Diagnostic value of gadolinium-enhanced dynamic MR imaging for parotid gland tumors

Objective

This study aimed to evaluate the value of gadolinium-enhanced dynamic MR imaging for differentiating benign and malignant parotid gland tumors, and for characterizing the various histological types.

Patients and methods

Non-enhanced T1-weighted (T1-W), fat-suppressed T2-weighted (T2-W), and gadolinium-enhanced fat-suppressed dynamic T1-weighted images were obtained preoperatively in 27 patients (28 parotid gland tumors), by using a 1.5 or 3 T MR imaging unit (GE, Signa Exite). The tumor margins and the enhancement curve patterns on dynamic MR imaging were analyzed. All patients underwent a parotidectomy with histopathologic analysis.

Results

Pleomorphic adenomas depict a gradual enhancement pattern. Warthin’s tumors depict an early peak of enhancement and a high washout pattern. Malignant tumors depict an early peak of enhancement and a low washout pattern.

Conclusion

Gadolinium-enhanced dynamic MR imaging improved the performance of MR imaging in differentiating benign from malignant parotid gland tumors and characterizing the different histological types of benign tumors.     

磁共振波谱及扩散加权成像在唾液腺肿瘤诊断中的价值

目的 回顾性分析、评价氢质子磁共振波谱(~1H-MRS)及扩散加权成像(DWI)在鉴别唾液腺良性或恶性肿瘤中的价值.资料与方法 应用1.5 TMR成像仪,对39例唾液腺肿瘤患者进行常规MRI、DWI及~1H-MRS检查,(1)DWI采用单次激发自旋回波一回波平面成像(SE-EPI)序列,扩散敏感系数(b值)为0 s/mm~2及1000 s/mm~2,并计算每例患者平均表观扩散系数(ADC)值和高、中、低ADC值所占的比例,(2)~1H-MRS采用单体素点分辨表面线圈(PRESS)序列,TR 1500 ms,TE 136 ms,在谱线中计算胆碱与肌酸的比值(Cho/Cr).最后与肿瘤的组织病理学结果进行对比,进行非参数秩和检验.结果 39例唾液腺肿瘤患者均获得了满意的检查结果,其中良性肿瘤31例(混合瘤21例,腺淋巴瘤10例),恶性肿瘤8例(腺囊腺癌3例、黏液表皮样癌3例、混合腺癌1例、恶性淋巴瘤1例).(1)DWI:ADC图提示良性肿瘤与恶性肿瘤的平均ADC值分别为(1.65±0.41)×10~(-3)mm~2/s和(1.15±0.39)×10~(-3) mm~2/s,其间无明显差异,但良性肿瘤ADC值增高的区域则明显多于恶性肿瘤,尤其是混合瘤.(2)~1H-MRS:在TE为136 ms时共获得满意的波谱曲线35例,计算得出恶性肿瘤、腺淋巴瘤、混合瘤的Cho/Cr分别为1.69±0.51、5.89±1.42、2.81±0.72,恶性肿瘤、腺淋巴瘤、混合瘤之间均存在显著差异.结论 DWI及~1H-MRS可以作为鉴别唾液腺肿瘤的特异性检查手段,但仍需要大量研究样本来进行验证.     

Warthin tumor of the parotid gland: diagnostic value of MR imaging with histopathologic correlation

