Evaluation of T2-weighted and dynamic contrast-enhanced MRI in localizing prostate cancer before repeat biopsy

We assessed the accuracy of T2-weighted (T2w) and dynamic contrast-enhanced (DCE) 1.5-T magnetic resonance imaging (MRI) in localizing prostate cancer before transrectal ultrasound-guided repeat biopsy. Ninety-three patients with abnormal PSA level and negative prostate biopsy underwent T2w and DCE prostate MRI using pelvic coil before repeat biopsy. T2w and DCE images were interpreted using visual criteria only. MR results were correlated with repeat biopsy findings in ten prostate sectors. Repeat biopsy found prostate cancer in 23 patients (24.7%) and 44 sectors (6.6%). At per patient analysis, the sensitivity, specificity, positive and negative predictive values were 47.8%, 44.3%, 20.4% and 79.5% for T2w imaging and 82.6%, 20%, 24.4% and 93.3% for DCE imaging. When all suspicious areas (on T2w or DCE imaging) were taken into account, a sensitivity of 82.6% and a negative predictive value of 100% could be achieved. At per sector analysis, DCE imaging was significantly less specific (83.5% vs. 89.7%, p < 0.002) than T2w imaging; it was more sensitive (52.4% vs. 32.1%), but the difference was hardly significant (p = 0.09). T2w and DCE MRI using pelvic coil and visual diagnostic criteria can guide prostate repeat biopsy, with a good sensitivity and NPV.     

T2-weighted hypointense lesions within prostate gland: Differential diagnosis using wash-in rate parameter on the basis of dynamic contrast-enhanced magnetic resonance imaging—Hystopatology correlations

Background and aims

Dynamic contrast enhanced magnetic resonance improves prostate cancer detection. The aims of this paper are to verify whether wash-in-rate parameter (speed of contrast uptake in dynamic contrast enhanced magnetic resonance) can help to differentiate prostate cancer from non-neoplastic T2-weighted hypointense lesions within prostate gland and to assess a cut-off for prostate cancer diagnosis.

Methods

Prospective, monocentric, multi-departmental study. Thirty consecutive patients underwent T2-weighted and dynamic contrast enhanced magnetic resonance, and re-biopsy. T2-weighted hypointense lesions, >5 mm in size, were noted. Lesions were assessed as cancerous (showing mass effect, or no defined margin within transitional zone) and non cancerous (no mass effect) and were compared with histopathology by 2 × 2 tables. Wash-in-rate of each lesion was calculated and was correlated with histopathology. Student's t-test was adopted to assess significant differences. Receiver operating characteristic (ROC) analysis was employed to identify the best cut-off for wash-in-rate in detecting prostate cancer.

Results

At re-biopsy, cancer was proven in 43% of patients. On T2-weighted MRI, 111 hypointense lesions ≥5 mm in size were found. Sensitivity, specificity and accuracy of T2-weighted MRI were 80% (±12.4 CI 95%), 74.6% (±10.1 CI 95%), and 76.5% (±7.9 CI 95%), respectively. Mean WR was 5.8 ± 1.9/s for PCa zones and 2.96 ± 1.44/s for non-PCa zones (p < 0.00000001). At ROC analysis, the best area under curve (AUC) for wash-in-rate parameter was associated to 4.2/s threshold with 82.5% sensitivity (CI ± 7.07), 97.2% specificity (CI ± 4.99) and 91.2% accuracy (CI ± 5.27). Eighteen false positive lesions on T2-weighted MRI showed low wash-in-rate values suggesting non-cancer lesions, while in 5/8 false negative cases high wash-in-rate values correctly suggested prostate cancer. Nine lesions with surgically proven cancer were not included in the saturation biopsy scheme, in 2/9 cases the only site of cancer.

Conclusions

Wash-in-rate parameter allows to differentiate prostate cancer from non-neoplastic lesions, helping cancer detection in areas not included in the biopsy scheme.     

