Comparison of pharmacokinetic MRI and [18F] fluorodeoxyglucose PET in the diagnosis of breast cancer: initial experience

It was the aim of this methodology-oriented clinical pilot study to compare the potential of dynamic MRI and 2-[18F]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) for the detection and characterization of breast cancer. Fourteen women with suspicious breast lesions were examined. The MRI data were acquired with a turbo fast low-angle shot sequence and analyzed using a pharmacokinetic model. Emission data were detected in the sensitive 3D modus, iteratively reconstructed, and superimposed onto corresponding transmission images. In the 14 patients, 13 breast masses with a suspicious contrast enhancement and FDG uptake were detected. For these lesions, no statistically significant correlation between evaluated MR and PET parameters was found. Of the 9 histologically confirmed carcinomas, 8 were correctly characterized with MRI and PET. Two inflammatory lesions were concordantly classified as cancer. Moreover, dynamic MRI yielded another false-positive finding. In 6 patients, PET detected occult lymph node and/or distant metastases. Although both functional imaging techniques provide independent tissue information, the results concerning the diagnosis of primary breast lesions were almost identical. An advantage of PET, however, is its ability to localize lymph node involvement and distant metastases as an integral part of the examination.

Postoperative fluid-attenuated inversion recovery MR imaging of cerebral gliomas: initial results

Fluid-attenuated inversion-recovery (FLAIR) imaging has shown to be a valuable imaging modality in the assessment of intra-axial brain tumors; however, no data are available about the role of this technique in the clinically important postoperative stage. The purpose of this study was to evaluate the diagnostic potential of FLAIR MR imaging in residual tumor after surgical resection of cerebral gliomas. Fifteen patients with residual cerebral gliomas were examined within the first 18 days after partial surgical resection of cerebral gliomas. The imaging protocol included T1-weighted spin echo, T2- and proton-density-weighted fast spin echo, and FLAIR imaging with identical slice parameters. T1 and FLAIR were repeated after contrast media application. Detection and delineation of residual tumor were the primary parameters of the image analysis. Additionally, the influence of image artifacts on the image interpretation was assessed. On FLAIR images residual signal abnormalities at the border of the resection cavities were observed in all patients, whereas T2- and T1-weighted images present residual abnormalities in 13 of 15 and 10 of 15 patients, respectively. The FLAIR imaging was found to be superior to conventional imaging sequences in the delineation of these changes and comparable to contrast enhanced T1-weighted imaging in the delineation of residual enhancing lesions. Because of protein cell components and blood byproducts within the resection cavity, FLAIR imaging was unable to suppress the cerebrospinal fluid (CSF) in 4 patients. After the decomposition of proteins and blood, CSF could again be completely suppressed and residual or recurrent tumors were clearly identified. Our preliminary study has shown that FLAIR may be a valuable diagnostic modality in the early postoperative MR imaging after resection of cerebral gliomas due to its better delineation of residual pathologic signal at the border of the resection cavity. It should therefore be integrated into the early and/or intraoperative MR imaging protocol.

[Diffusion weighted MRI: ischemic and traumatic injuries of the central nervous system]

Diffusion weighted magnetic resonance imaging (DWI) represents a recent development that extends imaging from the depiction of the neuroanatomy into the field of functional and physiologic processes. DWI measures a fundamentally different physiologic parameter than conventional MRI. Image contrast is related to differences in the microscopic motion (diffusion) of water molecules within brain tissue rather than a change in total tissue water. Consequently, DWI can reveal pathology where conventional T1- and T2-weighted MR images are negative. DWI has clinically proven its value in the assessment of acute cerebral stroke and trauma by showing cerebral injury early due to ist ability to discriminate between lesions with cytotoxic edema (decreased diffusion) from lesions with vasogenic edema (increased diffusion). Full tensor DWI allows to calculate a variety of functional maps, the most widely used maps include maps of apparent diffusion coefficients and isotropic diffusion. In addition maps of anisotropic diffusion can be calculated which are believed to give information about the integrity and location of fiber tracts. This functional-anatomical information will most probably play an increasingly important role in the early detection of primary and secondary tissue injury from various reasons and could guide and validate current and future neuroprotective treatments.

[Progress in understanding spinal cord injuries. Clinical aspects, imaging, pathological correlations]

Close inspection of MR images in all stages of SCI can reveal alterations which are important for our understanding of the changes which occur in SCI and may be crucial for planning surgical intervention. Importantly also, these observations may assist in the evaluation of novel therapies in SCI, such as cellular transplantation. It is hopeful that MR strategies which are currently in routine use in the brain, such as diffusion weighted imaging, perfusion studies, spectroscopy, and magnetization transfer can be adopted for use in the spine [8]. Because of the small size of the cord, the magnetic susceptibility problems caused by surrounding air and bone, and nearby vascular and CSF flow/pulsations, these techniques are currently very difficult to employ in the cord. They will however evolve over time and give us greater insights into the in-vivo status of the injured cord.

[MRI in spinal injuries]

The improvement of preclinical emergency medicine has increased the long-term survival of patients which sustained severe injuries of the spinal cord. However, the incidence of late complications has been increased due to the long-term survival. With the increasing use of magnetic resonance imaging (MRI) in this patient group the diagnosis of typical late complications of the spinal cord has improved. In this article we suggest the following terms to describe late complications of the spinal cord: syrinx, atrophy, cyst, malacia, disruption, and thethering.

Bone marrow microcirculation analysis in multiple myeloma by contrast-enhanced dynamic magnetic resonance imaging

The aim of our study was to investigate the quantitative microcirculation parameters amplitude A (hypothetical intravascular volume) and exchange rate constant k(21) (hypothetical vascular permeability) by contrast-enhanced dynamic magnetic resonance imaging (dMRI) as markers of angiogenesis in multiple myeloma (MM). Therefore lumbar spine and spina iliaca superior posterior of 16 normal controls and 41 patients with active MM were assessed using a dMRI protocol with a pump controlled bolus infusion of Gadolinium-DTPA. Pharmacokinetic parameters, amplitude A and exchange rate constant k(21) were calculated according to a 2-compartment model. Color-coded parameter images were generated from pharmacokinetic data analysis and superimposed onto the conventional MR images. Amplitude A and k(21) parameters were significantly increased in patients with MM compared with controls (p = 0.001; median A(ctr), 0.2 [range, 0.09-0.4]; median A(MM), 0.93 [range, 0.2-2.2]; median k(21ctr), 0.09 min(-1) [range, 0.03-0.9]; median k(21MM), 4.58 [range, 0.22-23.8]). Within the group of MM patients the pattern of color-coded parameter images were found to be either of "diffuse" (n = 13, 31%) or "focal" (n = 28, 69%) type of distribution of microcirculation. Comparison of amplitude A in patients with "focal" vs. "diffuse" pattern of the pharmacokinetic maps revealed a significant increase in the median of amplitude A in the "focal" group. Amplitude A values allowed a classification of patients according to severe osteolytic bone involvement (p = 0.023) with the best cutoff value of 0.7 for amplitude A. Downmodulation of amplitude A was observed in a MM patient treated with standard VAD chemotherapy. Our data demonstrate that dMRI is a novel imaging technique for the detection and monitoring of MM bone lesions. It provides independent evidence for angiogenesis in MM.

Fluid-attenuated inversion-recovery MR imaging of gliomatosis cerebri

Magnetic resonance imaging has been shown to be the most sensitive imaging modality in the assessment of gliomatosis cerebri. Recent studies have shown that fluid-attenuated inversion-recovery (FLAIR) is a valuable MR sequence in the delineation of cerebral pathologies including intra-axial tumors. However, no data are available about the role of this novel technique in the assessment of gliomatosis lesions. The purpose of this study was therefore to evaluate the diagnostic potential of FLAIR MR imaging in patients with suspected gliomatosis cerebri. Seven patients suspected of having lesions of gliomatosis cerebri were examined by T1-weighted spin echo (SE), T2-weighted fast spin echo (FSE), and FLAIR MR imaging with identical slice parameters. T1 and FLAIR were repeated after contrast media administration. Delineation and extent of gliomatosis were the primary parameters of the image analysis. The FLAIR imaging clearly delineated the extent of gliomatosis lesions in all patients. Due to the suppression of cerebrospinal fluid, the delineation was superior to conventional T2-weighted FSE images. Especially the detection and delineation of cortical spread and the infiltration of the corpus callosum was best seen on FLAIR images. The FLAIR MR imaging is a valuable diagnostic modality in the assessment of patients with gliomatosis cerebri. Due to its better delineation of tumor spread, it was found to be the imaging method of choice and should therefore be integrated into the MR imaging protocol of these patients.