BACKGROUND AND PURPOSE: The purpose of our study was to describe the MR imaging appearance of Warthin tumors multiple MR imaging techniques and to interpret the difference in appearance from that of malignant parotid tumors. METHODS: T1-weighted, T2-weighted, short inversion time inversion recovery, diffusion-weighted, and contrast-enhanced dynamic MR images of 19 Warthin tumors and 17 malignant parotid tumors were reviewed. MR imaging results were compared with those of pathologic analysis. RESULTS: Epithelial stromata and lymphoid tissue with slitlike small cysts in Warthin tumors showed early enhancement and a high washout rate (> or =30%) on dynamic contrast-enhanced images, and accumulations of complicated cysts showed early enhancement and a low washout ratio (< 30%). The areas containing complicated cysts showed high signal intensity on T1-weighted images, whereas some foci in those areas showed low signal intensity on short tau inversion recovery images. The mean minimum signal intensity ratios (SIRmin) of Warthin tumor on short tau inversion recovery (0.29 +/- 0.22 SD) (P < .01) and T2-weighted images (0.28 +/- 0.09) (P < .05) were significantly lower than those of malignant parotid tumors (0.53 +/- 0.19, 0.48 +/- 0.19). The average washout ratio of Warthin tumors (44.0 +/- 20.4%) was higher than that of malignant parotid tumors (11.9 +/- 11.6%). The mean apparent diffusion coefficient of Warthin tumors (0.96 +/- 0.13 x 10(-3)mm2/s) was significantly lower (P < .01) than that of malignant tumors (1.19 +/- 0.19 x 10(-3)mm2/s). CONCLUSION: Detecting hypointense areas of short tau inversion recovery and T2-weighted images or low apparent diffusion coefficient values on diffusion-weighted images was useful for predicting whether salivary gland tumors were Warthin tumors. The findings of the dynamic contrast-enhanced study also were useful.     

Diagnostic value of dynamic magnetic resonance imaging for salivary gland diseases: a preliminary study

OBJECTIVES: To determine the diagnostic value of dynamic MR imaging for the differentiation between benign tumours, malignant tumours, and inflammatory lesions in the major salivary glands. METHODS: T1- and T2-weighted spin-echo and dynamic gadolinium-enhanced T1-weighted spin-echo imaging sequences were performed in 27 patients (28 salivary gland lesions). The enhancement curve patterns and tumour margins on dynamic MR imaging were analysed. RESULTS: All pleomorphic adenomas showed a continuous gradual or rapid increase in the enhancement pattern, whereas other benign tumours had a rapid or gradual enhancement-attenuation pattern. Malignant tumours generally showed a gradual enhancement-attenuation pattern. Inflammatory lesions showed a rapid or gradual enhancement-attenuation pattern. A well-defined margin was observed in all 13 (100%) benign tumours and three of six (50%) malignant tumours. CONCLUSIONS: Our study suggests that dynamic curve patterns and tumour margin appearance may help to differentiate between benign tumours, malignant tumours and inflammatory lesions.     

Salivary gland tumors at in vivo proton MR spectroscopy

PURPOSE: To prospectively evaluate whether proton magnetic resonance (MR) spectroscopy can be used to characterize salivary gland tumors (SGTs). MATERIALS AND METHODS: Ethics committee approval and informed consent were obtained. Hydrogen 1 ((1)H) MR spectroscopy was performed with echo times of 136 and 272 msec at 1.5 T in both SGTs and normal parotid glands. Spectra were analyzed in the time domain by using prior knowledge in the fitting procedure to obtain peak amplitudes of choline (Cho), creatine (Cr), and unsuppressed water. Mean Cho/Cr and Cho/water ratios for each subgroup of SGTs were obtained, and results were compared by using a nonparametric t test. RESULTS: Successful spectra were acquired in 56 patients (35 men, 21 women; mean age, 56 years) with a total of nine malignant tumors and 47 benign SGTs (24 Warthin tumors, 22 pleomorphic adenomas, one oncocytoma). At an echo time of 136 msec, Cho/Cr ratios were obtained in 26 (47%) of 55 spectra, with a mean value (+/- standard deviation) of 1.73 +/- 0.47, 5.49 +/- 1.86, 3.46 +/- 0.84, and 2.45 for malignant tumors, Warthin tumors, pleomorphic adenomas, and oncocytoma, respectively. Differences were significant between Warthin tumors and pleomorphic adenomas (P = .028) and between benign SGTs and malignant tumors (P < .001). At an echo time of 272 msec, Cho/Cr ratios were obtained in 16 (30%) of 53 spectra, with a mean value of 2.27 +/- 0.69, 6.92 +/- 1.47, and 3.67 +/- 1.23 for malignant tumors, Warthin tumors, and pleomorphic adenomas, respectively. Differences were also significant between Warthin tumors and pleomorphic adenomas (P = .041) and benign SGTs and malignant tumors (P = .004). There was a significant difference in mean Cho/water ratio for Warthin tumors versus pleomorphic adenomas at echo times of 136 msec (P = .003) and 272 msec (P = .002) but not for benign SGTs versus malignant tumors. CONCLUSION: (1)H MR spectroscopy may be used to characterize SGTs, but a larger study is required to validate these initial results.     

