Breast lesions: evaluation with dynamic contrast-enhanced T1-weighted MR imaging and with T2*-weighted first-pass perfusion MR imaging

PURPOSE: To evaluate the diagnostic value of an imaging protocol that combines dynamic contrast-enhanced T1-weighted magnetic resonance (MR) imaging and T2*-weighted first-pass perfusion imaging in patients with breast tumors and to determine if T2*-weighted imaging can provide additional diagnostic information to that obtained with T1-weighted imaging. MATERIALS AND METHODS: One hundred thirty patients with breast tumors underwent MR imaging with dynamic contrast-enhanced T1-weighted imaging of the entire breast, which was followed immediately with single-section, T2*-weighted imaging of the tumor. RESULTS: With T2*-weighted perfusion imaging, 57 of 72 carcinomas but only four of 58 benign lesions had a signal intensity loss of 20% or more during the first pass, for a sensitivity of 79% and a specificity of 93%. With dynamic contrast-enhanced T1-weighted imaging, 64 carcinomas and 19 benign lesions showed a signal intensity increase of 90% or more in the first image obtained after the administration of contrast material, for a sensitivity of 89% and a specificity of 67%. CONCLUSION: T2*-weighted first-pass perfusion imaging can help differentiate between benign and malignant breast lesions with a high level of specificity. The combination of T1-weighted and T2*-weighted imaging is feasible in a single patient examination and may improve breast MR imaging.     

潘生丁负荷增强超高速MRI评价心肌灌注储备的初步研究

目的 评价潘生丁负荷心肌首过灌注储备磁共振成像技术对缺血性心性心脏病的诊断作用。方法 采用１．５ＴＭＲ成像设备对３０位健康志愿者和２１位经核素心肌灌注显像及冠状动脉造影检查确定有心肌缺血的患者进行潘生丁负荷心肌首过灌注储备ＭＲＩ的研究。并对心肌灌液储备的相关参数进行定量分析以及对比研究。结果 以信号强度－时间曲线的峰时（ｔｐ）、最大信号强度增加值（ＳＩｍ）、最大上升斜率（ｓｌｏｐｅ）和平均通过时间     

Comparison of breath-hold T1-weighted MR sequences for imaging of the liver

Three rapid T1-weighted gradient-echo techniques for imaging of the liver were compared: fast low-angle shot (FLASH) and section-selective (SSTF) and non-section-selective (NSTF) inversion-recovery TurboFLASH. Ten healthy volunteers were imaged at 1.5 T, with breath-hold images acquired in the transaxial and coronal planes and non-breath-hold images in the transaxial plane. Breath-hold images were evaluated quantitatively and qualitatively, and non–breath-hold images were evaluated qualitatively. FLASH images had significantly higher (P <.001) spleenliver signal difference–to-noise ratios (SD/Ns) than NSTF and SSTF images. Liver signal-to-noise ratios (S/Ns) were significantly higher (P <.001) on FLASH images than on NSTF and SSTF images. With breath hold. FLASH images were rated as having the highest quality in the axial plane, followed by NSTF and SSTF images. In the coronal plane, NSTF images were rated as having the highest quality. For images acquired during patient respiration, NSTF images had the highest quality and showed the least degradation. The results suggest that FLASH images have the highest SD/N and S/N for liver imaging and have the highest quality in the axial plane. In patients who cannot suspend respiration, NSTF images may be least affected by breathing artifact and provide reasonable image quality.     