前列腺癌治疗前后动态增强MRI评价

目的：应用MRI和动态增强MRI药物代谢动力学模型评价前列腺癌治疗前后的疗效，确定MRI的价值。方法：对16例经组织学证实的前列腺癌分别在治疗前后进行常规和动态增强MRI检查。治疗分别为单纯激素替代治疗(7例)和激素替代治疗加外放射治疗(9例)。MRI检查常规应用GE Signa Advantage 1．5T超导磁共振成像仪，静脉注射Gd-DTPA(0.1mmol/kg体重)。应用两室药物代谢动力学模型分别计算肿瘤病灶、前列腺良性增生和正常前列腺周围带的最大增强指数、对比剂吸收幅度、对比剂的交换率和对比剂分布指数。结果：治疗前PSA由39.54ng/ml降为10．39ng/ml(P＝0．046)，由MRI测量获得的肿瘤体积明显缩小(2．85cm^3至0．84cm^3，P＝0．01)，前列腺良性增生和正常前列腺周围带也明显缩小(P＜0．01)。治疗前后肿瘤病灶最大增强指数和对比剂分布指数降低，但未见统计学差异；对比剂吸收幅度和交换率明显降低(P＝0．004，0．002)。前列腺良性增生的最大增强指数和对比剂分布指数降低(P＝0．284，0．221)；对比剂吸收幅度和交换率明显降低(P＝0．01，0．007)。正常周围带的对比剂吸收幅度、交换率和分布指数明显降低(P＝0．003，0．01，0．04)。结论：动态增强MRI能够全面反映前列腺癌治疗前后的变化，是有效评价前列腺癌治疗疗效的可靠手段。     

Algorithms for calculation of kinetic parameters from T1-weighted dynamic contrast-enhanced magnetic resonance imaging

PURPOSE: To quantify the errors involved in calculating dynamic parameters (K(trans) and ve) from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) scans, and to develop alternative analyses to improve accuracy or increase processing speed. MATERIALS AND METHODS: This paper presents three different ways of handling the discrete samples of the arterial input and tissue response data with increasing fidelity, with which this continuous arterial input function (AIF) is represented. Also, a new noniterative approach to parameter estimation was developed from one used previously for analysis of radioactive tracer concentrations in radioangiography. The analysis methods were tested using simulated data. RESULTS: The more sophisticated schemes for data processing give more accurate parameter estimates when data are sparsely sampled, at least for the AIF that we modeled. The noniterative algorithm is very rapid in execution, but was more susceptible to measurement errors. CONCLUSION: The improved algorithms presented should be useful when the AIF and tissue response are sparsely sampled. The noniterative approach may be suitable for semiquantitative visualization, or where the AIF and tissue response are sampled accurately and with a small time interval between samples.     

Dynamic contrast-enhanced quantitative perfusion measurement of the brain using T1-weighted MRI at 3T

PURPOSE: To develop a method for the measurement of brain perfusion based on dynamic contrast-enhanced T(1)-weighted MR imaging. MATERIALS AND METHODS: Dynamic imaging of the first pass of a bolus of a paramagnetic contrast agent was performed using a 3T whole-body magnet and a T(1)-weighted fast field echo sequence. The input function was obtained from the internal carotid artery. An initial T(1) measurement was performed in order to convert the MR signal to concentration of the contrast agent. Pixelwise and region of interest (ROI)-based calculation of cerebral perfusion (CBF) was performed using Tikhonov's procedure of deconvolution. Seven patients with acute optic neuritis and two patients with acute stroke were investigated. RESULTS: The mean perfusion value for ROIs in gray matter was 62 mL/100g/min and 21 mL/100g/min in white matter in patients with acute optic neuritis. The perfusion inside the infarct core was 9 mL/100g/min in one of the stroke patients. The other stroke patient had postischemic hyperperfusion and CBF was 140 mL/100g/min. CONCLUSION: Absolute values of brain perfusion can be obtained using dynamic contrast-enhanced MRI. These values correspond to expected values from established PET methods. Furthermore, at 3T pixelwise calculation can be performed, allowing construction of CBF maps.     

