Recent advances in magnetic resonance imaging of renal masses

Examination of the kidney with conventional spin-echo magnetic resonance imaging has met with some success. However, image degradation, resulting from artifacts caused by breathing, and suboptimal lesion conspicuity, caused by the similarity of solid neoplasms and renal parenchyma in T1-weighted and T2-weighted images, have limited the value of its use. In this paper, I describe two breath-holding techniques that allow dynamic contrast-enhanced examination of the kidney. It is hoped that these new sequences will improve the clinical value of magnetic resonance in imaging renal masses.     

Pictorial essay: magnetic resonance imaging of adrenal masses

In many cases, adrenal lesions are incidentally discovered during ultrasonography or computed tomography in the staging or follow-up of patients with primary malignancies. The most important issue in the radiological management of adrenal masses is the differential diagnosis between benign and malignant lesions. Magnetic resonance (MR) plays an important role in the characterization of such lesions. Our aim was to present the MR techniques and to review the MR features of most common adrenal masses.     

Vaginal masses: magnetic resonance imaging features with pathologic correlation

The detection of vaginal lesions has increased with the expanding use of cross-sectional imaging. Magnetic resonance imaging (MRI)—with its high-contrast resolution and multiplanar capabilities—is often useful for characterizing vaginal masses. Vaginal masses can be classified as congenital, inflammatory, cystic (benign), and neoplastic (benign or malignant) in etiology. Recognition of the typical MR imaging features of such lesions is important because it often determines the treatment approach and may obviate surgery. Finally, vaginal MR imaging can be used to evaluate post-treatment changes related to previous surgery and radiation therapy. In this article, we will review pertinent vaginal anatomy, vaginal and pelvic MRI technique, and the MRI features of a variety of vaginal lesions with pathological correlation.     

Retroperitoneal masses: magnetic resonance imaging findings with pathologic correlation

Primary retroperitoneal masses are a rare but diverse group of benign and malignant processes. Magnetic resonance (MR) imaging is playing an increasing role in evaluating retroperitoneal soft-tissue masses. Since the MR imaging features of most retroperitoneal soft-tissue masses are nonspecific, prediction of a specific histologic diagnosis remains a challenge for the radiologist. However, there are certain specific MR imaging appearances that are helpful. Dynamic enhancement patterns can reflect the vascularity of masses, differentiating benign from malignant soft-tissue masses. This article pictorially illustrates the MR imaging features of various common and uncommon retroperitoneal masses.     

Cystic masses of the knee: magnetic resonance imaging findings

Cystic masses of the knee comprise a diverse group of pathologic entities ranging from simple cysts to complications of underlying disease to tumors. Although their presentations may be similar, the appropriate treatment and patient management can differ greatly. In this article, we review radiographic and magnetic resonance imaging characteristics of both common and uncommon cystic masses of the knee.     

Focal cortical dysplasia on magnetic resonance imaging: a case report

A case report of an 11 years old boy with new onset of a seizure disorder is presented. A computed tomography scan demonstrated a noncalcified, nonenhancing focal region of abnormal cortex. A magnetic resonance imaging scan delineated both an isointense area of abnormally thickened gyri and linear areas of abnormal high signal intensity in the subjacent white matter. A review of the radiologic and pathologic literature suggests that this lesion represents the entity focal cortical dysplasia as described by Taylor, et al. This abnormality is part of a spectrum of disorders including hamartomas (of tuberous sclerosis), focal cortical dysplasia and heterotopias.     

Magnetic resonance imaging of renal masses at 0.02 tesla

To determine the usefulness of extremely low field magnetic resonance imaging (MRI) in the evaluation of renal masses 19 patients with 15 tumors (13 renal and 2 renal pelvic carcinomas) and 8 cysts were examined in a 0.02 tesla MRI unit. The findings were compared with results of computed tomography (CT) and ultrasound. Cavography was performed in 6 patients. MRI enabled differentiation between cysts and solid tumors. Tumor extension into the inferior vena cava could be demonstrated in one case and liver metastases in two patients. The image quality was inferior to that reported at higher field strengths and the tumors were more precisely staged by CT and ultrasound. At present, it is unlikely that low field MRI will play any substantial role in the evaluation of renal masses.     

Diffusion-weighted magnetic resonance imaging in evaluation of primary solid and cystic renal masses using the Bosniak classification

Purpose

Our purpose was to determine whether quantitative diffusion-weighted MR imaging (DWI) could be used in discrimination of benign and malignant primary solid and cystic renal tumors.

Materials and methods

A total of 105 consecutive patients with renal masses and 30 healthy controls were enrolled in this prospective study. Dynamic contrast enhanced routin renal images and DWI (with b factors of 0, 500 and 1000 s/mm²) was performed at 1.5 T unit. Renal masses were divided into two groups as cystic or solid and all cystic lesions were prospectively assigned to a Bosniak classification number. The median apparent diffusion coefficient (ADC) values along with b 500 and 1000 signal intensities of normal kidneys, solid components of mixed renal masses and total of cystic lesions were calculated.