3.0T MR动脉自旋标记对腮腺肿瘤的鉴别诊断价值

目的:初步探讨3.0T磁共振动脉自旋标记技术(ASL)对腮腺肿瘤的鉴别诊断价值。方法:前瞻性搜集2017年3月-2020年1月因腮腺肿物于本院就诊及治疗的患者作为研究对象,所有研究对象均行常规MR平扫及ASL扫描,测量ASL序列图像上肿瘤组织的肿瘤血流量(TBF),并将计算出的标准化肿瘤血流量(nTBF)与病理结果进行对比分析。结果:本研究总共纳入45例经术后病理证实的腮腺肿瘤患者。其中良性肿瘤28例,包括腺淋巴瘤14例,多形性腺瘤14例;恶性肿瘤共17例。测量并经计算得出腺淋巴瘤、多形性腺瘤、恶性腮腺肿瘤的nTBF分别为:3.71±1.65、0.89±0.25、1.55±0.60。腺淋巴瘤的nTBF明显高于多形性腺瘤(P<0.01)和恶性肿瘤(P<0.01),但是多形性腺瘤和恶性肿瘤的nTBF差异无统计学意义(P=0.073)。ASL能将腮腺腺淋巴瘤从多形性腺瘤及恶性肿瘤中鉴别出来,但是无法鉴别多形性腺瘤与恶性肿瘤。ASL诊断腮腺腺淋巴瘤的ROC曲线下面积为0.935,nTBF的诊断阈值为2.03,诊断腺淋巴瘤的敏感度和特异度分别为92.9%、93.5%。结论:3.0T MR ASL技术可以无创地、定量地评价腮腺肿瘤的TBF,并对腺淋巴瘤的诊断和鉴别诊断具有较高的价值。     

Oncocytoma: the vanishing parotid mass

Parotid gland oncocytoma is an uncommon, benign salivary neoplasm composed of mitochondria-rich oncocytes. The purpose of this study was to correlate MR imaging and histopathology of parotid gland oncocytomas and to define the features that may distinguish these neoplasms from other benign and malignant parotid gland tumors. The MR imaging features in 9 patients with a pathologic diagnosis of oncocytoma were retrospectively reviewed. The imaging features were strikingly similar for 8 of the 9 patients. All lesions appeared T1 hypointense but isointense to the native parotid gland on fat-saturated T2 and postcontrast T1 imaging. On MR imaging, parotid gland oncocytomas share specific imaging characteristics that have not been described for benign or malignant parotid gland tumors. Oncocytomas are isointense to native parotid gland on fat-saturated T2 and T1 postcontrast MR images. Preoperative identification of correct histology may help surgical planning.     

Inter- and intratumoral variability in magnetic resonance imaging of pleomorphic adenoma: an attempt to interpret the variable magnetic resonance findings

OBJECTIVES: The purpose of our study was to describe the various magnetic resonance (MR) findings of pleomorphic adenoma and to interpret these findings. METHODS: MR studies of 33 pleomorphic adenomas and 13 malignant tumors in the major salivary glands were reviewed. RESULTS: High signal intensity on short-inversion-time inversion recovery (STIR) and T2-weighted (T2W) images, progressive enhancement on dynamic MR images, and high apparent diffusion coefficient (ADC) values on diffusion-weighted (DW) images reflected myxoid-dominant components in pleomorphic adenomas. Hypercellularity with less-myxoid stroma showed reduced signal intensity on STIR and T2W images and also reduced ADC values on DW images, and the peak of time versus signal intensity curves (TICs) was reached earlier on dynamic MR images. CONCLUSIONS: The MR images of hypercellularity components in pleomorphic adenoma overlap with those of malignant parotid tumors. Detecting myxoid components by STIR, T2W, DW, and dynamic MR images is useful for predicting whether salivary gland tumors are pleomorphic adenoma or not.     

Malignant parotid tumors: clinical use of MR imaging and histologic correlation.