Precision in measurements of perfusion and microvascular permeability with T1-weighted dynamic contrast-enhanced MRI.

Dynamic contrast-enhanced MRI is used to estimate microvascular parameters by tracer kinetics analysis. The time for the contrast agent to travel from the artery to the tissue of interest (bolus arrival time (BAT)) is an important parameter that must be measured in such studies because inaccurate estimates or neglect of BAT contribute to inaccuracy in model fitting. Furthermore, although the precision with which these parameters are estimated is very important, it is rarely reported. To address these issues, two investigations were undertaken. First, simulated data were used to validate an independent method for estimation of BAT. Second, the adiabatic approximation to the tissue homogeneity model was fitted to experimental data acquired in prostate and muscle tissue of 22 patients with prostate cancer. A bootstrap error analysis was performed to estimate the precision of parameter estimates. The independent method of estimating BAT was found to be more accurate and precise than a model-fitting approach. Estimated precisions for parameters measured in the prostate gland were 14% for extraction fraction (median coefficient of variation), 19% for blood flow, 28% for permeability-surface area product, 35% for volume of the extravascular-extracellular space, and 36% for blood volume. Techniques to further reduce uncertainty are discussed.     

应用药物代谢动力学模型评价前列腺不同组织的MRI增强作用

目的：应用两室药物代谢动力学模型评价前列腺癌、前列腺增生和正常前列腺周围带的MRI增强特点。方法：对78例经病理组织学证实的前列腺癌,使用GE Signa Advantage 1.5T超导磁共振成像仪,采用FMPSPGR序列针对前列腺（4层或5层）进行动态增强扫描,层厚7mm,层间间隔2mm,连续扫描采样35次,Gd-DTPA经肘静脉置留导管按0.1mmol/kg体重在扫描开始的同时快速注射。将扫描数据传送的计算机工作站,应用两室药物代谢动力学模型进行分析,分别计算出不同ROI,前列腺癌、前列腺良性增生和正常前列腺周围带的最大增强指数（maxim enhancementi index）、对造影剂的吸收幅度（amplitude of uptake)、造影剂的交换率（exchange rate）和造影剂分布系数（distribution index)。结果：最大增强指数、对造影剂的吸收幅度、造影剂的交换率和造影剂分布指数以前列腺癌最高,前列腺增生次之,正常前列腺周围带最低。前列腺癌和正常前列腺周围带之间所有参数均存在极显著统计学差异（P≤0.006),而前列腺增生和正常前列腺周围带之间所有参数也存在显著统计学差异（P≤0.03）。结论：MRI药物代谢动力学模型能够更加准确的反映前列腺肿瘤组织和非肿瘤组织的血液供应特点,在前列腺病变的诊断和鉴别诊断方面具有较高的临床应用价值。     

功能MRI在前列腺癌治疗后评估中的临床应用与进展

前列腺癌治疗后临床多采用前列腺特异抗原水平进行评价,但其受多种因素影响。目前肿瘤的评价主要以肿瘤体积的改变为评价指标,但滞后于肿瘤微循环改变及肿瘤细胞坏死等功能性改变。如何在前列腺癌治疗后早期准确评估其治疗疗效并早期发现肿瘤残存或复发是非常重要的。动态增强MRI、扩散加权成像、体素内不相干运动成像、磁共振波谱等多种功能MRI技术已在前列腺癌早期诊断中发挥重要的作用。就多种功能MRI技术应用于前列腺癌治疗后评估及随访的价值进行综述。     

动态增强MRI在评价前列腺肿瘤微血管生成的临床应用

血管生成是前列腺癌(PCa)发生、发展及转移的关键因素.动态增强磁共振成像(DCE-MRI)是静脉注射小分子质量的钆螯合物通过T1WI 及T2*WI 技术来无创地反映肿瘤组织复杂的血流动力学情况(如灌注异常,微血管的高通透性等),从而了解前列腺肿瘤血管的生成及微血管密度情况.就DCE-MRI 与前列腺肿瘤组织中微血管生成的相关性进行综述.     

