MR扩散成像在子宫肌瘤HIFU术后早期疗效评价中的价值

目的:探讨磁共振扩散成像在子宫肌瘤高强度聚焦超声治疗后早期疗效评价中的价值。方法:15例患者共21个肌瘤经1次性HIFU刀治疗,术前、术后0.5及24h进行常规磁共振成像及DWI成像,观察肌瘤术前、术后在常规MRI、DWI上信号及ADC值变化特点并进行分析。结果:术后18个肌瘤增强扫描无灌注区,在DWI序列上均有不同程度的信号增高;肌瘤消融区术后0.5h平均ADC值[(1.287±0.213)×10-3 mm2/s]低于术前平均ADC值[(1.442±0.233)×10-3 mm2/s]及残留未消融区平均ADC值[(1.513±0.271)×10-3 mm2/s],术后24h复查,消融靶区平均ADC值[1.369±0.220)×10-3 mm2/s]回升。术前、术后0.5及24h消融区及残留未消融区平均ADC值差异有统计学意义(P<0.05);术后0.5h消融区在DWI上高信号主要分布于外周,中央部信号强度相对较低,呈较有特征性环形高信号改变,而且外周部ADC值低于中央部ADC值。结论:DWI和ADC值是早期评价子宫肌瘤高强度聚焦超声治疗术后疗效的有效手段。     

Feasibility of ultrasound-guided high intensity focused ultrasound ablating uterine fibroids with hyperintense on T2-weighted MR imaging

Purpose

To retrospectively investigate whether uterine fibroids with hyperintense on pretreatment T2-weighted magnetic resonance imaging (MRI) could be treated with ultrasound-guided high intensity focused ultrasound (USgHIFU).

Materials and methods

282 patients with 282 symptomatic uterine fibroids who underwent USgHIFU treatment were retrospectively analyzed. Based on the signal intensity of T2-weighted MRI, uterine fibroids were classified as hypointense, isointense and hyperintense. Hyperintense fibroids were subjectively further subdivided into heterogeneous hyperintense, slightly homogeneous hyperintense and markedly homogeneous hyperintense based on the signal intensity of fibroid relative to myometrium and endometrium on T2-weighted MRI. Enhanced MRI was performed within one month after HIFU treatment. Non-perfused volume (NPV, indicative of successful ablation) ratio, treatment time, treatment efficiency, energy effect ratio and adverse events were recorded.

Results

The median volume of uterine fibroids was 70.3 cm³ (interquartile range, 41.1–132.5 cm³). The average NPV ratio, defined as non-perfused volume divided by the fibroid volume after HIFU treatment, was 76.8 ± 19.0% (range, 0–100%) in the 282 patients. It was 86.3 ± 11.9% (range, 40.9–100.0%) in the group with hypointense fibroids, 77.1 ± 16.5% (range, 32.2–100.0%) in isointense fibroids, and 67.6 ± 23.9% (range, 0–100.0%) in hyperintense fibroids. The lowest NPV ratio, lowest treatment efficiency, more treatment time, more sonication energy and pain scores were observed in the slightly homogeneous hyperintense fibroids, and the NPV ratio was 55.8 ± 26.7% (range, 0–83.9%) in this subgroup.

Conclusion

Based on our results, the heterogeneous and markedly homogeneous hyperintense fibroids were suitable for USgHIFU, and only the slightly homogeneous hyperintense fibroids should be excluded.     

Uterine leiomyomas: MR imaging-guided focused ultrasound surgery--results of different treatment protocols

