of pancreatic malignancy. Twenty-one patients with suspected pancreatic malignancy underwent dynamic, contrast-en-hanced breath-hold MRI with MRCP prior to surgical evaluation. Results of this study were correlated with operative results and pathologic findings. The sensitivity, specificity, and accuracy of MRI with MRCP in detecting a mass, determining the nature of the mass, and predicting lymph node involvement and resectability were determined. MRI with MRCP correctly identified the presence of a pancreatic mass in all 21 of these patients. Following pathologic correlation, it was determined that MRI with MRCP was 81 % accurate in determining the benign or malignant nature of the pancreatic mass and 43% accurate in predicting lymph node involvement. In predicting resectability, MRI with MRCP had a sensitivity of 100%, specificity of 83%, positive predictive value of 94%, negative predictive value of 100%, and accuracy of 95%. MRI with MRCP is an accurate, noninvasive technique in the preoperative evaluation of pancreatic malignancy. Information obtained from MRI with MRCP including identification of a mass and predicting tumor resectability may be of value in staging and avoiding unnecessary invasive diagnostic procedures in patients with pancreatic cancer. Presented at the Thirty-Ninth Annual Meeting of The Society for Surgery of the Alimentary Tract, New Orleans, La., May 17–20, 1998.     

Magnetic Resonance Imaging of Patients with Increased Blood Pressure and Altered Blood Pressure Response to Exercise After Coarctation Repair

Objective—Patients successfully operated for calactation of the aorta are frequently subjected to altered blood pressure (BP) at rest and BP response during exercise. The relationship between these variables and blood flow, peak velocity, restenosis and other morphological features of the thoracic aorta as revealed by magnetic resonance imaging (MRI) was evaluated.

Design—Fifty-one patients subjected to coarctectomy of the aorta were examined by MRI. In addition, a control group of 23 healthy volunteers was evaluated. Morphology of the aorta was demonstrated with both ECG-triggered SE imaging and gadolinium-enhanced MR aortography. Flow-weighted MRI was applied for quantitative flow and velocity measurements.

Results—Structural alteration of the aorta was more commonly seen in those patients having increased BP at rest or altered BP response during exercise than those with a normal BP profile. The luminal diameter of the narrowest site of the aorta was decreased in all patient groups. Accordingly, the peak velocity at the corresponding site was significantly (p < 0.01) increased. However, blood flow was significantly (p < 0.01) decreased among those patients with normal BP profile compared with the other patient groups as well as the controls.

Conclusion—Other structural changes than restenosis may contribute as well to the altered BP profile of patients subjected to coarctectomy. Reduced blood flow appears to correlate with normal BP profile, whereas the peak velocity measurements that are obtained by MRI are not able to differentiate between the patient groups. The comprehensive and reliable data obtained by non-invasive techniques, i.e. MRI and Doppler, may rep lace catheterization when deciding the need for intervention.     

Magnetic separation of encapsulated islet cells labeled with superparamagnetic iron oxide nano particles

Islet cell transplantation is a promising option for the restoration of normal glucose homeostasis in patients with type 1 diabetes. Because graft volume is a crucial issue in islet transplantations for patients with diabetes, we evaluated a new method for increasing functional tissue yield in xenogeneic grafts of encapsulated islets. Islets were labeled with three different superparamagnetic iron oxide nano particles (SPIONs; dextran‐coated SPION, siloxane‐coated SPION, and heparin‐coated SPION). Magnetic separation was performed to separate encapsulated islets from the empty capsules, and cell viability and function were tested. Islets labeled with 1000 μg Fe/ml dextran‐coated SPIONs experienced a 69.9% reduction in graft volume, with a 33.2% loss of islet‐containing capsules. Islets labeled with 100 μg Fe/ml heparin‐coated SPIONs showed a 46.4% reduction in graft volume, with a 4.5% loss of capsules containing islets. No purification could be achieved using siloxane‐coated SPIONs due to its toxicity to the primary islets. SPION labeling of islets is useful for transplant purification during islet separation as well as in vivo imaging after transplantation. Furthermore, purification of encapsulated islets can also reduce the volume of the encapsulated islets without impairing their function by removing empty capsules.     

