Assessment of tumor microcirculation: a new role of dynamic contrast MR imaging

Differential diagnosis of prostate cancer and noncancerous tissue in the peripheral zone and central gland using the quantitative parameters of DCE-MRI: A meta-analysis

BACKGROUND

The objective of this meta-analysis was to evaluate the clinical usefulness of K, Kep, and Ve values in the differential diagnosis of prostate cancer (PCa) and noncancerous tissue in the peripheral zone (PZ) and central gland (CG).

METHODS

A search was conducted of the PubMed, MEDLINE, EMBASE, Cochrane Library, China National Knowledge Infrastructure, and Wanfang databases from January 2000 to October 2015 using the search terms "prostate cancer," " dynamic contrast-enhanced (DCE)," "magnetic resonance imaging," "K," "Kep," and "Ve." Studies were selected and included according to strict eligibility criteria. Standardized mean differences (SMDs) and 95% confidence intervals (CIs) were used to compare K, Kep, and Ve values between PCa and noncancerous tissue.

RESULTS

Fourteen studies representing 484 patients highly suspicious for prostate adenocarcinoma were selected for the meta-analysis. We found that K values measured by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) were significantly higher in PCa tissue than in noncancerous tissue in the PZ (SMD 1.57, 95% CI 0.98-2.16; z = 5.21, P <0.00001) and CG (SMD 1.19, 95% CI 0.46-1.91; z = 3.21, P = 0.001). Kep values measured by DCE-MRI were significantly higher in PCa than in noncancerous tissue in the PZ (SMD 1.41, 95% CI 0.92-1.91; z = 5.59, P < 0.00001) and CG (SMD 1.57, 95% CI 0.69-2.46; z = 3.49, P = 0.0005). Ve values generated by DCE-MRI were slightly higher in PCa than in noncancerous tissue in the PZ (SMD 0.72, 95% CI 0.17-1.27; z = 2.58, P = 0.010), but sensitivity analysis found that the Ve value was unstable for differentiation between PCa and noncancerous PZ tissue. However, there was no significant difference in the Ve value between PCa and noncancerous CG tissue (SMD -0.29, 95% CI -1.18, 0.59; z = 0.65, P = 0.51).

CONCLUSION

Our meta-analysis shows that K and Kep were the most reliable parameters for differentiating PCa from noncancerous tissue and were critical for evaluation of the internal structure of cancer. The Ve value was not helpful for distinguishing PCa from noncancerous CG tissue; its ability to distinguish between PCa and noncancerous PZ tissue remains uncertain.

In vivo monitoring of angiogenesis during tendon repair: a novel MRI-based technique in a rat patellar tendon model

PURPOSE

Recent in vivo studies were able to show the impairing effect of neoangiogenesis in degenerative tendon diseases. Clinical in vivo monitoring of angiogenesis in injured tendons therefore seems to be crucial for an accurate therapeutic approach. The aim of this study was to develop a novel magnetic resonance imaging (MRI)-based technique for observing angiogenesis during tendon healing in vivo.

METHODS

Tendinopathy was induced by an in situ freezing model of rat patellar tendon and monitored after 7, 14, and 28 days. Animals were randomly divided into an imaging and immunohistochemical group. MRI with a 'blood pool' contrast agent was used to determine neoangiogenesis during tendon healing. MRI was compared to histochemical staining and quantification of blood vessels in injured and native tendons.

RESULTS

MRI data revealed a peak in changes in the transverse relaxation rate (ΔR 2*), which is proportional to relative blood volume, 7 days after surgery and decrease until day 28. Histological microvessel density and vascular endothelial growth factor synthesis were also most evident at day 7 and decreased over time.

CONCLUSIONS

The current results are demonstrating a time-dependent correlation between microvessel density and ΔR 2*. Thus, MRI-based evaluation of angiogenesis in the tendon might be a new promising technique for in vivo monitoring of angiogenesis and therapy response in the future.

Perspectives in molecular imaging through translational research, human medicine, and veterinary medicine

The concept of molecular imaging has taken off over the past 15 years to the point of the renaming of the Society of Nuclear Medicine (Society of Nuclear Medicine and Molecular Imaging) and Journals (European Journal of Nuclear Medicine and Molecular Imaging) and offering of medical fellowships specific to this area of study. Molecular imaging has always been at the core of functional imaging related to nuclear medicine. Even before the phrase molecular imaging came into vogue, radionuclides and radiopharmaceuticals were developed that targeted select physiological processes, proteins, receptor analogs, antibody-antigen interactions, metabolites and specific metabolic pathways. In addition, with the advent of genomic imaging, targeted genomic therapy, and theranostics, a number of novel radiopharmaceuticals for the detection and therapy of specific tumor types based on unique biological and cellular properties of the tumor itself have been realized. However, molecular imaging and therapeutics as well as the concept of theranostics are yet to be fully realized. The purpose of this review article is to present an overview of the translational approaches to targeted molecular imaging with application to some naturally occurring animal models of human disease.

Rectal cancer: dynamic contrast-enhanced MRI correlates with lymph node status and epidermal growth factor receptor expression

PURPOSE

To evaluate correlations between dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and clinicopathologic data as well as immunostaining of the markers of angiogenesis epidermal growth factor receptor (EGFR) and CXC-motif chemokine receptor 4 (CXCR4) in patients with rectal cancer.

MATERIALS AND METHODS

Presurgical DCE-MRI was performed in 41 patients according to a standardized protocol. Two quantitative parameters (k21 , A) were derived from a pharmacokinetic two-compartment model, and one semiquantitative parameter (TTP) was assessed. Standardized surgery and histopathologic examinations were performed in all patients. Immunostaining for EGFR and CXCR4 was performed and evaluated with a standardized scoring system.

RESULTS

DCE-MRI parameter A correlated significantly with the N category (P = 0.048) and k21 with the occurrence of synchronous and metachronous distant metastases (P = 0.029). A trend was shown toward a correlation between k21 and EGFR expression (P = 0.107). A significant correlation was found between DCE-MRI parameter TTP and the expression of EGFR (P = 0.044). DCE-MRI data did not correlate with CXCR4 expression.

CONCLUSION

DCE-MRI is a noninvasive method which can characterize microcirculation in rectal cancer and correlates with EGFR expression. Given the relationship between the dynamic parameters and the clinicopathologic data, DCE-MRI data may constitute a prognostic indicator for lymph node and distant metastases in patients with rectal cancer.

Rectal cancer: assessment of response to neoadjuvant chemoradiation by dynamic contrast-enhanced MRI

PURPOSE

To assess pretreatment functional and morphological tumor characteristics with magnetic resonance imaging (MRI) in advanced rectal carcinoma and to identify factors predicting response to neoadjuvant chemoradiation.

MATERIALS AND METHODS

In a prospective study, 95 patients with rectal carcinoma underwent dynamic contrast-enhanced MRI before and after chemoradiation. Quantitative parameters were derived from a pharmacokinetic two-compartment model. Tumors were also characterized with regard to mucinous status at pretreatment high-resolution MRI as nonmucinous or mucinous. Response to treatment was defined as a downshift in the local tumor stage.

RESULTS

The parameter k21 (contrast medium exchange rate) was higher at pretreatment MRI in nonmucinous compared with mucinous carcinomas (P < 0.001). The effect of chemoradiation on dynamic MR parameters was higher in nonmucinous carcinomas than in the mucinous subtype (P < 0.001). A higher rate of response to treatment was linked with nonmucinous morphology (P < 0.001). Multivariate analysis revealed an association between mucinous tumor morphology and poor response (odds ratio [95% confidence interval]: 0.113 [0.032-0.395], P < 0.001) as well as an association between a high 75th percentile of k21 and a higher response rate (odds ratio: 1.043 [1.001-1.086], P = 0.019).

CONCLUSION

Functional and morphological parameters of pretreatment MRI can assess tumor characteristics associated with the effectiveness of chemoradiation before treatment initiation.

Evaluation of the tibial tunnel after intraoperatively administered platelet-rich plasma gel during anterior cruciate ligament reconstruction using diffusion weighted and dynamic contrast-enhanced MRI

PURPOSE

To evaluate effect of platelet-rich plasma gel (PRPG), locally administered during the anterior cruciate ligament (ACL) reconstruction, with two MRI methods. The proximal tibial tunnel was assessed with diffusion weighted imaging (DWI) and with dynamic contrast-enhanced imaging (DCE-MRI).

MATERIALS AND METHODS

In 50 patients, standard arthroscopic ACL reconstructions were performed. The patients in the PRPG group (n = 25) received a local application of PRPG. The proximal tibial tunnel was examined by DWI and DCE-MRI, which were used to calculate apparent diffusion coefficient (ADC) values, as well as the contrast enhancement gradient (G(enh)) and enhancement factor (F(enh)) values.