Results

The mean ADC value of normal renal parenchyma in control group was 2.18 ± 0.13 × 10⁻³ mm²/s. Solid renal tumors had significant lower ADC values (median: 1.16 ± 0.27 × 10⁻³ mm²/s), in contrast to cystic tumors (median: 2.73 ± 0.44 × 10⁻³ mm²/s). The mean ADC value of the Bosniak Category I cysts was significantly higher (3.09 ± 0.14 × 10⁻³ mm²/s) than normal renal parenchyma (p < 0.01). A statistical significance was achieved between the signal intensity of Bosniak Category I and Category II–III cysts with b 1000 (p < 0.05). Among the different histologic subtypes of renal cell carcinoma, the mean ADC value of chromophobe cell carcinoma (1.41 ± 0.09 × 10⁻³ mm²/s) was significantly higher than that of papillary cell carcinoma (0.90 ± 0.16 × 10⁻³ mm²/s) and clear cell carcinoma (1.23 ± 0.13 × 10⁻³ mm²/s).

Conclusion

Accurate assessment of renal masses is important for establishing whether tumors require surgical intervention or not. While MRI is a useful modality as an investigative tool for diagnosing, characterizing and staging renal masses, DWI contributes additional value by promising differentiation benign from malignant renal tumors, even histologically subtyping of renal cell cancer.     

Role of novel magnetic resonance imaging sequences in characterization of ovarian masses

Introduction

Differentiating a benign from a malignant adnexal mass would provide a basis for optimal preoperative planning and may also reduce the number of unnecessary laparotomies patients undergoing treatment for benign disease. MRI provides additional information on the composition of soft-tissue masses using differences in MR relaxation properties seen in various types of tissue. More recently developed MRI sequences, like diffusion weighted, susceptibility weighted, and dynamic contrast enhancement sequences provided additional capacities for adnexal lesion tissue characterization.

Aim of the work

The aim of this work was to study the role of MRI including the novel sequences, namely dynamic contrast enhanced MRI (DCE–MRI), diffusion weighted images (DWI) and susceptibility weighted images (SWI) in the characterization of ovarian masses.

Patients and methods

This study included 25 patients having indeterminate adnexal masses at ultrasound. They were subjected to pelvic MRI, including T1, T2, T1 fat sat sequences, as well as the DWI, SWI, and DCE sequences. Final diagnosis was reached through histopathological data, or therapeutic response.

Results

All endometriomas showed blooming on SWI. All malignant lesions showed restricted diffusion and type III DCE curves.

Conclusion

MRI, especially the more recent sequences (DWI, SWI and DCE) allows accurate characterization of ovarian lesions.     

Problems and errors of magnetic resonance in the diagnosis of renal masses

Since the impact of MRI on the diagnostic evaluation of renal masses is affected by the intrinsic complexity of the modality, the problems related to the specific knowledge, on the part of the radiologist, of the examination itself to make a correct diagnosis are carefully analyzed. The problems related to the technical features of the equipment are presented as well, with a special emphasis on the still inadequate spatial resolution of MRI, and on its long acquisition time and unfavorable signal-to-noise ratio. On the other hand, its good contrast resolution is mentioned, which will be further improved by the new gradient-echo sequence (GRE) and by the use of paramagnetic contrast media. As for diagnostic problems, the results are analyzed of a series of 62 patients showing US "solid" renal mass. MRI allowed lesion detection in 59/62 cases, with 95.1% sensitivity. False negatives were due solely to the poor image quality determined by motion artifacts. MRI did not provide significant information in the structural evaluation of the lesions when tissue characterization was concerned, but was helpful in the correct assessment of necrotic foci (thus allowing the calculation of viable neoplastic mass) and in the detection of collateral vessels. Finally, the spatial relationships of the mass could be easily assessed by MRI, thanks to both its multiplanarity and to its good capabilities in the visualization of vascular involvement.     

Low field magnetic resonance imaging of focal hepatic masses at 0.02 T

The diagnostic utility of extremely low field magnetic resonance (MR) imaging was evaluated in 25 patients with focal hepatic masses, including 17 with primary (n = 7) or secondary (n = 10) malignant neoplasms and 8 with benign lesions (6 hemangiomas). The findings were compared with the results of computed tomography (CT). Out of 16 patients with malignant tumors demonstrated by both modalities, the diagnostic information from MR imaging was equal to or better than that from CT in 6 patients and inferior to CT in 10. Shortcomings of MR were mainly due to low signal-to-noise ratio and poor spatial resolution, resulting in an image quality inferior to that obtained at higher field strengths. Considering these facts, together with the long imaging times required, low field MR cannot be recommended for general use in the evaluation of hepatic masses. On the other hand, our results indicate that this technique may be useful in establishing the diagnosis of hepatic hemangioma.     

