MRI-detected tumor deposits in cT3 and cT4 rectal cancer following neoadjuvant chemoradiotherapy.

OBJECTIVES: To evaluate the identification of tumor deposits (TDs) and the prognostic significance of an MRI tumor regression grade for TDs in patients with rectal cancer treated with neoadjuvant chemoradiotherapy (nCRT). METHODS: Ninety-one patients with cT3 or cT4 rectal cancer who underwent surgery following nCRT between August 2014 and June 2020 were retrospectively analyzed. Changes in pre-nCRT MRI-detected TDs (mrTDs) were described as mrTD regression grade. The diagnostic performance of post-nCRT MRI-detected TDs (ymrTDs) was compared with histopathological reference standard. The correlation between ymrTDs, mrTD regression grade, and disease-free survival (DFS) was assessed. RESULTS: The sensitivity and specificity of ymrTDs were 88.00% and 89.39%, respectively. The area under the receiver operating characteristic curve was 0.887 (95% confidence interval [CI]: 0.803-0.944). The 3-year DFS of patients with positive ymrTDs was significantly lower than of the negative group (44.83% vs 82.73%, p < 0.001). The 3-year DFS was 33.33% for patients with poor regression of mrTDs following nCRT and 55.56% for those with moderate regression, compared to 69.23% in good responders and 83.97% in patients without mrTDs (p < 0.001). On multivariable Cox regression, mrTD regression grade was the only independent MRI factor associated with DFS (p = 0.042). CONCLUSIONS: Diagnostic performance of ymrTDs was moderate. The mrTD regression grade was independently correlated with DFS, which may have a prognostic implication for treatment and follow-up. CLINICAL RELEVANCE STATEMENT: Patients with poor regression of MRI-detected tumor deposits may benefit from more aggressive treatments, such as chemoradiation therapy plus induction or consolidation chemotherapy. KEY POINTS: • MRI provides a preoperative and noninvasive way to visualize tumor deposits (TDs) after neoadjuvant chemoradiotherapy (nCRT). • Post-nCRT MRI-detected TDs are a poor prognostic marker in cT3 and cT4 rectal cancer patients. • The regression of MRI-detected TDs after nCRT is associated with an improved disease-free survival.

Dictionary learning LASSO for feature selection with application to hepatocellular carcinoma grading using contrast enhanced magnetic resonance imaging.

Introduction: The successful use of machine learning (ML) for medical diagnostic purposes has prompted myriad applications in cancer image analysis. Particularly for hepatocellular carcinoma (HCC) grading, there has been a surge of interest in ML-based selection of the discriminative features from high-dimensional magnetic resonance imaging (MRI) radiomics data. As one of the most commonly used ML-based selection methods, the least absolute shrinkage and selection operator (LASSO) has high discriminative power of the essential feature based on linear representation between input features and output labels. However, most LASSO methods directly explore the original training data rather than effectively exploiting the most informative features of radiomics data for HCC grading. To overcome this limitation, this study marks the first attempt to propose a feature selection method based on LASSO with dictionary learning, where a dictionary is learned from the training features, using the Fisher ratio to maximize the discriminative information in the feature. Methods: This study proposes a LASSO method with dictionary learning to ensure the accuracy and discrimination of feature selection. Specifically, based on the Fisher ratio score, each radiomic feature is classified into two groups: the high-information and the low-information group. Then, a dictionary is learned through an optimal mapping matrix to enhance the high-information part and suppress the low discriminative information for the task of HCC grading. Finally, we select the most discrimination features according to the LASSO coefficients based on the learned dictionary. Results and discussion: The experimental results based on two classifiers (KNN and SVM) showed that the proposed method yielded accuracy gains, compared favorably with another 5 state-of-the-practice feature selection methods.

[Adenovirus mediated gene transfer of tyrosinase gene on HepG2 cell by magnetic resonance imaging].