RESULTS

At 1 month, the calculated average ADC value in the PRPG group was significantly lower than in the control group. At 2.5 and at 6 months, G(enh) was significantly higher in the PRPG group. There were no significant differences in F(enh) between the groups at any control examination.

CONCLUSION

DWI and DCE-MRI measurements indicate a reduced extent of edema during the first postoperative month as well as an increased vascular density and microvessel permeability in the proximal tibial tunnel at 1 and 2.5 postoperative months as the effect of the application of PRPG.

Parametric histogram analysis of dynamic contrast-enhanced MRI in multiple myeloma: a technique to evaluate angiogenic response to therapy?

RATIONALE AND OBJECTIVES

From dynamic contrast-enhanced magnetic resonance imaging, it is known that microcirculation patterns in multiple myeloma differ depending on the infiltration pattern. The purpose of this study was to evaluate histogram analysis of dynamic contrast-enhanced magnetic resonance imaging in MM to monitor early treatment response on the basis of microcirculation patterns.

MATERIALS AND METHODS

A total of 51 patients with multiple myeloma requiring therapy were examined. Dynamic contrast-enhanced magnetic resonance imaging of the lumbar spine was performed before and after conventional or high-dose chemotherapy with autologous stem cell transplantation. Statistical analysis included 245 vertebrae and dynamic microcirculation parameters as displayed in histograms. Resulting parameters (amplitude, exchange rate constant, skewness, kurtosis, and left shift) were correlated with therapeutic response.

RESULTS

More than 70% of histograms derived from the microcirculation parameters showed a difference between the maximum peak before and after therapy (left shift). However, there was no significant difference between the particular treatment. Significantly different skewness of amplitude in 98% and kurtosis of exchange rate constant (94.1% and 98%) were seen in the patients who responded to treatment (P for each < .05).

CONCLUSIONS

Histogram analysis revealed early changes after therapy resulting in a shift toward more (kurtosis) and lower values (skewness) of microcirculation parameters. Therefore, histogram analysis can determine and describe if a chosen therapy works at all. However, there were no differences between the chosen therapies. This needs to be reevaluated in a larger number of treated patients. Histogram analysis can also be an adjunct to a subjective visual analysis but is hampered by heterogeneous infiltration pattern seen in multiple myeloma.

Feasibility of pseudocontinuous arterial spin labeling at 7 T with whole-brain coverage

Object

We studied the feasibility of pseudocontinuous arterial spin labeling (pCASL) at 7 T.

Materials and methods

Simulations were performed to find the optimal labeling parameters for pCASL, with particular attention to the maximum-allowed specific absorption rate (SAR). Subsequently, pCASL experiments (four volunteers) were performed to find the B1 efficiency at the labeling position with and without high-permittivity pads placed around the head, and to study the optimal labeling duration (four separate volunteers). Finally, feasibility of whole-brain pCASL imaging was tested.

Results

Simulations showed that a lower B1 efficiency should be compensated by a lower effective flip angle of the labeling, a moderately shorter labeling duration, and a longer repetition time. B1 efficiency in the internal carotid arteries just below the carotid siphon was approximately 55% and 35% with and without high-permittivity pads, respectively. In vivo experiments showed an optimal labeling duration of 1,500 ms, although longer labeling durations up to 2,500 ms resulted in similar signal-to-noise efficiency. Whole-brain pCASL imaging was demonstrated in a single volunteer.

Conclusion

Despite decreased B1 efficiency, sufficient labeling efficiency can be achieved for whole-brain pCASL at 7 T with high-permittivity pads. However, image quality is still limited compared with 3 T, probably due to imaging instabilities, and further research is needed to elucidate this.

Perfusion parameters analysis of the vertebral bone marrow in patients with Ph¹⁻ chronic myeloproliferative neoplasms (Ph(neg) MPN): a dynamic contrast-enhanced MRI (DCE-MRI) study

PURPOSE

To evaluate perfusion parameters of the vertebral bone marrow in patients with Philadelphia negative chronic myeloproliferative neoplasms (Ph(neg) MPN) using dynamic contrast-enhanced MRI (DCE-MRI).

MATERIALS AND METHODS

The study enrolled 24 patients with Ph(neg) MPN: 12 patients with myelofibrosis (Group A), 6 with essential thrombocythemia (ET), and 6 with polycythemia vera (PV) (Group B) who underwent DCE-MRI of the lumbosacral spine. Twelve normal individuals served as control group (Group C). Wash-in (WIN), wash-out (WOUT), maximum contrast-enhancement (CE  max), time-to-peak (TTPK), time-to-maximum slope (TMSP), and the WIN/TMSP ratio (WTSP) were calculated.

RESULTS

WIN, CE(max) , and WTSP parameters were higher in Group A than in Group C (P < 0.05). These parameters were significant (P < 0.0001) in discriminating patients with myelofibrosis from normal individuals with sensitivities 74.14%, 87.93%, 74.14%, and specificities 91.07%, 83.93%, 91.07%, respectively. WIN, WOUT, CE(max) , and WTSP parameters were higher in Group A than in Group B (P < 0.05). Group B exhibited no differences in perfusion parameters as compared with Group C with the exception of WOUT.

CONCLUSION

Patients with myelofibrosis exhibited increased perfusion parameters in vertebral bone marrow, which could be consisted with increased vascularity, probably related to neoangiogenesis as opposed to ET or PV patients showing no increased perfusion. DCE-MRI may be of value in discriminating subgroups of Ph(neg) MPN patients and in indicating those progressing to myelofibrosis.

Dynamic susceptibility contrast-enhanced MRI evaluation of cerebral intraventricular tumors: preliminary results

INTRODUCTION

The aims of the present study were to determine the perfusion characteristics of several types of intraventricular tumors and to evaluate the usefulness of dynamic contrast-enhanced MRI in making the differential diagnosis.

METHODS

A total of 28 patients with intraventricular tumors (five meningiomas, five papillomas, three ependymomas, four subependymomas, seven central neurocytomas, two subependymal giant cell astrocytomas and two metastases) underwent conventional and dynamic susceptibility contrast-enhanced MRI. Cerebral blood volume (CBV) maps were obtained and the relative CBV (rCBV) calculated for each tumor. Mean rCBV(max) values were compared across the different types of tumors (ANOVA, P=0.05).

RESULTS

Intraventricular tumors presented with three different patterns of vascularization: highly vascularized tumors (mean rCBV(max)>3), including papillomas, meningiomas and renal carcinoma metastases; poorly vascularized tumors (mean rCBV(max)<2), including ependymomas and subependymomas; and intermediately vascularized tumors (mean rCBV(max)>2 but<3), including central neurocytomas and lung metastases. There was a significant difference between the highly vascularized (papillomas, meningiomas) and poorly vascularized (subependymomas) tumors. In cases of suspected meningioma, papilloma or neurocytoma, low rCBV values (<3) point to a diagnosis of neurocytoma rather than either of the other tumor types.

CONCLUSION

Susceptibility contrast-enhanced MRI can provide additional information on the vascularization of intraventricular cerebral tumors and may help in making the differential diagnosis.

In vivo correlation of tumor blood volume and permeability with histologic and molecular angiogenic markers in gliomas

BACKGROUND AND PURPOSE

Tumor angiogenesis is very heterogeneous and in vivo correlation of perfusion imaging parameters with angiogenic markers can help in better understanding the role of perfusion imaging as an imaging biomarker. The purpose of this study was to correlate PCT parameters such as CBV and PS with histologic and molecular angiogenic markers in gliomas.

MATERIALS AND METHODS

Thirty-six image-guided biopsy specimens in 23 patients with treatment-naive gliomas underwent PCT examinations. We correlated MVD, MVCP, VEGFR-2 expression, tumor cellularity, and WHO grade of the image-guided biopsy specimens with the PCT parameters. Histologic sections were stained with hematoxylin-eosin, CD34, and VEGFR-2 and examined under a light microscope. These histologic and molecular angiogenic markers were correlated with perfusion parameters of the region of interest corresponding to the biopsy specimen. Pearson correlation coefficients and multiple regression analyses by using clustering methods were performed to assess these correlations.

RESULTS

CBV showed a significant positive correlation with MVD (r = 0.596, P < .001), whereas PS showed a significant positive correlation with MVCP (r = 0.546, P = .001). Both CBV (r = 0.373, P = .031) and PS (r = 0.452, P = .039) also showed a significant correlation with WHO grade. VEGFR-2 positive specimens showed higher PS and CBV; however, neither was statistically significant at the .05 level.