Correlation of perfusion parameters on dynamic contrast-enhanced MRI with prognostic factors and subtypes of breast cancers

Purpose:

To investigate whether a correlation exists between perfusion parameters obtained from dynamic contrast‐enhanced (DCE) magnetic resonance imaging (MRI) and prognostic factors or immunohistochemical subtypes of breast cancers.

Materials and Methods:

Quantitative parameters (K^trans, k_ep, and v_e) of 70 invasive ductal carcinomas were obtained using DCE‐MRI as a postprocessing procedure. Correlations between parameters and prognostic factors, including tumor size, axillary nodal status, histologic grade, nuclear grade, expression of estrogen receptor (ER), progesterone receptor (PR), Ki‐67, p53, bcl‐2, and human epidermal growth factor receptor 2 (HER2) and subtypes categorized as luminal (ER or PR‐positive), triple negative (ER or PR‐negative, HER2‐negative), and HER2 (ER and PR‐negative, HER2 overexpression) were analyzed.

Results:

Mean K^trans was higher in tumors with a high histologic grade than with a low histologic grade (P = 0.007), with a high nuclear grade than with a low nuclear grade (P = 0.002), and with ER negativity than ER positivity (P = 0.056). Mean k_ep was higher in tumors with a high histologic grade than with a low histologic grade (P = 0.005), with a high nuclear grade than with a low nuclear grade (P = 0.001), and with ER negativity than with ER positivity (P = 0.043). Mean v_e was lower in tumors with a high histologic grade than with a low histologic grade (P = 0.038) and with ER negativity than with ER positivity (P = 0.015). Triple‐negative cancers showed a higher mean k_ep than the luminal type (P = 0.015).

Conclusion:

Breast cancers with higher K^trans and k_ep, or lower v_e, had poor prognostic factors and were often of the triple‐negative subtype. J. Magn. Reson. Imaging 2012;36:145–151. © 2012 Wiley Periodicals, Inc.     

Single breath-hold multiarterial dynamic MRI of the liver at 3T using a 3D fat-suppressed keyhole technique

PURPOSE: To evaluate the feasibility of single breath-hold, multiarterial MRI of the liver using the THRIVE-CENTRA-keyhole technique. MATERIALS AND METHODS: Twenty-eight patients with 63 focal hepatic lesions underwent liver MR examinations that included the three-dimensional THRIVE-CENTRA-keyhole sequence. Three or six phases were obtained for arterial phase scanning during a single breath-hold. Central k-space data were collected for each phase but the remaining peripheral k-space data were collected only once. The enhancement pattern of each hepatic lesion was analyzed according to the specific diagnosis. RESULTS: Hepatocellular carcinomas (n = 24) enhancement patterns included: rim enhancing (n = 9), homogeneous (n = 7), nodule-in-nodule (n = 5), or heterogeneous (n = 3). A late peritumoral rim was observed in four (17%) of the hepatocellular carcinomas. Most metastases (17 of 18; 94%) demonstrated peripheral rim enhancement. The progressive centripetal enhancement of hemangiomas (n = 6) was clearly depicted. Focal nodular hyperplasia (n = 4) showed early homogeneous enhancement and one lesion demonstrated a central scar. CONCLUSION: The THRIVE-CENTRA-keyhole technique can be used to acquire single breath-hold, multiarterial images depicting improved enhancement characteristics of focal hepatic lesions. This technique will allow accurate timing of arterial scanning with 3D acquisition and high temporal resolution.     