OBJECTIVE: To evaluate the transfect results of recombinant adenovirus vector carrying tyrosinase gene (Ad-tyr) in vitro by magnetic resonance imaging (MRI) after the Ad-tyr was transfected into HepG2 cell. METHODS: The Ad-tyr which carried the full-length cDNA of tyrosinase gene was transfected into HepG2 cell. The transfected cells were scan by MRI sequences of T1 weighted image (T1WI) , T2 weighted image (T2WI) , and short time inversion recovery (STIR) to observe the MRI signals of expressed melanin. Masson-Fontana staining was performed to search for melanin granules in transfected cells. Real-time PCR method was used to search for cDNA of tyrosinase gene. RESULTS: Ad-tyr was transfected into HepG2 cells and synthesized a large amount of melanin inside. The synthesized melanin of 1 x 10(6) cells which had been transfected by Ad-tyr with the 50, 150, and 300 multiplicity of infection separately were all sufficient to be detected by MRI and showed high signals in MRI T1WI, T2WI, and STIR sequences. The signal intensities of MRI were positively correlated to the amounts of transfected Ad-tyr. The melanin granules were found in HepG2 cells in Masson-Fontana staining. The cDNA amount of tyrosinase gene in transfected HepG2 cells, which was detected by real-time PCR, was remarkably higher than that in nontransfected cells. CONCLUSION: The synthesized melanin of HepG2 cells, which controlled by expression of exogenous gene, can be detected by MRI, indicating that the adenovirus vector can efficiently carry the tyrosinase gene into HepG2 cells.

[Value of magnetic resonance imaging in displaying the parotid gland segments of the facial nerve].

OBJECTIVE: To evaluate the value of magnetic resonance imaging (MRI) in displaying the parotid gland segments of the facial nerve. METHODS: Sixteen volunteers (9 males and 7 females) and 132 surgically confirmed patients with parotid tumors locating in the deep or shallow lobe of the parotid gland (including 89 with benign and 43 with malignant tumors) underwent MRI using T1WI and T2WI. The transverse images were obtained with the plane tilted 35 degrees to the foot, and the coronal images were acquired using conventional scanning. RESULTS: On transverse T1WI, the parotid gland segments of the facial nerve displayed low signal with arc-shaped curve in the cross-section, showing a symmetrical dot-like low signal in the coronal plane. The facial nerve in 63% of the patients with parotid tumors in the cross-section could be displayed, but in the coronal plane the proportion reached 83%. MRI could accurately reveal the position of the parotid tumors in the deep or shallow lobe of the parotid gland. CONCLUSION: MRI can show the major portion of the parotid gland segments of the facial nerve and has important value in locating the parotid tumors and displaying the relationship between the tumor and facial nerve.

[Magnetic resonance imaging for diagnosis of parotid malignant tumors and the pathological basis].

OBJECTIVE: To investigate magnetic resonance imaging (MRI) features of parotid malignant tumors and study their pathological basis. METHODS: Forty-seven patients with parotid malignant tumors confirmed by surgery (41 patients) or biopsy (6 patients) were enrolled in this study. A comparative analysis was conducted of the pathological and MRI findings in 30 patients with the entire lesions available. Each of the MRI features was analyzed retrospectively and the typical MRI findings of common parotid malignant tumors were summarized. RESULTS: MRI allowed accurate diagnosis of parotid malignant tumors. Four patients with low-grade mucoepidermoid carcinoma showed well-defined tumor margin and were difficult to distinguish from benign tumors. Six patients with high-grade mucoepidermoid carcinoma had obscure margin of the tumor which easily underwent necrosis with liable lymph node involvement. The 8 cases of adenoid cystic carcinoma was characterized by extensive invasion surrounding the parotid gland. Most of 8 cases of malignant pleomorphic adenoma still showed high and heterogeneous signal on T2WI, with irregular shape and poorly defined margin. Nine cases of lymphoma all had secondary lesions characterized by extensive involvement and presence of multiple nodules. The 4 cases of acinic cell carcinoma showed either regular or irregular tumor morphology, presenting with high signal intensity on T1WI and T(2)WI. CONCLUSION: MRI is an important modality for the diagnosis of parotid malignant tumors. Most of the common parotid malignant tumors have characteristic MRI and pathological features, which make possible their differential diagnosis.

[MRI performance and diagnosis of schwannomas from cranial nerves in posterior cranial fossae].