CONCLUSIONS

CBV showed a significant positive correlation with MVD, whereas PS showed a significant positive correlation with MVCP, suggesting that these 2 perfusion parameters represent different aspects of tumor vessels; hence, in vivo evaluation of these could be important in a better understanding of tumor angiogenesis.

Predicting control of primary tumor and survival by DCE MRI during early therapy in cervical cancer

PURPOSE

To assess the early predictive power of MRI perfusion and volume parameters, during early treatment of cervical cancer, for primary tumor control and disease-free-survival.

MATERIALS AND METHODS

Three MRI examinations were obtained in 101 patients before and during therapy (at 2-2.5 and 4-5 weeks) for serial dynamic contrast enhanced (DCE) perfusion MRI and 3-dimensional tumor volume measurement. Plateau Signal Intensity (SI) of the DCE curves for each tumor pixel of all 3 MRI examinations was generated, and pixel-SI distribution histograms were established to characterize the heterogeneous tumor. The degree and quantity of the poorly-perfused tumor subregions, which were represented by low-DCE pixels, was analyzed by using various lower percentiles of SI (SI%) from the pixel histogram. SI% ranged from SI2.5% to SI20% with increments of 2.5%. SI%, mean SI, and 3-dimensional volume of the tumor were correlated with primary tumor control and disease-free-survival, using Student t test, Kaplan-Meier analysis, and log-rank test. The mean post-therapy follow-up time for outcome assessment was 6.8 years (range: 0.2-9.4 years).

RESULTS

Tumor volume, mean SI, and SI% showed significant prediction of the long-term clinical outcome, and this prediction was provided as early as 2 to 2.5 weeks into treatment. An SI5% of <2.05 and residual tumor volume of > or =30 cm(3) in the MRI obtained at 2 to 2.5 weeks of therapy provided the best prediction of unfavorable 8-year primary tumor control (73% vs. 100%, P = 0.006) and disease-free-survival rate (47% vs. 79%, P = 0.001), respectively.

CONCLUSIONS

Our results show that MRI parameters quantifying perfusion status and residual tumor volume provide very early prediction of primary tumor control and disease-free-survival. This functional imaging based outcome predictor can be obtained in the very early phase of cytotoxic therapy within 2 to 2.5 weeks of therapy start. The predictive capacity of these MRI parameters, indirectly reflecting the heterogeneous delivery pattern of cytotoxic agents, tumor oxygenation, and the bulk of residual presumably therapy-resistant tumor, requires future study.

Bone marrow angiogenesis magnetic resonance imaging in patients with acute myeloid leukemia: peak enhancement ratio is an independent predictor for overall survival

Emerging evidence suggests that progression of hematologic malignancies is associated with angiogenesis. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can provide global and functional imaging of tumor angiogenesis. In this study, we performed bone marrow DCE-MRI prospectively at diagnosis and after induction chemotherapy in 78 de novo acute myeloid leukemia (AML) patients and correlated it with treatment outcome. An algorithm to assess bone marrow angiogenesis by measuring the DCE-MRI time-intensity curve pixel by pixel was developed using 3 distinct parameters: peak enhancement ratio (Peak) to indicate tissue blood perfusion; amplitude (Amp) to reflect vascularity; and volume transfer constant (K trans) to indicate vascular permeability. The Peak and Amp decreased significantly at remission status after induction chemotherapy. Patients with higher Peak or Amp at diagnosis had shorter overall survival and disease-free survival than others. Cox multivariate analysis identified higher Peak value (hazard ratio, 9.181; 95% confidence interval, 1.740-48.437; P = .009) as an independent predictor for overall survival in addition to unfavorable karyotype and old age. Our findings provide evidence that increased bone marrow angiogenesis measured by DCE-MRI can predict adverse clinical outcome in AML patients. DCE-MRI may help to select high-risk phenotype AML patients for tailored antiangiogenic therapy and to monitor treatment response.

Perfusion MRI in the evaluation of cerebral blood volume and mean transit time in untreated and recurrent glioblastomas

Perfusion MRI by means of dynamic contrast-enhanced T2-weighted MR imaging allows quantitative analysis of cerebral blood volume (CBV) and mean transit time (MTT) in intra-axial brain tumors. Our aim was to compare recurrent glioblastomas to untreated glioblastomas, determining if there are differences in perfusion parameters between the two groups. Serial MR examinations were performed in 26 patients with glioblastoma histologically demonstrated before surgical resection and in 19 patients with recurrent glioblastoma after surgery and radiotherapy. Tumor recurrence was established using both histological and clinical criteria. Normalized CBV and MTT ratios were considered and compared between the two groups. A statistically significant difference, both in average and maximum normalized CBV ratios between the two groups was found. In particular, average and maximum normalized CBV ratios were greater in untreated than in recurrent glioblastomas. On the contrary, average and maximum normalized MTT ratios were greater in the recurrent glioblastomas, than in untreated tumors. Perfusion MRI by means of dynamic contrast-enhanced T2-weighted MR imaging is a valuable adjunct to conventional MR imaging in assessing different hemodynamic features between untreated and recurrent glioblastomas. In particular, tumor recurrence must be suspected even if the average and maximum normalized CBV ratios are far below those of untreated glioblastomas. In addition, increased average and maximum MTT ratios could be considered typical markers of neoplastic recurrence in irradiated cerebral tissue.

Use of permeability surface area-product to differentiate intracranial tumours from abscess

Background and Purpose

Clinical and radiological findings of intracranial abscesses may mimic the findings of brain tumours and vice versa. However, the discrimination is of great clinical importance in planning treatment and in following prognosis and response to therapy. This study evaluates the Computed Tomography (CT) perfusion parameters, especially the permeability index, with the aim of evaluating the usefulness of dynamic CT perfusion imaging as an alternative tool to differentiate necrotic brain tumours and intracerebral abscesses.

Materials and Methods

A total of 21 patients underwent perfusion CT study and were divided into 2 groups: Group 1, patients with necrotic brain tumours (n=13); and Group 2, patients with cerebral abscesses (n=8). The mean perfusion parameters were obtained from the enhancing part of the lesion. The relative ratios were then calculated by using the results from mirrored regions within the contralateral hemisphere as reference.

Results

The results of this study showed that there was significant difference in the relative permeability surface values between necrotic brain tumours and cerebral abscesses (p=0.005). By applying the ROC curve, a value of 25.1 for rPS was found to be the best estimate to distinguish necrotic brain tumours from cerebral abscesses with a specificity of 88 % and sensitivity of 70 %.

Conclusion

CT perfusion, especially permeability surface, may allow for better differentiation of cerebral abscesses from brain tumours, making it a strong additional imaging modality in the early diagnosis of these two entities.

Recent advances in breast MRI and MRS

Breast MRI is an area of intense research and is fast becoming an important tool for the diagnosis of breast cancer. This review covers recent advances in breast MRI, MRS, and image post-processing and analysis. Several studies have explored a multi-parametric approach to breast imaging that combines analysis of traditional contrast enhancement patterns and lesion architecture with novel methods such as diffusion, perfusion, and spectroscopy to increase the specificity of breast MRI studies. Diffusion-weighted MRI shows some potential for increasing the specificity of breast lesion diagnosis and is even more promise for monitoring early response to therapy. MRS also has great potential for increasing specificity and for therapeutic monitoring. A limited number of studies have evaluated perfusion imaging based on first-pass contrast bolus tracking, and these clearly identify that vascular indices have great potential to increase specificity. The review also covers the relatively new acquisition technique of MR elastography for breast lesion characterization. A brief survey of image processing algorithms tailored for breast MR, including registration of serial dynamic images, segmentation and extraction of morphological features of breast lesions, and contrast uptake modeling, is also included. Recent advances in MRI, MRS, and automated image analysis have increased the utility of breast MR in diagnosis, screening, management, and therapy monitoring of breast cancer.

Dynamic contrast-enhanced magnetic resonance imaging pharmacodynamic biomarker study of sorafenib in metastatic renal carcinoma

PURPOSE

Sorafenib is an antiangiogenic agent with activity in renal cancer. We conducted a randomized trial to investigate dynamic contrast magnetic resonance imaging (DCE-MRI) as a pharmacodynamic biomarker.

PATIENTS AND METHODS

Patients were randomly assigned to placebo or 200 or 400 mg twice per day of sorafenib. DCE-MRI was performed at baseline and 4 weeks. DCE-MRI parameters, area under the contrast concentration versus time curve 90 seconds after contrast injection (IAUC(90)), and volume transfer constant of contrast agent (K(trans)) were calculated for a metastatic site selected in a blinded manner. Primary end point was change in K(trans).