Magnetic resonance (MR) imaging was performed in 116 patients in whom a parotid mass lesion was clinically suspected. Eighty-six patients had benign disease. The 30 patients in whom a malignant tumor was found were further evaluated. To determine which features are characteristic of malignant parotid tumors, spin-echo T1- and T2-weighted images of malignant lesions in the parotid gland were compared with those of benign disease. In our series, tumor margins, homogeneity, or signal intensity were not discriminative factors to correctly predict benign or malignant disease. Infiltration into deep structures (eg, the parapharyngeal space, muscles, and bone) was observed only in malignant tumors. Infiltration into subcutaneous fat was noticed in malignant as well as in inflammatory disease. No statistically significant correlation was found between tumor grade and MR imaging features in malignant disease. MR imaging is useful in delineating malignant tumors but is unreliable in correctly predicting the histologic nature of a mass lesion in the parotid gland.     

Salivary gland tumors of the parotid gland: CT and MR imaging findings with emphasis on intratumoral cystic components

Introduction

The purpose of this study was to assess computed tomography (CT) and magnetic resonance (MR) imaging findings of salivary gland tumors of the parotid gland with emphasis on intratumoral cystic components.

Methods

Seventy-two histopathologically confirmed salivary gland tumors of the parotid gland (44 benign and 28 malignant), which underwent both CT and MR imaging including contrast-enhanced study, were included in this study. We retrospectively reviewed images for the presence, number, occupying rate, margin characteristics, distribution, and predominant MR signal intensity of intratumoral cystic components.

Results

The prevalence of cystic components was greater in malignant than benign tumors (79 vs. 50 %, p?p?p?p?p?p?p?Conclusion Imaging features of intratumoral cystic components may help to differentiate benign from malignant tumors of the parotid salivary gland.     

Parotid gland: plain and gadolinium-enhanced MR imaging

The purpose of this study was to show the typical appearance of lesions of the parotid gland with plain MR imaging and MR imaging enhanced with gadopentetate dimeglumine. Seventeen patients with inflammatory changes and 43 with benign and malignant tumors were studied. The examinations were carried out with plain T1-weighted sequences with a repetition time (TR) of 500 msec and an echo time (TE) of 25 msec (TR/TE = 500/25), T2-weighted sequences (1,600/90), and gadolinium-enhanced T1-weighted sequences in axial, coronal, and sagittal orientations. For identifying normal anatomic structures such as the facial nerve and the main duct, the administration of gadopentetate dimeglumine was helpful. In inflammatory changes, gadolinium-enhanced images showed no diagnostic advantages. Gadopentetate dimeglumine proved helpful in delineating tumorous lesions and in differentiating benign and malignant lesions. However, an exact differentiation of the different histologic types was not possible. Post-operative fibrosis could be differentiated from recurrent tumors after administration of gadolinium. If a question regarding infiltration or definition of the boundaries of a lesion cannot be answered with non-enhanced MR imaging, gadopentetate dimeglumine administration is advised. However, for routine imaging of the parotid gland, its use is not recommended.     

Minor salivary gland tumors in the oral cavity: diagnostic value of dynamic contrast-enhanced MRI

Objective

To evaluate the diagnostic value of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for minor salivary gland tumors in the oral cavity.

Materials and methods

Thirty-two patients with minor salivary gland tumors were examined preoperatively using DCE-MRI. Their maximum contrast index (CImax), time of CImax (Tmax), Tpeak; i.e., the time that corresponded to the CImax × 0.90, and washout ratios (WR300 and WR600) were determined from contrast index (CI) curves. We compared these parameters between benign and malignant tumors and among the different histopathological types of minor salivary gland tumors. Then, we categorized the patients’ CI curves into four patterns (gradual increase, rapid increase with high washout ratio, rapid increase with low washout, and flat).

Results

Statistically significant differences in Tmax (P = 0.004) and Tpeak (P = 0.002) were observed between the benign and malignant tumors. Regarding each histopathological tumor type, significant differences in Tmax (P < 0.001), Tpeak (P < 0.001), and WR600 (P = 0.026) were observed between the pleomorphic adenomas and mucoepidermoid carcinomas. It was difficult to distinguish between benign and malignant tumors using our CI curve classification because that two-thirds of the cases were classified into the same type (gradual increase).

