磁共振弥散加权成像、T2加权成像及动态增强联合运用对前列腺癌的诊断价值

目的 探讨磁共振弥散加权成像(DWI)、T2加权像(T2WI)及动态增强(DCE)联合应用对前列腺癌的诊断价值.方法 100例前列腺疾病中前列腺癌49例和非癌病例51例(包括46例前列腺增生、3例外周带炎症及2例前列腺结核).所有病例在常规MR检查基础上加扫DCE及DWI序列,DWI的b值为800 s/mm2.比较T2WI、DCE、DWI及三者联合诊断前列腺癌的敏感性;统计分析前列腺组织与非癌组织的ADC值是否存在差异.结果 在DWI图像上,前列腺癌多呈明显高信号,6例局限于中央带前列腺癌得到正确诊断.前列腺癌组织的平均ADC值为(0.96±0.22)×10-3mm2/s,前列腺增生组织的平均ADC值为(1.56±0.23)×10-3mm2/s,两者之间有统计学差异(P＝0.001),但ADC值有小部分重叠.T2WI、DCE、DWI及三者联合诊断前列腺癌的敏感性分别为85.7%、87.8%、93.9%、100%.结论 T2WI、DCE及DWI三者联合应用可以弥补各自的缺点,提高前列腺癌诊断的敏感性.     

3.0 T磁共振扩散加权成像在直肠癌诊断中的价值

目的 探讨MR扩散加权成像(DWI)在直肠癌诊断中的临床应用价值.资料与方法对50例直肠癌患者和17名无直肠病变的自愿者行盆腔T2WI和DWI,由两名放射诊断医师采用肓法随机进行MRI阅片后对比分析单纯T2WI与T2WI结合DWI对直肠癌诊断的特异性和敏感性差异,并对直肠癌和正常肠壁的表观扩散系数(ADC)值进行定量分析.结果两名医师单纯应用T2WI与T2WI结合DWI检出直肠癌的ROC曲线下面积(Az)值分别为0.873与0.978(P＜0.05)、0.905与0.986(P＜0.05).Kappa一致性检验表明两名医师具有良好的一致性(Kappa值分别为0.860和0.828,P＜0.05).直肠癌和其癌周正常肠壁ADC值的平均值±标准差分别为(0.93±0.14)×10-3 mm2/s、(1.40±0.17)×10-3 mm2/s,直肠癌与正常肠壁的ADC值间差异有统计学意义(t=17.43,P＜0.01).结论 3.0 T MR DWI能较直观地显示直肠癌,其作为常规T2WI的补充检查序列可以明显提高对直肠癌的检出率.     

不同b值下前列腺外周带癌灶ADC值的初步定量分析

目的:探讨DWI在不同b值下前列腺外周带癌灶ADC值的参考值范围。方法:对28例前列腺外周带癌(PCa)的DWI在b值分别为300、600、8001、000 s/mm2时所得前列腺外周带癌灶和正常外周带ADC值进行定量分析。结果:b值分别为300、600、800、1000s/mm2下外周带癌灶的平均ADC值分别为(1.12±0.24)×10-3、(0.95±0.19)×10-3(、0.88±0.14)×10-3(、0.81±0.17)×10-3mm2/s,外周带非癌区平均ADC值分别为(1.93±0.39)×10-3、(1.78±0.23)×10-3、(1.61±0.21)×10-3、(1.53±0.21)mm2/s,同b值下2者比较有统计学意义(P<0.05)。b值分别为300、600、8001、000 s/mm2下外周带癌灶ADC值参考范围分别为(0.63～1.61)×10-3(、0.56～1.34)×10-3(、0.59～1.17)、(0.46～1.16)×10-3mm2/s。结论:前列腺外周带癌区和非癌区ADC值随b值变化而变化,通过ADC值测量可以定量分析前列腺外周带癌,提高前列腺癌诊断的准确率。     