Contrast-dose relation in first-pass myocardial MR perfusion imaging

PURPOSE: To determine the regime of linear contrast enhancement in human first-pass perfusion cardiovascular magnetic resonance (CMR) imaging to improve accuracy in myocardial perfusion quantification. MATERIALS AND METHODS: A total of 10 healthy subjects were studied on a clinical 1.5T MR scanner. Seven doses of Gd-DTPA ranging from 0.00125 to 0.1 mmol/kg of body weight (b.w.) were administered as equal volumes by rapid bolus injection (6 mL/second). Resting periods of 15 minutes were introduced after delivery of Gd doses >0.01 mmol/kg b.w. For each subject, two series of rest perfusion scans were performed using two different multislice saturation-recovery perfusion sequences. Maximum contrast enhancement and maximum upslope were obtained in the blood pool of the left ventricular (LV) cavity and in the myocardium. The range of linear contrast-dose relation was determined by linear regression analysis. RESULTS: MR signal intensity increased linearly for contrast agent concentrations up to 0.01 mmol/kg b.w. in the LV blood pool and up to 0.05 mmol/kg b.w. in the myocardium. For Gd concentrations exceeding these thresholds the signal intensity response was not linear with respect to the contrast agent dose. CONCLUSION: Quantitative evaluation of cardiac MR perfusion data needs to account for signal saturation in both the LV blood pool and the myocardium.     

Recent myocardial infarction: assessment with unenhanced T1-weighted MR imaging

The purpose of the study was to prospectively evaluate a T1-weighted technique for detection of myocardial edema resulting from recent myocardial infarction (MI) or intervention. This study was HIPAA compliant and institutional review board approved. Fifteen men and one woman (mean age, 57.8 years+/-11.5 [standard deviation]) were examined with T1-weighted magnetic resonance (MR) imaging and inversion-recovery cine pulse sequence in two groups, recent MI and chronic MI, and gave informed consent. T1 relaxation times of MI and adjacent myocardium were compared (Student t test and correlation analysis). In patients with recent MI, areas of myocardial edema were well depicted with T1-weighted MR imaging. T1 relaxation times of recent infarcts were longer than those of older MIs (925 msec+/-169 vs 551 msec+/-107, P<.001). From local edema, T1 relaxation time of infarcted myocardium is increased, may remain elevated for 2 months, and enables imaging with T1-weighted techniques.     

Acute myocardial infarction: comparison of T2-weighted and T1-weighted gadolinium-DTPA enhanced MR imaging

Magnetic resonance images were obtained from 32 patients with acute myocardial infarction, using a four-echo technique (echo time (TE) = 30, 60, 90, and 120 ms) pregadolinium(Gd)-DTPA injection and a TE = 30 ms sequence pre- and post-Gd-DTPA. Intensity ratios of infarcted and normal myocardium were calculated, as were contrast-to-noise and signal-to-noise ratios. The four intensity ratios pre-Gd-DTPA were 1.20 +/- 0.15, 1.42 +/- 0.22, 1.78 +/- 0.38, and 1.99 +/- 0.60 for TE = 30, 60, 90, and 120 ms, respectively, and 1.42 +/- 0.19 post-Gd-DTPA (p = NS for post-Gd-DTPA vs TE = 60, p = 0.007 for TE = 90 vs TE = 120, p less than 0.0001 for all other comparisons). The four contrast-to-noise ratios pre-Gd-DTPA were 1.69 +/- 0.97, 2.69 +/- 1.13, 3.17 +/- 1.15, and 2.90 +/- 1.09 for TE = 30, 60, 90, and 120 ms, respectively, and 2.71 +/- 1.26 post-Gd-DTPA (p = NS for post-Gd-DTPA vs TE = 60, 90, and 120, p = NS for TE = 120 vs TE = 60 and 90, p less than 0.01 for all other comparisons). The four signal-to-noise ratios pre-Gd-DTPA were 8.67 +/- 1.47, 6.52 +/- 0.76, 5.20 +/- 0.64, 4.17 +/- 0.53 for TE = 30, 60, 90, and 120 ms, respectively, and 9.17 +/- 1.92 post-Gd-DTPA (p = 0.03 for post-Gd-DTPA vs TE = 30, p less than 0.0001 for all other comparisons). In conclusion, the detectabilities of acute myocardial infarction were similar at TE = 60 ms and at Gd-DTPA enhanced short-TE MR imaging. However, image quality proved to be superior using the Gd-DTPA enhanced short-TE technique.     