Transient enlargement of contrast uptake on MRI after linear accelerator (linac) stereotactic radiosurgery for brain metastases

PURPOSE/OBJECTIVE

With the increasing number of patients successfully treated with stereotactic radiosurgery for brain metastases, decision making after therapy based on follow-up imaging findings becomes more and more important. Magnetic resonance imaging (MRI) is the most sensitive means for follow-up studies. The objective of this study was to investigate the treatment outcome of our radiosurgery program and to describe the response of brain metastases to contrast-enhanced MRI after linear accelerator (linac) stereotactic radiosurgery and identify factors to distinguish among local control and local failure.

METHODS AND MATERIALS

Using serial MRI, we followed the course of 87 brain metastases in 48 consecutive patients treated between September 1996 and November 1997 with linac-based radiosurgery with 15-MV photons. Treatment planning was performed on an MR data cube. For spherical metastases, radiosurgery was delivered using a 9 noncoplanar arc technique with circular-shaped collimators. For irregularly shaped targets, radiosurgery was delivered using a manually driven multi-leaf collimator with a leaf width of 1.5 mm projected to the isocenter. Median radiosurgery dose was 20 Gy prescribed to the 80% isodose. Together with whole brain radiotherapy (20 x 2 Gy, 5/w), a median radiosurgical dose of 15 Gy was delivered. Median follow-up was 8 (range 2--36) months. Factors influencing local control and survival rates were analyzed with respect to MRI response, and Kaplan-Meier curves were calculated.

RESULTS

Actuarial local tumor control was 91% at one and two years. Patient survival at one and two years was 30% and 18%. Median survival was 9 months. During follow-up in 70 (81%) of the 87 treated metastases, the contrast-enhancing volumes on T1W images were stable or disappeared partly or completely. A transient enlargement of contrast-enhancing volumes was observed in 11 (12%) of the 87 lesions treated, while a progressive enlargement due to local treatment failure was observed in 6 (7%) of the 87 treated metastases. Younger age, early contrast onset after radiosurgery, and previous chemotherapy were associated with this transient enlargement of contrast-enhancing lesion volume.

CONCLUSIONS

Linac-based radiosurgery is an effective, noninvasive, and safe treatment option for patients with brain metastases. A marked enlargement of the contrast-enhancing volume on T(1)-weighted MR images after radiosurgery is a sensitive predictor for, but not equivalent with, local failure. In as many as two-thirds of the cases with contrast enlargement in MRI follow-up, the contrast enlargement is transient with no need for further treatment. While some MRI findings are more likely if transient enlargement is present, a clear decision cannot be made based on MRI, and ultimately the clinical status dictates further action.

[Functional magnetic resonance tomography in the diagnosis and therapy monitoring in multiple myeloma]

AIM OF THE STUDY

Investigation of the quantitative microcirculation parameters amplitude A and exchange rate constant k21 determined by contrast-enhanced dynamic magnetic resonance imaging (d-MRI) in multiple myeloma (MM).

METHODS

d-MRT of lumbar spine and right spina iliaca superior posterior of 16 controls (ctr) and 35 patients with active MM. Generation of colour-coded images of microcirculation parameters superimposed onto static MRI images.

RESULTS

Amplitude A and k21 parameters were significantly increased in patients with MM and down modulated by therapy in 7 of 8 MM cases in a follow-up investigation [p < 0.01; median Actr = 0.2 (0.09-0.4); median AMM = 0.93 (0.2-1.52); median k21ctr = 0.09 min-1 (0.03-0.9); median k21MM = 4.57 min-1 (0.21-23.8)]. Thirteen patients revealed a "diffuse" and 22 a "focal" pattern of distribution of microcirculation parameters. Bone marrow biopsies in 8 cases revealed an correlation between bone marrow plasma cell infiltration and increased microcirculation parameters.

CONCLUSION

Identification of microcirculation changes by d-MRI is a novel imaging technique for the detection and monitoring of MM bone lesions.

Assessment of cerebral gliomas by a new dark fluid sequence, high intensity REduction (HIRE): a preliminary study

The purpose of this study was to assess the diagnostic potential of a new dark fluid sequence, high intensity reduction (HIRE) in the diagnostic workup of patients with cerebral gliomas. The HIRE sequence utilizes a very long T(2) value of the cerebrospinal fluid (CSF) to suppress its high signal contribution in T(2)-weighted imaging by a image subtraction technique. Fifteen patients with histologically confirmed cerebral gliomas were examined with T(2)-weighted fast spin-echo (FSE), T(1)-weighted SE, fast fluid-attenuated inversion recovery (FLAIR), and HIRE imaging using identical scan parameters. In patients with enhancing lesions, fast FLAIR and HIRE were added to the contrast-enhanced T(1)-weighted SE images. Images were analyzed in a qualitative and quantitative evaluation. In the qualitative analysis, lesion detection, lesion delineation, and differentiation between enhancing and non-enhancing tumor tissue were assessed in a two-reader study. For the quantitative analysis, lesion-to-background and lesion-to-CSF contrast and contrast-to-noise ratios were determined in a region of interest analysis. HIRE achieved a significant reduction of the CSF signal without losing the high gray-to-white matter contrast of T(2)-weighted sequences. In the quantitative analysis, the contrast ratios of the HIRE images were lower compared with the FLAIR images due to a relatively high background and CSF signal. After administration of contrast media, HIRE images presented a significant signal increase in enhancing lesions, which subsequently increased the contrast and contrast-to-noise ratios. In the qualitative analysis, both readers found all tumors clearly delineated on HIRE imaging. Compared with T(2)-weighted FSE, the tumor delineation with HIRE was better in nine patients, equal in four patients, and less in one patient. Compared with the FLAIR images, HIRE was rated superior in three patients, equal in nine patients, and inferior in another three patients. Delineation of the enhancing tumor parts was possible with HIRE in all patients. HIRE images had significantly fewer image artifacts than FLAIR images due to reduced inflow effects. The T(2)-based HIRE sequence presented is an alternative to the T(1)-based FLAIR sequence, with the advantage of better gray-to-white matter contrast and shorter measurement time. Due to the subtraction technique, signal intensities from tissues with relaxation times in the range T(2 WM) < < T(2) < T(2 CSF) are also gradually affected, corresponding to their T(2) values. With respect to this unwanted effect, an improvement in HIRE imaging will be possible by using a self-weighted subtraction algorithm. In a forthcoming study this concept will first be tested on appropriate phantom fluids.

[Improved tumor contrast and delineation in the stereotactic radiotherapy planning of cerebral gliomas and metastases with contrast media-supported FLAIR imaging]

BACKGROUND

FLAIR MR imaging has shown to be a valuable imaging modality in pathologic lesions of the brain including intra-axial brain tumors. The aim of the study was to assess the value of a FLAIR technique in the planning process of stereotactic radiotherapy in patients with cerebral gliomas and metastases.

PATIENTS AND METHODS

Thirty-five patients with cerebral gliomas and 12 patients with a total of 39 cerebral metastases were examined by T2/PD-weighted fast spin-echo, fast FLAIR prior and after contrast and contrast enhanced T1-weighted spin-echo using identical slice parameters. The images were evaluated by using quantitative and qualitative criteria. Quantitative criteria were tumor-to-background and tumor-to-cerebrospinal fluid contrast and contrast-to-noise. The qualitative evaluation was performed as a multireader analysis concerning lesion detection, lesion delineation and image artifacts.

RESULTS

In the qualitative evaluation (Table 3 and 6), all readers found the fast FLAIR images to be superior to fast spin-echo in the exact delineation of cerebral tumors (p < 0.001) and the delineation of enhancing and non enhancing tumor parts. Fast FLAIR was superior in the delineation of cortically located and small lesions but was limited in lesions adjacent to the ventricles. Fast FLAIR provided a significantly better tumor-to-CSF contrast and tumor-to-CSF contrast-to-noise (p < 0.001) (Tables 1, 2a, 2b, 4, 5). The tumor-to-background contrast and tumor-to-background contrast-to-noise of the fast FLAIR images were lower than that of T2-weighted spin-echo images but were significantly increased after the application of contrast media. FLAIR images had more image artifacts, but the image interpretation was not influenced.

