MR of denervated tongue: temporal changes after radical neck dissection.

PURPOSEThe purpose of this study was to evaluate the temporal changes of MR imaging in the denervated tongue after a radical neck dissection.METHODSOne hundred seventy-four consecutive MR studies in 116 patients with radical neck dissections for malignant tumors of the head and neck were evaluated retrospectively. Patients with tumors involving the tongue or hypoglossal nerve were not included in this study.RESULTSAbnormal signal intensity and/or hemiatrophy on the side of the tongue operated on was seen in 22 patients who had hypoglossal paralysis after radical neck dissection. The denervated side of the tongue appeared hypointense to hyperintense relative to the normal side on T1-weighted images and hyperintense on T2-weighted images. Signal intensity ratios of the abnormal to normal muscles were 0.9-1.6 on T1-weighted images and 1.3-2.8 on T2-weighted images. High signal intensity on T1-weighted images appeared 5 months or more after the dissection, whereas on T2-weighted images, the most prominent increases in signal intensity appeared in the first several months after denervation. Hemiatrophy of the tongue was observed on MR images obtained more than 6 months after surgery.CONCLUSIONMR findings in the denervated tongue are compatible with histologic changes and are characterized by an enlarged extracellular fluid space or fatty infiltration. The pattern of signal intensity and the degree of hemiatrophy suggest the duration of denervation.     

In vivo and in vitro MR imaging of renal tumors: histopathologic correlation and pulse sequence optimization

Magnetic resonance (MR) imaging has given mixed results in the detection of renal masses. To identify the reasons for this and to determine the optimal pulse sequences for evaluating renal tumors, the authors imaged 12 primary renal tumors in vivo and 17 in vitro at 0.35 T. Histopathologic findings for each specimen were closely correlated with the MR images. Four of seven solid tumors imaged in vivo were isointense with surrounding normal renal parenchyma at all pulse sequences. The other three tumors were hyperintense in vivo at T2-weighted sequences. At heavily T2-weighted sequences eight solid tumors were hyperintense in vitro and four were hypointense. There was no correlation between signal intensity and specific tissue type or histologic pattern for solid tumors. The five cystic tumors were well seen both in vivo and in vitro on T2-weighted images. However, the signal intensity of the cyst fluid was an unreliable indicator of benignancy. SE MR imaging at 0.35 T has significant limitations in the detection of solid renal masses.     

Spinal angiolipomas: MR features.

PURPOSETo determine the MR features of spinal angiolipomas and to compare these findings with their histologic appearance.METHODSThe MR examinations of three patients with surgically proved angiolipomas were reviewed for tumor location and extent, signal characteristics, and pattern of contrast enhancement, and were then compared with the histologic findings.RESULTSFour tumors were found in the three patients, all located in the posterior epidural compartment, averaging about 2.5 vertebral bodies in length. On noncontrast T1-weighted images, all lesions were inhomogeneous and hypointense relative to epidural fat. Inhomogeneous enhancement was seen in three lesions on postcontrast T1-weighted images obtained with fat-saturation techniques. Angiolipomas were least conspicuous on T2-weighted images. A high vascular content correlated with the presence of large hypointense regions on T1-weighted images.CONCLUSIONSpinal angiolipomas are typically hyperintense on noncontrast T-1-weighted images relative to other tumors. Angiolipomas that contain large hypointense foci on noncontrast T1-weighted images can be expected to have a high degree of vascularity.     

Variable MR findings in ovarian functional hemorrhagic cysts

PURPOSE: To describe the magnetic resonance (MR) findings in ovarian functional hemorrhagic cysts (FHC). MATERIALS AND METHODS: A total of 21 patients with 22 FHC, proven by follow-up ultrasound (US) in 11 women and surgery in 10 women, had US and MR examinations within 24 hours. The study was limited to cysts with obvious an echogenic pattern. All patients had T2-weighted fast spin echo (FSE), T1-weighted spin echo (SE), and T1-weighted SE fat-suppressed sequences. RESULTS: Four cysts (18%) were hypointense on T1-weighted-images without and with fat suppression, and hyperintense on T2-weighted-images. Five cysts (23%) were hypointense on T1-weighted images without and with fat suppression but heterogenous on T2-weighted images. Five cysts (23%) were hypointense on T1-weighted images but showed intermediate signal intensity on T1-weighted fat suppression images and heterogenous signal intensity on T2-weighted images. Two cysts (9%) were entirely intermediate on T1-weighted images. Five cysts (23%) displayed high signal intensity occupying less than 30% of the cystic content on T1-weighted images and one cyst (5%) displayed high signal intensity occupying more than 30% of the cystic content. CONCLUSION: Despite an obvious echogenic pattern on US, 64% of FHC were hypointense on T1-weighted images and 18% were also hyperintense on T2-weighted images. Only 36% demonstrated intermediate or high signal intensity on T1-weighted images.     