梗死心肌的MRI评价及病理对照实验研究

目的　通过MR影像与病理对照的方法明确心肌梗死后 7～ 10dMRI延迟强化区与梗死心肌的关系 ,以期为MRI评价心肌活性提供病理依据。方法　利用 6只猪无再灌注和再灌注的心肌梗死模型 ,行短轴面MR心肌延迟强化扫描。扫描结束后将心脏离体 ,沿短轴面将心脏切成断面行氯化三苯基四氮唑 (TTC)染色。比较心肌梗死区和正常对照区的延迟强化信号强度的差异 ;比较相应层面的MRI延迟强化区和TTC染色所示梗死区的关系。结果　在心肌梗死的 7～ 10d ,无论有无再灌注 ,MR延迟强化扫描均可见心肌梗死区信号较正常对照区明显升高 ,无再灌注组梗死区信号( 2 0 81± 6 49)是正常对照区 ( 2 68± 1 10 )的 7 76倍 (t =11 68,P <0 0 1) ,再灌注组梗死区信号( 14 2 8± 1 64)是正常对照区 ( 1 44± 0 52 )的 9 92倍 (t =3 1 69,P <0 0 1) ;无再灌注组的延迟强化区[占同层面左室面积的百分率为 ( 15 49± 6 0 7) % ]与梗死心肌 [( 14 95± 7 3 6) % ]一致 (t =-0 78,P>0 0 5) ,再灌注组的延迟强化区 [( 12 52± 5 93 ) % ]包括梗死区 [( 11 13± 5 81) % ]和梗死周围区 ,过度估计梗死心肌范围约 12 47% (t =-14 48,P <0 0 1)。结论　在心肌梗死的 7～ 10d ,MR延迟强化扫描可较准确地反映梗死心肌的范围     

Fast breath-hold T2-weighted MR imaging reduces interobserver variability in the diagnosis of adenomyosis

OBJECTIVE: We compared two rapid MR imaging T2-weighted pulse sequences with high-resolution turbo spin-echo for the diagnosis of adenomyosis, and we evaluated interobserver variability. SUBJECTS AND METHODS: Fifty-six consecutive patients referred for hysterectomy prospectively underwent MR imaging. Two fast pulse sequences using a breath-hold technique-true fast imaging with steady-state free precession (FISP) and turbo inversion recovery-and turbo spin-echo T2-weighted images of the pelvis were obtained in each patient. The images were analyzed in a blinded manner and independently by three reviewers with different levels of experience for the accuracy of adenomyosis diagnosis, image quality, anatomic visualization, and image artifacts. The accuracy for the diagnosis of adenomyosis on turbo spin-echo T2-weighted imaging combined with one or two fast pulse sequences was evaluated for each reviewer. RESULTS: Twenty-four patients (42.9%) had a histologic diagnosis of adenomyosis. The accuracy for the diagnosis of adenomyosis for reviewers 1, 2, and 3 using turbo spin-echo T2-weighted, true FISP, and turbo inversion recovery sequences was 83.9%, 67.8%, 75%; 83.9%, 67.8, 78.5%; and 87.5%, 73.2%, and 75%, respectively. A difference in the accuracy rate was found among the observers for the three sequences (p < 0.001). Whatever the pulse sequence, the accuracy rate was higher for the reviewer with more experience in gynecologic imaging. The combination of turbo spin-echo T2-weighted imaging with at least one rapid sequence increased the accuracy of observers with little experience in gynecology. With turbo inversion recovery sequences, the image quality score was low for the three reviewers compared with turbo spin-echo T2-weighted and true FISP sequences. The combination of turbo spin-echo T2-weighted and true FISP sequences gave the highest image quality scores. CONCLUSION: Breath-hold T2-weighted sequences optimize the accuracy of MR imaging for the diagnosis of adenomyosis and reduce interobserver variability.     