BACKGROUND & OBJECTIVE: Cranial nerve schwannomas originate frequently in posterior cranial fossae and have various and complex MRI performances, some of which are still not well known. This study was to explore MRI performances and features of schwannomas from cranial nerves in posterior cranial fossae. METHODS: The MRI performances of 75 cases of schwannoma from cranial nerves in posterior cranial fossae, including trigeminal (n=9), facial (n=1), acoustic (n=53), 9th-11th (n=9) and hypoglossal (n=3) schwannomas, confirmed by surgical and pathologic findings, were analyzed retrospectively. RESULTS: Most of schwannomas in posterior cranial fossae were solid-cystic lesions when their sizes were larger than 1.5 cm in diameter. Small lesions (less than 1.5 cm in diameter) may be completely solid, which were closely related to cranial nerves. On T1WI, the solid part of tumor appeared iso- or slightly hypointense, while cystic part was hypointense. On T2WI, solid part appeared high or slightly high signal intensity, but cystic part appeared very high signal intensity. On contrast-enhanced T1WI, there was obvious enhancement in the solid part, but not in the cystic part. Some typical signs were very useful to infer tumor origin, such as, dumbbell-shaped trigeminal schwannoma extended across the middle and posterior cranial fossa, enlargement of internal auditory canal, widened jugular foramen and hypoglossal foramen caused by acoustic schwannoma, the 9th-11th shcwannoma, and hypoglossal schwannoma, respectively. The correct ratio for qualitative diagnosis of schwannoma was 92% using MRI, but the incorrect ratio for identifying the nerve of tumor origin was 8.7%. CONCLUSION: MRI is a good method in qualitative diagnosis of schwannoma and identifying cranial nerves of tumor origin in posterior cranial fossae.

[Types of liver metastases on MR imaging and characteristics of uncommon types].

BACKGROUND & OBJECTIVE: Although liver metastases are very common, some of them would be misdiagnosed because of their specific appearance on imaging. This study was to summarize the types of liver metastases according to the magnetic resonance imaging (MRI) appearance, and explore the characteristics of uncommon types to improve the accuracy of diagnosis. METHODS: A total of 174 consecutive patients with liver metastases were screened from the patients with diagnosis or suspicion of liver metastases according to plate or enhanced MRI scan. Liver metastases were confirmed through pathologic examination, medical imaging, or follow-up. Lesions were categorized as nodular, segment, and diffusion classes by shape, and categorized as common, mimicking hemangioma, and mimicking cyst patterns according to the characteristics of signal intensity. RESULTS: Common primary tumors of liver metastases were colon and rectum carcinomas (31.0%). According to the shape of lesions, the proportions of nodular, segment, and diffusion classes were 96.6%, 2.3%, and 1.1%, respectively. According to the characteristics of signal intensity, the proportions of common, mimicking hemangioma, and mimicking cyst patterns were 87.9%, 4.0%, and 8.1%, respectively. CONCLUSIONS: Most liver metastases are nodular in shape, and present as common pattern, but some uncommon types also exist. MRI scan and clinical follow-up could increase the accuracy of diagnosis.

[Magnetic resonance imaging (MRI) in evaluation of tyrosinase gene expression in HepG2 cell].

BACKGROUND & OBJECTIVE: Gene therapy is the frontier of life science. There is no perfect method to evaluate gene expression without invasion at present. Medical imaging connecting with molecular biology might be helpful; however, the technology is just on the horizon. The authors conducted this study in vitro by transferring reporter tyrosinase gene into HepG2 cell to apply magnetic resonance imaging (MR) for evaluating gene expression. METHODS: The plasmid of pcDNA3tyr carried the full-length cDNA of tyrosinase gene was transfected into HepG2 cell by lipofectin, its property of synthesizing melanin was used to produce high signal in T1WI MR image and then to evaluate gene expression. Further identification were performed with searching melanin granules by Fontana staining and searching cDNA of tyrosinase gene using reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: (1)The melanin granules were found in HepG2 cell using Fontana staining. (2)The cDNA fragment of tyrosinase gene was detectable in transferred HepG2 cell by RT-PCR. (3)Plasmid of pcDNA3tyr was transfected into HepG2 cell and synthesized a large amount of melanin in HepG2 cell; the synthetic melanin appeared high signal in T1WI MR imaging as same as natural melanin and was enough to be detected by MR. And further, the signal intensity was positively related to the amount of transferred plasmid. CONCLUSION: The fact that synthetic melanin of HepG2 cell can be detected by MR demonstrates that medical imaging connecting with molecular biology can be used to evaluate the result of gene expression in vitro.

[MRI performance and diagnosis of meningioma--a report of 126 cases].