RESULTS

Of the 56 assessable patients, 48 underwent two MRIs; 44 MRIs were assessable for study end points. Mean K(trans) log ratios were 0.131 (standard deviation [SD], 0.315), -0.148 (SD, 0.382), -0.271 (SD, 0.499) in placebo, 200- and 400-mg cohorts, respectively (P = .0077 for trend) corresponding to changes of +14%, -14%, and -24%. IAUC(90) log ratios were 0.041 (SD, 0.197), -0.040 (SD, 0.132), -0.356 (SD, 0.411), respectively (P = .0003 for trend), corresponding to changes of +4%, -4%, and -30%. Using a log-rank test, IAUC(90) and K(trans) changes were not associated with progression-free survival (PFS). Patients with high baseline K(trans) had a better PFS (P = .027).

CONCLUSION

IAUC(90) and K(trans) are pharmacodynamic biomarkers for sorafenib, but variability is high and magnitude of effect is less than previously reported. Changes in DCE-MRI parameters after 4 weeks of sorafenib are not predictive of PFS, suggesting that these biomarkers are not surrogate end points. The value of baseline K(trans) as a prognostic or predictive biomarker requires additional study.

Assessment of tumor microcirculation with dynamic contrast-enhanced MRI in patients with esophageal cancer: initial experience

PURPOSE

To investigate the feasibility and impact of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) on tumor characterization and response to radiochemotherapy (RCT) in patients with esophageal cancer.

MATERIALS AND METHODS

A total of 48 patients underwent DCE-MRI to assess tumor microcirculation based on a two-compartment model function. Effects of RCT on kinetic parameters were studied in 12 patients with squamous cell carcinoma.

RESULTS

Tumor microcirculation differs with respect to histological subtype: squamous cell carcinomas showed lower values of amplitude A (leakage space, P = 0.015) and higher contrast agent exchange rates (k(21), P = 0.225) compared with adenocarcinomas. RCT led to a significant decrease of the contrast agent exchange rate (P = 0.005), while amplitude A increased moderately after therapy (P = 0.136).

CONCLUSION

DCE-MRI is feasible in patients with esophageal cancer, reveals therapeutic effects, and may thus be useful in therapy management and monitoring.

MR Perfusion Imaging of Intracranial Tumors

This retrospective study evaluated magnetic resonance (MR) perfusion imaging in the study of intracranial tumors; 218 patients were studied with 509 MR examinations. The first aim was to establish the usefulness of perfusion imaging for the differential diagnosis between neoplastic tissue and other lesions both in the first MR examination and in the post therapeutic controls (differentiation of tumor recurrence from radionecrosis). Then we evaluated the presence of infiltrating neoplastic tissue in CBV maps outside the enhancement area to differentiate infiltrating gliomas from metastases. In addition, post surgical evaluation was performed to identify residual neoplastic tissue, mainly if bleeding or inflammatory post surgical cerebral damage did not allow a definitive diagnosis with conventional morphologic images. Lastly, it was assessed whether hypervascularization (evaluated in CBV maps) is a favourable prognostic factor for a positive outcome to radiotherapy. The diagnostic gain of perfusion imaging in all these cases was established evaluating our case records.

Analysis of metabolic indices in regions of abnormal perfusion in patients with high-grade glioma

BACKGROUND AND PURPOSE

MR spectroscopic imaging (MRSI) and dynamic susceptibility-contrast MR imaging (DSC-MR imaging) are functional in vivo techniques for assessing tumor metabolism and vasculature characteristics. Because tumor hypoxia is influenced by tortuous, degraded, swollen, and angiogenic tumor vasculature, regions of abnormal perfusion parameters should coexist with changes in lactate and creatine metabolite levels.

MATERIALS AND METHODS

DSC-MR imaging and lactate-edited MRSI were performed on 38 treatment-naive patients with high-grade gliomas (17 grade III, 21 grade IV) before surgical diagnosis. Regions of abnormal perfusion were determined from peak height and percent recovery maps for each voxel within the spectroscopic imaging volume. Choline, creatine, and lactate levels within voxels experiencing only abnormal peak height (aPH), only abnormal recovery (aRec), and both abnormal peak height and recovery (aPH+aRec) were determined and compared to the surrounding T2 hyperintensity (T2h) and normal-appearing white matter.

RESULTS

There were decreasing trends in volume from aPH to aRec to aPH+aRec regions for both grade III and grade IV gliomas. Grade IV gliomas exhibited significantly elevated choline in all abnormal perfusion regions, with reduced creatine and increased lactate in the aRec region relative to the surrounding T2h. Grade III gliomas showed trends toward increased creatine within the aPH region and reduced levels within the aRec region.

CONCLUSION

Depressed creatine and elevated lactate levels confirmed the lack of oxygenation within regions of compromised vascular integrity. Identification of regions with leaky or dense vasculature and metabolic markers of hypoxia and cellular proliferation could be useful in determining the more aggressive part of the tumor for targeting, monitoring, and assessing effects of treatment.

Dynamic T(1) mapping predicts outcome of chemoradiation therapy in primary rectal carcinoma: sequence implementation and data analysis

PURPOSE

To describe details about the implementation of a dynamic T(1)-mapping technique and a simple data analysis strategy that can be used to predict therapy outcome in primary rectal carcinoma and to investigate the physiologic meaning of the obtained parameter.

MATERIALS AND METHODS

Contrast-enhanced dynamic T(1) mapping was achieved with a snapshot fast low-angle shot (FLASH) T(1) mapping sequence implemented on a 1.5 T MR scanner. This method was applied to 58 patients with primary rectal cancer before onset of chemoradiation therapy. A simple data analysis strategy based on the calculation of the maximum slope of the tissue concentration-time curve divided by the maximum of the arterial input function (AIF) was used as a measure of tumor microcirculation (PI values).

RESULTS

The snapshot FLASH (SFL) T(1)-mapping technique is accurate and sensitive enough to detect inhomogeneous uptake kinetics within tumor tissue. Classifying the patients into two groups according to therapy response showed lower mean PI values for responders as compared to nonresponders. PI was found to combine information about permeability surface area product (PS) and blood volume.

CONCLUSIONS

The described method based on dynamic T(1) mapping has the potential to be a clinical tool for predicting therapy outcome of preoperative chemoradiation in patients with primary rectal carcinoma.

Has the degree of contrast enhancement with MR imaging in laryngeal carcinoma added value to anatomic parameters regarding prediction of response to radiation therapy?

BACKGROUND AND PURPOSE

Our aim was to retrospectively investigate the prognostic significance of the degree of contrast enhancement in tumors and its additional value in previously considered MR imaging parameters with regard to local control of laryngeal cancer treated with radiation therapy (RT) alone.

MATERIALS AND METHODS

Pretreatment MR images of 64 consecutive patients (54 men and 10 women, 43-80 years of age) with supraglottic and glottic cancer were retrospectively reviewed on clinical and previously considered MR imaging parameters such as tumor involvement of specific laryngeal anatomic subsites, including laryngeal cartilages, tumor volume, extralaryngeal tumor spread, and, in addition, the degree of contrast enhancement. Clinical and MR imaging parameters were associated with regard to local control at 2 years by using the Cox regression model. "Local control" was defined as absence of primary tumor recurrence.

RESULTS

When using a threshold of the mean average contrast enhancement of 77%, the 2-year local control rate in the groups of patients with a degree of enhancement below and above this threshold was 57% and 70%, respectively (P=.3). Enhancement of tumor tissue in pre-epiglottic space (PES) was low, most probably due to its adipose tissue and poor vascular content, whereas tumor tissue involving paraglottic space (PGS) did enhance. Results of multivariate analysis indicated that the degree of contrast enhancement yielded the prognostic information (P=.07) with 2 independent prognostic factors: primary tumor volume (P=.007) and subglottic extension (P=.002) with regard to local control. Using these previously mentioned 3 MR imaging parameters as potential risk factors, we defined 4 categories, resulting in the following local control rates respectively: 90% for the group without risk factors, 73% for the group with 1, 60% for the group with 2, and finally 0% for the group with 3 risk factors, which was significantly lower than the rates in previous risk groups (P < .001).

CONCLUSION

PES has a lower degree of contrast enhancement than the PGS and may correlate with the worse outcome. Including a low degree of contrast enhancement as a parameter to primary tumor volume and subglottic extension may increase the predictive value of MR imaging for local outcome and may be helpful to identify a subset of patients whose tumors all recurred locally within 2 years after primary RT.