T2-weighted MR imaging in the assessment of cirrhotic liver

PURPOSE: To assess if T2-weighted magnetic resonance (MR) imaging provides added diagnostic value in combination with dynamic gadolinium-enhanced MR imaging in the detection and characterization of nodular lesions in cirrhotic liver. MATERIALS AND METHODS: Two readers retrospectively and independently analyzed 54 MR imaging studies in 52 patients with cirrhosis. In session 1, readers reviewed T1-weighted and dynamic gadolinium-enhanced images. In session 2, readers reviewed T1-weighted, dynamic gadolinium-enhanced, and respiratory-triggered T2-weighted fast spin-echo images. Readers identified and characterized all focal lesions by using a scale of 1-4 (1, definitely benign; 4, definitely malignant). Multireader correlated receiver operating characteristic (ROC) analysis was employed to assess radiologist performance in session 2 compared with session 1. The difference in the areas under the ROC curves for the two sessions was tested. In a third session, readers assessed conspicuity of biopsy-proved lesions on T2-weighted MR images by using a scale of 1-3 (1, not seen; 3, well seen) and identified causes of reduced conspicuity. RESULTS: Two additional benign lesions were detected by each reader in session 2. Fifty-five lesions had pathologic verification, including 32 malignant, three high-grade dysplastic, and 20 benign nodules. There was no significant difference in the area under the ROC curves between the two sessions (P =.48). Thirty-two lesions were inconspicuous on T2-weighted MR images because of parenchymal heterogeneity, breathing artifacts (particularly in patients with ascites), and lesion isointensity with liver parenchyma. T2-weighted MR imaging was useful in the evaluation of cysts and lymph nodes. CONCLUSION: T2-weighted MR imaging does not provide added diagnostic value in the detection and characterization of focal lesions in cirrhotic liver.     

Occlusive myocardial infarction: investigation of bis-gadolinium mesoporphyrins-enhanced T1-weighted MR imaging in a cat model

PURPOSE: To test whether bis-gadolinium mesoporphyrins-enhanced magnetic resonance (MR) imaging can accurately depict irreversibly damaged myocardium in occlusive myocardial infarction. MATERIALS AND METHODS: Ten cats were subjected to 90 minutes of occlusion of the left anterior descending coronary artery. Bis-gadolinium mesoporphyrins-enhanced T1-weighted MR imaging was performed in the cats for 6 hours. Histopathologic examinations with 2'3'5-triphenyl tetrazolium chloride (TTC) staining and electron microscopy were performed on the resected specimens. The time course and pattern of signal intensity enhancement were evaluated. The size of the infarcted myocardium was estimated on the MR images by measuring the size of the signal intensity-enhanced area. RESULTS: In eight of 10 cats, it was impossible to distinguish infarcted myocardium from normal myocardium at visual inspection of T1-weighted MR images. The contrast ratio between infarcted and normal myocardium did not increase significantly over time. In one of the two remaining cats, a doughnut pattern of signal intensity enhancement was noted. The other cat showed intensely homogeneous enhancement of infarcted myocardium at MR imaging. The size of the area of signal intensity enhancement at MR imaging in these two cats was accurately mapped to that of the infarction on the TTC-stained specimens. CONCLUSION: Occlusive myocardial infarction cannot be accurately detected at bis-gadolinium mesoporphyrins-enhanced MR imaging.     

Gadolinium-enhanced MR imaging, T2-weighted MR imaging, and transurethral ultrasonography

PURPOSE: To assess the value and problems of dynamic gadolinium-enhanced MR imaging, T2-weighted MR imaging, and transurethral ultrasonography(TUUS) in staging of urinary bladder cancer. MATERIALS AND METHODS: Dynamic gadolinium-enhanced MR imaging and FSE T2-weighted MR imaging of 64 patients with urinary bladder cancer who subsequently had surgery were retrospectively reviewed and compared with TUUS findings. RESULTS: Specificity for muscular invasion was 90.5% with TUUS, significantly better than with dynamic MR imaging (64.9%) (p < 0.05). The rates of overestimation of superficial cancer(pT1) with dynamic MRI and T2-weighted MR imaging were 35.1%(13/37) and 24.3%(9/37), respectively. The staging accuracy of invasive cancer(pT2 or over) was 85.2% with dynamic MR imaging, which was better than the rate of 75.0% achieved with T2-weighted MR imaging. CONCLUSION: Although TUUS was a better modality for diagnosing superficial cancer(pT1), dynamic MR imaging was found to be better for diagnosing invasive(pT2 or over) cancer.     