肝细胞癌的低场MR征象分析(附33例报告)

目的分析肝细胞癌在低场MR的征象.方法收集33例手术病理证实的肝细胞癌的术前低场MR资料进行分析.结果1.肿瘤实质信号均匀区的信号配对主要分为三类1T1WI稍低、T2WI稍高信号18例;2T1WI等、T2WI稍高信号13例;3T1WI稍高、T2WI稍高信号2例.2.肿瘤实质内MR异常信号区1T1WI低、T2WI高信号(斑点状24例,片状9例,条状5例);2T1WI稍低、T2WI高信号(斑点状8例,片状2例,条状3例);3T1WI高、T2WI高信号(斑点状4例,片状2例);④T1WI低、T2WI低信号(斑点状5例,片状6例,条状2例).3.肿瘤边缘在T2WI上分三种1边缘清楚无分叶21例,其中11例可以见到"包膜征”;2边缘清楚伴分叶5例;3边缘不清7例.结论1低场MR中,肝细胞癌的肿瘤实质在T1WI可以是多种信号,缺乏特征性,但在T2WI均为稍高信号.2MR诊断肝细胞癌一定要有瘤内异常信号.3肝细胞癌的MR边缘部的形态应以T2WI为准,肿瘤边缘可以光滑清楚,也可以分叶状或边缘不清,"包膜征”有诊断意义.     

Infantile fibromatosis in childhood: findings on MR imaging and pathologic correlation

AIM: The objective of this study was to analyse the MR imaging findings of infantile fibromatosis of childhood and to correlate them with histopathological features. MATERIALS AND METHODS: Seven patients with histologically proven infantile fibromatosis were included in this study. The findings on MR images were retrospectively evaluated and then correlated with the pathological features. Findings on MR imaging evaluated included signal intensity, extent of hyperintense area on T2-weighted images, margins of the lesion, the degree and pattern of enhancement and the presence of fatty tissue. Pathological features evaluated included cellularity, collagenization, and myxoid change. A five point scale was used for the evaluation of the extent of hyperintense area on MR imaging, and each of pathological features. RESULTS: On T1-weighted images, the lesions were iso-intense in two patients; iso- and hypointense in three; and iso-, hypo- and hyperintense in two. On T2-weighted images, iso-, hypo- and hyperintense areas were mixed in all patients, the hyperintense area being the largest portion of the lesion. The margins of the lesions were infiltrative in four patients (57%), smooth in two (29%) and mixed in one (14%). Enhancement was marked in five patients (72%) and diffuse in five (71%). Regardless of the hyperintense signal intensity on T2-weighted images, the grades of each pathologic feature were variable. CONCLUSION: Infantile fibromatosis on MR imaging causes an enhancing mass, that is largely hyperintense on T2-weighted images. Areas of high signal intensity on T2-weighted images corresponded to variable grades of cellularity, collagenization, or myxoid change.     

Intradural schwannomas of the spine: MR findings with emphasis on contrast-enhancement characteristics.

Intradural extramedullary schwannomas are nerve sheath neoplasms that consist of focal proliferations of Schwann cells involving a spinal nerve. We reviewed the MR findings in seven patients with pathologically proved intradural schwannomas. The contrast-enhancement characteristics on MR images were determined and compared with the histologic features of the tumor. Six lesions were variably hyperintense on T2-weighted images and one was uniformly hypointense compared with the signal intensity of the spinal cord. Signal on T1-weighted images ranged from hypointense to isointense. All seven tumors showed heterogeneous enhancement; in five, the enhancement involved only the periphery of the lesion. The pattern of enhancement did not correlate with the signal characteristics noted on unenhanced T1- and T2-weighted images. Pathologically, hyaline thickening of vessel walls and cyst formation were prevalent in the peripherally enhancing lesions. However, enhancement did not correlate with the relative proportion of Antoni type A and type B tissue. Recognition of the MR characteristics of intradural extramedullary schwannomas may be helpful in the differential diagnosis of spinal tumors. In particular, peripheral contrast enhancement of an intradural extramedullary tumor on MR images should suggest the diagnosis of schwannoma.     