Assessment of Bone Marrow Angiogenesis in Patients with Acute Myeloid Leukemia by Using Contrast-enhanced MR Imaging with Clinically Approved Iron Oxides: Initial Experience

PURPOSE

To prospectively assess bone marrow (BM) angiogenesis in patients with acute myeloid leukemia (AML) by using iron oxide-enhanced magnetic resonance (MR) imaging.

MATERIALS AND METHODS

The study was institutional ethics committee approved. Informed signed consent was obtained from each study participant. The requirement for informed consent for use of data from a reference database was waived. Eleven patients (seven women, four men; mean age, 53 years+/-4.40 [standard deviation]) with an initial diagnosis of AML were enrolled in the study and underwent T2*-weighted two-echo echo-planar MR imaging of the pelvis before and after intravenous injection of a clinically approved iron oxide blood-pool contrast agent. Six healthy control subjects (one woman, five men; mean age, 35 years+/-2.31) were examined with the same MR protocol. The iron oxide-induced change in R2* relaxation rate (DeltaR2*) was calculated, and the vascular volume fraction (VVF) of the BM was derived by dividing the DeltaR2* of the BM by the DeltaR2* of the muscle. Parametric DeltaR2* maps were calculated to visualize vessel distribution. Patients underwent BM biopsy for correlative determination of microvessel density (MVD) and vascular endothelial growth factor (VEGF). Differences in DeltaR2*, VVF, VEGF, and MVD were compared by using the Wilcoxon rank sum test.

RESULTS

DeltaR2* maps showed prominent areas of highly vascularized BM in the patients with AML, whereas the control subjects had moderately vascularized BM with homogeneous vessel distribution. Quantitative analysis revealed VVF values to be significantly higher in patients with AML than in control subjects: The mean VVF in the pelvis was 9.18%+/-1.54 for patients versus 3.91%+/-0.61 for control subjects (P=.010). In accordance with MR results, MVD (P=.009) and VEGF expression (P=.017) were significantly elevated in the AML group compared with values in the control group.

CONCLUSION

Iron oxide-enhanced MR imaging enables assessment of BM angiogenesis in patients with AML.

Magnetic resonance imaging measurements of vascular permeability and extracellular volume fraction of breast tumors by dynamic Gd-DTPA-enhanced relaxometry

Vascular permeability (k(ep), min(-1)) and extracellular volume fraction (v(e)) are tissue parameters of great interest to characterize malignant tumor lesions. Indeed, it is well known that tumors with high blood supply better respond to therapy than poorly vascularized tumors, and tumors with large extracellular volume tend to be more malignant than tumors showing lower extracellular volume. Furthermore, the transport of therapeutic agents depends on both extracellular volume fraction and vessel permeability. Thus, before treatment, these tissue parameters may prove useful to evaluate tumor aggressiveness and to predict responsiveness to therapy and variations during cytotoxic therapies could allow to assess treatment efficacy and early modified therapy schedules in case of poor responsiveness. As a consequence, there is a need to develop methods that could be routinely used to determine these tissue parameters. In this work, blood-tissue permeability and extracellular volume fraction information were derived from magnetic resonance imaging dynamic longitudinal relaxation rate (R(1)) mapping obtained after an intravenous bolus injection of Gd-DTPA in a group of 92 female patients with breast lesions, 68 of these being histologically proven to be with carcinoma. For the sake of comparison, 24 benign lesions were studied. The measurement protocol based on two-dimensional gradient echo sequences and a monoexponential plasma kinetic model was that validated in the occasion of previous animal experiments. As a consequence of neoangiogenesis, results showed a higher permeability in malignant than in benign lesions, whereas the extracellular volume fraction value did not allow any discrimination between benign and malignant lesions. The method, which can be easily implemented whatever the imaging system used, could advantageously be used to quantify lesion parameters (k(ep) and v(e)) in routine clinical imaging. Because of its large reproducibility, the method could be useful for intersite comparisons and follow-up studies.

Comparison of cerebral blood volume and permeability in preoperative grading of intracranial glioma using CT perfusion imaging

INTRODUCTION

Regional cerebral blood volume (rCBV) and permeability surfaces (rPS) permit in vivo assessment of glioma microvasculature, which provides quite important pathophysiological information in grading gliomas. The aim of our study was to simultaneously examine rCBV and rPS in glioma patients to determine their correlation with histological grade using CT perfusion imaging.

METHODS

A total of 22 patients with gliomas underwent multislice CT perfusion imaging preoperatively. Low-grade and high-grade groups were categorized corresponding to WHO grade II gliomas and WHO grade III or IV gliomas, respectively, as determined by histopathological examination. rCBVs and rPSs were obtained from regions of maximal abnormality in tumor parenchyma on CBV and PS color perfusion maps. Perfusion parameters were compared using the Kruskal-Wallis test in order to evaluate the differences in relation to tumor grade. The Pearson coefficients of rCBV and rPS for each tumor grade were assessed using SPSS 13.0 software.

RESULTS

rCBV and rPS provided significant P-value in differentiating glioma grade (low-grade gliomas 3.28+/-2.01 vs 2.12+/-3.19 ml/100 g/min, high-grade gliomas 8.87+/-4.63 vs 12.11+/-3.18 ml/100 g/min, P<0.05). Receiver operating characteristic (ROC) curves revealed better specificity and sensitivity in PS than in CBV for glioma grade. A significant correlation between rCBV and rPS was observed in high-grade gliomas (r=0.684). rCBVs in oligodendrogliomas were higher than in other low-grade gliomas, whereas their rPS values did not show a parallel difference.

CONCLUSION

Perfusion CT provides useful information for glioma grading and might have the potential to significantly impact clinical management and follow-up of cerebral gliomas.

Tumor angiogenesis: pathophysiology and implications for contrast-enhanced MRI and CT assessment

The process of tumor neoangiogenesis plays a central role in the growth and spread of tumors. It is currently a leading theme in oncology, and many new drugs targeting the tumor neoangiogenic process are under development. Expanding tumors become hypoxic and tumor cells express transcription factors, such as the hypoxia-inducible factor (HIF), which induce the release of proangiogenic growth factors such as vascular endothelial growth factors (VEGF) and transforming growth factors that promote the formation of new capillaries by recruiting, activating, and stimulating endothelial cells. Activated endothelial cells secrete matrix metalloproteases, which degrade the basement membrane and the extracellular matrix, and adhesion receptors such as integrins alphavbeta(3), which allow their migration into the extracellular matrix toward the tumor cells. The newly grown vessels are immature and differ from normal capillaries. They are tortuous and irregular, resulting in poorly efficient perfusion, they are leaky (especially to macromolecules), and they are independent of the normal mechanisms of regulation of the capillary blood flow. Moreover, tumor microcirculation is heterogeneous. Evaluation of angiogenesis can be used as a prognostic marker to evaluate the aggressiveness of tumor and as a potential predictive marker of antiangiogenic treatment response. Histopathologic techniques of microvascular density indexes require invasive tissue sampling and need to be standardized. Hemodynamic characteristics of immature neovessels can be noninvasively assessed by dynamic contrast-enhanced magnetic resonance imaging or computed tomography. Tissue enhancement depends on arterial input function, kinetic of distribution of blood into the capillary bed, leakage across the capillary walls, and volume of the interstitial space. Pharmacodynamic models allow the evaluation of microvascular parameters of tissue blood flow, tissue blood volume, tissue interstitial volume, mean transit time, and permeability by surface of capillary wall. Methods based on dynamic contrast enhancement have been shown to correlate with conventional outcome methods such as histopathologic studies and survival. Radiologists must be convinced that, by using this emerging and promising approach, it is becoming possible to gain functional information during routine tumor imaging.

Magnetic resonance brain perfusion imaging with voxel-specific arterial input functions

PURPOSE

To propose an automatic method for estimating voxel-specific arterial input functions (AIFs) in dynamic contrast brain perfusion imaging.

MATERIALS AND METHODS

Voxel-specific AIFs were estimated blindly using the theory of homomorphic transformations and complex cepstrum analysis. Wiener filtering was used in the subsequent deconvolution. The method was verified using simulated data and evaluated in 10 healthy adults.

RESULTS

Computer simulations accurately estimated differently shaped, normalized AIFs. Simple Wiener filtering resulted in underestimation of flow values. Preliminary in vivo results showed comparable cerebral flow value ratios between gray matter (GM) and white matter (WM) when using blindly estimated voxel-specific AIFs or a single manually selected AIF. Significant differences (P < or = 0.0125) in mean transit time (MTT) and time-to-peak (TTP) in GM compared to WM was seen with the new method.

CONCLUSION

Initial results suggest that the proposed method can replace the tedious and difficult task of manually selecting an AIF, while simultaneously providing better differentiation between time-dependent hemodynamic parameters.