Extended graphical model for analysis of dynamic contrast‐enhanced MRI

Kinetic analysis with mathematical models has become increasingly important to quantify physiological parameters in computed tomography (CT), positron emission tomography (PET), and dynamic contrast‐enhanced MRI (DCE‐MRI). The modified Kety/Tofts model and the graphical (Patlak) model have been widely applied to DCE‐MRI results in disease processes such as cancer, inflammation, and ischemia. In this article, an intermediate model between the modified Kety/Tofts and Patlak models is derived from a mathematical expansion of the modified Kety/Tofts model. Simulations and an in vivo experiment involving DCE‐MRI of carotid atherosclerosis were used to compare the new extended graphical model with the modified Kety/Tofts model and the Patlak model. In our simulated circumstances and the carotid artery application, we found that the extended graphical model exhibited lower noise sensitivity and provided more accurate estimates of the volume transfer constant (K^trans) and fractional plasma volume (v_p) than the modified Kety/Tofts model for DCE‐MRI acquisitions of total duration less than 100–300 s, depending on kinetic parameters. In comparison with the Patlak model, we found that the extended graphical model exhibited 74.4–99.8% less bias in estimates of K^trans. Thus, the extended graphical model may allow kinetic modeling of DCE‐MRI results with shortened data acquisition periods, without sacrificing accuracy in estimates of K^trans and v_p. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

低场磁共振T1 FLAIR在前列腺检查中的应用(与SE序列比较)

目的：评估低场磁共振T1 FLAIR对前列腺检查的价值。方法：分析50例志愿者的前列腺MRI正常解剖;评估42例前列腺癌,76例前列腺增生,48例前列腺炎的磁共振诊断价值。结果：T1 FLAIR在显示前列腺内部结构、包膜和神经血管束方面与SE T1 WI(T1—SE)在统计学上差异有显著性意义;T1 FLAIR对疾病诊断价值的评分明显高于T1-SE。结论：T1 FLAIR在前列腺检查中有较高的使用价值。     

0.5 T MRI of small renal masses: value of T2-weighted and Gd-DOTA-enhanced images

We compared the value of T2-weighted and Gd-DOTA-enhanced T1-weighted images for the detection and characterisation of 33 small renal masses (14 clear cell carcinomas, 6 angiomyolipomas, 3 angiomyomas, 4 adenomas, 3 papillary carcinomas, 3 oncocytomas, 1 haemorrhagic cyst). Dynamic enhanced MRI was performed to study the tumoral vascular supply (19 cases). MRI depicted all the masses more than 1 cm in diameter, but missed all the lesions less than 1 cm (4 false-negative). The results of T2-weighted images and Gd-DOTA-enhanced images were similar as regards detection; however, Gd-DOTA-enhanced images depicted more clearly the tumours smaller than 2 cm (11 cases). MRI enabled the characterisation of only 3 masses (2 angiomyolipomas, 1 haemorrhagic cyst). New MRI features are described for oncocytomas (low signal intensity on T1-weighted images, high signal intensity on T2-weighted images, early and marked enhancement on dynamic enhanced MRI). Dynamic enhanced MRI did not contribute to the differentiation of benign from malignant tumours. Correspondence to: O. Hélénon     

Use of cardiac output to improve measurement of input function in quantitative dynamic contrast‐enhanced MRI

Purpose

To validate a new method for converting MR arterial signal intensity versus time curves to arterial input functions (AIFs).

Materials and Methods

The method constrains AIF with patient's cardiac output (Q). Monte Carlo simulations of MR renography and tumor perfusion protocols were carried out for comparison with two alternative methods: direct measurement and population‐averaged input function. MR renography was performed to assess the method's inter‐ and intraday reproducibility for renal parameters.

Results

In simulations of tumor perfusion, the precision of the parameters (K^trans and v_e) computed using the proposed method was improved by at least a factor of three compared to direct measurement. Similar improvements were obtained in simulations of MR renography. Volunteer study for testing interday reproducibility confirmed the improvement of precision in renal parameters when using the proposed method compared to conventional methods. In another patient study (two injections within one session), the proposed method significantly increased the correlation coefficient (R) between GFR of the two exams (0.92 vs. 0.83) compared to direct measurement.