Visceral metastases from melanoma: findings on MR imaging.

Typical ocular and CNS melanomas are hyperintense on T1-weighted MR images and hypointense on T2-weighted MR images. We performed MR imaging in 48 patients with melanoma metastatic to visceral organs. Images were reviewed retrospectively in order to determine whether there were predominant MR features specific for visceral melanoma and to see if visceral metastases have MR characteristics similar to metastases in the CNS. Eleven patients also were examined after injection of gadopentetate dimeglumine to evaluate the enhancement characteristics of these tumors. Two hundred sixty-one lesions were found. Lesions were classified according to their signal intensities relative to uninvolved liver on T1-weighted, T2-weighted, and short TI inversion recovery (STIR) pulse sequences. Most commonly, lesions were either hypointense or isointense on T1-weighted sequences and hyperintense on T2-weighted and STIR sequences (185 lesions). Less frequently, lesions were hyperintense on T1-weighted sequences and hypointense or isointense on T2-weighted and STIR sequences (59 lesions). A mixed pattern was seen on T1- and T2-weighted sequences in 17 lesions. The patterns did not correlate with lesion size. Of the three sequences studied by subjective comparison, the STIR sequence in our series had the highest sensitivity for lesion detection and yielded the highest lesion conspicuity. Injection of gadopentetate dimeglumine in 11 patients did not increase either the number or the conspicuity of lesions seen. Our results show that visceral metastases from melanoma have a wide variety of appearances on MR images. The STIR sequence appears to be optimal, and the metastases do not enhance with gadopentetate dimeglumine.     

Predicting the effect of gonadotropin-releasing hormone (GnRH) analogue treatment on uterine leiomyomas based on MR imaging

PURPOSE: To test the hypothesis that the simple assessment of signal intensity on T2-weighted MR images is predictive of the effect of hormonal treatment with gonadotropin-releasing hormone (GnRH) analogue. MATERIAL AND METHODS: The correlation between T2-weighted MR imaging of uterine leiomyomas and histologic findings was evaluated using 85 leiomyomas from 62 females who underwent myomectomy or hysterectomy. We also correlated the pretreatment MR images features obtained in 110 women with 143 leiomyomas with the effect of GnRH analogue treatment. The size (length x width x depth) of the leiomyoma was evaluated before and at 6 months after treatment by ultrasound. RESULTS: The proportion of leiomyoma cell fascicles and that of extracellular matrix affected signal intensities of uterine leiomyomas on T2-weighted MR images. The amount of extracellular matrix was predominant in hypointense leiomyomas on T2-weighted images, while diffuse intermediate signal leiomyomas were predominantly composed of leiomyoma cell fascicles. Marked degenerative changes were noted in leiomyomas with heterogenous hyperintensity. The homogeneously intermediate signal intensity leiomyomas showed significant size reduction after treatment (size ratio; posttreatment volume/pretreatment volume 0.29+/-0.11). The size ratio for the hypointense tumors was 0.82+/-0.14, and 0.82+/-0.18 for the heterogeneously hyperintense tumors. There was a significant difference in the response to treatment between the homogeneously intermediate signal intensity leiomyomas and the hypointense or heterogeneously hyperintense leiomyomas (both p<0.01). CONCLUSION: Signal intensity on T2-weighted MR images depends on the amount of leiomyoma cell fascicles and extracellular matrix. Simple assessment of the MR signal intensity is useful in predicting the effect of GnRH analogue on uterine leiomyomas.     

Configurational MR characteristics of metastatic brain tumors

Magnetic resonance (MR) characteristics of metastatic brain tumors (MBTs) were studied using 15 cases (13 males and 2 females whose ages ranged from 32–78 yr, with the mean age of 57.8 yr;12 adenocarcinomas, 2 squamous-cell carcinomas, 2 large-cell carcinomas). Nine cases showed hypointensities and five showed isointensities on T1-weighted images. Six cases showed markedly hypo- or hypointensities, two showed isointensities, and six showed markedly hyper- or hyperintensities on T2-weighted images. One case was markedly hyperintense on both T1- and T2-weighted images. The decrease of the signal intensity on the T2-weighted image was the main MR characteristic. A hypointense peritumoral rim was seen in four of the six hyperintense tumors on T2-weighted images. There was no correlation between the signal intensity and the histological classification.     

