Diffusion-weighted MR imaging sequence in the detection of postoperative recurrent cholesteatoma

PURPOSE: To prospectively evaluate a fast spin-echo (SE) diffusion-weighted sequence for magnetic resonance (MR) imaging of recurrent cholesteatoma in patients who have undergone middle ear surgery. MATERIALS AND METHODS: The study was approved by the institutional review board, and informed consent was obtained from all patients. Twenty-four patients (10 female and 14 male patients; mean age, 44 years) who had undergone resection of cholesteatoma were referred for MR imaging. MR imaging was performed with a 1.5-T unit by using unenhanced diffusion-weighted fast SE imaging at b factors of 0 and 800 sec/mm(2), unenhanced T2-weighted fast SE imaging, unenhanced T1-weighted SE imaging, and delayed contrast material-enhanced T1-weighted imaging. Two radiologists evaluated the diffusion-weighted fast SE images for the presence of a high-signal-intensity cholesteatoma. Results from MR imaging were compared with reports from second- or third-look surgery. Interobserver agreement was assessed with the kappa statistic. RESULTS: A recurrent cholesteatoma was correctly identified in 13 of 14 patients with diffusion-weighted fast SE images obtained with a b factor of 800 sec/mm(2), for a positive predictive value of 93%. In patients without recurrent cholesteatoma, all diffusion-weighted fast SE MR images obtained with a b factor of 800 sec/mm(2) were correctly interpreted as showing no high signal intensity. Thus, the negative predictive value was 100%. Sensitivity and specificity were 100% (13 of 13 patients) and 91% (10 of 11 patients), respectively. Interobserver agreement was excellent (kappa = 0.92). The smallest recurrent cholesteatoma was 5 mm in diameter, and this was correctly detected with the diffusion-weighted fast SE sequence. CONCLUSION: Diffusion-weighted fast SE imaging enables the depiction of recurrent cholesteatoma in patients who have undergone middle ear surgery.     

Diffusion-weighted MR imaging in postoperative follow-up: Reliability for detection of recurrent cholesteatoma

Introduction

Cholesteatoma is a progressively growing process that destroy the neighboring bony structures and treatment is surgical removal. Follow-up is important in the postoperative period, since further surgery is necessary if recurrence is present, but not if granulation tissue is detected. This study evaluates if diffusion-weighted MR imaging alone can be a reliable alternative to CT, without use of contrast agent for follow-up of postoperative patients in detecting recurrent cholesteatoma.

Materials and methods

26 consecutive patients with mastoidectomy reporting for routine follow-up CT after mastoidectomy were included in the study, if there was loss of middle ear aeration on CT examination. MR images were evaluated for loss of aeration and signal intensity changes on diffusion-weighted sequences. Surgical results were compared with imaging findings.

Results

Interpretation of MR images were parallel with the loss of aeration detected on CT for all 26 patients. Of the 26 patients examined, 14 were not evaluated as recurrent cholesteatoma and verified with surgery (NPV: 100%). Twelve patients were diagnosed as recurrent cholesteatoma and 11 were surgically diagnosed as recurrent cholesteatoma (PPV: 91.7%). Four of these 11 patients had loss of aeration size greater than the high signal intensity area on DWI, which were surgically confirmed as granulation tissue or fibrosis accompanying recurrent cholesteatoma.

Conclusion

Diffusion-weighted MR for suspected recurrent cholesteatoma is a valuable tool to cut costs and prevent unnecessary second-look surgeries. It has the potential to become the MR sequence of choice to differentiate recurrent cholesteatoma from other causes of loss of aeration in patients with mastoidectomy.     

Diffusion-weighted MR imaging for detection of extrahepatic cholangiocarcinoma

Objectives

To measure the sensitivity of diffusion-weighted imaging (DWI) and determine the most appropriate b value for DWI; to explore the correlation between the apparent diffusion coefficient (ADC) value and the degree of extrahepatic cholangiocarcinoma differentiation.

Methods

Preoperative diffusion-weighted imaging and magnetic resonance examinations were performed for 31 patients with extrahepatic cholangiocarcinoma. Tumor ADC values were measured, and the signal-to-noise ratio, contrast-to-noise ratio, and signal-intensity ratio between the diffusion-weighted images with various b values as well as the T2-weighted images were calculated. Pathologically confirmed patients were pathologically graded to compare the ADC value with different b values of tumor at different degrees of differentiation, and the results were statistically analyzed by using the Friedman test.