PTK787/ZK222584, a tyrosine kinase inhibitor of vascular endothelial growth factor receptor, reduces uptake of the contrast agent GdDOTA by murine orthotopic B16/BL6 melanoma tumours and inhibits their growth in vivo

Assessment of tumour vascularity may characterize malignancy as well as predict responsiveness to anti-angiogenic therapy. Non-invasive measurement of tumour perfusion and blood vessel permeability assessed as the transfer constant, K(trans), can be provided by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Using the orthotopic murine tumour model B16/BL6 melanoma, the small contrast agent GdDOTA (DOTAREM(R); Guerbet, Paris) was applied to assess the vascular transfer constant, K(trans), and interstitial leakage space, whereas intravascular iron oxide nanoparticles (Endorem(R); Guerbet, Paris) were used to detect relative tumour blood volume (rTBV), and in one experiment blood flow index (BFI). No correlations were observed between these four parameters (r(2) always <0.05). The B16/BL6 primary tumour and lymph-node cervical (neck) metastases produced high levels of the permeability/growth factor, VEGF. To probe the model, the novel VEGF receptor (VEGF-R) tyrosine kinase inhibitor, PTK787/ZK222584 (PTK/ZK) was tested for anti-tumour efficacy and its effects on DCE-MRI measured parameters of tumour vascularity. Data from the non-invasive measure of tumour vascularity were compared with a histological measurement of vasculature using the DNA-staining dye H33342. PTK/ZK inhibited growth of the primary and, particularly, cervical tumour metastases following chronic treatment for 2 weeks (50 or 100 mg/kg daily) of 1-week-old tumours, or with 1 week of treatment against more established (2-week-old) tumours. After chronic treatment with PTK/ZK, DCE-MRI detected significant decreases in K(trans) and interstitial leakage space, but not rTBV of both primary tumours and cervical metastases. Histological data at this time-point showed a significant decrease in blood vessel density of the cervical metastases but not the primary tumours. However, in the cervical metastases, the mean blood vessel width was increased by 38%, suggesting overall no marked change in blood volume. After acute (2-4 day) treatment, DCE-MRI of the cervical metastases demonstrated a significant decrease in K(trans) and interstitial leakage space and also in the initial area under the enhancement curve for GdDOTA (IAUC), but no change in the rTBV or BFI. Thus, significant changes could be detected in the DCE-MRI measurement of tumour uptake of a small contrast agent prior to changes in tumour size, which suggests that DCE-MRI could be applied in the clinic as a rapid and sensitive biomarker for the effects of VEGF-R inhibition on tumour blood vessel permeability and thus may provide an early marker for eventual tumour response.

Dynamic contrast-enhanced magnetic resonance imaging in radiotherapeutic efficacy in the head and neck tumors

PURPOSE

The purpose to this study is to identify correlations between pathology and dynamic contrast-enhanced magnetic resonance imaging (MRI) and to assess the utility of this technique in the evaluation of radiation response for head and neck cancer.

MATERIALS AND METHODS

MRI was prospectively performed after radiotherapy in 27 patients with various head and neck tumors. After bolus injection of contrast material, a dynamic study was performed using a spoiled gradient-recalled imaging sequence. The maximum slope of increase (MSI) on the time-intensity curve was displayed as a color-coded image. The ratio of MSI (MSIR) was obtained for tumor and normal muscles. Pathological specimens were obtained after MRI in all cases. Histological grading of irradiation changes was classified into 5 grades (0-4). Correlations between MSIR and histological grade were examined.

RESULTS

Histologically, 18 tumors were classified as grade 2 (presence of viable tumor cells), 4 were grade 3 (nonviable tumor cells), and 5 were grade 4 (no tumor cells). Although the mean +/- SD of MSIR in patients with histological grade 2 or 3 was 7.4 +/- 7.9, MSIR in patients with grade 4 was 1.8 +/- 0.73, representing a significant difference ( P < .05). Every patient with grade 4 displayed an MSIR of 2.5 or less, although 5 of 22 patients with grade 2 or 3 had an MSIR of 2.5 or less.

CONCLUSIONS

MSI quantitatively reflects response to radiotherapy for head and neck cancer. Color-coded MSI display is feasible for depicting permeability changes after radiotherapy.

Comparison of tumor blood perfusion assessed by dynamic contrast-enhanced MRI with tumor blood supply assessed by invasive imaging

PURPOSE

To evaluate the potential of Gd-DTPA-based dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for providing high-resolution tumor blood perfusion images.

MATERIALS AND METHODS

Xenografted tumors from two amelanotic human melanoma lines (A-07 and R-18) were used as preclinical models of human cancer. DCE-MRI was performed at a voxel size of 0.5 x 0.2 x 2.0 mm(3) with the use of spoiled gradient recalled sequences. We produced tumor images of E . F (where E is the initial extraction fraction, and F is perfusion) by subjecting the DCE-MRI data to Kety analysis, and then compared those images with images of tumor blood supply. We obtained high-resolution tumor blood supply images using the Bioscope silicon strip detector system to measure the uptake of Na(99m)TcO(4) in histological preparations. We assessed the global blood supply by measuring the tumor uptake of three freely diffusible blood flow tracers: (86)RbCl, [(14)C]IAP, and Na(99m)TcO(4).

RESULTS

E . F was found to mirror the blood supply well in A-07 and R-18 tumors. The mean E . F differed between the A-07 and R-18 tumors by a factor of approximately 1.6, and this difference was similar to the difference in the global blood supply. The intratumor heterogeneity in E . F was significant for tumors of both lines, and this heterogeneity was similar to the intratumor heterogeneity in the blood supply. The intratumor heterogeneity in the blood supply differed slightly between the A-07 and R-18 tumors, and even this difference was mirrored by the E . F images.

CONCLUSION

E . F images of xenografted tumors reflect blood perfusion. This implies that E . F may be a useful parameter for improving cancer diagnostics and individualizing cancer treatment. This possibility deserves to be investigated thoroughly in clinical studies.

Solitary Pulmonary Nodules

OBJECTIVE

The aim of this prospective study was to compare the diagnostic performances of dynamic MR imaging and CT for the differentiation of benign and malignant solitary pulmonary nodules (SPNs).

METHODS

Eighty-one patients with SPNs (32 malignant, 49 benign) underwent dynamic MR imaging (n=31), dynamic CT (n=27), or both (n=23). The degree of peak enhancement of benign and malignant SPNs was compared on both dynamic MR imaging and CT. Receiver operating characteristic (ROC) analysis was performed to compare the diagnostic performances of dynamic MR imaging and CT.

RESULTS

The malignant SPNs revealed significantly greater degrees of peak enhancement on dynamic MR imaging (mean +/- SD [p%SI] 131.2 +/- 46.1 versus 54.2 +/- 45.3; range [p%SI] 82.6-260.0 versus -0.7-171.7; P <0.0001) and CT (mean +/- SD [DMI] 37.8 +/- 15.1 versus 17.9 +/- 21.8; range [DMI] 14.1-68.2 versus -5.4-107.6; P=0.0004). Although dynamic MR imaging was somewhat superior to dynamic CT, the diagnostic performances of the 2 modalities based on ROC analysis were not statistically significant.

CONCLUSIONS

Dynamic MR imaging and CT seem to be equally well suited for the differentiation between benign and malignant SPNs.

Differentiation between completely hyalinized uterine leiomyomas and ordinary leiomyomas: three-phase dynamic magnetic resonance imaging (MRI) vs. diffusion-weighted MRI with very small b-factors

PURPOSE

To assess the possibility of differentiating between completely hyalinized leiomyomas and ordinary leiomyomas by using diffusion-weighted (DW) magnetic resonance imaging (MRI) (DWI) employing very small b-factors (b = 1.51 and 55.3 seconds/mm(2)) in comparison with three-phase dynamic MRI.

MATERIALS AND METHODS

The subjects were 25 patients with 52 histopathologically confirmed uterine leiomyomas. All leiomyomas were divided into two histopathologic subtypes (5 completely hyalinized leiomyomas and 47 ordinary leiomyomas). For each leiomyoma, the enhancement index (EI) at three-phase dynamic MRI and apparent diffusion coefficient (ADC) were obtained and then compared.

RESULTS

The EIs at second and third dynamic phases clearly differentiated the two types of leiomyomas without overlap of values. ADCs also clearly differentiated the two types of leiomyomas without overlap of values. Moreover, there were significant positive correlations between ADCs and EIs at all dynamic phases (r = 0.41-0.50, P < 0.01).

CONCLUSION

Not only three-phase dynamic MRI but also DWI with very small b-factors could be useful for differentiating completely hyalinized leiomyomas from ordinary leiomyomas.