Conclusion

A new method significantly improves the precision of dynamic contrast‐enhanced (DCE) parameters. The method may be especially useful for analyzing repeated DCE examinations, such as monitoring tumor therapy or angiotensin converting enzyme‐inhibitor renography. J. Magn. Reson. Imaging 2009;30:656–665. © 2009 Wiley‐Liss, Inc.     

Wash-in rate on the basis of dynamic contrast-enhanced MRI: usefulness for prostate cancer detection and localization

PURPOSE: To evaluate the usefulness of the wash-in rate based on dynamic contrast-enhanced (DCE) MRI for the detection and localization of prostate cancer. MATERIALS AND METHODS: In 53 patients, the wash-in rate was measured in the cancer area and in three normal areas (the peripheral zone, inner portion of the transitional zone, and outer portion of the transitional zone). On the basis of these data, parametric imaging was generated and then its accuracy for cancer detection and location was evaluated compared to that of T2-weighted imaging without the use of an endorectal coil. For that purpose the entire prostate was divided into 18 segments. RESULTS: The wash-in rate value was greater in cancer tissue (9.2/second) than in three normal tissues (3.3/second, 6.7/second, and 3.2/second, respectively; P<0.001). The sensitivity and specificity were greater on parametric imaging of the wash-in rate compared to T2-weighted imaging in the entire prostate (96% and 82% vs. 65% and 60%, respectively) and the peripheral zone (96% and 97% vs. 75% and 53%; P<0.05). In the transitional zone, the sensitivity was greater on parametric imaging (96%) than on T2-weighted imaging (45%; P=0.016), but the specificity was similar (51% vs. 73%; P=0.102). CONCLUSION: The wash-in rate based on DCE-MRI is a useful parameter for prostate cancer detection and localization.     

Fast T2*-weighted MRI of the prostate at 3 Tesla

Purpose:

To describe a rapid T2*‐weighted (T2*W), three‐dimensional (3D) echo planar imaging (EPI) sequence and its application in mapping local magnetic susceptibility variations in 3 Tesla (T) prostate MRI. To compare the sensitivity of T2*W EPI with routinely used T1‐weighted turbo‐spin echo sequence (T1W TSE) in detecting hemorrhage and the implications on sequences sensitive to field inhomogeneities such as MR spectroscopy (MRS).

Materials and Methods:

B₀ susceptibility weighted mapping was performed using a 3D EPI sequence featuring a 2D spatial excitation pulse with gradients of spiral k‐space trajectory. A series of 11 subjects were imaged using 3T MRI and combination endorectal (ER) and six‐channel phased array cardiac coils. T1W TSE and T2*W EPI sequences were analyzed quantitatively for hemorrhage contrast. Point resolved spectroscopy (PRESS MRS) was performed and data quality was analyzed.

Results:

Two types of susceptibility variation were identified: hemorrhagic and nonhemorrhagic T2*W‐positive areas. Post‐biopsy hemorrhage lesions showed on average five times greater contrast on the T2*W images than T1W TSE images. Six nonhemorrhage regions of severe susceptibility artifact were apparent on the T2*W images that were not seen on standard T1W or T2W images. All nonhemorrhagic susceptibility artifact regions demonstrated compromised spectral quality on 3D MRS.

Conclusion:

The fast T2*W EPI sequence identifies hemorrhagic and nonhemorrhagic areas of susceptibility variation that may be helpful in prostate MRI planning at 3.0T. J. Magn. Reson. Imaging 2011;33:902–907. © 2011 Wiley‐Liss, Inc.     

Efficient method for calculating kinetic parameters using T1-weighted dynamic contrast-enhanced magnetic resonance imaging.