Results

A total of 29 cases of extrahepatic cholangiocarcinoma were detected by DWI. As the b value increased, tumor signal-to-noise ratio and contrast-to-noise ratio between the tumor and normal liver gradually decreased, but the tumor signal-intensity ratio gradually increased. When b = 800 s/mm², contrast-to-noise ratio between tumor and normal liver, tumor signal-intensity ratio, and tumor signal-to-noise ratio of diffusion-weighted images were all higher than those of T2-weighted images; the differences were statistically significant (P < 0.05). As the b value increased, the tumor ADC value gradually declined. As the degree of differentiation decreased, the tumor ADC value declined.

Conclusion

The b value of 800 s/mm² was the best in DWI of extrahepatic cholangiocarcinoma; the lesion ADC value declined as the degree of cancerous tissue differentiation decreased.     

Enhanced four-detector row computed tomography imaging of laryngeal and hypopharyngeal cancers

PURPOSE: Four-detector row computed tomography (4D CT) enables imaging of the larynx and hypopharynx with high temporal resolution and rapid reformatting of coronal planes. The aim of our study was to assess the usefulness of postcontrast biphasic 4D CT in diagnosing tumor extent. METHODS: Forty-seven patients with laryngeal or hypopharyngeal cancer were investigated using 4D CT. Two radiologists retrospectively evaluated transverse and reformatted coronal images in both the early and late phases. RESULTS: Images in the late phase were superior to those in the early phase in the conspicuity of the depicted lesions. The coronal images facilitated assessment of the craniocaudal extension of tumors and obliteration of the paraglottic space. The maximal diameter of tumors tended to be larger on the coronal image than on the transverse image. CONCLUSIONS: Images in the late phase were more informative than images in the early phase to demonstrate tumor extension. Reformatted coronal imaging was useful in evaluating craniocaudal extension.     

Diffusion-weighted MR imaging after angioplasty or angioplasty plus stenting of arteries supplying the brain

BACKGROUND AND PURPOSE: There has been concern regarding the safety of revascularization procedures of vessels supplying the brain vessels because of the risk of cerebral embolization during the procedure. We have observed a high incidence of hyperintense lesions on diffusion-weighted MR images of the brain after stenting at the carotid bifurcation. The hypothesis of this study is that diffusion-weighted MR imaging of the brain can reveal new diffusion abnormalities after angioplasty or angioplasty plus stenting of arteries supplying the brain, other than at the carotid bifurcation. Therefore, we prospectively obtained diffusion-weighted MR images of the brain before and after such revascularization procedures. METHODS: Thirty-seven revascularization procedures were performed in 32 patients. Eleven interventions were performed at the distal internal carotid artery, two at the external carotid artery, two at the common carotid artery, five at the innominate artery, five at the vertebral artery, and 12 at the proximal subclavian artery. Diffusion-weighted MR imaging of the brain was performed before and 24 hours after the procedures. RESULTS: After eight (22%) of 37 procedures, new hyperintensities were visible on the diffusion-weighted MR images. With six of these eight procedures, the hyperintensities occurred in the vascular territory supplied by the treated vessel. In total, 35 new cerebral lesions could be seen, 33 (94%) of which occurred in the vascular territory supplied by the treated vessel. None of the patients in whom new diffusion abnormalities were found had new neurologic symptoms or deficits. No new lesions could be seen after procedures at the subclavian artery. CONCLUSION: Revascularization procedures of arteries supplying the brain were associated with new lesions on the diffusion-weighted MR images of the brain after 22% of the procedures, provided that MR imaging could be performed, indicating the occurrence of cerebral microemboli during such procedures. Diffusion-weighted MR imaging of the brain can be used as a tool to assess the impact of modifications of procedural technique and/or the use of cerebral protection devices on the occurrence of such lesions.     

Detection of residual or recurrent meningioma after surgery: value of enhanced vs unenhanced MR imaging.