MR扩散加权成像在前列腺病变中的诊断价值

目的：探讨DWI在前列腺病变诊断中的价值。方法：分别对30例前列腺癌（PCa）、30例良性前列腺增生（BPH）患者和30名健康志愿者进行前列腺DWI扫描,分析三者的DWI图、ADC图的信号表现,以及癌灶、增生结节灶、正常前列腺的ADC值,以及前两者病灶ADC值与其周围正常外周带ADC值的相对比值变化规律。所有BPH和PCa病例均经手术或穿刺活检病理证实。结果：①PCa、BPH患者和健康志愿者（各30例）DWI表现：PCa表现为高信号影为主;增生结节呈稍高信号为主,强度低于外周带,并且信号不均匀;健康志愿者外周带呈稍高信号为主,中央带呈等信号为主,外周带信号高于中央带,二者分界清晰;②PCa癌灶平均ADC值（0.878±0.056）×10^-3mm^2/s;BPH增生结节灶平均ADC值（1.379±0.201）×10^-3mm^2/s;健康者前列腺中央带平均ADC值（1.287±0.041）×10^-3mm^2/s;健康者前列腺外周带平均ADC值（1.636±0.064）×10^-3mm^2/s;③PCa癌灶、BPH增生结节灶（各30例）的平均ADC值与其周围正常外周带ADC值的相对比值平均分别为0.54±0.05,0.85±0.06。结论：正常前列腺外周带、BPH、正常前列腺中央带、PCa在DWI图像上信号有较大差别,PCa癌灶信号最高。正常前列腺外周带、BPH、正常前列腺中央带、PCa癌灶的ADC值依次下降。BPH、PCa癌灶ADC值与其周围正常外周带组织ADC值的相对比值有明显差别。ADC值≤0.97×10^-3mm^2/s,特别是同时ADC相对比值≤0.62,是PCa DWI诊断的可靠依据,有临床诊断意义。     

DWI结合T2WI在包膜期脑脓肿与囊性转移瘤鉴别诊断中的价值

目的 探讨磁共振扩散加权成像(DWI)结合T2WI在包膜期脑脓肿和囊性脑转移瘤鉴别诊断中的价值.方法 回顾性分析经病理或临床随访证实的23例包膜期脑脓肿和24例脑囊性转移瘤患者的MRI常规平扫、增强及DWI检查资料,b值取0、500 s/mm2、1000 s/mm2,根据信噪比(SNR)及图像质量指数(QI)取最佳b值的DWI,分别测量病灶囊变区、囊壁、对侧正常脑组织平均ADC值并计算3项rADC值,两组间采用两独立样本t检验进行统计学分析.结果 包膜期脑脓肿T2WI低信号暗带及靶环征是鉴别囊性转移瘤的MRI特征性表现.取b值1000s/mm2时,脑囊性转移瘤囊变坏死区DWI呈低信号22例,高信号1例,囊变坏死区、囊壁、对侧正常脑组织平均ADC值分别为(0.64±0.14)×10-3mm2/s、(1.56 ±0.17)×10-3mm2/s、(0.79±0.18)×10-3mm2/s,脑囊性转移瘤囊壁rADC值、病灶rADC值、囊液rADC值分别为1.19±0.37、0.48 ±0.25、2.74±0.75.包膜期脑脓肿囊液DWI呈高信号,包膜期脑脓肿囊变区、囊壁、对侧正常脑组织平均ADC值分别为(2.10±0.28)×10-3mm2/s、(1.51±0.09)×10-3mm2/s、(0.81±0.15)×10-3mm2/s,包膜期脑脓肿囊壁rADC值、病灶rADC值、囊液rADC值分别为1.37±0.48、1.49±0.62、0.95±0.50.包膜期脑脓肿与脑囊性转移瘤囊液ADC值、病灶rADC值、囊液rADC值差异均有显著统计学意义(P＜0.01),囊壁ADC值、囊壁rADC值差异均无统计学意义(P＞0.05).结论 包膜期脑脓肿壁上T2WI特征性的低信号暗带及靶环征有别于囊性转移瘤,b值=1000 s/mm2时囊液DWI、囊液ADC值、病灶rADC值、囊液rADC值能有效反映包膜期脑脓肿与囊性脑转移瘤的不同囊液性质,DWI结合T2WI对包膜期脑脓肿与囊性脑转移瘤的鉴别诊断具有重要价值.     