Heterogeneity of Trabecular Bone Structure in the Calcaneus Using Magnetic Resonance Imaging

The purpose of this study was to quantify the heterogeneity in the trabecular bone structure in the calcaneus. Magnetic resonance (MR) images of the calcaneus were obtained in the sagittal plane at an inplane resolution of 195 μm and a slice thickness of 1000 μm in 12 young normal subjects. Regions of interest (ROI) were selected to cover the calcaneus using a grid of square boxes (10 mm per side). A thresholding technique based on the regional intensity histogram was used to segment the images into trabecular bone and marrow phases and to calculate measures such as apparent trabecular bone area fraction, apparent trabecular spacing, apparent trabecular thickness and apparent trabecular number. Bone mineral density (BMD) of the calcaneus was assessed using dual-energy X-ray absorptiometry (DXA). Histological sections of three calcanei were also analyzed using transmission light illumination, and the results used to calibrate our computational software. For a relatively narrow inter-subject variation in posterior BMD, a significant inter-subject variation was seen in MRI-derived structural parameters. Furthermore, the spatial heterogeneity of the structural parameters in the posterior region was as high as 40%. Thus, the posterior tuberosity of the calcaneus, a typical site for BMD and single-point ultrasound assessments, can demonstrate significant regional variation in trabecular bone structure.     

术前功能磁共振在脑功能区肿瘤切除中的应用

目的探讨术前功能磁共振（fMRI）在功能区肿瘤切除中的临床应用价值。方法10例肿瘤邻近脑运动功能区患者，平均51．3岁，7例肢体无力，2例抽搐，1例口角偏斜，术前Karnofsky评分平均82分。常规行头颅核磁增强扫描，证实肿瘤位于功能区，再行fMRI检查。依据fMRI中活化区与肿瘤的位置关系决定全切或者次全切除肿瘤，术中避免活化区的损伤。术后观察肢体肌力恢复情况、进行术后Karnofsky评分并复查核磁了解术后肿瘤切除情况，与术前进行对比。结果10例fMRI活化区显示清晰，8例活化区被肿瘤挤压移位，拉伸变形。肿瘤边缘与活化区的最近距离0～26mm，平均13．6mm。本组肿瘤全切7例，次全切除3例。术后肌力好转7例，2例抽搐患者术后未再出现抽搐；1例口角歪斜患者术后面神经功能分级减轻。术后1个月Karnofsky评分平均93分。术后1周复查MRI显示：肿瘤消失7例，余3例肿瘤缩小95％～99％。结论fMRI对邻近脑运动功能区肿瘤患者的术前评价有重要临床意义，对手术切除脑功能区周围肿瘤并保留运动功能有重要的指导作用。     

Multiparametric Magnetic Resonance Imaging for the Detection of Clinically Significant Prostate Cancer: What Urologists Need to Know. Part 2: Interpretation

BackgroundThere is large variability among radiologists in their detection of clinically significant (cs) prostate cancer (PCa) on multiparametric magnetic resonance imaging (mpMRI).ObjectiveTo reduce the interpretation variability and achieve optimal accuracy in assessing prostate mpMRI.Design, setting, and participantsHow the interpretation of mpMRI can be optimized is demonstrated here. Whereas part 1 of the “surgery-in-motion” paper focused on acquisition, this paper shows the correlation between (ab)normal prostate anatomical structures and image characteristics on mpMRI, and how standardized interpretation according to Prostate Imaging Reporting and Data System version 2 (PI-RADS v2) should be performed. This will be shown in individual patients.Surgical procedureTo detect csPCa, three mpMRI “components” are used: “anatomic” T2-weighted imaging, “cellular-density” diffusion-weighted imaging, and “vascularity” dynamic contrast-enhanced MRI.MeasurementsBased on PI-RADS v2, the accompanying video shows how mpMRI interpretation is performed. Finally, the role of mpMRI in detecting csPCa is briefly discussed and the main features of the recently introduced PI-RADS v2.1 are evaluated.Results and limitationsWith PI-RADS v2, it is possible to quantify normal and abnormal anatomical structures within the prostate based on its imaging features of the three mpMRI “components.” With this knowledge, a more objective evaluation of the presence of a csPCa can be performed. However, there still remains quite some space to reduce interobserver variability.ConclusionsFor understanding the interpretation of mpMRI according to PI-RADS v2, knowledge of the correlation between imaging and (ab)normal anatomical structures on the three mpMRI components is needed.Patient summaryThis second surgery-in-motion contribution shows what structures can be recognized on prostate magnetic resonance imaging (MRI). How a radiologist performs his reading according to the so-called Prostate Imaging Reporting and Data System criteria is shown here. The main features of these criteria are summarized, and the role of prostate MRI in detecting clinically significant prostate cancer is discussed briefly.     