Dynamic MRI in indirect estimation of microvessel density, histologic grade, and prognosis in colorectal adenocarcinomas

The relations of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters to microvessel density (MVD), histologic grade, and presence of metastasis were evaluated to establish new prognostic indicators in colorectal cancer (CRC). Fast-low angle shot DCE-MRI parameters (time-intensity curves, TICs; maximal relative enhancement within the first minute, E(max/1); maximal relative enhancement of the entire study, Emax; steepest slope of the contrast enhancement curve; and time to peak enhancement) of 21 CRCs (seven Duke stage B, 12 Duke stage C, and two Duke stage D) were retrospectively evaluated and correlated with corresponding postoperative MVD measurements, histologic grades, and presence of metastasis at 2 years. TICs were classified as type A in nine (43%), type B in seven (33%), and type C in five cases (24%). There was a significant difference between TIC types with regard to MVD (p < 0.05-0.001). Time to peak enhancement, steepest slope of TIC, and E(max/1) were strongly correlated with MVD (r = -0.765, p < 0.01; r = 0.681, p < 0.01; r = 0.634, p < 0.01; respectively). MVD, steepest slope of the enhancement curve, E(max/1), and Emax strongly correlated with histologic grade (r = 0.475, p < 0.05; r = 0.683, p < 0.01; r = 0.687, p < 0.01; r = 0.791, p < 0.01; respectively). There was a significant difference between groups of patients with and without metastasis with regard to histologic grade (p < 0.05) and two of the DCE-MRI parameters (p < 0.005 for E(max/1) and p < 0.05 for time to peak enhancement). Discriminant analysis correctly predicted the metastatic occurrence at 2 years in 90.5% of cases using E(max/1) (p < 0.001). Histologic grade resulted in lower rates of discrimination (66.7%; p < 0.05). DCE-MRI parameters may help in the prediction of MVD and histologic grade in CRC and may be used to predict therapeutic outcome.

Dynamic Contrast-enhanced CT of Intracranial Meningioma: Comparison of Distributed and Compartmental Tracer Kinetic Models—Initial Results

Dynamic contrast material-enhanced computed tomographic images of intracranial meningioma were analyzed by using both distributed-parameter and conventional compartmental tracer kinetic models. The distributed-parameter models were found to yield consistently better fitting of data sets than were conventional compartmental models. Although linear correlations were found between the kinetic parameters of the two models, some of these parameters (such as perfusion and mean transit time) did not correspond quantitatively. For all models, the kinetic parameters associated with the extravasation of tracer were found to be distinctly higher in meningiomas than in normal white- and gray-matter tissues.

Contribution of dynamic contrast MR imaging to the differentiation between dural metastasis and meningioma

PURPOSE

To determine the perfusion-sensitive characteristics of cerebral dural metastases and compare them with the data on meningiomas.

METHODS

Twenty-two patients presenting with dural tumor underwent conventional and dynamic susceptibility-contrast MR imaging: breast carcinoma metastases, two patients; colorectal carcinoma metastasis, one patient; lung carcinoma metastasis, one patient; Merkel carcinoma metastasis, one patient; lymphoma, one patient; meningiomas, 16 patients. The imaging characteristics were analyzed using conventional MR imaging. The cerebral blood volume (CBV) maps were obtained for each patient and the relative CBV (rCBV) in different areas was calculated using the ratio between the CBV in the pathological area (CBVp) and in the contralateral white matter (CBVn).

RESULTS

The differentiation between a meningioma and a dural metastasis can be difficult using conventional MR imaging. The rCBVs of lung carcinoma metastasis (1 case: 1.26), lymphoma (1 case: 1.29), breast carcinoma metastasis (2 cases: 1.50,1.56) and rectal carcinoma metastasis (1 case: 3.34) were significantly lower than that of meningiomas (16 cases: mean rCBV = 8.97+/-4.34, range 4-18). Merkel carcinoma metastasis (1 case: 7.56) showed an elevated rCBV, not different from that of meningiomas.

CONCLUSION

Dural metastases are sometimes indistinguishable from meningiomas using conventional MR imaging. rCBV mapping can provide additional information by demonstrating a low rCBV which may suggest the diagnosis of metastasis.

Estimation of relative blood volume in head and neck squamous cell carcinomas

PURPOSE

MR based first-pass method can be utilized to obtain hemodynamic information in the head and neck region. The purpose of this study was to estimate the regional relative blood volume (rBV) in head and neck tumors, which is useful for tumor staging and tumor biopsy.

METHODS

Eighteen patients with head and neck tumors (17 squamous cell carcinomas, 1 hemangiopericytoma) were studied on a 1.5-T system. Conventional T1-weighted MR images and T2-weighted images and sequential T2*-weighted images were obtained. During repetitive image sequence acquisition, a bolus (0.2 mmol/kg) of gadopentetate dimeglumine was mechanically injected. Image processing of the dynamic raw data was performed on a pixel-by-pixel basis.

RESULTS

Regional relative blood volume maps of the head and neck were successfully reconstructed in all (18/18) patients. The regional relative blood volume values within the tumor area of squamous cell carcinoma were 7.0 +/- 2.8, normalized on muscle, whereas the rBV of a single hemangiopericytoma was 11.6. The difference of rBV values of tumor and muscle was highly significant at statistical evaluation (p < 0.001).

CONCLUSIONS

Relative blood volume imaging of head and neck tumors is valid using MR-based first-pass method. This method provides hemodynamic information which is not available from conventional MR imaging and is promising for further characterization of head and neck tumors

Assessment of tumor blood perfusion by high-resolution dynamic contrast-enhanced MRI: A preclinical study of human melanoma xenografts

A noninvasive method to obtain high-resolution images of tumor blood perfusion is needed for individualized cancer treatments. In this study we investigated the potential usefulness of dynamic contrast-enhanced MRI (DCE-MRI), using human melanoma xenografts as models of human cancer. Gadopentetate dimeglumine (Gd-DTPA) was used as the contrast agent, and DCE-MRI was performed at a voxel size of 0.5 x 0.2 x 2.0 mm3 with spoiled gradient-recalled sequences. We obtained images of E. F (where E is the extraction fraction, and F is perfusion) by subjecting DCE-MR images to Kety analysis. We obtained highly reproducible E. F images, which we verified by imaging heterogeneous tumors twice. We hypothesized that the extraction fraction of Gd-DTPA would be high and would not vary significantly in tumor tissue, implying that E. F should be a well-suited parameter for describing tumor blood perfusion. Observations consistent with this hypothesis were made by comparison of E. F-images with immunostained histological preparations from the imaged sections. The E. F images mirrored the histological appearance of the tumor tissue perfectly. Quantitative studies showed that E. F was highest in nonhypoxic tissue with high microvascular density, second highest in nonhypoxic tissue with low microvascular density, third highest in hypoxic tissue, and lowest in necrotic tissue. Moreover, the radial heterogeneity in E. F was almost identical to that in the blood supply, as assessed by the use of Na99mTcO4 as a perfusion tracer. Taken together, our observations show that high-resolution images reflecting tumor blood perfusion can be obtained by DCE-MRI.

Tumor microcirculation and diffusion predict therapy outcome for primary rectal carcinoma

PURPOSE

The aim of our study was to correlate perfusion indices and apparent diffusion coefficients with therapy outcome after chemoradiation.

METHODS AND MATERIALS

In 34 patients with primary rectal carcinoma (cT3) undergoing preoperative chemoradiation, pretherapeutic perfusion indices and apparent diffusion coefficients were obtained by dynamic or diffusion-weighted magnetic resonance imaging. Therapy response was defined if the pathologic observation revealed no invasion into the perirectal fat after chemoradiation.

RESULTS

In 18 patients, a response and in 16, no response was observed. Statistically significant differences were found for the mean perfusion index (p < 0.001; 7.5 +/- 1.5 mL/min/100 g vs. 10.7 +/- 2.7 mL/min/100 g) and for the intratumoral cumulative fraction of pixels with perfusion-indices > 12 mL/min/100 g (p < 0.001, 3.7 +/- 4.0% vs. 24.7 +/- 17.9%). A three-way ANOVA resulted in significant effects for therapy responder/nonresponder (p < 0.001) and for apparent diffusion coefficient and the individual patients.

CONCLUSION

Perfusion indices and apparent diffusion coefficients inside the tumor region seem to be of predictive value for therapy outcome of preoperative therapy in patients with primary rectal carcinoma. Higher parameter levels in the nonresponding group could be explained by increased shunt flow or increased angiogenic activity in aggressive tumor cell clusters resulting in reduced nutrients supply and higher fraction of intratumoral necrosis respectively.