It has become increasingly important to quantitatively estimate tissue physiological parameters such as perfusion, capillary permeability, and the volume of extravascular-extracellular space (EES) using T(1)-weighted dynamic contrast-enhanced MRI (DCE-MRI). A linear equation was derived by integrating the differential equation describing the kinetic behavior of contrast agent (CA) in tissue, from which K(1) (rate constant for the transfer of CA from plasma to EES), k(2) (rate constant for the transfer from EES to plasma), and V(p) (plasma volume) can be easily obtained by the linear least-squares (LLSQ) method. The usefulness of this method was investigated by means of computer simulations, in comparison with the nonlinear least-squares (NLSQ) method. The new method calculated the above parameters faster than the NLSQ method by a factor of approximately 6, and estimated them more accurately than the NLSQ method at a signal-to-noise ratio (SNR) of < approximately 10. This method will be useful for generating functional images of K(1), k(2), and V(p) from DCE-MRI data.     

Quantifying angiogenesis in VEGF-enhanced tissue-engineered bladder constructs by dynamic contrast-enhanced MRI using contrast agents of different molecular weights

PURPOSE: To compare Gadomer, a macromolecular magnetic resonance (MR) contrast agent, and gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) for quantifying angiogenesis in tissue-engineered bladder constructs. MATERIALS AND METHODS: Constructs enhanced with vascular endothelial growth factor (VEGF) were grafted onto the bladder of 12 rabbits (N= 3/VEGF, VEGF = 0,10,15,20 ng/g tissue). After eight days dynamic contrast-enhanced MRI (DCE-MRI) was performed in each animal using Gadomer and Gd-DTPA, separated by a one-hour interval. DCE-MRI parameters were calculated from two-compartment pharmacokinetics (plasma volume fraction, v(p); transfer constant, K(trans)) and model-free analysis, area under the concentration-time curve (AUC). Histology assessment of microvessel density (MVD) and Evans blue permeability were compared to DCE-MRI. RESULTS: MVD was elevated (P < 0.05) at the highest VEGF but not among lower levels; permeability differences were absent. Contrast enhancement increased with VEGF and was better resolved with Gadomer than Gd-DTPA. Gadomer was the better assay for estimating plasma volume: v(p) provided the best distinction (P < 0.005), but both v(p) and AUC were correlated to MVD. With Gd-DTPA, only AUC distinguished MVD differences (P< 0.05). Changes in K(trans) were insignificant. CONCLUSION: Macromolecular contrast agents are valuable for monitoring angiogenesis in tissue-engineered bladder grafts. Compared to Gd-DTPA, Gadomer provides more accurate and precise quantification of microvessel function, and is better suited to pharmacokinetic analysis for accurate physiological quantification.     

3D T2-weighted fast spin-echo MRI sialography of the parotid gland

The diagnostic value of 3D T2-weighted MRI sialography and 2D T2-weighted fast spin-echo (FSE) images for delineation of the normal duct system and characterisation of parotid gland duct pathology was compared in a prospective study. We studied eight healthy volunteers and 18 patients with pathology of the parotid gland (tumours in 3, sialolithiasis in 6, Sjögren's disease in 4, recurrent or chronic parotitis in 4, post-traumatic stricture of the main parotid duct in 1). A heavily T2-weighted 3D FSE sequence was compared with a conventional 2D T2-weighted FSE sequence. The normal main parotid duct was always visible on 3D sialography and seen in 68 % of the 2D T2-weighted FSE studies. The diagnostic reliability of both sequences for diagnosis of luminal concretions in sialolithiasis and dilatation of the duct in duct stricture or chronic parotitis was equal, although slight intraglandular dilatation was appreciated only on 3D sialography. Extraductal pathology resulting in obstruction or displacement of ducts was better characterised on 2D T2-weighted images. However, 3D MRI sialography offered the advantage of postprocessing with overview images and multiple maximum-intensity projection images in any plane.