Validation of the European Society of Urogenital Radiology Scoring System for Prostate Cancer Diagnosis on Multiparametric Magnetic Resonance Imaging in a Cohort of Repeat Biopsy Patients

Background

Wide variations in acquisition protocols and the lack of robust diagnostic criteria make magnetic resonance imaging (MRI) detection of prostate cancer (PCa) one of the most challenging fields in radiology and urology.

Objective

To validate the recently proposed European Society of Urogenital Radiology (ESUR) scoring system for multiparametric MRI (mpMRI) of the prostate.

Design, setting, and participants

An institutional review board–approved multicentric prospective study; 129 consecutive patients (1514 cores) referred for mpMRI after at least one set of negative biopsies.

Intervention

Transfer of mpMRI-suspicious areas on three-dimensional (3D) transrectal ultrasound images by 3D elastic surface registration; random systematic and targeted cores followed by core-by-core analysis of pathology and mpMRI characteristics of the core locations. The ESUR scores were assigned after the procedure on annotated Digital Imaging and Communications in Medicine archives.

Outcome measurements and statistical analysis

Relationships between ESUR scores and biopsy results were assessed by the Mann-Whitney U test. The Yates correction and Pearson χ² tests evaluated the association between categorical variables. A teaching set was randomly drawn to construct the receiver operating characteristic curve of the ESUR score sum (ESUR-S). The threshold to recommend biopsy was obtained from the Youden J statistics and tested in the remaining validation set in terms of sensitivity, specificity, positive predictive value, negative predictive value, and accuracy.

Results and limitations

Higher T2-weighted, dynamic weighted imaging and dynamic contrast-enhanced ESUR scores were observed in areas yielding cancer-positive cores. The proportion of positive cores increased with the ESUR-S aggregated in five increments (ESUR-S 3–5: 2.9%; ESUR-S 6–8: 11.1%; ESUR-S 9–10: 38.2%; ESUR-S 11–12: 63.4%; and ESUR-S 13–15: 83.3%; p < 0.0001). A threshold of ESUR-S ≥9 exhibited the following characteristics: sensitivity: 73.5%; specificity: 81.5%; positive predictive value: 38.2%; negative predictive value: 95.2%; and accuracy: 80.4%. Although the study was not designed to compare repeat biopsy strategies, more targeted cores than random systematic cores were found to be positive for cancer (36.3% compared with 4.9%, p < 0.00001).

Conclusions

In the challenging situation of repeat biopsies, the ESUR scoring system was shown to provide clinically relevant stratification of the risk of showing PCa in a given location.     

Multiparametric Magnetic Resonance Imaging for the Detection of Clinically Significant Prostate Cancer: What Urologists Need to Know. Part 1: Acquisition