儿童心脏良性肿瘤的CMR影像特征分析

目的 研究儿童心脏良性肿瘤的心脏MR（CMR）特征及其对儿童良性肿瘤的诊断价值。方法 回顾性收集2006年9月-2018年3月于我院进行CMR检查的心脏肿瘤病例资料,共38例心脏良性肿瘤患儿纳入研究,其中男21例,女17例,年龄0.2~153.3个月,中位年龄13个月。分析各病理类型肿瘤在CMR上的特征,包括累及部位、大小、信号特点、血流动力学改变等,以及是否伴发心包和胸腔积液。通过与病理结果对照,计算CMR对心脏良性肿瘤诊断的敏感度和准确度。结果 肿瘤累及心肌、心腔、心包、心室流出道及纵隔,形态大小不一,临床症状与肿瘤发生部位有一定相关性而不具有特异性,但各类肿瘤具有一定的影像特征。所有的心脏肿瘤均被CMR清晰显示,CMR的诊断与病理结果相符的有32例,诊断的敏感度及准确度分别为100%（38/38）和84.21%（32/38）。结论 CMR能够同时提供心脏良性肿瘤的形态学特征及组织学信号特征,对心脏良性肿瘤诊断的敏感性及准确性均较高,是评估心脏肿瘤的重要检查方法。     

Fast and ultrafast magnetic resonance imaging in renal lesions

Our purpose was to analyze and compare the image quality and contrast-to-noise ratio (CNR) of different fast T1- and T2-weighted sequences with conventional spin-echo sequences in renal MRI. Twenty-three patients with focal renal lesions were examined with a T2-weighted ultrafast turbo spin-echo (UTSE) sequence with and without frequency selective fat suppression (SPIR), a combined gradient-and-spin-echo sequence (GraSE), and a conventional spin-echo sequence (SE). In addition, T1-weighted images were obtained pre-and postcontrast, using a fast spin-echo sequence (TSE) with and without SPIR and the conventional SE sequence. Among the T2-weighted images, the highest CNR and the best image quality were obtained with the UTSE sequence, followed by the fat-suppressed UTSE sequence. GraSE and conventional SE sequences showed a significantly lower CNR and image quality (p < 0.05). The T1-weighted sequences did not show significant differences, in either precontrast or postcontrast measurements. T2-weighted UTSE with and without fat suppression combined excellent image quality and high CNR for imaging and detection of renal lesions. The T1-weighted fast sequences provided no alternative to the gradient-echo or to the conventional SE sequences. The results of this systematic study suggest the use of T2-weighted fast techniques for improved diagnostic accuracy of renal MRI.     

肾脏MR扩散峰度成像研究进展

MR扩散峰度成像（DKI）基于多项式模型,能够量化组织中水分子的扩散运动与自由高斯运动的偏差。DKI技术可以定量评价组织微环境的复杂性和异质性,近年来已用于评价肾脏功能及相关疾病,在肾脏肿瘤的分级,以及在梗阻性肾病、糖尿病肾病、高尿酸血症肾病等常见疾病的早期诊断中具有一定的应用价值。就DKI成像原理及在正常肾脏和肾脏常见疾病中的研究进展予以综述。     

Focal nodular hyperplasia: intraindividual comparison of dynamic gadobenate dimeglumine- and ferucarbotran-enhanced magnetic resonance imaging

PURPOSE: To intraindividually compare the enhancement pattern of focal nodular hyperplasia (FNH) after dynamic administration of two bolus-injectable liver-specific MR contrast agents, ferucarbotran and gadobenate dimeglumine. MATERIALS AND METHODS: A total of 19 patients with 24 FNHs underwent gadobenate dimeglumine- and ferucarbotran-enhanced MRI during the hepatic arterial-dominant phase (HAP; 25 seconds), the portal-venous phase (PVP; 60 seconds), and the equilibrium phase (EP; 180 seconds). Hepatospecific phases were acquired on T1-weighted images 120 minutes after gadobenate dimeglumine administration, and on T2-weighted images 10 minutes after ferucarbotran administration. Lesion enhancement was independently analyzed by two observers. The kappa statistic was determined to evaluate the agreement between the enhancement patterns of the lesions. RESULTS: On gadobenate dimeglumine-enhanced MR images during HAP, PVP, and EP, FNHs were: hyperintense (24/20/13); isointense (0/4/11); and hypointense (0/0/0). On ferucarbotran-enhanced MR images during HAP, PVP, and EP, FNHs were: hyperintense (2/0/0); isointense (16/9/14); and hypointense (6/15/10). Overall, poor agreement between both contrast agents was observed. During the hepatospecific phases, most (20/24; 83%) FNHs showed a typical enhancement pattern during the delayed hepatospecific phase. CONCLUSION: The dynamic enhancement pattern of FNHs is significantly different between gadobenate dimeglumine- and ferucarbotran-enhanced MRI. With respect to hepatospecific phase, the majority of FNHs showed a typical behavior on both contrast agents.