Contrast in rapid MR imaging: T1- and T2-weighted imaging

Partial saturation (PS) is an imaging technique that is useful in applications that require rapid image acquisitions (imaging time less than 1 min). Image contrast in PS imaging, as in other magnetic resonance methods, depends on the often conflicting effects of differences in proton density, T1, and T2. Previous analyses of pulse sequence optimization to maximize image contrast have assumed 90 degrees pulses and examined the effects of varying repetition times (TR) and echo times (TE). In this paper we present theoretical calculations and images made with a 0.6 T imager to show that the radiofrequency pulse tip angle alpha, and not the pulse sequence timing parameters, is the most important parameter for producing image contrast. For large tip angles (alpha greater than or equal to 60 degrees), contrast is primarily determined by differences in T1, but for small tip angles (alpha approximately equal to 25 degrees), contrast is primarily due to differences in T2. The T2-weighted images can be produced as quickly as T1-weighted images by using a small pulse angle and a long TE; it is not necessary to use a long TR to reduce the effects of T1 differences. Optimum pulse angles are calculated, and the potential advantages and disadvantages of T2-weighted and T1-weighted PS imaging are discussed.     

Added diagnostic value of T2-weighted MR imaging to gadolinium-enhanced three-dimensional dynamic MR imaging for the detection of small hepatocellular carcinomas

Purpose

To assess the added value of T2-weighted MRI to gadolinium-enhanced dynamic MRI for detection of HCCs.

Materials and methods

Two readers retrospectively analyzed MRIs of 115 patients with 131 HCCs (size; 0.6–2.0 cm) that had been diagnosed by histology (n = 41) or imaging findings (n = 90). Two separate blind image analyses of the gadolinium set and the combined T2-weighted imaging and gadolinium sets were performed. Diagnostic accuracy was evaluated using the alternative-free response receiver operating characteristic method with four-point scale. Sensitivity and positive predictive value were also calculated.

Results

For both observers, the Az values and sensitivities with the combined T2-weighed imaging and gadolinium set (mean Az 0.806, sensitivity 84.7) were significantly higher than those with the gadolinium set (mean Az 0.660, sensitivity 59.9) (p < 0.05). The addition of T2-weighted imaging led to a change in diagnosis for 27 lesions by both observers, which at gadolinium set were assigned a confidence level of 1 or 2 but at additional reading of T2-weighted imaging were assigned a confidence level of 3 or 4. For the positive predictive values, each image set showed a similar value for each observer.

Conclusion

The addition of T2-weighted imaging to gadolinium-enhanced 3D dynamic imaging could be helpful in the detection of HCC by increasing reader confidence for HCCs with equivocal findings on gadolinium-enhanced MRIs.     

Solitary hepatic metastasis: Comparison of dynamic contrast-enhanced CT and MR imaging with fat-suppressed T2-weighted,Breath-hold T1-weighted FLASH,and dynamic gadolinium-enhanced FLASH sequences

Twenty consecutive cancer patients with a solitary hepatic metastasis detected with dynamic contrast-material—enhanced computed tomography (CT) who were considered for hepatic resection underwent magnetic resonance (MR) imaging within 18 days after CT. Histologic confirmation was obtained in all lesions. CT depicted 20 solitary lesions. MR imaging showed a solitary lesion in 14 patients, two lesions in three patients, and more than two lesions in three patients, for a total of 37 lesions. Twenty-three lesions less than 2 cm in diameter were missed with CT, and six lesions less than 1.3 cm in diameter were missed with MR imaging. MR imaging was superior to CT in the detection of hepatic metastases on a patient-by-patient basis (P <.01). The results suggest that MR imaging is superior to dynamic contrast-enhanced CT for the detection of hepatic metastases.     