CONCLUSIONS

FLAIR MR imaging was found to be a valuable sequence in the planning protocol of stereotactic radiotherapy. The concurrent presentation of enhancing and non enhancing tumor tissue on contrast enhanced fast FLAIR imaging enables to use a single imaging sequence in the treatment protocol. This enables to load a reduced image amount into the radiotherapy planning software, is therefore time saving and reduces potential errors.

[Angiogenesis in cervical cancer]

Angiogenesis is a factor of spread and metastatization. This fact has been established for many malignancies, but the data concerning cervical cancer are rather conflicting. In a study including 42 patients affected by cervical cancer stages IB to IVA, the authors assess the mean capillary density and the correlations between this parameter and the other anatomoclinical parameters: the VEGF expression, tumoral oxygenation and the data obtained from dynamic MRI. The histologic assessment of the capillary density and the data obtained by dynamic MRI enable us at the same time to quantify the tumoral angiogenesis and establish the prognosis. The two methods could be used routinely as markers of prognosis. VGEF surely plays a role in angiogenesis linked with cervical cancer growth, but its regulation is not definitively clear at the moment. The impact of tumoral oxygenation (whose place as a prognostic marker is clearly established) on tumoral angiogenesis and vessels' permeability as well as its control is currently not clearly established. Further studies on larger populations are necessary.

Abdominal aortic aneurysm. Detection of multilevel vascular pathology by time-resolved multiphase 3D gadolinium MR angiography: initial report

OBJECTIVE

To evaluate multiphasic 3D gadolinium-enhanced magnetic resonance angiography (3D-Gd-MRA) for detection of vascular pathology at multiple levels of the aorta and iliac arteries.

METHODS

In 18 patients with abdominal aortic aneurysm (n = 13), dissection (n = 3), or both (n = 2), multiphase 3D-Gd-MRA was performed acquiring five consecutive (6.8 seconds) 3D data sets in a single breath-hold. In each of the five time-resolved phases, vessel visibility of the abdominal aortic branches and iliac arteries was assessed. The extent of vessel involvement by the aneurysm or dissection seen on multiphase 3D-Gd-MRA was compared with standard imaging and surgical findings. Digital subtraction angiography was available for comparison in 4 cases, CT angiography in 10 cases.

RESULTS

Due to the delayed filling of the aortic aneurysm, the proximal aortic branches and the aneurysm neck demonstrated an inversely related enhancement compared with the distal abdominal and iliac vessels (P < 0.001). Review of all five phases of multiphase 3D-Gd-MRA allowed optimal visualization of each vessel segment without any artifacts due to parenchymal or venous overlay. In dissections, review of three phases was required (P < 0.001) for diagnostic evaluation of the true and false lumens. Substantially more vessel involvement was detected on multiphase 3D-Gd-MRA; this was surgically confirmed in 10 of 11 cases and affected therapy management in 11 of 18 cases.

CONCLUSIONS

Multiphase 3D-Gd-MRA is a convenient, robust, and safe technique for presurgical anatomic mapping of complex aortic aneurysms and dissections.

Comprehensive MR evaluation of renovascular disease in five breath holds

To detect a renal artery stenosis and assess its hemodynamic and functional significance in five breath holds. In a single MR exam, T1 weighted FLASH and T2 weighted fast spin echo techniques are used to assess renal morphology, multiphase 3D gadolinium (Gd) MRA to evaluate the renal arteries, and a segmented EPI cine phase-contrast technique to measure renal artery blood flow. A standardized image analysis is performed to assess kidney size, corticomedullar differentiation (CMD), parenchymal enhancement, the degree of renal artery stenosis, abnormalities in blood flow pattern, and any associated abdominal vascular disease. Multiphase 3D-Gd-MRA accurately assesses atherosclerotic renal artery disease particularly in the presence of an associated aortic aneurysm. Delayed parenchymal enhancement, loss of CMD, and decrease in kidney size can be detected. In combination with decreased systolic velocity components, the diagnosis of a hemodynamically and functionally significant stenosis can be made. High-resolution single-phase 3D-Gd-MRA is preferable for evaluation of fibromuscular dysplasia or hypoplastic vessels. The combination of different breath hold techniques in a single, standardized MR exam allows to detect the hemodynamic and functional significance of a renal artery stenosis.

Evaluation of angiogenesis and perfusion of bone marrow lesions: role of semiquantitative and quantitative dynamic MRI

Magnetic resonance imaging (MRI) is a noninvasive technique that complements computed tomography (CT), conventional X-ray, and bone marrow biopsies by sampling a large volume of musculoskeletal bone and providing information that aids the diagnosis, staging, and follow-up of various lesions. Although less sensitive to the mineral components of bones, the MRI appearance of physiologic bone marrow is mainly a reflection of the relative amounts of red marrow, yellow marrow, and trabecular bone. Therefore, use of T1-and T2-weighted MR sequences with or without fat suppression currently remains the most common approach to musculoskeletal bone lesion imaging. An additional imaging strategy to characterize various bone lesions is the application of contrast-enhanced dynamic MRI. This article examines semiquantitative and quantitative dynamic imaging, evaluation, and postprocessing techniques in various benign and malignant musculoskeletal lesions. Practical guidelines for performing a dynamic contrast-enhanced MR examination are proposed.

MR microcirculation assessment in cervical cancer: correlations with histomorphological tumor markers and clinical outcome

This article reviews the experience available to date on microcirculation assessment in cancer of the cervix including correlation studies of magnetic resonance (MR) microcirculatory parameters with histo-morphometric predictors and direct correlation with patient outcome. The data suggest that MR microcirculation parameters do not always correlate with histo-morphometric parameters, while there is evidence that MR parameters predict patients' treatment outcome. These observations raise the issue that perhaps the histo-morphometric parameters, accepted gold standards for tumor angiogenesis and prognostic factors, reflect anatomical information at a "static" single time point and may not always provide sufficient information on the "dynamic" microcirculation function of the tumor. MR microcirculation assessment reflects both anatomical and functional information and may provide this additional information on the "dynamic" angiogenic and metabolic status of a tumor. Therefore, assessment of tumor microcirculation may augment the individual risk profile in cervical cancer patients and has the potential to impact on therapy selection and treatment outcome.

Cervical carcinoma: standard and pharmacokinetic analysis of time-intensity curves for assessment of tumor angiogenesis and patient survival

Since detailed knowledge regarding the pathophysiological properties which in turn are responsible for differences in contrast enhancement--remain fairly undetermined, it was the aim of this study (i) to examine the association of standard and pharmacokinetic analysis of time-intensity curves in dynamic MRI with histomorphological markers of tumor angiogenesis (microvessel density [MVD]; vascular endothelial growth factor [VEGF]); and (ii) to determine the ultimate value of a histomorphological and a dynamic MRI approach by correlation of those data with disease outcome in patients with primary cancer of the uterine cervix. Pharmacokinetic parameters (amplitude A, exchange rate constant k21) and standard parameters (maximum signal intensity (SI)-increase [SI-I] over baseline and steepest SI-upslope per second [SI-U/s]) were calculated from contrast-enhanced dynamic MR imaging series in 37 patients with biopsy-proven primary cervical cancer. On the surgical whole mount specimens, histomorphological markers of tumor angiogenesis (MVD, VEGF) were compared with similar sized and positioned regions-of-interest (ROIs) on the MRI-derived parameters. For MRI and histomorphological data, Kaplan-Meier survival curves were calculated and compared using log-rank statistics. A significant association was found between MVD and amplitude A (P < 0.01) and SI-I (P < 0.05). No significant relationships were observed between the VEGF expression and all dynamic MRI parameters. Kaplan-Meier curves based on k21 and SI-U/s showed that tumors with high k21 and SI-U/s values had a significantly (P < 0.05, 0.001, respectively) worse disease outcome than tumors with low k2, and SI-U/s values. None of the histomorphological gold standard markers for assessing tumor angiogenesis (MVD, VEGF) had any significant power to predict patient survival. It is concluded that (1) the pathophysiological basis for differences in dynamic MRI is MVD but not VEGF-expression; (2) a functional, dynamic MRI approach (both standard and a pharmacokinetic analysis) may be better suited to assess angiogenic activity in terms of patient survival than current histomorphological-based markers of tumor angiogenesis; and [3] compared with standard analysis, a simple pharmacokinetic analysis of time-intensity curves is not superior to assess MVD or patient survival.