磁共振扩散加权成像在膀胱病变的应用初探

目的 初步探讨扩散加权成像(DWI)及表观弥散系数(ADC)在膀胱癌诊断评估中的应用价值.方法 对45例膀胱癌占位患者行DWI及常规MR序列扫描.比较不同b值下膀胱病灶的ADC值及图像效果;分析DWI与常规序列显示膀胱病灶能力的差异;比较膀胱病灶与周围组织ADC值有无差异.结果 b值取700 s/mm2时膀胱病灶平均ADC值显著高于1500 s/mm2的ADC值.DWI发现膀胱病灶的准确率为98.1%,常规MR序列为96.2%.b值取1500 s/mm2时膀胱癌平均ADC值(0.75±0.12)×10-3mm2/s,显著低于膀胱炎(1.39±0.13)×10-3mm2/s、病灶周围正常膀胱壁(1.42±0.07)×10-3mm2/s、尿液(2.69±0.13)×10-3mm2/s(P<0.05).结论 DWI及ADC值对膀胱癌的诊断评估具有较好的应用价值,是对常规MR检查有意义的补充.     

前列腺癌的磁共振DWI诊断价值

目的：分析前列腺癌（PCa）和良性前列腺增生（BPH）的MR扩散加权成像（DWI）和表观扩散系数（ADC）图的表现及其ADC值的差异,探讨DWI在PCa诊断中的价值。方法：对27例PCa,38例BPH进行MR扩散加权成像,分析DWI和ADC图表现,测量PCa区域、BPH的中央腺体区增生结节及外周带的ADC值。结果：PCa在DWI图上表现为高信号,ADC图上表现为低信号;BPH在DWI和ADC图上外周带信号较均匀,中央腺体信号欠均匀。前列腺癌Ca灶及中央腺体非癌灶区平均ADC值分别为（1.091±0.214）×10-3mm2/s和（1.497±0.318）×10-3mm2/s;前列腺增生外周带及中央腺体区增生结节的平均ADC值分别为（1.839±0.190）×10-3mm2/s和（1.509±0.225）×10-3mm2/s。PCa灶的ADC值明显低于BPH外周带及中央腺体区增生结节（P〈0.05）,其间ADC值差异具有显著性意义。结论：MR扩散加权成像对PCa有重要的诊断价值,在常规MRI形态学的基础上,结合DWI图上病变的信号特点及ADC值提供的病理变化信息,能提高对PCa的定性诊断,提高诊断准确率。     

3.0T磁共振扩散加权成像在子宫内膜癌诊断中的价值

目的 探讨3.0T MR扩散加权成像(DWI)在子宫内膜癌诊断中的临床应用价值.方法 对48例子宫内膜癌患者和20例无子宫内膜病变者行盆腔T2WI和DWI,由2名MRI诊断医师采用盲法随机进行MRI阅片后,采用5分制评分,以受试者工作特征曲线(ROC)对比分析单纯T2WI与DWI结合T2WI诊断子宫内膜癌的敏感性和特异性,并对内膜癌和正常内膜的表观扩散系数(ADC)值进行定量分析.结果 2名医师单纯应用T2WI与DWI结合T2WI检出子宫内膜癌的ROC曲线下面积(Az)值分别为0.831与0.944、0.877与0.954,2名医师DWI结合T2WI对内膜癌诊断的准确性均高于单纯应用T2WI(P<0.05).Kappa一致性检验表明2名医师具有良好的一致性(Kappa值分别为0.843和0.898,P<0.01).子宫内膜癌和正常内膜的ADC值分别为(0.954±0.139)×10-3mm2/s、(1.468±0.161)×10-3mm2/s,子宫 内膜癌与正常内膜的ADC值间差异有统计学意义(t=-13.217,P<0.01).结论 3.0T MR-DWI作为常规T2WI的补充检查序列可以明显提高对子宫内膜癌的检出率.     