The enhanced and unenhanced MR examinations obtained after surgery for meningioma in 38 patients were reviewed to determine the value of enhanced vs unenhanced MR imaging for the detection of residual or recurrent tumor. Enhanced images improved delineation of the extent of tumor in seven of 13 cases in which meningioma was identified on unenhanced images and allowed more definitive detection or exclusion of residual or recurrent meningioma in 18 of 21 cases with equivocal findings on unenhanced images. In addition, enhanced images were helpful for detecting small recurrences, identifying en plaque growth, and showing subtle progression on serial studies. Enhanced MR imaging also allowed detection of two morphologic patterns of dural enhancement adjacent to the surgical bed: (1) thin and smooth, which was seen in patients both with and without residual or recurrent tumor, and (2) thick and nodular, which was seen only in patients with findings indicative of, or at least suggestive of, residual or recurrent meningioma. Unenhanced images failed to detect, or poorly detected, these dural abnormalities. Unenhanced sequences were necessary for accurate interpretation of the enhanced images (e.g., identification or exclusion of hemorrhage). The combination of unenhanced and enhanced MR imaging is recommended for the detection of residual or recurrent meningioma after surgery.     

99 Tcm-MIBI SPECT在原发性鼻咽癌诊断、放疗后残余或复发监测中的应用

目的：评价^99Tc^m-甲氧基异丁基异腈(MIBI)SPECT显像对原发性鼻咽癌的诊断和鼻咽癌放疗后局部残余或复发的鉴别价值。方法：20例经病理检查证实的原发性鼻咽癌患者于治疗前、放疗后3和6个月分别行^99Tc^m-MIBI SPECT显像，与同期CT和(或)MRI结果对照，分别计算肿瘤或正常鼻咽部与头皮的放射性计数比值，作为^99Tc^m-MIBI摄取指数(MUI)。以接受器工作特性(ROC)曲线确定MUI判别阈值。以鼻咽部内镜检查、病理活组织检查及18个月的临床随访资料作为鼻咽癌残余或复发的依据。结果以MUI≥2．15为阳性标准，^99Tc^m-MIBISPECT显像诊断原发性鼻咽癌的灵敏度、特异性和准确性均为95％。以MUI≥1．32为阳性标准，^99Tc^m-MIBI SPECT显像监测鼻咽癌残余或复发的灵敏度为3／4例，特异性93．8％，准确性90．0％。CT和(或)MRI监测鼻咽癌残余或复发的灵敏度为3／4例，特异性81．3％，准确性80．0％。^99Tc^m-MIBISPECT显像与CT和(或)MRI联合鉴别鼻咽癌残余或复发的灵敏度、特异性和准确性分别为2／2例、92．9％和93．8％。结论:^99Tc^m-MIBI SPECT显像对确定鼻咽癌原发灶范围有一定价值；与CT和(或)MRI联合，可提高对放疗后鼻咽癌残余或复发的早期诊断效能。     

MR imaging of osteoradionecrosis of the mandibula following radiotherapy for head and neck cancers

Magnetic resonance (MR) images of 13 patients with osteoradionecrosis of the mandibula were analyzed. Abnormalities were noted in all patients and could be classified into three groups. In nine patients, MR signals were homogeneously low in intensity on both T1 weighted images (T1WI) and T2 weighted images (T2WI), suggesting fibrosis of bone marrow. These nine patients had suffered radiologically and/or clinically overt osteoradionecrosis more than ten months previously, and inflammatory symptoms had settled down by the time of MR study. Two patients showed low signal intensity on T1WI and an area of inhomogeneous high intensity in a diffuse area of low signal intensity on T2WI, suggesting acute inflammation in the irradiated fibrous bone marrow. Both patients suffered pathologic fracture due to osteoradionecrosis and showed severe inflammatory symptoms at the time MR study. In one of the two patients, these pathologic changes were confirmed in surgically excised mandibulectomy specimens. The other two patients showed homogeneous low signal intensity on T1WI and high signal intensity on T2WI, a finding that may be due to slight inflammation. However, in one of the two patients, this signal feature possibly indicated loose fibrosis with marked cellularity.     

Diffusion-weighted MR imaging offers no advantage over routine noncontrast MR imaging in the detection of vertebral metastases