BackgroundAcquiring multiparametric magnetic resonance images of the prostate is not a simple “push-button” approach.ObjectiveTo show how image acquisition of prostate multiparametric Magnetic Resonance Imaging (mpMRI) can be optimized.Design, setting, and participantsImage protocols, magnetic field strength choice, and the use of receiver coils are discussed. In addition, patient preparation and the recognition, prevention, and mitigation of artifacts are evaluated.Surgical procedureBased on expert prostate MRI technologists (MRI radiographers) opinion, the optimal protocol is reviewed, and potential artifacts are determined.MeasurementsThe entire acquisition process is presented from initial patient preparation until the end of the imaging. The choice of the used equipment, pulse sequences, and prevention of patient- and imaging-related artifacts are presented. This will be shown in individual patients.Results and limitationsAlthough the Prostate Imaging Reporting and Data System guidelines (2012 and 2016) describe minimal and optimal acquisition protocols for prostate mpMRI, these standards are not always met in daily practice. A major challenge in mpMRI is to obtain high image quality and reduce its variability for radiologic interpretations. A summary of evidence and guidelines for the acquisition of mpMRI of the prostate can set a basic guideline to reduce these variabilities.ConclusionsThis article and an accompanying video can be used as a guide by MRI technologists (MRI radiographers) to improve their image acquisitions by optimizing protocols, magnetic field strength choice, and use of receiver coils. We also discuss patient preparation and the recognition, prevention, and mitigation of artifacts.Patient summaryIn this first surgery-in-motion contribution, we will show how optimized image acquisition is performed to detect prostate cancer. Both MRI-dependent and patient related factors are discussed.     

Diagnostic Performance of Magnetic Resonance Imaging for the Detection of Bone Metastasis in Prostate Cancer: A Systematic Review and Meta-analysis

Context

Magnetic resonance imaging (MRI) has been tested for detecting bone metastasis and has shown promising results. Yet, consensus has not been reached regarding whether it can replace the role of bone scintigraphy in this clinical setting or not.

Multiparametric Magnetic Resonance Imaging for the Detection of Clinically Significant Prostate Cancer: What Urologists Need to Know. Part 3: Targeted Biopsy

BackgroundAfter a lesion has been assessed adequately on multiparametric magnetic resonance imaging (mpMRI), magnetic resonance (MR)-guided biopsy (MRGB) is the logical next step. The choice of the MRGB technique, however, is difficult.ObjectiveTo show the advantages and disadvantages of the three commonly used MRGB techniques—MRI-ultrasound fusion MRGB (fus-MRGB), direct in-bore MRGB (inbore-MRGB), and cognitive MRGB (cog-MRGB), and to determine when each of the techniques can be used.Design, setting, and participantsBased on expert opinion and literature overview, the advantages, disadvantages, and challenges of fus-MRGB, inbore-MRGB, and cog-MRGB are evaluated. Further, the clinical setting of each biopsy strategy is assessed.Surgical procedureBased on expert opinion and literature data, the three biopsy procedures are evaluated, and the important pros and cons are determined.MeasurementsThe basic concept of each biopsy technique is reviewed, which would result in a clinical recommendation. This will be shown in individual patients.Results and limitationsThe accompanying video shows how fus-MRGB and inbore-MRGB are performed in our hospital. An important advantage of fus-MRGB is its generally availability; however, it has fusion-error limitations. Although not supported by evidence, inbore-MRGB seems to be better suited for smaller lesions, but is rather expensive. Cog-MRGB is easy to use and inexpensive, but is more operator dependent as it requires knowledge about both ultrasound and MR images. Readers should be aware that our MRGB approach is largely based on expert opinion and, where possible, supported by evidence.ConclusionsThis article and the accompanying video show different MRGB techniques. The advantages and disadvantages of the three biopsy techniques, as well as the clinical setting in which each biopsy strategy is being used in our hospital, are discussed. Fus-MRGB is our first choice for prostate biopsy. Direct inbore-MRGB is used in difficult lesions but is mainly used as a “problem solver” (eg, a negative biopsy with a high suspicion for clinically significant prostate cancer). In our opinion, cog-MRGB is best for sampling larger and diffuse lesions.Patient summaryThis third surgery in motion contribution shows our approach in magnetic resonance (MR)-guided biopsy (MRGB). Fusion MRGB is our first choice for prostate biopsy. In-bore MRGB is used in selected, difficult cases, mainly as a problem solver. In our point of view, cognitive MRGB seems to be best for sampling larger lesions and diffuse processes.