3.0T磁共振DWI结合T2WI鉴别前列腺移行区的良恶性结节

目的 探讨分别应用T2WI、DWI以及综合应用2种成像序列对前列腺移行区良恶性结节的鉴别诊断价值.方法 收集2006-08-2010-04在本院3.0T磁共振行常规及DWI扫描(b值分别为0 s/mm2和800 s/mm2)的前列腺疾病患者,其中70例前列腺移行区见到结节样异常信号者被纳入本研究,本组患者后来均行超声引导下经直肠前列腺穿刺活检术.分析良恶性结节的MRI表现,比较其ADC值.采用5分制评分,将所得结果与病理结果对照,用SPSS11.5分别做受试者工作特征曲线(ROC),分析比较各组方法诊断的敏感度和特异度.结果 病理证实54例患者为前列腺移行区良性结节,16例为移行区前列腺癌(prostate cancer,PCa),良性和恶性结节的ADC值分别为(1.352±0.088 5)×10-3 mm2/s和(0.931±0.079 5)×10-3 mm2/s,恶性结节的ADC值明显低于良性结节(P<0.05).联合DWI和T2WI 2种成像序列鉴别前列腺移行区良恶性结节的ROC曲线下面积(AUC)最大(0.993,95%CI:0.935~0.995),其与单独应用T2WI 的AUC之间的差异有统计学意义(Z=2.093,P<0.05),但是与单独应用DWI的AUC之间的差异无统计学意义(Z=0.905,P=0.365);T2WI鉴别前列腺移行区良恶性结节的AUC低于DWI的,但两者之间的差异无统计学意义(Z=1.629,P=0.103),2种序列结合鉴别前列腺移行区良恶性结节的特异度和敏感度最高.结论 前列腺移行区恶性结节的ADC值明显低于良性结节;联合应用DWI和T2WI鉴别诊断良恶性结节的特异度和敏感度最高.     

MR扩散加权成像对前列腺癌的诊断价值

目的 探讨磁共振扩散加权成像(DWI)在前列腺癌的诊断及鉴别诊断中的应用价值.资料与方法 40例前列腺疾病中17例前列腺癌及23例前列腺增生.所有病例行MR DWI扫描,b值为800 s/mm2.分析各病例的DWI和表观扩散系数(ADC)图表现,并分别测量癌区、前列腺增生组织以及膀胱内尿液的ADC值,统计分析组间是否存在差异.结果 17例前列腺癌中15例在DWI上呈明显高信号,ADC图呈低信号,能直观显示肿瘤的范围.前列腺癌组织的平均ADC值为(1.03±0.32)×10-3 mm2/s,前列腺增生组织的平均ADC值为(1.62±0.16)×10-3 mm2/s,两者之间有统计学意义(P=0.002);前列腺癌与前列腺增生的膀胱内尿液的平均ADC值分别为(3.24±0.30)×10-3 mm2/s、(3.25±0.29)×10-3 mm2/s,两者之间无统计学意义(P=0.834).结论 DWI可显示前列腺癌的位置和侵犯范围;根据DWI信号特点以及ADC值可以提高前列腺癌的诊断准确率,对前列腺癌与前列腺增生具有较高的鉴别诊断价值.     

Fast T1- and T2-weighted pulmonary MR-imaging in patients with bronchial carcinoma