BACKGROUND AND PURPOSE: Diffusion-weighted MR imaging of the spine has been used to differentiate benign from pathologic vertebral body compression fractures. We sought to determine the utility of diffusion-weighted MR imaging in the detection of vertebral metastases and to compare it with conventional noncontrast T1- and T2-weighted MR imaging. METHODS: Fifteen patients with metastases to the spine were studied using conventional MR imaging and diffusion-weighted imaging. Blinded review of all images was undertaken, and patients were categorized according to whether they had focal or multiple lesions. The signal intensity of the lesions was compared on T1-, T2- (fast spin-echo), and diffusion-weighted images. RESULTS: In five patients with focal disease, metastases were hypointense on T1-weighted images; hypointense (n = 2), isointense (n = 1), or hyperintense (n = 2) on T2-weighted images; and hypointense (n = 3) or hyperintense (n = 2) on diffusion-weighted images with respect to presumed normal bone marrow. In 10 patients with disease in multiple sites, all lesions were hypointense on T1-weighted images; hypointense (n = 2), isointense (n = 4), hyperintense (n = 2), or mixed (n = 2) on T2-weighted images; and hypointense (n = 5), hyperintense (n = 3), or mixed (n = 2) on diffusion-weighted images with respect to presumed normal bone marrow. CONCLUSION: As used in this study, diffusion-weighted MR imaging of the spine showed no advantage in the detection and characterization of vertebral metastases as compared with noncontrast T1-weighted imaging, but was considered superior to T2-weighted imaging.     

Diffusion-weighted MR imaging (DWI) in the evaluation of epidural spinal lesions

Introduction Epidural spinal cord compression is one of the most critical emergency conditions requiring medical attention and requires prompt and adequate treatment. The aim of our study was to assess the role of diffusion-weighted magnetic resonance (MR) imaging (DWI) in the diagnosis and differentiation of epidural spinal lesions. Methods Three patients with epidural lymphoma, two with sarcoma and three with epidural metastatic disease were imaged on a 1.5T MRI unit. DWI was performed using navigated, interleaved, multi-shot echo planar imaging (IEPI). Three region of interest (ROI)-measurements were obtained on corresponding apparent diffusion coefficient (ADC) maps, and the mean ADC value was used for further analysis. The cellularity of tumors was determined as the N/C ratio (nucleus/cytoplasma ratio) from histological samples. The ADC values and N/C ratios of lesions were compared using a Kruskal-Wallis test. Results The mean ADC of the lymphomas was 0.66 × 10⁻³ mm²/s, that of the sarcomas was 0.85 × 10⁻³ mm²/s and the ADC of the metastatic lesions was 1.05 × 10⁻³ mm²/s; however, the differences were not statistically significant. Mean N/C ratios in the lymphoma, sarcomas and metastases were 4:1, 2:1, and 2.6:1, respectively, with a statistically significant difference between the groups (p < 0.025). Conclusion Although not statistically significant due to the small patient sample, our results clearly show a tendency toward decreased diffusivity in neoplastic lesions with higher cellularity. The data from our study suggest that DWI is a feasible and potentially useful technique for the evaluation of epidural lesions that cause spinal cord compression on a per-patient basis.     

Primary staging of laryngeal and hypopharyngeal cancer: CT,MR imaging and dual-energy CT

Laryngeal and hypopharyngeal cancer, in particular T4a disease associated with cartilage invasion and extralaryngeal spread, needs to be evaluated accurately because treatment can impact heavily on a patient's quality of life. Reliable imaging tools are therefore indispensible. CT offers high spatial and temporal resolution and remains the preferred imaging modality. Although cartilage invasion can be diagnosed with acceptable accuracy by applying defined criteria for combinations of erosion, lysis and transmural extralaryngeal spread, iodine-enhanced tumors and non-ossified cartilage are sometimes difficult to distinguish. MR offers high contrast resolution for images without motion artifacts, although inflammatory changes in cartilage sometimes resemble cartilage invasion. With dual-energy CT, combined iodine overlay images and weighted average images can be used for evaluation of cartilage invasion, since iodine enhancement is evident in tumor tissue but not in cartilage. Extralaryngeal spread can be evaluated from CT, MR or dual-energy CT images and the routes of tumor spread into the extralaryngeal soft tissue must be considered; (1) via the thyrohyoid membrane along the superior laryngeal neurovascular bundle, (2) via the inferior pharyngeal constrictor muscle, and (3) via the cricothyroid membrane. Radiologists need to understand the advantages and limitations of each imaging modality for staging of laryngeal and hypopharyngeal cancer.     