[Multiphase, contrast-enhanced 3D-MR angiography for morphological and functional focal lesion detection. Initial results]

PURPOSE

To investigate the value of multiphase breath-hold 3D gadolinium (Gd)-enhanced MR angiography (MRA) for lesion detection and characterization of focal liver lesions.

MATERIALS AND METHODS

Breath-hold 3D Gd-enhanced MRA was performed in 25 patients with benign and malignant hepatic lesions on a 1.5-T MR system using an ultrafast 3D spoiled gradient echo sequence (TR/TE =5/2 ms, FOV=300-450 mm, matrix=256x168, voxel volume=1.8x2.3 x2.5 mm, 64 partitions, central k-space reordering; acquisition time=27 s). Three measurements were done in the arterial, portal venous, and late venous phase.

RESULTS

The analysis of the spatial and temporal evolution of contrast enhancement of the 3D-MRA improved significantly (P<0.01) lesion detection and characterization if compared with T1 precontrast, T2-weighted, and T1 postcontrast images.

CONCLUSION

Multiphase breath-hold 3D Gd-enhanced MRA imaging is a robust new technique to significantly improve morphological detection of benign and malignant lesions during the early arterial phase and further improves functional characterization of liver lesions by a combination of an arterial, a portal venous, and a late venous phase. Schlüssselwörter Multiphasisch. MR-Angiographie. Leberläsionen

Renal arteries: optimization of three-dimensional gadolinium-enhanced MR angiography with bolus-timing-independent fast multiphase acquisition in a single breath hold

PURPOSE

To compare two different three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) angiographic techniques.

MATERIALS AND METHODS

In 26 patients suspected of having renal artery stenosis, results with fast multiphase 3D MR angiography were compared to those with standard 3D MR angiography in 37 patients. With both techniques, 31-second breath-hold acquisitions were performed. Multiphase angiography comprised five discrete 6.4-second acquisitions without bolus timing, and standard angiography comprised a single acquisition based on test-bolus timing. Two readers evaluated images obtained with both techniques in terms of image quality, artifacts, and vessel conspicuity. Accuracy of findings on the multiphase 3D MR angiograms for assessment of renal artery stenosis was determined by comparing them to digital subtraction angiograms and surgical findings.

RESULTS

In the early arterial phase, multiphase 3D MR angiograms showed no image degradation by venous overlay, whereas standard 3D MR angiograms depicted at least minor overlay in 53 of 83 renal arteries (P < .001). Less parenchymal enhancement in the early arterial phase resulted in a higher vessel conspicuity for the divisions and segmental arteries (P < .001). Both readers detected and correctly graded 18 of 20 stenoses on the multiphase angiograms with almost perfect interobserver agreement (kappa > 0.89).

CONCLUSION

Renal multiphase 3D MR angiography is an accurate technique requiring no bolus timing. The performance of early arterial phase imaging leads to improved depiction, particularly of the distal renovascular tree, compared to that with standard single-phase 3D MR angiography.

[MRI of the kidneys. New diagnostic strategies]

AIM

New diagnostic strategies for evaluation of the kidney by fast MR imaging techniques.

MATERIAL AND METHODS

A comprehensive morphologic and functional evaluation of the kidney is proposed using fast MR imaging of renal morphology, multiphase 3D gadolinium MR angiography, MR urography and MR flow measurements. A single MR examination is designed to grade renovascular disease and assess the hemodynamic and functional significance, detect and characterize renal lesions and evaluate the urinary tract.

RESULTS

The combined analysis of morphologic and functional data allows reliable assessment of renal artery stenosis, benign and malignant renal masses and diseases of the renal collecting system and ureters, as well as congenital abnormalities in good agreement to the results of conventional imaging modalities. The improved tissue contrast and additional functional information compensates for the disadvantage of a lower spatial resolution.

CONCLUSION

Combined morphologic and functional MR examination represents a reliable, non-invasive and cost-effective alternative imaging modality for comprehensive diagnostic evaluation of renal disease.

[Value of clinically established MRI procedures concerning the pretherapeutic evaluation of maximal tumor diameter in primary or recurrent cervix cancer in relation to palpation findings and histopathologic whole mount specimens]

OBJECTIVE

The maximal tumor diameter of cervical cancer is one of the most important prognosis factors concerning patients' survival. The purpose of this study was to investigate the efficiency of different MRI-procedures in relation to clinical palpation concerning pretherapeutic tumor diameter assessment.

MATERIAL AND METHODS

Thirty-one patients with biopsy proven primary cervical cancer and its recurrence (n = 10), respectively, underwent dynamic and conventional MRI before further treatment. The results of maximal tumor diameters were compared to palpatory findings and then correlated to the whole mount specimen as gold standard.

RESULTS

The contrast-enhanced dynamic and T2-weighted MRI allows a significantly better (p < 0.05) assessment of maximal tumor diameter of cervical cancer than the conventional T1-weighted MRI. The T2-weighted MRI showed the highest correlation (r = 0.83) in respect to the whole mount specimen up to FIGO-IIB disease. The contrast-enhanced dynamic MRI and the palpation were characterized by the highest correlation coefficients of r = 0.77, r = 0.70 respectively, in advanced cervical cancer > FIGO-IIB disease.

CONCLUSIONS

The MRI procedures offer no evident advantage in relation to clinical palpation to determine the maximal tumor diameter of cervical cancer or its recurrency and seems not to be indicated generally.

Cervical carcinoma: standard and pharmacokinetic analysis of time-intensity curves for assessment of tumor angiogenesis and patient survival

Since detailed knowledge regarding the pathophysiological properties which in turn are responsible for differences in contrast enhancement--remain fairly undetermined, it was the aim of this study (i) to examine the association of standard and pharmacokinetic analysis of time-intensity curves in dynamic MRI with histomorphological markers of tumor angiogenesis (microvessel density [MVD]; vascular endothelial growth factor [VEGF]); and (ii) to determine the ultimate value of a histomorphological and a dynamic MRI approach by correlation of those data with disease outcome in patients with primary cancer of the uterine cervix. Pharmacokinetic parameters (amplitude A, exchange rate constant k21) and standard parameters (maximum signal intensity (SI)-increase [SI-I] over baseline and steepest SI-upslope per second [SI-U/s]) were calculated from contrast-enhanced dynamic MR imaging series in 37 patients with biopsy-proven primary cervical cancer. On the surgical whole mount specimens, histomorphological markers of tumor angiogenesis (MVD, VEGF) were compared with similar sized and positioned regions-of-interest (ROIs) on the MRI-derived parameters. For MRI and histomorphological data, Kaplan-Meier survival curves were calculated and compared using log-rank statistics. A significant association was found between MVD and amplitude A (P < 0.01) and SI-I (P < 0.05). No significant relationships were observed between the VEGF expression and all dynamic MRI parameters. Kaplan-Meier curves based on k21 and SI-U/s showed that tumors with high k21 and SI-U/s values had a significantly (P < 0.05, 0.001, respectively) worse disease outcome than tumors with low k2, and SI-U/s values. None of the histomorphological gold standard markers for assessing tumor angiogenesis (MVD, VEGF) had any significant power to predict patient survival. It is concluded that (1) the pathophysiological basis for differences in dynamic MRI is MVD but not VEGF-expression; (2) a functional, dynamic MRI approach (both standard and a pharmacokinetic analysis) may be better suited to assess angiogenic activity in terms of patient survival than current histomorphological-based markers of tumor angiogenesis; and [3] compared with standard analysis, a simple pharmacokinetic analysis of time-intensity curves is not superior to assess MVD or patient survival.