PURPOSE: To prospectively assess patient response (after 12 months) to magnetic resonance (MR) imaging-guided focused ultrasound surgery in treatment of uterine leiomyomas by using two treatment protocols. MATERIALS AND METHODS: This prospective clinical trial was approved by institutional review boards and was HIPAA compliant. After giving informed consent, patients with symptomatic leiomyomas were consecutively enrolled and treated at one of five U.S. centers by using an original or a modified protocol. Outcomes were assessed with the symptom severity score (SSS) obtained at baseline and 3, 6, and 12 months after treatment. Adverse events (AEs) were recorded. Statistical analysis included Student t test, Fisher exact test, analysis of covariance, Spearman correlation, and logistic regression. RESULTS: One hundred sixty patients had a mean SSS of 62.1 +/- 16.3 (standard deviation) at baseline, which decreased to 35.5 +/- 19.5 at 3 months (P<.001) and to 32.3 +/- 19.8 at 6 months (P<.001) and was 32.7 +/- 21.0 at 12 months (P<.001). Ninety-six patients (mean age, 46.0 years +/- 4.6) were treated with an original protocol, and 64 (mean age, 45.9 years +/- 3.9) were treated with a modified protocol. Patients in the modified group had a significantly greater SSS decrease at 3 months (P=.037) than those in the original group, and 73% of those in the original group and 91% of those in the modified group reported a significant decrease in SSS (of 10 points or greater) at 12 months. No serious AEs were recorded. Fewer AEs were reported in the modified group than in the original group (25% vs 13% reporting no event). Of evaluable patients, fewer in the modified group chose alternative treatment (28%) than in the original group (37%). CONCLUSION: MR imaging-guided focused ultrasound surgery results in symptomatic improvement, sustained to 12 months after treatment. Treatment with a modified protocol results in greater clinical effectiveness and fewer AEs.     

脑白质疏松症的MR扩散加权成像及波谱研究

目的通过MR扩散加权成像(DWI)及MR波谱(MRS)分析脑白质疏松症(LA)的表观扩散值(ADC)和不同代谢产物比值的变化,探讨LA中脑白质缺血过程中出现的病理、生化改变与MR功能成像改变之间的关系。方法30例经常规MRI检查诊断为LA患者,及30例年龄相匹配的正常脑白质表现的患者作为对照组,进行DWI检查,分析病变不同区域ADC值的变化,同时对LA患者进行MRS分析N-乙酰天门冬氨酸(NAA)/肌酸(Cr)、胆碱复合物(Cho)/肌酸(Cr)比值的变化,比较不同位置和不同程度病变在ADC值和代谢变化中的差异。结果LA患者病灶区(双侧侧脑室枕角、体部旁脑白质)ADC值升高与对照组差异有显著的统计学意义(P<0.01),相应病灶区的NAA/Cr均值明显降低,Cho/Cr均值升高,与正常白质比较差异有显著统计学意义(P<0.01),而枕角的NAA/Cr均值低于体部,差异有显著统计学意义(P<0.01)。结论磁共振功能成像能够反映脑白质疏松症发展中的微观结构变化和局部代谢的异常。     

Computed diffusion-weighted MR imaging for visualization of pancreatic adenocarcinoma: Comparison with acquired diffusion-weighted imaging

ObjectiveTo assess the feasibility of computed diffusion-weighted imaging (cDWI) in comparison with directly acquired DWI for visualizing pancreatic adenocarcinomas.Materials and methodsPatients with pancreatic adenocarcinoma underwent DWI at b-values of 0, 1000 (DWI₁₀₀₀), 1500 (DWI₁₅₀₀) and 2000 (DWI₂₀₀₀) s/mm². From DWIs at b-values of 0 and 1000 s/mm², we generated cDWIs at b-values of 1500 (cDWI₁₅₀₀) and 2000 (cDWI₂₀₀₀) s/mm². DWI findings of pancreatic adenocarcinomas (clear hyperintensity; hyperintensity with an unclear distal border; and isointensity), the image quality and the tumor to pancreas contrast ratio (CR) were compared between directly acquired DWI and cDWI.ResultsAmong the 63 included patients, clear hyperintense tumors were seen in 35 on DWI₁₀₀₀, 50 on DWI₁₅₀₀, 50 on cDWI₁₅₀₀, 53 on DWI₂₀₀₀ and 44 on cDWI₂₀₀₀. Incidence of clear hyperintense tumors was significantly higher on cDWI₁₅₀₀ than on DWI₁₀₀₀ (P = 0.013). There was no significant difference in the incidence of clear hyperintense tumors between DWI₁₅₀₀ and cDWI₁₅₀₀ (P > 0.999), but a lower incidence was seen on cDWI₂₀₀₀ than on DWI₂₀₀₀ (P = 0.028). Image quality was lower on cDWI than on DWI at b-values of 1500 (P = 0.002) and 2000 s/mm² (P < 0.001). The tumor to distal pancreas CR was significantly higher on cDWI₂₀₀₀ than on cDWI₁₅₀₀ (P < 0.001), and on cDWI₁₅₀₀ than on DWI₁₀₀₀ (P < 0.001). The cDWI showed a significantly higher tumor to distal pancreas CR than DWI at b-values of 1500 (P = 0.004) and 2000 s/mm² (P < 0.001).ConclusionscDWI₁₅₀₀ generated from b-values of 0 and 1000 s/mm² should be considered more effective than DWI₁₀₀₀ and at least as effective as DWI₁₅₀₀.     