BACKGROUND & OBJECTIVE: In MRI study of meningioma, it was lack of large group of patients to evaluate MRI qualitative diagnosis, and no consensus had been achieved concerning problems such as peritumoral edema in meningioma. This study was to summarize main clues for diagnosing meningioma through analyzing MRI performance of 126 patients with meningioma. METHODS: Among 126 patients with meningioma, 32 were syncytial, 35 were fibroblastic, 24 were psammomatous, 9 were angioblastic, 18 were transitional, 3 were papillary, and 5 were malignant. All patients were scanned with T1, T2-weighted imaging (T1WI, T2WI), and contrast-enhanced T1WI. RESULTS: Convexity of brain was more likely to be involved, among 126 cases of meningioma, 45 (35.7%) tumors located at convexity of brain. The size of tumor ranged from 1.4 to 9.9 cm. Eighty-one percent of tumors were round or oval in shape. Isointensity or slight hyperintensity of T2WI signals detected in 70.6% patients. The rates of tail sign, and pseudo-capsule were 62.7%, and 49.2%. Extruding sign of brain parenchyma was observed in 83.8% (57/68)of patients with tumor size of > 4 cm. Significantly even and increasing sign in contrast-enhanced T1WI were observed in 104 patients (82.5%). Peritumoral edema occurred in 57 patients (45.1%), and related to tumor size. Other rare signs included cystic changes, bleeding, calcification, osteal changes, and introtumoral vessel symptoms. The correct rate of diagnosis was 95.2%. CONCLUSIONS: MRI performances of meningioma are various. Judgment of extra-brain tumor, typical T2WI signals, tail sign, and significantly even and increasing sign are key factors for diagnosing meningioma.

[Value of manifestations of magnetic resonance imaging (MRI) in diagnosis of parotid tumors and their pathological bases].

BACKGROUND & OBJECTIVE: The pathologic types of parotid tumor are very complicated and the advantage of magnetic resonance imaging (MRI) in diagnosis of these tumors is very obvious; however, there is not still accordance at several areas of MRI diagnosis of them. A large amount of cases are needed for analyzing these MRI features and their pathological fundament. This study was conducted to summarize the MRI manifestations of common benign and malignant tumors and to explore the value of the morphological features of MRI in histological diagnosis of parotid tumor. METHODS: The MRI manifestations for 132 cases(140 lesions) of parotid tumor/lesion were collected, including 89 benign tumors/lesions and 43 malignant tumors. Of them, 112 cases were proved by surgery, 17 cases by biopsy, and 3 cases by clinic observation. MRI features were completely compared with pathological results of surgical samples slice by slice in 58 cases. T(1)WI and T(2)WI sequence were used in MRI unenhancement scan; 108 cases (115 lesions) were examined with both unenhancement and enhancement. Chi-square test was used for statistic analysis. RESULTS: (1) The MRI features of common parotid benign tumors were as following: 40 cases of Warthin's tumors enhanced slightly and more than half of them (25 cases) appeared low or equal signal intensity in T(2)WI; 22 cases of pleomorphic adenoma appeared high and unhomogeneous signal intensity in T(2)WI; 5 cases of hemangioma were characterized by their vascular structures which were enlarged than normal; 3 cases of lymphangioma not only appeared specially irregular shape but also surrounded adjacent structures of parotid gland (3 cases). The features of 4 cases of parotid lipoma were same as those in other position of the body.(2) The MRI features of common parotid malignant tumors were as following: 8 cases of malignant pleomorphic adenoma appeared high and unhomogeneous signals in T(2)WI together with irregular shape and ill-defined margin; 7 cases of adenoid cystic carcinoma characterized by invasion of very large range surrounding parotid gland. In 8 cases of malignant mucoepidermoid carcinoma, 3 cases showed low-grade malignant mucoepidermoid carcinomas, which had well-defined margin and were difficult to distinguish from benign tumor. However, 5 cases of high-grade malignant mucoepidermoid carcinoma showed ill-defined margin, their features were tend to undergo necrosis and invade lymph node; 9 cases of lymphomas were all secondary lesions and there were two characters in their imaging, one was the wide involved range, the other was they consisted of several nodes. The shapes of 3 cases acinic cell carcinoma could be either regular or irregular, the cystic areas could be found in them with high signal intensity both on T(1)WI and T(2)WI. CONCLUSION: There are certain characters for each of common benign and malignant parotid tumors in MRI and these may be helpful for histological diagnosis in most of them.