[Fluid-attenuated-inversion-recovery (FLAIR) imaging in the diagnosis of cerebral gliomas and metastases]

This study demonstrates the value of a fast fluid-attenuated inversion-recovery (FLAIR) technique in the assessment of cerebral gliomas and metastases. Thirty-five patients with cerebral gliomas and 12 patients with a total of 39 cerebral metastases were examined by T2/proton density-weighted fast spin echo, fast FLAIR with and without contrast medium and contrast-enhanced T1-weighted spin echo using identical slice parameters. The images were evaluated using quantitative and qualitative criteria. Quantitative criteria were tumor-to-background and tumor-to-cerebrospinal fluid contrast and contrast-to-noise. The qualitative evaluation was performed as a multireader analysis concerning lesion detection, lesion delineation and image artifacts. In the qualitative evaluation, all readers found fast FLAIR to be superior to fast spin echo in the exact delineation of cerebral tumors (P < 0.001) and the delineation of enhancing and non-enhancing tumor parts. Fast FLAIR was superior in the delineation of cortically located and small lesions but was limited in lesions adjacent to the ventricles. Fast FLAIR provided significantly better tumor-to-CSF contrast and tumor-to-CSF contrast-to-noise (P < 0.001). The tumor-to-background contrast and tumor-to-background contrast-to-noise of the fast FLAIR images were lower than that of T2-weighted spin-echo images but were significantly increased after the application of contrast medium. FLAIR images had a more image artifacts, but these influenced the image interpretation in only two patients. Signal hyperintensities at the ventricular border were present in 92% of the patients. These are common findings in fast FLAIR and should be included in image interpretation.

Cerebral gliomas and metastases: assessment with contrast-enhanced fast fluid-attenuated inversion-recovery MR imaging

The effect of contrast material on fast fluid-attenuated inversion-recovery (FLAIR) magnetic resonance images was evaluated for 16 patients with enhancing gliomas and 12 patients with cerebral metastases. Because of a marked T1 effect, fast FLAIR imaging provided a marked contrast enhancement, resulting in the highest tumor-to-background contrast ratio compared with standard imaging techniques.

Hepatic lesions: morphologic and functional characterization with multiphase breath-hold 3D gadolinium-enhanced MR angiography--initial results

PURPOSE

To investigate multiphase (arterial, portal venous, and late venous phases) breath-hold three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) angiography for the detection and functional characterization of hepatic lesions.

MATERIALS AND METHODS

Breath-hold fast spoiled gradient-echo 3D gadolinium-enhanced MR angiography was performed in 18 patients with 35 hepatic lesions. Measurements of signal intensity were obtained for 27 seconds in each phase, with 23-second delays between the three phases. Lesion-liver visibilities at each phase on the MR angiographic, precontrast T1-weighted, T2-weighted, and postcontrast T1-weighted images were compared. The MR angiographic functional lesion characterization was based on the combined assessment of spatial variations and the evolution of contrast material enhancement in all three phases.

RESULTS

All 35 lesions were correctly characterized on the MR angiographic images, which is significantly (P < .01) better than the precontrast T1-weighted (n = 14 [40%]), T2-weighted (n = 23 [66%]), and postcontrast T1-weighted (n = 25 [71%]) imaging results. Analysis of the spatial variations and the evolution of contrast material enhancement significantly (P < .01) improved lesion characterization in 66% (23 of 35) of all lesions.

CONCLUSION

Multiphase breath-hold 3D gadolinium-enhanced MR angiography is feasible and robust and significantly improves the morphologic detection of benign or malignant lesions during the early arterial phase. It further improves the functional characterization of hepatic lesions, combining an arterial, portal-venous, and late MR angiographic phase of contrast enhancement.

[Detection of angiogenesis-dependent parameters by functional MRI: correlation with histomorphology and evaluation of clinical relevance as prognostic factor using cervix carcinoma as an example]

PURPOSE

Purpose of this study is to compare functional MRI parameters with histomorphological markers of tumor microvessel density (MVD) and permeability (vascular endothelial growth factor) and to determine the ultimate value of both approaches by correlation with disease outcome in patients with primary cancer of the uterine cervix.

METHOD

Pharmacokinetic parameters were calculated from contrast-enhanced dynamic MR imaging series in 37 patients with biopsy-proven primary cervical cancer. On the operative whole mount specimens, histomorphological markers of tumor angiogenesis (MVD, VEGF) were compared with the MRI-derived parameters. For MRI and histomorphological data, Kaplan-Meier survival curves were calculated and compared using logrank statistics.

RESULTS

Significant (p < 0.05-0.01) associations were found between MVD and dynamic MRI parameters. No significant relationships were observed between VEGF expression and dynamic MRI parameters. Disease outcome was better assessed with dynamic MRI parameters than with the histomorphological approach.

CONCLUSIONS

It is concluded that 1) the pathophysiological basis for the amplitude A in dynamic MRI is MVD but not VEGF expression; and 2) a functional, dynamic MRI approach may be more suited to assess angiogenic activity in terms of patient survival than current histomorphological-based markers of tumor angiogenesis.

[Integration of functional and morphologic MRI data for preoperative 3D visualization of tumors. Example: cervical carcinoma]

PURPOSE

The goal of this exemplary study was to integrate morphological and functional MRI to establish computer-based, pre-operative therapy planning for tumors, instancing cervical carcinoma.

METHODS

For morphological representation T1-weighted, filtered 3D sequences were investigated within a hierarchical segmentation approach. Using a method for image registration, segmented structures were combined and overlaid with functional information of contrast medium-enhanced, dynamic MRI. After assigning colour attributes to the segmented structures, they were presented using a method for direct volume visualisation.

RESULTS

Segmentation of organs and vessels as well as tissue differentiation yielded a morphological visualisation of anatomical structures that were overlaid with pharmacokinetic parameters derived from dynamic MRI, subsequently. Thereby, three-dimensional, arbitrary views on the functional data were displayed.

CONCLUSIONS

Image analysis and visualisation of the acquired MR data establishes both a morphologic and functional evaluation of suspect lesions and adjacent organs. By integrating morphologic and functional MRI additional information can be gathered that possibly impinge on preoperative planning.

Angiogenic activity of cervical carcinoma: assessment by functional magnetic resonance imaging-based parameters and a histomorphological approach in correlation with disease outcome

Angiogenesis plays a fundamental role in tumor growth and metastasis. What is needed is a quantitative, noninvasive, and repeatable assay to estimate functional angiogenic activity of the entire tumor. The aims of the present study were to: (a) examine the relationship between functional magnetic resonance imaging (MRI)-based parameters with established histomorphological markers of tumor angiogenesis [histological microvessel density (HMVD) and vascular endothelial growth factor expression (VEGF)]; and (b) determine the ultimate value of both approaches to assess functional angiogenic active hotspots as markers of disease outcome in patients with cancer of the uterine cervix. Pharmacokinetic parameters (amplitude A, tissue exchange rate constant k21) were calculated from contrast-enhanced dynamic MRI series in 57 patients (mean age, 49 +/- 14 years) with biopsy proven uterine cervical cancer. Both pharmacokinetic parameters were correlated to histomorphologically determined areas of high HMVD and VEGF expression obtained from the operative specimens after radical surgery. In addition, the functional MRI and histomorphological data were used to assess disease outcome. A significant association was found between HMVD and the amplitude A (P < 0.001) and a less pronounced association with k21, (P < 0.05), respectively. No significant associations were found between the pharmacokinetic parameters (A, k21) and VEGF expression. When stratified into high and low median k21 groups, median k21 values >5.4 min(-1) were the only significant (P < 0.05) factors in predicting poor patient survival. None of the histomorphological markers of angiogenesis (HMVD or VEGF expression) showed any predictive power. We have found that: (a) focal hotspots of HMVD are the pathophysiological basis for differences in functional MRI; (b) areas of high microvessel density and microvessel permeability do not necessarily coincide, as demonstrated by the histomorphological and functional MRI findings; (c) the functional angiogenic activity of a tumor may not be sufficiently characterized by a histomorphological approach but rather by a functional MRI-based approach; and (d) functional MRI-based analysis may assess tumor angiogenic activity in terms of disease outcome more comprehensively than the histomorphological approach.