MRI对高强度聚焦超声治疗骨肉瘤疗效的随访

目的评估MRI对高强度聚焦超声(high intensity focused ultrasound，HIFU)治疗骨肉瘤疗效随访的价值。方法前瞻性分析了经病理证实的16例骨肉瘤在HIFU治疗前后的MR平扫和多时相动态增强表现与诊断，并与^99m锝-亚甲基二磷酸盐(^99mTc-MDP)静态骨显像对照。结果MRI可正确判断14例骨肉瘤在HIFU治疗后的疗效。HIFU治疗前，16例骨肉瘤在T1WI上呈低信号、T2WI为混杂高信号，多时相动态扫描各期明显强化^99mTc—MDP骨显像显示瘤灶放射性异常浓聚。HIFU治疗后1～4周，瘤灶在T1WI上呈稍高信号、多时相动态扫描各期无强化、灭活区边缘见1条薄的强化带；^99mTc-MDP骨显像显示瘤灶的放射性异常浓聚消失。HIFU治疗后3～25个月，瘤灶逐渐缩小，T1WI上的信号缓慢下降。结论HIFU是一种有效局部治疗骨肉瘤的方法，MRI能准确评估HIFU治疗骨肉瘤的疗效。     

Uterine leiomyomas: MR imaging-based thermometry and thermal dosimetry during focused ultrasound thermal ablation

PURPOSE: To retrospectively evaluate magnetic resonance (MR) imaging-based thermometry and thermal dosimetry during focused ultrasound treatments of uterine leiomyomas (ie, fibroids). MATERIALS AND METHODS: All patients gave written informed consent for the focused ultrasound treatments and the current HIPAA-compliant retrospective study, both of which were institutional review board approved. Thermometry performed during the treatments of 64 fibroids in 50 women (mean age, 46.6 years +/- 4.5 [standard deviation]) was used to create thermal dose maps. The areas that reached dose values of 240 and 18 equivalent minutes at 43 degrees C were compared with the nonperfused regions measured on contrast material-enhanced MR images by using the Bland-Altman method. Volume changes in treated fibroids after 6 months were compared with volume changes in nontreated fibroids and with MR-based thermal dose estimates. RESULTS: While the thermal dose estimates were shown to have a clear relationship with resulting nonperfused regions, the nonperfused areas were, on average, larger than the dose estimates (means of 1.9 +/- 0.7 and 1.2 +/- 0.4 times as large for areas that reached 240- and 18-minute threshold dose values, respectively). Good correlation was observed for smaller treatment volumes at the lower dose threshold (mean ratio, 1.0 +/- 0.3), but for larger treatment volumes, the nonperfused region extended to locations within the fibroid that clearly were not heated. Variations in peak temperature increase were as large as a factor of two, both between patients and within individual treatments. On average, the fibroid volume reduction at 6 months increased as the ablated volume estimated by using the thermal dose increased. CONCLUSION: Study results showed good correlation between thermal dose estimates and resulting nonperfused areas for smaller ablated volumes. For larger treatment volumes, nonperfused areas could extend within the fibroid to unheated areas.     