Conclusion

The DCE-MRI parameters of minor salivary gland tumors contributed little to their differential diagnosis compared with those for major salivary gland tumors. During the diagnosis of minor salivary gland tumors, Tmax is useful for distinguishing between benign and malignant tumors.     

Characterization of adrenal masses using MR imaging with histopathologic correlation.

OBJECTIVE: The purpose of this study was to evaluate the sensitivity, specificity, and accuracy of MR imaging in the characterization of adrenal masses by correlating imaging findings with histopathologic results. In addition, adrenal tumors that were of an indeterminate nature on MR imaging were analyzed. SUBJECTS AND METHODS: For 114 patients with 134 adrenal masses, MR findings were compared with histologic results. In all patients, MR imaging was performed using T2-weighted fast spin-echo imaging and unenhanced and gadolinium-enhanced T1-weighted spin-echo imaging. Chemical-shift imaging was performed in 92 patients and dynamic gadolinium-enhanced studies in 108 patients. Chemical-shift images were analyzed quantitatively and qualitatively, and dynamic gadolinium-enhanced studies were qualitatively assessed. RESULTS: The sensitivity of MR imaging in differentiating between benign and malignant adrenal masses was 91%, the specificity was 94%, and the accuracy was 93%. The diagnosis at MR imaging differed from that at histology in 12 (9%) of 134 patients. Results of quantitative analyses of chemical-shift imaging techniques showed significant differences between adenomas and nonadenomas (-36.0% versus -3.7%; p < .001). Qualitative analysis provided a similar diagnostic confidence compared with quantitative analysis. Both chemical-shift and dynamic gadolinium-enhanced studies proved to be unreliable in characterizing borderline tumors (epithelial tumors with high malignant potential). Moreover, such imaging failed to allow correct diagnosis of adenomas in two patients. CONCLUSION: The characterization of an adrenal mass can be made with high sensitivity and specificity using MR imaging. The increased reliance on MR imaging seems to be based mainly on findings from chemical-shift and dynamic gadolinium-enhanced studies. The need to perform histologic sampling of incidentally discovered adrenal masses may be reduced to some problematic lesions, which will remain during the era of MR imaging.     

Multiparametric magnetic resonance imaging for the differentiation between benign and malignant salivary gland tumors

Purpose:

To evaluate the stepwise approach in differentiating between benign and malignant salivary gland tumors using time‐intensity curves (TICs) and apparent diffusion coefficients (ADCs).

Materials and Methods:

TICs and ADCs were analyzed on the tumor‐by‐tumor (overall) and pixel‐by‐pixel (TIC and ADC maps) bases in patients with benign (n = 52) or malignant (n = 18) salivary gland tumor. TICs were categorized into Types 1 (<20% increment ratio), 2 (≥20% increment ratio and >120 sec peak time), 3 (≥20% increment ratio, ≤120 sec peak time, and <30% washout ratio), or 4 (≥20% increment ratio, ≤120 sec peak time, and ≥30% washout ratio). ADCs were classified as extremely low (<0.6 × 10^?3 mm²/sec), low (<1.2), intermediate (<1.8), or high (≥1.8).

Results:

Malignant tumors had small (<30%) areas with Type 1 TIC with one of the following magnetic resonance imaging (MRI) characteristics: Type 3 overall TIC patterns, Type 4 overall TIC patterns and extremely low (<0.60 × 10^?3 mm²/sec) overall ADCs, or Type 2 overall TIC patterns and large (>40%) areas with low or extremely low ADCs.

Conclusion:

We propose a stepwise approach by using multiparametric MRI techniques as an effective tool for differentiating between benign and malignant salivary gland tumors J. Magn. Reson. Imaging 2010;31:673–679. © 2010 Wiley‐Liss, Inc.