MRI of ganglioneuroma: histologic correlation study

PURPOSE: The purpose of this study was to evaluate the MR findings of ganglioneuroma and to correlate imaging and histologic features. METHOD: Conventional SE and contrast-enhanced dynamic MRI was used to examine 10 patients with pathologically confirmed ganglioneuroma. The morphologic features, signal intensity, and dynamic enhancement pattern of the tumors were retrospectively analyzed and correlated with histologic features. RESULTS: Capsules were present in all tumors histologically and were also detected in five tumors on postcontrast T1-weighted images. A whorled appearance corresponding to interlacing bundles of Schwann cells and collagen fibers on histologic specimens was visualized in five tumors on T1-and/or T2-weighted images. Tumors with markedly high signal intensity on T2-weighted images consisted histologically of a large amount of myxoid stroma and relatively few cellular and fibrous components. Tumors with intermediate to high signal intensity consisted of numerous cellular and fibrous components and little myxoid stroma. Early enhancement of tumors was usually lacking in dynamic MR studies; however enhancement gradually increased. CONCLUSION: The results suggest that the MR features of ganglioneuroma are well correlated with histologic findings.     

Intracranial tuberculoma: comparison of MR with pathologic findings.

PURPOSETo compare the MR signal intensity patterns and enhancement pattern of intracranial tuberculomas with their histopathologic features.METHODSMR images of six patients with surgically proved intracranial tuberculoma were reviewed retrospectively and were compared with histologic findings of the resected specimen. Detailed histologic examination was performed to look for the extent and characteristics of caseation necrosis, fibrosis, and inflammatory cellular infiltrates at each area of different signal intensities and at the enhancing areas on MR. Signal intensities for T1- and T2-weighted images were compared with normal gray matter.RESULTSOn T1-weighted images, the granulomas showed a slightly hyperintense rim surrounded by a complete or partial rim of slight hypointensity and central isointensity or mixed isointensity and hyperintensity in five patients and homogeneous isointensity in one patient. Histologically, the zone of central isointensity or mixed intensity corresponded to caseation necrosis plus adjacent cellular infiltrates. The hyperintense and hypointense rims corresponded to the layers of collagenous fiber and the layers of the inflammatory cellular infiltrates, respectively. On T2-weighted images, the entire portion of the granuloma showed slightly heterogeneous isointensity or hypointensity with small markedly hypointense foci in five patients, and a hyperintense center surrounded by a hypointense rim in one patient. Histologic layers were not discriminated on T2-weighted images. On postcontrast T1-weighted images, there were single or multiple conglomerate ring enhancements within a tuberculoma in all six patients, corresponding to the layers of both collagenous and inflammatory cells.CONCLUSIONCombination of the described signal intensity patterns and conglomerate ringlike enhancing appearance of the lesion is characteristic of tuberculoma, and may play an important role in differentiating intracranial tuberculomas from other ring-enhancing brain lesions.     

MR imaging of spinal neurinomas with pathological correlation

Eight patients with nine spinal neurinomas were examined with magnetic resonance (MR) imaging. We attempted to correlate MR images with the gross and microscopic characteristics of the tumors. On T1-weighted images (T1WIs) all tumors were iso- to slightly hyperintense to CSF, although two comprised hyperintense areas. On the T2-weighted pulse images (T2WIs), available for seven tumors, two tumors were markedly and two relatively hyperintense to CSF. Three tumors exhibited mixed signal intensity. On macroscopic examination, the markedly hyperintense areas on T2WIs corresponded to the cystic portions and relatively hyperintense areas to the solid portions. Areas that were hypointense on T2WIs and isointense or markedly hyperintense on T1WIs corresponded to hemorrhage. On microscopic examination it was impossible to establish a correlation between Antoni A and Antoni B tissue types and features recognized on T1WIs and T2WIs. Gadolinium-diethylenetriamine pentaacetic acid enhanced T1WIs were performed in four patients with five tumors. All tumors enhanced, demonstrating the tumor contours and the cystic degeneration within.     