Uterine artery embolization for symptomatic fibroids with imaging follow up

The aim of this study was to determine the effectiveness of uterine artery embolization (UAE) as a primary treatment method in treatment of symptomatic fibroids, whether there are any preembolization MRI characteristics of fibroid predictive of reduction in volume and assess reduction in uterine and dominant fibroid volumes using ultrasound (US) and MRI. Study was carried out in total of 32 patients aged 25-49 years (mean 40.9 years). Uterine and dominant fibroid volume were determined using US and MRI before UAE, MRI and US at 3 months and US alone at 6 and 12 months post-UAE, supplemented by clinical evaluation at interval of 3, 6 and 12 months. Procedure was carried out through unilateral femoral puncture using poly vinyl alcohol (PVA) particles 355-500 microm in size. All 32 patients had successful procedures. Overall, 25 patients responded, giving a clinical success rate of 78.12%. Mean reduction in volume of uterus and fibroid was 33 and 59.7% and 48.9 and 75.5% on US at 3 and 12 months respectively, and 33.3 and 58.6% on MRI at 3 months. Volume reduction on US and MRI at 3 months was highly correlative. There was no statistical difference in size reduction in volume of fibroids, which were hypointense or hyperintense on T2-weighted image (T2WI) on pre-UAE MRI. Uterine artery embolization leads to good technical success and fibroid volume reduction. Ultrasound alone may be used for follow up of patients post-UAE. Preprocedure signal characteristics on T2WI are not predictors of volume reduction after UAE.     

High-b-value diffusion-weighted MR imaging for pretreatment prediction and early monitoring of tumor response to therapy in mice

PURPOSE: To evaluate the use of diffusion-weighted magnetic resonance (MR) imaging with standard and high b values for pretreatment prediction and early detection of tumor response to various antineoplastic therapies in an animal model. MATERIALS AND METHODS: Mice bearing C26 colon carcinoma tumors were treated with doxorubicin (n = 25) and with aminolevulinic acid-based photodynamic therapy (n = 23). Fourteen mice served as controls. Conventional T2-weighted fast spin-echo and diffusion-weighted MR images were acquired once before therapy and at 6, 24, and 48 hours after treatment. Pretreatment and early (1-2 days) posttreatment water diffusion parameters were calculated and compared with later changes in tumor volumes measured on conventional MR images by using the Pearson correlation test. RESULTS: In chemotherapy-treated tumors, a significant correlation (P <.002, r = 0.6) was observed between diffusion parameters that reflected tumor viability, measured prior to treatment, and changes in tumor volumes after therapy. This correlation implies that tumors with high pretreatment viability will respond better to chemotherapy than more necrotic tumors. In tumors treated with photodynamic therapy, no such correlation was found. Changes observed in water diffusion 1-2 days after treatment significantly correlated with later tumor growth rate for both therapies (P <.002, r = 0.54 for photodynamic therapy; P <.0003, r = 0.61 for chemotherapy). CONCLUSION: High-b-value diffusion-weighted MR imaging has potential use for the early detection of response to therapy and for predicting treatment outcome prior to initiation of chemotherapy.     

Uterine neoplasms: MR imaging

Magnetic resonance (MR) studies were performed on 20 healthy volunteers and 41 patients with proved cervical and uterine neoplasms. MR imaging demonstrated normal uterine landmarks in all patients. On T2-weighted images, the normal uterine wall could be differentiated into three distinct layers: a central high-intensity zone, a junctional low-intensity band, and a peripheral medium-intensity area. While most of the normal cervices had only two distinct zones (central high-intensity zone and peripheral low-intensity zone), a small percentage had three layers of signal intensity, similar to the uterine body. Primary cervical and uterine neoplasms could be identified on MR images. In 18 of 22 patients with proved carcinoma, a mass with a signal intensity higher than that of normal cervical lips was seen on T2-weighted images. Endometrial carcinoma was most often identified as expansion of the central high-intensity area; discrete tumor nodules were visible in nine of 15 patients. Mixed müllerian sarcoma appeared as a large pelvic mass with complete obliteration of normal uterine landmarks. MR imaging delineates primary cervical and endometrial carcinoma better than computed tomography does.     

MR imaging of shear waves generated by focused ultrasound.

This study has shown that magnetic resonance elastography (MRE) can detect shear waves excited by focused ultrasound (FUS) in both gel phantoms and ex vivo muscle. Good agreement was shown between the shear modulus measured from MRE images generated using FUS and that using previously reported MRE techniques. The shear wave displacement amplitude at the FUS focus was studied and found to be proportional with both FUS ultrasonic pulse intensity and the FUS modulation pulse period over the range tested.     