PURPOSE: A prospective study to evaluate the diagnostic potential and limitations of three fast MRI sequences in patients with bronchial carcinoma based on the comparison with spiral CT. MATERIAL AND METHODS: Three fast chest MRI sequences from 20 patients with central or peripheral bronchial carcinoma were evaluated by two observers for relation of tumour to adjacent structures, lymph node enlargement, additional pulmonary lesions and artefacts. The information from MR-imaging was compared with the results from spiral CT. MRI comprised a T1-3D-GRE breath-hold examination ("VIBE", TR/TE 4.5/1.9 ms, flip-angle 12 degrees , matrix 502 x 512, 2.5 mm coronal slices), a breath-hold, T2-HASTE sequence (TR/TE 2000/43 ms, matrix 192 x 256, 10 mm coronal slices) and a respiration-triggered T2-TSE sequence (TR/TE 3000-6000/120 ms, matrix 270 x 512, 6 mm transverse slices). The FOV was adapted individually (380-480 mm). RESULTS: The presence of the primary bronchial carcinoma and infiltration of thoracic structures by tumour tissue could be demonstrated by all sequences. VIBE sequence was more suitable for detecting small pulmonary nodules than the other MRI examinations, but compared to CT still 20% of these lesions were missed. Contrary to VIBE and T2-weighted TSE scans, HASTE sequence was limited in imaging mediastinal lymph nodes due to missing relevant findings in 2/20 patients. HASTE images significantly provided the lowest rate of artefacts in imaging lung parenchyma (P < 0.001 in peripheral parenchyma), but spatial resolution was limited in this sequence. Concerning the differentiation between tumour and adjacent atelectasis (n = 8), T2-weighted TSE imaging was superior to CT and VIBE in all cases and to HASTE sequence in 4/8 patients. CONCLUSION: The combination of VIBE and HASTE sequence allows for an adaequate imaging of thoracic processes in patients with bronchial carcinoma, limited only in visualizing small pulmonary nodules. To obtain more detail resolution and to differentiate tumour tissue from adjacent atelectasis, T2-TSE examination may be added in selected cases.     

T1 and T2 alterations in the brains of patients with hepatic cirrhosis.

PURPOSETo determine whether previously reported T1-weighted MR hyperintensities in the brains of patients with hepatic cirrhosis are accompanied by changes in T2.METHODSWe measured T1 and T2 in the brains of 10 patients with chronic liver disease and 7 age-matched healthy volunteers, using classic spin-echo sequences with multiple saturation recovery times and multiple echoes.RESULTSBoth T1 and T2 were shortened in the basal ganglia, cortex, and white matter of the patients, with the greatest shortening in the globus pallidus, where 1/T1 was increased by 0.76 s-1 or 74% and 1/T2 by 1.45 s-1 or 11%.CONCLUSIONSThe T1 changes were accompanied by T2 changes of greater magnitude that were not as visible because T2 is normally much shorter than T1, especially in the globus pallidus.     

T1rho MRI of menisci and cartilage in patients with osteoarthritis at 3T

Objective

To assess and compare subregional and whole T1rho values (median ± interquartile range) of femorotibial cartilage and menisci in patients with doubtful (Kellgren–Lawrence (KL) grade 1) to severe (KL4) osteoarthritis (OA) at 3T.

Materials and methods

30 subjects with varying degrees of OA (KL1–4, 13 females, 17 males, mean age ± SD = 63.9 ± 13.1 years) were evaluated on a 3T MR scanner using a spin-lock-based 3D GRE sequence for T1rho mapping. Clinical proton density (PD)-weighted fast spin echo (FSE) images in sagittal (without fat saturation), axial, and coronal (fat-saturated) planes were acquired for cartilage and meniscus Whole-organ MR imaging score (WORMS) grading. Wilcoxon rank sum test was performed to determine whether there were any statistically significant differences between subregional and whole T1rho values of femorotibial cartilage and menisci in subjects with doubtful to severe OA.

Results

Lateral (72 ± 10 ms, median ± interquartile range) and medial (65 ± 10 ms) femoral anterior cartilage subregions in moderate–severe OA subjects had significantly higher T1rho values (P < 0.05) than cartilage subregions and whole femorotibial cartilage in doubtful–minimal OA subjects. There were statistically significant differences in meniscus T1rho values of the medial posterior subregion of subjects with moderate–severe OA and T1rho values of all subregions and the whole meniscus in subjects with doubtful–minimal OA. When evaluated based on WORMS, statistically significant differences were identified in T1rho values between the lateral femoral anterior cartilage subregion in patients with WORMS5–6 (advanced degeneration) and whole femorotibial cartilage and all cartilage subregions in patients with WORMS0–1 (normal).