In vivo quantification of optical contrast agent dynamics in rat tumors by use of diffuse optical spectroscopy with magnetic resonance imaging coregistration

We present a study of the dynamics of optical contrast agents indocyanine green (ICG) and methylene blue (MB) in an adenocarcinoma rat tumor model. Measurements are conducted with a combined frequency-domain and steady-state optical technique that facilitates rapid measurement of tissue absorption in the 650-1000-nm spectral region. Tumors were also imaged by use of contrast-enhanced magnetic resonance imaging (MRI) and coregistered with the location of the optical probe. The absolute concentrations of contrast agent, oxyhemoglobin, deoxyhemoglobin, and water are measured simultaneously each second for approximately 10 min. The differing tissue uptake kinetics of ICG and MB in these late-stage tumors arise from differences in their effective molecular weights. ICG, because of its binding to plasma proteins, behaves as a macromolecular contrast agent with a low vascular permeability. A compartmental model describing ICG dynamics is used to quantify physiologic parameters related to capillary permeability. In contrast, MB behaves as a small-molecular-weight contrast agent that leaks rapidly from the vasculature into the extravascular, extracellular space, and is sensitive to blood flow and the arterial input function.

Perfusion MRI in the evaluation of the relationship between tumour growth, necrosis and angiogenesis in glioblastomas and grade 1 meningiomas

Angiogenesis is a common characteristic of tumours, and it is reasonable to assume that it has an influence on tumour growth, depending on the grade of malignancy. We therefore studied angiogenesis in 25 patients: 14 with glioblastoma multiforme and 11 with grade I meningioma. Our aim was to assess how angiogenesis conditions growth and necrosis. The patients underwent MRI with standard and perfusion sequences. We calculated the volume of each tumour; for the glioblastomas the solid portion was taken as the difference between the overall volume and the volume of any necrotic portion. In the glioblastomas, we found an inverse relationship between blood volume and the size of the tumour, whereas in the meningiomas there was of a direct relationship. These correlations confirm in vivo the knowledge about necrosis in glioblastomas and its relationship to their inadequate vascular network. On the contrary, grade 1 meningiomas show an equilibrium between their microcirculation and the cellular component.

Angiogenesis in hematologic malignancies

Angiogenesis is defined as the formation of new capillaries from preexisting blood vessels and plays an important role in the progression of solid tumors. Recently a similar relationship has been described in several hematologic malignancies. Expression of the angiogenic peptides vascular endothelial growth factor (VEGF) and basic fibroblast growth factor correlates with clinical characteristics in leukemia and non-Hodgkin's-lymphoma and the serum/plasma concentrations serve as predictors of poor prognosis. Increased bone marrow microvessels in multiple myeloma (MM) are correlated with decreased overall survival. Thalidomide which has antiangiogenic effects and direct cytotoxic effects was found to be effective in MM, myelodysplastic syndrome and acute myeloid leukemia (AML). Preliminary data indicate activity of VEGF-tyrosine kinase inhibitors in AML. Clinical research is now aimed at testing antiangiogenic treatment strategies in several hematologic neoplasms as well as identifying the best candidate patients for specific approaches.

Measurements of extracellular volume fraction and capillary permeability in tissues using dynamic spin-lattice relaxometry: studies in rabbit muscles

Dynamic MR longitudinal R(1) relaxometry after administration of a gadolinium contrast bolus (Gd-DTPA) has been used for in vivo measurements of the extracellular volume fraction (v) and the capillary permeability (k min(-1)) in rabbit muscles to distinguish between red slow- and white fast-twitch muscle fiber types. For this purpose a protocol imaging sequence has been used which allows fast R(1) measurements during the contrast agent uptake. Physiological tissue parameters, k and v, were obtained by computing procedures assuming a simplified monoexponential plasma model. These were shown to be about twice as large in the slow-twitch semimembranosous proprius muscle (SP), containing 100% oxidative type-I fiber, that in the fast-twitch rectus femorus muscle (RF), containing only 6% type-I fiber type. The capillary permeability has been found to be 0.25 +/- 0.02 min(-1) for the (SP) and 0.10 +/- 0.01 min(-1) for the (RF). Similarly, the extracellular volume fractions were 0.189 +/- 0.015 and 0.082 +/- 0.006 respectively, in close agreement with literature data and experimental results obtained by invasive radionuclide measurements. For the pool of the 10 studied animals, no significant variation among animals was observed in the extracellular volume fraction and the capillary permeability for the different muscle fiber types. The dynamic relaxometry method used is easy to implement on conventional MR imagers and has potential applications in muscle diseases. The method has also potential applications for tissue characterization based on extracellular volume and capillary permeability quantification. In particular, the method can be used for the evaluation of tumors and their responses to therapies.

A physiologic model of capillary-tissue exchange for dynamic contrast-enhanced imaging of tumor microcirculation

We present a multiple compartment, mammillary distributed-parameter model for capillary-tissue exchange, which can be implemented with dynamic contrast-enhanced imaging to study kinetic heterogeneity in tumors. The proposed n-compartment model consists of a vascular distributed-parameter compartment in direct exchange with a number (n - 1) of interstitial compartments. It is applied to a prostate tumor case study to illustrate the possible co-existence of two kinetically distinct compartments in the tumor, and the estimation of useful physiological parameters (such as perfusion, mean transit time, fractional volumes, and transfer and rate constants) associated with tissue microcirculation. The present model exhibits the convenient property of a separable impulse residue response function in time domain, which can be used to provide further insights and understanding on the physiological basis of tissue enhancement parameters commonly used for correlation studies with tumor histological diagnosis.

Phase I clinical trial of recombinant human endostatin administered as a short intravenous infusion repeated daily

PURPOSE

To perform a phase I trial of recombinant human endostatin (rhEndostatin; EntreMed, Rockville, MD) given as a daily 20-minute intravenous (IV) injection in adult patients with refractory solid tumors.

PATIENTS AND METHODS

The daily dose was increased from 15 to 240 mg/m(2) by a factor of 100% in cohorts of three patients. In the absence of dose-limiting toxicity, uninterrupted treatment was continued until the tumor burden increased by more than 50% from baseline. Correlative studies included dynamic contrast-enhanced magnetic resonance imaging of tumor blood flow, urinary vascular endothelial growth factor and basic fibroblast growth factor levels, rhEndostatin serum pharmacokinetics, and monitoring of circulating antibodies to rhEndostatin.

RESULTS

There were no notable treatment related toxicities among 15 patients receiving a total of 50 monthly cycles of rhEndostatin. One patient with a pancreatic neuroendocrine tumor had a minor response and two patients showed disease stabilization. Linearity in the pharmacokinetics of rhEndostatin was indicated by dose-proportionate increases in the area under the curve for the first dose and the peak serum concentration at steady state. Daily systemic exposure to rhEndostatin in patients receiving 240 mg/m(2)/d was approximately 50% lower than that provided by the therapeutically optimal dose in preclinical studies.

CONCLUSION

rhEndostatin administered as a 20-minute daily IV injection at doses up to 240 mg/m(2) showed no significant toxicities. Evidence of clinical benefit was observed in three patients. Due to high variability between the peak and trough serum concentrations associated with the repeated short IV infusion schedule, daily serum drug levels only briefly exceeded concentrations necessary for in vitro antiangiogenic effects.

Evaluation of tissue perfusion in a rat model of hind-limb muscle ischemia using dynamic contrast-enhanced magnetic resonance imaging

PURPOSE

To evaluate the feasibility of using dynamic contrast-enhanced magnetic resonance imaging (MRI) for assessment of muscle perfusion in a rat model of hind-limb ischemia.

MATERIALS AND METHODS

The acute alteration and chronic recovery in muscle perfusion and perfusion reserve after femoral artery ligation were quantified using the maximum Gd-DTPA uptake rate obtained by a T(1)-weighted gradient-recalled echo sequence. Radionuclide-labeled microsphere blood flow measurements were performed for comparison with the MR perfusion measurement on a separate set of animals.

RESULTS

After femoral artery ligation, a significant reduction in resting muscle perfusion was only observed at 1 hour post-ligation during the 28-day follow-up period. Muscle perfusion reserve was severely diminished following the ligation. Despite significant recovery over time, perfusion reserve to the ligated limb reached only 63% of the perfusion capacity in the unaffected limb by 42 days post ligation. A strong correlation (r = 0.86) between MR perfusion and microsphere blood flow measurements was observed for evaluation of relative changes in muscle perfusion.

CONCLUSION

Dynamic contrast-enhanced MRI with Gd-DTPA is useful to assess time-dependent changes in muscle perfusion and perfusion reserve in this hind-limb ischemia model.