扩散加权成像对肝脏肿瘤局部特征的研究

摘要目的通过测定表观扩散系数、纯扩散系数、灌注相关的扩散系数以及灌注分数,确定扩散加权成像能否用来鉴别肝脏恶性肿瘤内的肿瘤存活组织、纤维组织和坏死区域。方法这项前瞻性研究得到机构评审委员会的同意,所有病人在检查前签署知情同意书。48例病人共51个肝脏恶性肿瘤纳入研究。利用11个b值(0～500s/mm2)的扩散加权成像(DWI)和钆增强的三维梯度回波T1WI,采集肝脏的MR影像。根据注射非特异性的钆螯合物后的增强方式、手术切除病变和相关的组织病理结果,将肿瘤分为存活肿瘤、纤维及坏死区。     

Reirradiation for recurrent head and neck cancers using charged particle or photon radiotherapy

Objective

To examine the outcomes of reirradiation for recurrent head and neck cancers using different modalities.

Methods

This retrospective study included 26 patients who received charged particle radiotherapy (CP) and 150 who received photon radiotherapy (117 CyberKnife radiotherapy [CK] and 36 intensity-modulated radiotherapy [IMRT]). Inverse probability of treatment weighting (IPTW) involving propensity scores was used to reduce background selection bias.

Results

Higher prescribed doses were used in CP than photon radiotherapy. The 1?year overall survival (OS) rates were 67.9% for CP and 54.1% for photon radiotherapy (p = 0.15; 55% for CK and 51% for IMRT). In multivariate Cox regression, the significant prognostic factors for better survival were nasopharyngeal cancer, higher prescribed dose, and lower tumor volume. IPTW showed a statistically significant difference between CP and photon radiotherapy (p = 0.04). The local control rates for patients treated with CP and photon radiotherapy at 1 year were 66.9% (range 46.3–87.5%) and 67.1% (range 58.3–75.9%), respectively. A total of 48 patients (27%) experienced toxicity grade ≥3 (24% in the photon radiotherapy group and 46% in the CP group), including 17 patients with grade 5 toxicity. Multivariate analysis revealed that younger age and a larger planning target volume (PTV) were significant risk factors for grade 3 or worse toxicity.

Conclusion

CP provided superior survival outcome compared to photon radiotherapy. Tumor volume, primary site (nasopharyngeal), and prescribed dose were identified as survival factors. Younger patients with a larger PTV experienced toxicity grade ≥3.

     

Efficacy and toxicity of (chemo)radiotherapy for primary subglottic cancer

Background and purpose

Primary subglottic cancer is a rare malignancy. We investigated the efficacy and toxicity of radiotherapy for subglottic cancer.

Patients and methods

Nineteen patients with primary squamous cell carcinoma of the subglottis received radiotherapy, 14 of whom also underwent chemotherapy. Of the 19 patients, 15 received definitive radiotherapy to the gross tumors with total doses of 70–70.2 Gy in 35–39 fractions, and 4 underwent preoperative radiotherapy with total doses of 37.8–55.8 Gy in 21–31 fractions, followed by total laryngectomy.

Results

Of the 19 patients, 5 developed local progression and 2 developed distant metastasis at the median follow-up period of 5 years. The 5-year local control and disease-free rates were 74 and 63%, respectively. Three patients died of tumor progression, and the 5-year overall and disease-free survival rates were 80 and 63%, respectively. Regarding acute toxicities, transient mucositis and dermatitis of grade 3 or lower were observed in all patients, but there were no late toxicities of grade 3 or higher.

Conclusion

Radiotherapy is a safe and effective treatment for patients with primary squamous cell carcinoma of the subglottis. The use of chemotherapy together with radiotherapy may enhance treatment efficacy and contribute to larynx preservation through good local control.     

MR imaging in the evaluation of chronic or recurrent headache

PURPOSE: To evaluate ability of magnetic resonance (MR) imaging to depict an abnormality in patients with chronic or recurrent headache without neurologic abnormality. MATERIALS AND METHODS: Institutional review board approval and patient informed consent were not required. A total of 306 patients with normal neurologic findings and chronic or recurrent headache were examined with MR imaging. Patients were divided into three groups: those with no abnormality, those with minor abnormality, and those with clinically important intracranial abnormality, which may result in chronic or recurrent headache. Literature review was also performed. Upper 99.5% confidence bound for frequency of abnormal MR findings was calculated. RESULTS: A total of 169 patients (55.2%) were placed in the first group, 135 (44.1%) were placed in the second group, and two (0.7%) were placed in the third group because they had a clinically important abnormality at MR imaging. Neither contrast material enhancement (n = 195) nor repeated MR imaging (n = 23) contributed to the diagnosis. Literature review revealed two previous studies concerning unspecified headache (in addition to the current study), including a total of 1036 MR imaging results and 22 (2.1%) clinically important results (upper 99.5% confidence bound, 3.4%). Twelve studies of migraine headache were found, with a total of 790 MR imaging examinations. Excluding the 19 patients with complicated migraine, the 99.5% confidence bound of the frequency of clinically important abnormality at MR imaging was estimated as 0.68%. Clinically important infarctions were noted on MR images in five (26.3%) of 19 patients with complicated migraine. CONCLUSION: MR imaging is an unrewarding technique in the evaluation of patients with chronic or recurrent headache and normal neurologic findings. Neither contrast enhancement nor repeated MR imaging contributed to diagnosis, although the number of patients in the latter category was small.     