Conclusion

T1rho values are higher in specific meniscus and femorotibial cartilage subregions. These findings suggest that regional damage of both femorotibial hyaline cartilage and menisci may be associated with osteoarthritis.     

T1 and T2 mapping in the identification of acute myocardial injury in patients with NSTEMI

Aims

To test T1 and T2 mapping in the assessment of acute myocardial injury in patients with non-ST-segment elevation myocardial infarction (NSTEMI), evaluated before revascularization.

Methods

Forty-seven patients with acute NSTEMI underwent cardiac magnetic resonance (CMR) at 1.5 T, including T1 and T2 mapping.

Results

Coronary angiography (CA) evidenced an obstructive coronary artery disease (CAD) in 36 patients (80%) and a non-obstructive CAD in 11 patients (20%). Edema was detected in 51.1/65.9% of patients in T1/T2 maps, respectively. This difference was due to artifacts in T1 maps. T1/T2 values were significantly higher in the infarcted myocardium (IM) compared with the remote myocardium (RM) (in T1: 1151.6?±?53.5 ms vs. 958.2?±?38.6 ms, respectively; in T2: 69?±?6 ms vs. 51.9?±?2.9 ms, respectively; p?<?0.0001 for both). We found both an obstructive CAD at CA and myocardial edema at CMR in 53.2% of patients, while 8.5% of patients had a non-obstructive CAD and no edema. However, 25.5% of patients had an obstructive CAD without edema, while 12.8% of patients showed edema despite a non-obstructive CAD. Furthermore, in 6 of the edema-positive patients with multi-vessels obstructive CAD, CMR identified myocardial edema in a vascular territory different from that of the lesion supposed to be the culprit at CA.

Conclusions

In a non-negligible percentage of NSTEMI patients, T1 and T2 mapping detect myocardial edema without significant stenosis at CA and vice versa. Therefore, CA and CMR edema imaging might provide complementary information in the evaluation of NSTEMI.

     

NMR relaxation times T1 and T2 of water in plasma from patients with lung carcinoma: correlation of T2 with blood sedimentation rate

The T1 and T2 NMR relaxation times of water protons in plasma, obtained from patients with lung carcinoma, healthy volunteers, and patients with nontumor diseases were measured at a resonance frequency of 20 MHz. Additionally hematologic parameters were determined. In tumor patients the mean plasma T2 was shortened by about 20%, and an increase in the blood sedimentation rate (BSR) was noted. Similar but less pronounced results were found for the nontumor group of patients, indicating that the shortening of T2 in plasma is a secondary host response. However, a plot of plasma 1/T2 versus BSR from tumor patients showed a significant correlation between these two parameters. No such correlation could be detected in the nontumor group of patients. The correlation of 1/T2 with BSR, found solely in the tumor patient group, increased the diagnostic sensitivity of T2 measurements and may help to differentiate between malignant and nonmalignant disease. No significant variation in the T1 spin-lattice relaxation time was observed.     

Feasibility, reproducibility, and reliability for the T*2 iron evaluation at 3 T in comparison with 1.5 T

This study aimed to determine the feasibility, reproducibility, and reliability of the multiecho T*₂ Magnetic resonance imaging technique at 3 T for myocardial and liver iron burden quantification and the relationship between T*₂ values at 3 and 1.5 T. Thirty‐eight transfusion‐dependent patients and 20 healthy subjects were studied. Cardiac segmental and global T*₂ values were calculated after developing a correction map to compensate the artifactual T*₂ variations. The hepatic T*₂ value was determined over a region of interest. The intraoperator and interoperator reproducibility for T*₂ measurements at 3 T was good. A linear relationship was found between patients' R (1000/T*₂) values at 3 and 1.5 T. Segmental correction factors were significantly higher at 3 T. A conversion formula returning T*₂ values at 1.5 T from values at 3 T was proposed. A good diagnostic reliability for T*₂ assessment at 3 T was demonstrated. Lower limits of normal for 3 T T*₂ values were 23.3 ms, 21.1 ms, and 11.7 ms, for the global heart, mid‐ventricular septum, and liver, respectively. In conclusion, T*₂ quantification of iron burden in the mid‐ventricular septum, global heart, and no heavy–moderate livers resulted to be feasible, reproducible, and reliable at 3 T. Segmental heart T*₂ analysis at 3 T may be challenging due to significantly higher susceptibility artifacts. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.     