Uterine cervical carcinoma: comparison of standard and pharmacokinetic analysis of time-intensity curves for assessment of tumor angiogenesis and patient survival

Dynamic studies of Gd-based contrast agents in magnetic resonance imaging (MRI) are increasingly being used for tumor characterization as well as for therapy response monitoring. Because detailed knowledge regarding the pathophysiological properties, which in turn are responsible for differences in contrast enhancement, remains fairly undetermined, it was the aim of this study to: (a) examine the association of standard and pharmacokinetic analysis of time-intensity curves in dynamic MRI with histomorphological markers of tumor angiogenesis [microvessel density (MVD) and vascular endothelial growth factor (VEGF)]; and (b) determine the ultimate value of a histomorphological and a dynamic MRI approach by the correlation of those data with disease outcome in patients with primary cancer of the uterine cervix. Pharmacokinetic parameters (amplitude, A; exchange rate constant, k21) and standard parameters [the maximum signal intensity increase over baseline (SI-I) and the steepest signal intensity-upslope per second (SI-U/s)] were calculated from a contrast-enhanced dynamic MRI series in 37 patients with biopsy-proven primary cervical cancer. On the surgical whole mount specimens, histomorphological markers of tumor angiogenesis (MVD and VEGF) were compared to MRI-derived parameters. For MRI and histomorphological data, Kaplan-Meier survival curves were calculated and compared using log-rank statistics. A significant association was found between MVD and A (P < 0.01) and SI-I (P < 0.05). No significant relationships were observed between VEGF expression and all dynamic MRI parameters. Kaplan-Meier curves based on k21 and SI-U/s showed that tumors with high k21 and SI-U/s values had a significantly (P < 0.05 and 0.001, respectively) worse disease outcome than did tumors with low k21 and SI-U/s values. None of the histomorphological gold standard markers for assessing tumor angiogenesis (MVD and VEGF) had any significant power to predict patient survival. It is concluded that in patients with uterine cervical cancer: (a) the pathophysiological basis for differences in dynamic MRI is MVD but not VEGF expression; (b) a functional, dynamic MRI approach (both standard and pharmacokinetic analysis) may be better suited to assess angiogenic activity in terms of patient survival than are the current histomorphological-based markers of tumor angiogenesis; and (c) compared with standard analysis, a simple pharmacokinetic analysis of time-intensity curves is not superior to assess MVD or patient survival.

Pharmacokinetic MRI for assessment of malignant glioma response to stereotactic radiotherapy: initial results

The purpose of this study was to assess the value of dynamic, contrast-enhanced MRI in patients with malignant glioma (a) to predict before stereotactic radiotherapy local tumor control, (b) to investigate temporal changes in tumor microcirculation after stereotactic radiotherapy, and (c) to analyze whether malignant glioma response may be predicted earlier by alterations in the tissue pharmacokinetics rather than in terms of tumor volume. Ninety MRI studies were performed of 18 patients with malignant glioma before and 6, 18, 26, 52, and 72 weeks after the end of stereotactic radiotherapy. The signal time courses of the contrast-enhanced tumors were analyzed using a pharmacokinetic two-compartment model that calculates for the parameter A, reflecting the degree of MRI signal enhancement [no units] and the exchange rate constant k21 [min(-1)]. Before radiotherapy, the amplitude A was significantly (P < .05) lower in patients with subsequent local tumor control (n = 8; mean A = .34 +/- .15) compared to patients without subsequent local tumor control (n = 10; mean A = .94 +/- .71). In the local tumor control group, early after stereotactic radiotherapy (at 6-18 weeks), there was a significant (P < .05) time-dependent decrease in the parameter k21, whereas there was still no alteration in the tumor volume. A low amplitude A before radiotherapy, combined with an early drop of k21 after stereotactic radiotherapy, reliably characterized the group of patients with subsequent tumor volume decrease. Our preliminary results suggest that two contrast-enhanced dynamic MR studies, one before and one early after stereotactic radiotherapy, offer important information on local tumor control within the first 6 to 18 weeks after stereotactic radiotherapy. Moreover, this response may be evidenced before tumor volume changes and provides a therapeutic window to broaden treatment options and to improve treatment outcome.

Fast fluid-attenuated inversion-recovery (FLAIR) MRI in the assessment of intraaxial brain tumors

This study demonstrates the value of a fast fluid-attenuated inversion-recovery (FLAIR) technique in the assessment of primary intraaxial brain tumors. Twenty-one patients with primary intraaxial brain tumors were examined by T2-weighted, proton-density-weighted fast spin echo, fast FLAIR, and contrast-enhanced T1-weighted spin echo using identical slice parameters. The images were evaluated using quantitative and qualitative criteria. Quantitative criteria were tumor-to-background and tumor-to-cerebrospinal fluid (CSF) contrast and contrast-to-noise ratio (CNR). The qualitative evaluation was performed as a multireader analysis concerning lesion detection, lesion delineation, and image artifacts. In the qualitative evaluation, all readers found the fast FLAIR to be superior to fast spin echo in the exact delineation of intraaxial brain tumors (P < .001) and the delineation of enhancing and nonenhancing tumor parts. Fast FLAIR was superior in the delineation of cortically located and small lesions but was limited in lesions adjacent to the ventricles. Fast FLAIR provided a significantly better tumor-to-CSF contrast and tumor-to-CSF CNR (P < .001). The tumor-to-background contrast and tumor-to-background CNR of the fast FLAIR images were lower than those of T2-weighted spin-echo images but higher than those of proton-density-weighted spin-echo images. FLAIR images had more image artifacts influencing the image interpretation in only two patients. Signal hyperintensities at the ventricular border were present in 92% of the patients. They are common findings in fast FLAIR and should be included into the image interpretation.

[Ultrafast MRI phlebography of the lungs]

AIM

Improved detection of pulmonary-venous pathologies by imaging the pulmonary veins without arterial overlay.

MATERIAL AND METHODS

Sequential 3D imaging of the pulmonary arterial and arteriovenous phase was performed with an ultrafast 3D FLASH sequence successively acquiring eight 3D data sets every 2.9 s within a single breathhold. For an 8 cm thick 3D slab an interpolated spatial resolution of about 1.4 x 1.9 x 3.3 mm could be achieved. Different protocols for contrast media dose and infusion rate were used. For selective visualization of the pulmonary veins, the pulmonary arterial phase was subtracted from a subsequent arteriovenous phase with the highest venous signal. 5 healthy volunteers, 8 patients with history of a cerebrovascular accident (CVA) of unknown etiology an suspected pulmonary-venous thrombosis and 9 patients with compression of the pulmonary vasculature by centrally growing malignancies were evaluated.

RESULTS

With higher infusion rate and lower contrast media dose, arteries and veins could be better separated by their enhancement kinetics. In all cases a complete visualization of the main pulmonary veins, segmental and subsegmental veins up to the fourth order of each lung segment was achieved without any overlay of pulmonary arteries. No thrombi of the pulmonary veins were found in patients with CVA. The obstruction of pulmonary arteries and veins due to vessel compression could be selectively visualized.

CONCLUSION

Ultrafast multiphase 3D-Gd-MRA is a new reliable method for selective 3D visualization of pulmonary veins.

[MRI imaging of the uterine arterial blood flow in normal and malignant uterine tissue by means of 2d-multiphase tagging technic]

PURPOSE

The aim of this pilot study was to evaluate a 2D-STAR technique as a non contrast-enhanced approach to demonstrate the uterine artery and its branches and to assess the cervical uterine blood flow in healthy volunteers and in patients with advanced uterine cervical carcinoma.

MATERIALS AND METHODS

Seven healthy volunteers (mean age, 29 years) and twenty-two patients (mean age, 52 years) with advanced cancer of the uterine cervix (FIGO IIB-IVA) were prospectively examined by 2D-STAR imaging at different inversion delay times (300 ms-1900 ms) which showed the passage of a blood bolus through normal and malignant tissue of the uterine cervix.

RESULTS

The uterine artery was well visualized with short inversion delay times of 300 ms to 500 ms. It was characterized as single or multiple helical loops before dividing into its intracervical branches. The intracervical branching was observed at inversion delay times of 500 ms-700 ms. With longer inversion delay times arterial signal enhancement disappeared and cervical tissue enhancement was noted. Enhancement of benign tissue was observed at inversion delay times of 1100 ms-1700 ms, and in malignant tissue at shorter inversion delay times of 900 ms-1300 ms. The maximum of this diffuse signal enhancement of benign tissue was seen at inversion delay times of 1500 ms (1100 ms-1700 ms), in malignant tissue at significantly (P < 0.05) shorter inversion delay times of 1100 ms (900 ms to 1300).