Role of diffusion-weighted echo-planar MR imaging in differentiation of residual or recurrent head and neck tumors and posttreatment changes

BACKGROUND AND PURPOSE: The purpose of this work was to evaluate whether diffusion-weighted MR imaging can be used in differentiating residual or recurrent head and neck tumors from postoperative or postradiation changes. MATERIALS AND METHODS: This study included 32 patients clinically suspected for recurrent head and neck tumor after surgery (n=3), radiation therapy (n=13), or both (n=16). Diffusion-weighted MR imaging was done by using a single-shot spin-echo echo-planar sequence. The apparent diffusion coefficient (ADC) value of the suspected lesion was calculated and correlated with pathologic results. RESULTS: Adequate diffusion-weighted MR images and ADC maps were obtained in 30 patients (93.8%). The mean ADC value of residual or recurrent lesions (1.17 +/- 0.33 x 10(-3) mm(2)/s) was less than that of posttherapeutic changes (2.07 +/- 0.25 x 10(-3) mm(2)/s), and the difference was statistically significant (P<.001). When an ADC value of 1.30 x 10(-3) mm(2)/s was used as a threshold value for differentiation, the best results were obtained with an accuracy of 87%, sensitivity of 84%, specificity of 90%, positive predictive value of 94%, and negative predictive value of 76%. CONCLUSIONS: Diffusion-weighted MR imaging with ADC measurement has promising results for differentiating residual or recurrent head and neck tumors from postoperative or postradiation changes.     

Diffusion-weighted MR imaging of the breast: Advantages and pitfalls

The aim of this paper is to review all clinical applications of diffusion weighted MR imaging (DWI) for breast pathology. The challenge of DWI is to obtain the best compromise between lesion detection and characterization. Technical factors affecting lesion characterization and detection are detailed including the effect of contrast administration, the choice of number of b and of b_max, the variation of diagnostic performance according to the type and the size of lesion studied.     

Using MR imaging to predict invasion of the recurrent laryngeal nerve by thyroid carcinoma

OBJECTIVE: We evaluated the accuracy of MR imaging findings for predicting invasion of the recurrent laryngeal nerve by thyroid carcinoma and established an optimal criterion on which to base this prediction. MATERIALS AND METHODS: We reviewed MR imaging findings (lesion size and posterior extension of tumor; encirclement of and invasion into the laryngeal cartilage, trachea, and esophagus by the tumor; and the amount of effaced fatty tissue in the tracheoesophageal groove or between the laryngeal cartilage and hypopharyngeal wall) in 66 patients with thyroid carcinoma. The amount of effaced fatty tissue was classified as one of five grades: 1, normal amount of fatty tissue; 2, partly effaced; 3, completely effaced in one MR imaging slice; 4, completely effaced in two contiguous MR slices; and 5, completely effaced in three or more contiguous MR slices. RESULTS: Thirty-two (48%) of the 66 patients had surgically or pathologically verified recurrent laryngeal nerve invasion. Logistic modeling revealed that the amount of effaced fatty tissue (p < 0.001) and the lesion size (p = 0.033) were the significant factors. Using the threshold values for the lesion size to predict invasion, we found that a threshold of more than 2.9 cm showed the highest accuracy, 76%, with 78% sensitivity and 74% specificity. For the amount of effaced fatty tissue, a grade of 3 or more had the highest accuracy, 88%, with 94% sensitivity and 82% specificity. Addition of the lesion size to this criterion did not improve the diagnostic accuracy of using the amount of effaced fatty tissue alone. CONCLUSION: Invasion of the recurrent laryngeal nerve by thyroid carcinoma was accurately predicted by the finding of effaced fatty tissue on MR imaging.