     

Salivary gland tumors: evaluation with two-phase helical CT

PURPOSE: To evaluate two-phase helical computed tomography (CT) in the characterization of salivary gland tumors. MATERIALS AND METHODS: Sixty-four patients with major salivary gland tumors underwent two-phase helical CT. The histopathologic diagnosis was obtained by means of surgical resection or biopsy in all patients. After the injection of 90 mL of contrast material at a rate of 3 mL/sec, helical CT scans were obtained at early and delayed phases with scanning delays of 30 and 120 seconds, respectively. The attenuation change and enhancement patterns in the tumors were assessed. The attenuation change in the tumor also was assessed quantitatively as the ratio of the CT number (in Hounsfield units) at delayed phase scanning to that at early phase scanning. RESULTS: There were 35 pleomorphic adenomas, nine Warthin tumors, and 20 malignant tumors. Two-phase helical CT showed increase in attenuation in 30 (86%) pleomorphic adenomas, decrease in eight (89%) Warthin tumors, and increase in 11 (55%) and no change in eight (40%) malignant tumors at delayed phase scanning. A multinodular enhancement pattern was found in only 12 (34%) pleomorphic adenomas. The ratio of CT numbers was significantly different between Warthin tumors and pleomorphic adenomas and between Warthin tumors and malignant tumors. CONCLUSION: The analysis of enhancement patterns by using two-phase helical CT will be helpful in the differential diagnosis of salivary gland tumors.     

Apparent diffusion coefficient mapping of salivary gland tumors: prediction of the benignancy and malignancy

BACKGROUND AND PURPOSE: Preoperative prediction of tumor malignancy is clinically very important, because this information strongly influences the surgical plan. We evaluate the preoperative apparent diffusion coefficient (ADC) maps of benign and malignant salivary gland tumors. MATERIALS AND METHODS: High-resolution MR imaging was performed on 31 patients with benign or malignant salivary gland tumors; ADC maps of the tumors were also obtained. Surface coils of 47 or 110 mm diameter were used to improve the image resolution. The ADCs were compared with histologic features of the excised tumors. RESULTS: The ADC maps effectively depicted the histologic features of the salivary gland tumors, such as presence of cancer cells, myxomatous tissues, fibrosis, necrosis, cyst formation, and lymphoid tissues. The ADC maps showed that more frequent areas with high ADCs (> or = 1.8 x 10(-3) mm(2)/s) were significantly greater in benign tumors than in malignant tumors. The sensitivity and specificity for high ADC occupying fewer than 5% of the area of a tumor was 89% and 100%, respectively, resulting in 97% accuracy, 100% positive predictive value, and 96% negative predictive value. CONCLUSION: The ADC may provide preoperative tissue characterization of the salivary gland tumors.     

MR imaging of salivary duct carcinoma

BACKGROUND AND PURPOSE: Salivary duct carcinoma (SDC) is regarded as a high-grade malignancy in the current classification of salivary gland neoplasms. The aim of our study was to describe the MR imaging features of SDC. METHODS: Nine patients with SDC underwent MR imaging study. The apparent diffusion coefficient (ADC) values of SDCs were measured from diffusion-weighted images. Time-signal intensity curves (TICs) of the tumors on dynamic MR images were plotted, and washout ratios were also calculated. TICs were divided into four types: type A, curve peaks <120 seconds after administration of contrast material with high washout ratio (> or =30%); type B, curve peaks <120 seconds with low washout ratio (<30%); type C, curve peaks >120 seconds; type D, nonenhanced. We correlated the MR findings of SDC with the pathologic findings. RESULTS: All tumors had ill-defined margins and showed low to moderately high signal intensity for contralateral parotid gland on T2-weighted images. The average of the ADC values of the SDCs was 1.16 +/- 0.14 [SD] x 10(-3)mm(2)/s. Seven of nine (78%) tumors had type B enhancement. On the other hand, six of nine (67%) tumors with rich fibrotic tissue also had type C enhancement. CONCLUSION: The findings of ill-defined margin, early enhancement with low washout ratio (type B), and low ADC value (1.22 x 10(-3)mm(2)/s) were useful for suggesting malignant salivary gland tumors. Although it was reported that type C enhancement was specific for pleomorphic adenoma, SDC frequently has type C-enhanced focus.     