Endometrial carcinoma in adenomyosis: assessment of myometrial invasion on T2-weighted spin-echo and gadolinium-enhanced T1-weighted images

OBJECTIVE: The aim of our study was to compare T2-weighted and contrast-enhanced dynamic T1-weighted images with histologic findings in assessing the depth of myometrial invasion by endometrial carcinoma in adenomyosis. MATERIALS AND METHODS: We retrospectively reviewed the MRIs of 11 patients who had a total of 12 lesions of endometrial carcinoma within adenomyosis. T2-weighted and contrast-enhanced dynamic T1-weighted images were compared with the histologic findings separately. We assessed the extent of myometrial invasion by endometrial carcinomas. The depth of myometrial invasion seen on MRI was classified as stage S (superficial invasion), stage D (deep invasion), or undetectable. The staging accuracies of each sequence were assessed. The tumor-myometrium contrast-to-noise ratios were calculated for each sequence. RESULTS: The histologic specimens revealed that myometrial invasion was deep in seven of 12 lesions and superficial in five. On T2-weighted images the depth of invasion was underestimated in two lesions and impossible to determine in five lesions. On dynamic T1-weighted images the depth of invasion was overestimated in one lesion and underestimated in one lesion. The staging accuracy on dynamic T1-weighted images (83%) was significantly higher than that on T2-weighted images (42%). The contrast-to-noise ratio was significantly higher on dynamic T1-weighted studies during the early phase (mean +/- SD, 2.68 +/- 0.94) than it was on T2-weighted studies (1.74 +/- 1.05) and during the delayed phase (2.01 +/- 0.86). CONCLUSION: When adenomyosis coexists with endometrial cancer at the same site on T2-weighted images, contrast-enhanced dynamic T1-weighted imaging improves the accuracy of staging.     

Comparison of microvascular permeability measurements, K(trans), determined with conventional steady-state T1-weighted and first-pass T2*-weighted MR imaging methods in gliomas and meningiomas

BACKGROUND AND PURPOSE: The widely accepted MR method for quantitating brain tumor microvascular permeability, K(trans), is the steady-state T1-weighted gradient-echo method (ssT1). Recently the first-pass T2*-weighted (fpT2*) method has been used to derive both relative cerebral blood volume (rCBV) and K(trans). We hypothesized that K(trans) derived from the ssT1 and the fpT2* methods will correlate differently in gliomas and meningiomas because of the unique differences in morphologic and functional status of each tumor vascular network. METHODS: Before surgery, 27 patients with newly diagnosed gliomas (WHO grade I-IV; n = 20) or meningiomas (n = 7) underwent conventional anatomic MR imaging and 12 dynamic ssT1 acquisitions followed by 60 dynamic fpT2* images before and after gadopentate dimeglumine administration. The 3 hemodynamic variables-fpT2* rCBV, fpT2* K(trans), and ssT1 K(trans)-were calculated in anatomically identical locations and correlated with glioma grade. The fpT2* K(trans) values were compared with ssT1 K(trans) for gliomas and meningiomas. RESULTS: All 3 hemodynamic variables displayed distinct distributions among grades 2, 3, and 4 gliomas by using the Kruskal-Wallis test. Only K(trans) values, and not rCBV, could differentiate between grade 4 and lower-grade gliomas by using the Wilcoxon rank sum test. The fpT2* K(trans) was highly predictive of ssT1 K(trans) for gliomas, with an estimated regression coefficient of 0.49 (P < .001). For meningiomas, however, fpT2* K(trans) values correlated poorly with ssT1 K(trans) values (r = 0.26; P = .74). CONCLUSION: Compared with rCBV, K(trans) values derived from either ssT1 or fpT2* were more predictive of glioma grade. The fpT2* K(trans) was highly correlated with ssT1 K(trans) in gliomas but not in meningiomas.