CONCLUSION

Our preliminary results show that the vascular supply and blood flow of the normal uterine cervix and of advanced cervical cancer can be assessed by non contrast-enhanced 2D STAR imaging and that malignant cervical tissue is earlier and stronger perfused than normal cervical tissue.

Magnetically labeled water perfusion imaging of the uterine arteries and of normal and malignant cervical tissue: initial experiences

PURPOSE

The aim of this pilot study was to evaluate a magnetically labeled water perfusion imaging technique as a non-contrast-enhanced approach to demonstrate the uterine artery, its branches, and to assess the cervical uterine blood flow in healthy volunteers and in patients with advanced uterine cervical carcinoma (FIGO IIB-IVA).

METHODS AND MATERIALS

Seven healthy volunteers (mean age, 29 years) and twenty-two patients (mean age, 52 years) with advanced cancer of the uterine cervix (FIGO IIB-IVA) were prospectively examined by magnetically labeled water perfusion imaging at different inversion delay times (300-900 ms). The magnetic resonance imaging (MRI) findings of all patients were matched to the findings of contrast-enhanced dynamic MRI and multiple biopsies (n = 5) and/or surgical whole mount specimens (n = 17), which were available in all patients.

RESULTS

The uterine artery was well visualized with short inversion delay times of 300-500 ms. It was characterized as single or multiple helical loops before dividing into its intracervical branches. The intracervical branching was observed at inversion delay times of 500-700 ms. With longer inversion delay times, arterial signal enhancement disappeared and cervical tissue enhancement was noted. Enhancement of benign tissue was observed at inversion delay times of 1100-1700 ms and in malignant tissue at shorter inversion delay times of 900-1300 ms. The maximum of this diffuse signal enhancement of benign tissue was seen at inversion delay times of 1500 ms (1100-1700 ms) in malignant tissue at significantly (p < 0.5) shorter inversion delay times of 1100 ms (900-1300 ms).

CONCLUSION

Our preliminary results show that the vascular supply and blood flow of the normal uterine cervix and of advanced cervical cancer can be assessed by magnetically labeled water perfusion imaging and that malignant cervical tissue is earlier and stronger perfused than normal cervical tissue.

Functional neuroimaging in the assessment of CNS neoplasms

Assessment of CNS neoplasms has focused traditionally on morphological analysis. Recent developments in MR sequence design now enable functional assessments. T1-weighted, as well as T2(*)-weighted, dynamic, gadolinium-enhanced, imaging can be used for assessment of vascularisation, permeability, and microcirculation of CNS neoplasms. Characterisation of cerebrovascular blood flow is possible using dynamic MR angiography, while neurofunctional imaging enables visualisation of local alterations in neuronal activity in stimulated cortical areas. Diffusion-weighted imaging can be used for improved delineation of neoplasms, while chemical shift imaging allows metabolic mapping of lesions and surrounding tissues. Implementation of these techniques can improve characterisation, information for therapy, planning and prognosis in clinical imaging of CNS neoplasms.

Serial MR imaging of intracranial metastases after radiosurgery

PURPOSE

To evaluate the spatiotemporal evolution of radiosurgical induced changes both in metastases and in normal brain tissue adjacent to the lesions by serial magnetic resonance (MR) imaging.

METHODS AND MATERIALS

Thirty-five intracranial metastases of different primaries were treated in 25 patients by single high-dose radiosurgery. MR images acquired before radiosurgery were available in all patients. Sixty-three follow-up MR studies were performed in these patients including T2- and contrast-enhanced T1-weighted MR images. The average follow-up time was 9 +/- 5 months (mean +/- standard deviation [SD]). Based on contrast-enhanced T1-weighted MR images, tumor response was radiologically classified in the following four groups: stable disease was assumed if the average tumor diameter after treatment did not show a tumor shrinkage of more than 50% and an increase of more than 25%, partial remission as a shrinkage of tumor size of more than 50%, a disappearance of contrast-enhancing tumor as a complete remission, and an increase of tumor diameter of more than 25% as tumor progress. Moreover, we analysed signal changes on T2-weighted images in brain parenchyma adjacent to the enhancing metastases.

RESULTS

The overall mean survival time was 10.5 +/- 7 months, with a 1-year actuarial survival rate of 40%. Stable disease, partial or complete remission of the metastatic tumor was observed in 22 patients (88%). Central or homogeneous loss of contrast enhancement appeared to be a good prognostic sign for stable disease or partial remission. This association was statistically significant (p < 0.05). Three patients (12%) suffered from tumor progression. In eight patients (32%) with stable disease or partial remission, signal changes on T2-weighted images were observed in tissue adjacent to the contrast enhancing lesions. A progression of the high signal on T2-weighted images was seen in seven of the eight patients between 3 and 6 months after therapy, followed by a signal regression 6-18 months after irradiation.

CONCLUSION

MR imaging is a sensitive imaging tool to evaluate tumor response as well as the presence or absence of adjacent parenchymal changes following radiosurgery. Loss of homogeneous or central contrast enhancement on Gd-enhanced MR images appeared to be a good prognostic sign for tumor response. Tumor shrinkage seems not to be dependent on time. In addition, most cases of radiation induced changes in normal brain parenchyma observed on T2-weighted images seem to be self limited.

[Angiogenesis of cervix carcinoma. Contrast enhanced dynamic MRI, histologic quantification of capillary density and lymphatic system infiltration]

PURPOSE

It was the aim of this project to examine (i) the relationships between contrast-enhanced dynamic MR imaging derived characteristics and histologic microvessel density counts--a recognized surrogate of tumor angiogenesis--from tumors in patients with primary or recurrent cancer of the uterine cervix, and (ii) to correlate these parameters with lymphatic involvement (i.e. lymphatic channels) to assess tumor biological aggressiveness in terms of lymphatic spread.

MATERIAL AND METHODS

Pharmacokinetic MR imaging parameters (amplitude A, exchange rate constant k21) were derived from contrast-enhanced dynamic MR imaging in thirty-three patients with biopsy proven cancer of the uterine cervix. The pharmacokinetic MR imaging characteristics were correlated to histologic capillary density counts obtained from whole mount specimen. In addition, these data were correlated to the angiogenic activity as a marker for lymphatic system involvement.

RESULTS

Pharmacokinetic MR imaging derived parameters (A, k21) showed a weak but significant (p < 0.05) correlation with microvessel density counts. Lymphatic involvement was more comprehensively assessed by the pharmacokinetic parameter k21 compared with histologic microvessel density, resulting in a significantly (p < 0.05) higher overall accuracy (85% vs. 64%), sensitivity (83% vs. 54%), and comparable specificity (89% vs. 89%), respectively.

CONCLUSION

Our first results show that the signal-time curves measured by contrast-enhanced MR imaging are only in part influenced by microvessel density. In addition, MR imaging derived characteristics may assess tumor biological aggressiveness in terms of lymphatic spread (i.e. lymphatic channels) more comprehensively than histologic microvessel density in patients with primary or recurrent cancer of the uterine cervix.

[MR tomographic monitoring of prostate carcinoma after cryotherapy: initial results]

PURPOSE

To assess the morphological changes in the prostate gland and adjacent tissue after cryosurgery by high resolution MRI in patients with histological proven prostatic carcinoma.

METHOD

15 patients (mean age 66 years) with histologically proven prostate carcinoma underwent T2- and contrast-enhanced T1-weighted high-resolution MRI examinations with fat suppression. Follow-up MRI with an identical imaging protocol were performed at different time intervals (24-72 h, 2-6, 12, 26-52 weeks).

RESULTS

Mean prostate volume had decreased by 30% in all patients 12-52 weeks after cryosurgery. After cryosurgery, zonal differentiation was lost in all patients with abnormalities in the periprostatic tissue in all patients, and rectal wall thickening in 47% of patients. Cryosurgery-induced changes in the prostate could not be differentiated from tumour recurrence.

CONCLUSION

High resolution MRI allows precise recognition of intraprostatic and adjacent tissue alterations after cryosurgery of prostatic carcinoma. However, reliable detection of tumour recurrence was impossible due to cryosurgically induced signal changes.

Staging of invasive cervical carcinoma and of pelvic lymph nodes by high resolution MRI with a phased-array coil in comparison with pathological findings

PURPOSE

Our goal was to stage invasive cervical carcinoma (pT1b-pT4a) and pelvic lymph nodes by high resolution MRI with a circularly polarized (cp) phased-array coil in correlation with the whole-mount specimen and the histopathological findings.