Differentiation of soft tissue benign and malignant peripheral nerve sheath tumors with magnetic resonance imaging

PURPOSE: The objective of this study was to differentiate the magnetic resonance (MR) imaging appearance of benign peripheral nerve sheath tumors (PNSTs) from that of malignant PNSTs. MATERIALS AND METHODS: Twenty-six patients who underwent MR imaging and had a histologic diagnosis of benign (schwannoma, n=16; neurofibroma, n=1) or malignant (n=9) PNST were retrospectively reviewed. The size, location, shape, margin, and signal intensities of the tumors on precontrast and gadolinium-enhanced MR imaging were analyzed. In each patient, the presence or absence of split fat, target, and fascicular signs was determined. RESULTS: The mean size of the benign PNSTs (3.4 cm, S.D.=2.5 cm) was significantly smaller than that of the malignant tumors (8.2 cm, S.D.=3.1 cm) (P<.001). Seventeen (65.4%) of the 26 tumors were spindle shaped or ovoid (12 benign and 5 malignant tumors). Contiguity with specific nerves was identified in 15 (88.2%) of the 17 benign PNSTs but in none of the malignant tumors (P<.05). Well-defined margins were noted in all 17 benign PNSTs but in only 3 (33.3%) of the 9 malignant tumors (P<.001). Five (55.6%) of the 9 malignant PNSTs but none of the benign tumors showed signal intensity change in adjacent soft tissue (P<.05). There was no significant difference in signal intensity between the benign and malignant tumors on T(1)-weighted, T(2)-weighted, and contrast-enhanced MR images. The split fat and target signs were present more frequently in the benign PNSTs than in the malignant PNSTs (P<.05).Conclusions: Benign and malignant PNSTs are often spindle shaped. Recognition of contiguity with adjacent nerves, a well-defined margin, and the presence of the split fat sign may suggest benignity. Imaging features suggestive of malignancy can be a larger size and an infiltrative margin.     

Ovarian lesions: detection and characterization with gadolinium-enhanced MR imaging at 1.5 T

Magnetic resonance (MR) imaging for detection and characterization of ovarian masses was assessed in 33 patients with a total of 60 lesions. Lesions were characterized prospectively as benign or malignant by using T2-weighted MR images and unenhanced and gadolinium-enhanced T1-weighted MR images. MR imaging findings were compared with results of surgical laparotomy performed for staging of lesions. When malignancy was suspected, staging with MR imaging was performed. MR imaging demonstrated 57 of 60 (95%) surgically proved ovarian masses (34 of 36 were benign, 23 of 24 were malignant). Five significant primary criteria and four ancillary criteria for malignancy were established. For all MR pulse sequences combined, characterization of either type of lesion was correct in 84% of cases (48 of 57) when the five primary criteria were used and 95% (54 of 57) were correct when the four ancillary criteria were added. With gadolinium-enhanced images, correct characterization of malignant lesions increased from 56% to 78% with use of the five primary criteria and from 83% to 100% with use of both sets of criteria. Malignancies were correctly staged with MR imaging in 12 of 16 patients. Staging accuracy was 63% with unenhanced images and 75% with the addition of enhanced images.     

MR factor analysis: improved technology for the assessment of 2D dynamic structures of benign and malignant salivary gland tumors

PURPOSE: To establish an MR factor analysis technique for two-dimensional (2D) MR dynamic structures of benign and malignant salivary gland tumors. MATERIALS AND METHODS: Dynamic contrast-enhanced MRI using a surface coil was performed on 36 patients with benign (N = 24) or malignant (N = 12) salivary gland tumors. Signal intensity kinetics in each pixel of the tumors after contrast medium injections were semiautomatically categorized into four patterns (slow uptake, rapid uptake with high washout, rapid uptake with low washout, and flat). The 2D distributions of the kinetic patterns in the tumors were compared with the histological features of the corresponding parts of the excised tumors and with overall kinetics obtained by a conventional analysis. RESULTS: The MR factor analysis technique allowed the pixel-to-pixel evaluation of the contrast enhancement kinetics of the salivary gland tumors. The 2D distributions of the time-intensity curve (TIC) patterns correlated well with the histological features of the salivary gland tumors and allowed more detailed dynamic structures of the tumors compared with the results obtained by the conventional dynamic study analysis. CONCLUSION: The proposed MR factor analysis would be clinically feasible to diagnose salivary gland tumors and tumor-like lesions.