MRI导航和温度监控下高强度聚焦超声治疗子宫肌瘤

目的 评价高强度聚焦超声(HIFU)在MR导航定位和靶区焦域温度监控下治疗子宫肌瘤的可行性和疗效.方法 采用西门子1.5 T Avanto TIM MR导航和温度监控JM-HIFU进行HIFU治疗52例子宫肌瘤共61个肌瘤.肌瘤大小(6.1±2.1)cm,其中浆膜下10枚、肌壁间46枚和黏膜下5枚.治疗前、后采用增强扫描MRI检查,测量肌瘤体积、消融坏死区域大小占肌瘤体积的比率,并记录治疗时间和超声释放剂量.治疗后3个月MRI检查观察肌瘤的缩小情况;同时观察和评估其并发症及不良反应事件发生,并对治疗前后患者症状变化进行评分.结果 MR导航HIFU(MRgHIFU)治疗前和治疗后3个月肌瘤平均体积分别为(113.3±87.7)cm3和(58.1±45.0)cm3,肌瘤体积平均缩小(48.7±16.4)%(P＜0.05);每个肌瘤被消融区域占整个肌瘤体积平均为(78.8±18.8)%(51%～100%);聚焦超声治疗时间(19.8±8.8)min,治疗所用的超声热剂量为(7.1±6.7)焦耳/mm3.患者症状平均总分治疗前、后从(24.7±4.8)下降至(16.7±3.2)分(P＜0.05),除1例术中出现腹壁皮下轻度烫伤,余无并发症及不良反应事件.结论 MRgHIFU治疗子宫肌瘤是一种可行、安全、有效的无创治疗方法,而且单次热消融可达到肌瘤大部分甚至完全凝固性坏死,并使其短期内缩小的治疗效果.     

被动声学图时空监测高强度聚焦超声治疗

目的探讨在体外牛组织中被动声学图标测高强度聚焦超声(HIFU)治疗的可行性,被动声学图由滤过通道射频数据重建的宽带和谐波发射构成。材料与方法用诊断超声仪对5个新鲜切除及离体的牛肝脏行180次HIFU曝     

Abdomen: diffusion-weighted MR imaging with pulse-triggered single-shot sequences

Magnetic resonance (MR) diffusion measurements of the abdomen were performed in 12 healthy volunteers by using a diffusion-weighted single-shot sequence both without and with pulse triggering for different trigger delays. Pulse triggering to the diastolic heart phase led to reduced motion artifacts on the diffusion-weighted MR images and to significantly improved accuracy and reproducibility of measurements of the apparent diffusion coefficients, or ADCs, of abdominal organs.     

Neonatal hypoxic-ischemic encephalopathy: detection with diffusion-weighted MR imaging

BACKGROUND AND PURPOSE: Although diffusion-weighted imaging has been shown to be highly sensitive in detecting acute cerebral infarction in adults, its use in detecting neonatal hypoxic-ischemic encephalopathy (HIE) has not been fully assessed. We examined the ability of this technique to detect cerebral changes of acute neonatal HIE in different brain locations. METHODS: Fifteen MR examinations were performed in 14 neonates with HIE (median age, 6.5 days; range, 2-11 days). Imaging comprised conventional T1-weighted, proton density-weighted, and T2-weighted sequences and echo-planar diffusion-weighted sequences. The location, extent, and image timing of ischemic damage on conventional and diffusion-weighted sequences and apparent diffusion coefficient (ADC) maps were compared. RESULTS: Although conventional sequences showed cerebral changes consistent with ischemia on all examinations, diffusion-weighted imaging showed signal hyperintensity associated with decreased ADC values in only seven subjects (47%). All subjects with isolated cortical infarction on conventional sequences had corresponding hyperintensity on diffusion-weighted images and decreased ADC values, as compared with 14% of subjects with deep gray matter/perirolandic cortical damage. The timing of imaging did not significantly alter diffusion-weighted imaging findings. CONCLUSION: Diffusion-weighted imaging, performed with the technical parameters in this study, may have a lower correlation with clinical evidence of HIE than does conventional MR imaging. The sensitivity of diffusion-weighted imaging in detecting neonatal HIE appears to be affected by the pattern of ischemic damage, with a lower sensitivity if the deep gray matter is affected as compared with isolated cerebral cortex involvement.