椎管内神经纤维瘤的MRI诊断

目的:探讨椎管内神经纤维瘤的MR特征。方法:回顾性分析17例19个经手术病理证实且资料完整的椎管内神经纤维瘤MR表现。结果:19个肿瘤中15个为孤立的神经纤维瘤,MR图像上边界清楚;4个丛状神经纤维瘤,MR图像上整个或部分边界模糊。全部肿瘤T1WI为等-稍高或稍低信号,T2WI为多样的高信号,17个为不均匀的T2加权高信号,其中12个显示中央低信号,周围高信号的“靶征”。增强扫描,呈多样的强化,其中11个显示中央强化。结论:T1WI等-稍高或稍低信号,T2WI多样的高信号,“靶征”是椎管内神经纤维瘤的特征,肿瘤呈多样的强化,常显示中央强化。边界模糊时,应考虑丛状神经纤维瘤。     

Epidural fibrosis and recurrent disk herniation in the lumbar spine: MR imaging assessment

Twenty patients were enrolled in a prospective study to evaluate MR imaging in the differentiation of epidural scar and herniated disk material. Fourteen patients had surgical verification of imaging findings. In 12 (86%) of these patients, the MR interpretations fully agreed with the observations at surgery. Careful integration of the findings on sagittal and axial T1-weighted images with more T2-weighted axial images was important for analysis. Anterior and lateral recess scars were hypo- or isointense on T1-weighted sequences and hyperintense on more T2-weighted sequences relative to the "parent" anulus intensity. Free fragments demonstrated a slightly hyperintense signal intensity on T1-weighted images relative to epidural fibrosis but had a similar hyperintense signal intensity on T2-weighted sequences. Prolapsed or extruded disk fragments were hypo- or isointense relative to the parent anulus on all sequences. Morphology, epidural location, mass effect, and often signal intensity were the important parameters by which scar and herniated disk could be differentiated with MR.     

肝脏孤立性坏死结节的MRI表现

目的 总结肝脏孤立性坏死结节(SNN)平扫和动态增强MRI特征性表现.方法 回顾性分析经手术病理证实的15例SNN的MRI征象,对病灶数目、形状、大小、部位、边界、平扫和增强后信号及强化方式进行评价.结果 病灶单发14例,另1例有2个病灶.平扫T1WI及T2WI各发现15和14个病灶,增强扫描发现16个病灶.14个病灶最大径≤3 cm.平扫T1WI病灶呈低信号5个,略低信号9个,1个呈等信号伴有周边低信号包膜及内部点状低信号.在T2WI病灶呈高信号5个,略高信号4个,略低信号3个,明显低信号2个,其中2个病灶内见点状或细线样极高信号.16例在增强扫描后各期均呈低信号,尤其在门静脉期及延迟期呈明显低信号,边界及形态显示清楚.12个病灶形状不规则,4个病灶呈圆形或卵圆形.增强后病灶内部均未见强化,3个病灶在门静脉期及延迟期可见细环状轻度强化的包膜.结论 SNN特征性MRI表现有助于与肝脏其他肿瘤鉴别.     

非酮症高血糖性舞蹈病的CT、MRI表现

目的 通过分析非酮症高血糖性舞蹈病的CT和MRI表现与临床表现之间的关系,以探讨该疾病的影像诊断价值.方法 回顾性分析6例非酮症高血糖性舞蹈病的影像表现和临床资料.6例均行CT平扫,其中1例行MR扫描.6例中3例行CT复查,1例行MR复查.结果 6例患者CT均表现为一侧或两侧纹状体密度增高,均累及壳核,其中5例同时累及苍白球外侧部或尾状核;3例CT复查表现为受累纹状体密度减低或密度增高影消失.1例T1WI表现为两侧豆状核高信号,T2WI表现为低信号;MRI复查示受累豆状核T1WI和T2WI信号无变化.所有患者的舞蹈病症状均在血糖控制后2～6 d内消失.结论 典型的CT和MRI表现有助于非酮症高血糖性舞蹈病的诊断     

Phyllodes tumor of the breast: correlation between MR findings and histologic grade