METHOD

Thirty-three patients (20-68 years old; mean age 55 years) with biopsy-proven primary cancer of the cervix were prospectively examined on a 1.5 T scanner by using a cp body phased-array coil. The MR protocol consisted of high resolution T2-weighted turbo-SE (TSE) and pre- and postcontrast T1-weighted SE (SE) sequences. Slice thickness was 5-7 mm with a pixel size of 0.3-0.4 mm2. All MRI findings were matched to the whole-mount specimens and the histopathological findings.

RESULTS

Pathological stages evaluated were pT1b (n = 5), pT2b (n = 16), and pT4a (n = 12). The overall accuracy rates for tumor staging were 79% for high resolution T2-weighted TSE and 76% for postcontrast T1-weighted SE images. The accuracy for high resolution T2-weighted TSE images in determining parametrial infiltration, pelvic side wall, and bladder and rectal wall infiltration was 84, 87, and 87%, respectively. In prospective analysis of the 1.0 cm criterion for diagnosis of a positive pelvic lymph node, MRI had a 72% accuracy, a 68% sensitivity, and a 78% specificity.

CONCLUSION

High resolution MRI with a cp body phased-array coil provides excellent and robust high resolution images in patients with invasive cervical carcinoma. However, accuracy, specificity, and sensitivity for staging invasive cervical carcinoma and pelvic lymph nodes with correlation to whole-mount specimens and histopathological findings did not improve compared with the results in the literature using a body coil with thicker slices and a lower spatial resolution.

[Contrast-enhanced MR "magnetization transfer technique". Improved tumor contrast, delineation and visibility of intracranial malignant gliomas and metastases in radiosurgical treatment planning]

AIMS

To improve tumor conspicuity and delineation on contrast-enhanced T1-weighted MR images with and without magnetization transfer (MT) contrast as a strategy to improve the macroscopic boost volume definition in the planning process of radiosurgery in patients with high grade gliomas or metastatic brain lesions.

PATIENTS AND METHODS

Thirty-two patients (mean age 47 years) with histologically proven or suspected high grade glioma (n = 12) or metastatic brain lesions (n = 20) were prospectively examined by MR imaging. After the administration of gadolinium dimeglumine (0.1 mmol/kg body weight) the lesions were imaged with a T1-weighted MT-fast low angle shot (FLASH) pulse sequence and with a conventional T1-weighted SE sequence without MT saturation.

RESULTS

The mean CNR of enhancing lesions on T1-weighted MT-FLASH was 15 +/- 5 compared to 11 +/- 4 on SE images, representing a significant (p < .01) improvement. The mean tumor diameter of malignant gliomas was significantly (p < .01) larger measured on T1-weighted MT-FLASH images compared to those obtained from T1-weighted SE images and were comparable for metastatic lesions. Lesion conspicuity and delineation were improved in 50% of patients with high grade gliomas and in 35% of patients with brain metastases. Lesion conspicuity was markedly improved in the posterior fossa. Additional contrast enhancing lesions were detected in 10% of patients with metastases on MT-FLASH images.

CONCLUSIONS

It is concluded that contrast-enhanced MT-FLASH images may improve lesion detection and delineation in the planning process of radiosurgery in patients with intracranial high grade gliomas or metastases or even alter the treatment approach.

Angiogenesis of uterine cervical carcinoma: characterization by pharmacokinetic magnetic resonance parameters and histological microvessel density with correlation to lymphatic involvement

Dynamic studies of Gd-based contrast agents in magnetic resonance imaging (MRI) are increasingly being used for tumor characterization as well as therapy response monitoring. Because detailed knowledge regarding the pathophysiological properties, which in turn are responsible for differences in contrast enhancement, remains fairly undetermined, it was the aim of this project to: (a) examine the relationship between contrast-enhanced dynamic MRI-derived characteristics and histological microvessel density counts, a recognized surrogate of tumor angiogenesis, from primary or recurrent cancers of the uterine cervix; and (b) correlate these parameters with lymphatic involvement to characterize tumor aggressiveness in terms of lymphatic spread. Pharmacokinetic parameters (amplitude, A; exchange rate constant, k21) were calculated from a contrast-enhanced dynamic MRI series in 55 patients (ages 25-72 years; mean, 50 years) with biopsy-proven primary (n = 42) or recurrent (n = 13) uterine cervical cancer. Both pharmacokinetic parameters were correlated to histologically determined microvessel density counts (factor VIII-related antigen) and other pathological tumor characteristics obtained from the operative specimens after radical surgery. In addition, the magnetic resonance and histological data were correlated to the presence or absence of lymphatic system involvement. Pharmacokinetic MRI-derived parameters (A and k21) increased with increasing histological microvessel density counts with r = 0.41 and 0.50, respectively. Lymphatic involvement was more comprehensibly assessed by the pharmacokinetic parameter k21 compared with histological microvessel density, resulting in a higher sensitivity, overall accuracy, and comparable specificity. Contrast-enhanced MRI parameters might prove to be applicable for estimation of tumor angiogenesis in uterine cervical cancer; thus, MRI may become an additional tool to characterize malignant progression in terms of lymphatic involvement in uterine cervical cancer.

[Classification of hemodynamic changes in renal artery stenosis using cine magnetic resonance phase contrast flow measurements]

PURPOSE

To evaluate the use of high-temporal resolution cine MR phase-contrast flow measurements for assessment of flow dynamics in renal artery stenosis (RAS).

MATERIAL AND METHODS

In a dog model, cine MR flow measurements were validated by comparing the MR flow data to an invasive transit-time ultrasound reference technique for different degrees of RAS. Cardiac-gated MR flow curves were recorded in 56 renal arteries of 28 patients with a temporal resolution of at least 32 ms. In all cases RAS was confirmed by digital subtraction angiography (DSA). Abnormalities of flow dynamics were assessed in the calculated flow curves using the MR parameters mean flow, maximum velocity, and time to systolic maximum.

RESULTS

By means of the MR blood flow parameters high-grade stenoses (> 50%, n = 23) were detected with sensitivity of 100% and specificity of 94% with reference to DSA. The overall differentiation between stenoses (n = 37) and non-stenosed vessels (n = 19) revealed a sensitivity of 87% and a specificity of 100%.

CONCLUSION

Analysis of cardiac-gated MR flow curves provides a non-invasive method to assess the hemodynamic significance of RAS and thus allows a functional evaluation in relation to the morphologic characteristics of the stenosis.

Contrast-enhanced magnetization transfer imaging: improvement of brain tumor conspicuity and delineation for radiosurgical target volume definition

PURPOSE

To assess the contrast-noise-ratio (CNR), and thus tumor conspicuity and delineation, on contrast-enhanced T1-weighted magnetization transfer (MT) images compared to conventional T1-weighted spin echo (SE) images as a strategy to improve definition of the macroscopic boost volume in radiosurgery treatment planning in patients with high grade gliomas or metastatic brain lesions.

MATERIALS AND METHODS

Fifty patients (mean age, 51 years) with histologically proven or suspected high grade glioma or cerebral metastases were prospectively examined by MR imaging. Following gadolinium dimeglumine administration (0.1 mmol/kg body weight) the brain was imaged with both a T1-weighted MT-fast low angle shot (FLASH) pulse sequence and with a conventional T1-weighted SE sequence without MT saturation. Lesion conspicuity, size and CNR were compared for both techniques.

RESULTS

The mean tumor diameter of malignant gliomas was significantly (P < 0.01) larger when measured on T1-weighted MT-FLASH images compared to T1-weighted SE images and was comparable for metastatic lesions. The mean CNR of enhancing lesions on T1-weighted MT-FLASH was 14 +/- 5 compared to 10 +/- 4 on SE images, representing a significant (P < 0.05) improvement. Lesion conspicuity and delineation was improved in 10 of 20 patients (50%) with high grade gliomas and in 15 of 30 patients (50%) with metastases. Additional contrast enhancing lesions were detected in 8 of 30 patients (27%) with metastases on MT-FLASH images. Lesion conspicuity was markedly improved in the posterior fossa.

DISCUSSION

Contrast-enhanced T1-weighted MT-FLASH images improve lesion detection and delineation in the planning process of radiosurgery in patients with intracranial high grade gliomas or metastases and may even alter the treatment approach.