T1rho relaxation mapping in human osteoarthritis (OA) cartilage: comparison of T1rho with T2

PURPOSE: To quantify the spin-lattice relaxation time in the rotating frame (T1rho) in various clinical grades of human osteoarthritis (OA) cartilage specimens obtained from total knee replacement surgery, and to correlate the T1rho with OA disease progression and compare it with the transverse relaxation time (T2). MATERIALS AND METHODS: Human cartilage specimens were obtained from consenting patients (N = 8) who underwent total replacement of the knee joint at the Pennsylvania Hospital, Philadelphia, PA, USA. T2- and T1rho-weighted images were obtained on a 4.0 Tesla whole-body GE Signa scanner (GEMS, Milwaukee, WI, USA). A 7-cm diameter transmit/receive quadrature birdcage coil tuned to 170 MHz was employed. RESULTS: All of the surgical knee replacement OA cartilage specimens showed elevated relaxation times (T2 and T1rho) compared to healthy cartilage tissue. In various grades of OA specimens, the T1rho relaxation times varied from 62 +/- 5 msec to 100 +/- 8 msec (mean +/- SEM) depending on the degree of cartilage degeneration. However, T2 relaxation times varied only from 32 +/- 2 msec to 45 +/- 4 msec (mean +/- SEM) on the same cartilage specimens. The increase in T2 and T1rho in various clinical grades of OA specimens were approximately 5-50% and 30-120%, respectively, compared to healthy specimens. The degenerative status of the cartilage specimens was also confirmed by histological evaluation. CONCLUSION: Preliminary results from a limited number of knee specimens (N = 8) suggest that T1rho relaxation mapping is a sensitive noninvasive marker for quantitatively predicting and monitoring the status of macromolecules in early OA. Furthermore, T1rho has a higher dynamic range (>100%) for detecting early pathology compared to T2. This higher dynamic range can be exploited to measure even small macromolecular changes with greater accuracy compared to T2. Because of these advantages, T1rho relaxation mapping may be useful for evaluating early OA therapy.     

MR colonoscopy at 3.0 T: comparison with 1.5 T in vivo and a colon model

PURPOSE: Retrospectively, magnetic resonance (MR) colonography images obtained from a colon model and in routine examinations of patients screened for polyps were compared in terms of whether, and to what degree, image quality improved at a higher field strength of 3.0 T compared to 1.5 T. MATERIALS AND METHODS: One hundred twenty-eight MR colonography images from 40 patients, of whom 20 had each been scanned at 1.5 and 3.0 T, respectively, using a four-element phased-array torso coil, were compared. At both field strengths, imaging included T1-weighted fat-suppressed spoiled gradient-echo (T1-fs-GE), T2/T1-weighted fast imaging employing steady-state acquisition (FIESTA), and T2-weighted single-shot fast spin-echo (T2-SSFSE), with breath-hold technique. Using receiver operating characteristic analysis performed by seven readers, the three types of images from the colon model and from 20 patients each at 1.5 and 3.0 T were compared. While a time window of 20 s was allowed for picture assessment in a chance-generated succession of images on a monitor, image quality was rated with a score of 1-5 (1=very good; 5=very bad). Statistical significance was calculated with Mann-Whitney U test. RESULTS: At both field strengths, T2-SSFSE images received the best ratings, followed by FIESTA images (P=.001). Although, overall, the 3.0-T images obtained scores worse than those of the 1.5-T images, a better detection of phantom polyps was noted in the colon model (P=.001). CONCLUSION: Although MR colonography with the breath-hold technique using the same four-element phased-array coil at 3.0 and 1.5 T does not perform better at a higher field strength in general, an improved detection of small polyps may be obtained.