PURPOSE: To retrospectively evaluate the magnetic resonance (MR) imaging findings of phyllodes tumor of the breast and to compare these findings with the histologic grade. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. The authors reviewed the MR findings in 30 female patients aged 16-73 years (mean, 40.2 years) with surgically confirmed phyllodes tumors. Analyzed MR findings included tumor shape, margin, internal enhancement, and size; signal intensity (SI) of tumor higher than that of normal breast tissue on T1-weighted images; SI of tumor lower than or equal to that of normal tissue on T2-weighted images; cyst wall appearance; kinetic curve assessment; and apparent diffusion coefficient (ADC). The MR findings and histologic grade were statistically analyzed to determine whether any correlations existed. Significant MR findings were compared with histopathologic findings. RESULTS: Nineteen benign, six intermediate (characterized by five to nine cell reproductions at 10 high-power fields, pushing or infiltrative margins, moderate stromal cellularity, and atypia and overgrowth), and five malignant phyllodes tumors were assessed. Irregular cyst wall (P = .003), tumor SI lower than or equal to normal tissue SI on T2-weighted images (P = .005), and low ADC (P = .001) correlated significantly with histologic grade. Tumor SI higher than normal tissue SI on T1-weighted images was more frequent in the malignant (in three of five tumors) and intermediate (in three of six tumors) groups than in the benign group (in two of 19 tumors); however, it was not a significant finding (P = .024). Tumor SI higher than normal tissue SI on T1-weighted images and irregular cyst wall corresponded histopathologically to hemorrhagic infarction and necrosis, respectively. Tumor SI lower than or equal to normal tissue SI on T2-weighted images and low ADC corresponded histopathologically to stromal hypercellularity. Other findings were not significant. CONCLUSION: Several MR findings can be used to help determine the histologic grade of phyllodes breast tumors.     

Nondysplastic nodules that are hyperintense on T1-weighted gradient-echo MR imaging: frequency in cirrhotic patients undergoing transplantation

OBJECTIVE: Our objective was to determine the frequency and MR imaging findings of nondysplastic nodules that are hyperintense on T1-weighted gradient-echo imaging in patients with cirrhosis who undergo liver transplantation. MATERIALS AND METHODS: Two observers retrospectively evaluated in-phase (4-5 msec), opposed-phase gradient-echo (2.0-2.4 msec), and turbo short tau inversion recovery (STIR) MR images in 68 patients with cirrhosis--but without dysplastic nodules or hepatocellular carcinoma--who underwent MR imaging at 1.5 T within 150 days before liver transplantation. The size, number, signal characteristics, and arterial enhancement pattern of nodules that appear hyperintense on T1-weighted gradient-echo images were evaluated as well as the presence or absence of signal loss on opposed-phase imaging. These imaging findings were correlated with pathologic findings of whole explanted livers. RESULTS: Eleven (16%) of 68 patients had at least one nondysplastic nodule that was hyperintense on T1-weighted MR imaging. Three patients had diffuse nondysplastic hyperintense nodules (>10 nodules) measuring less than 0.5 cm, and the remaining eight patients had 22 nondysplastic hyperintense nodules ranging in size from 0.5 to 2.5 cm (mean, 1.2 cm), of which 13 were isointense and nine were hypointense on turbo STIR images. No lesion lost signal on opposed-phase imaging or enhanced during the hepatic arterial phase. CONCLUSION: In cirrhotic patients undergoing liver transplantation, nondysplastic nodules that are hyperintense are common findings on T1-weighted gradient-echo MR imaging and do not lose signal intensity on opposed-phase imaging or enhance during the hepatic arterial phase. These nodules may be indistinguishable from dysplastic nodules.     

Correlation of MR imaging and histologic findings in mouse melanoma.

M2R melanoma tumors in male C57 black mice were used to correlate magnetic resonance (MR) images with the corresponding histologic slices and to determine if analysis of the achievable correlation can provide a basis for predicting gross histologic features with MR imaging alone. The MR imaging sections obtained at 4.7 T were each 680 microns thick, with an in-plane resolution of 195 microns. The distribution of melanin within the histologic slices correlated well with the high-signal-intensity regions on the T1-weighted images (T1WIs), while these regions had low signal intensity on the T2-weighted images (T2WIs), providing evidence that melanin or melanin-associated paramagnetic species are responsible for the observed proton relaxation rate enhancement. Viable melanoma cells typically showed intermediate signal intensity on T2WIs, T1WIs, and proton-density images. Necrosis typically had high signal intensity on T2WIs, T1WIs, and proton-density images. Quantitation of the MR imaging results, followed by statistical analysis, demonstrated statistically significant differences between melanin-rich, viable-melanoma, and necrotic regions on MR images.