Time-resolved two-dimensional thick-slice magnetic resonance digital subtraction angiography in assessing brain tumors

Strategies for Improved Intra-arterial Treatments Targeting Brain Tumors: a Systematic Review

Conventional treatments for brain tumors relying on surgery, radiation, and systemic chemotherapy are often associated with high recurrence and poor prognosis. In recent decades, intra-arterial administration of anti-cancer drugs has been considered a suitable alternative drug delivery route to intravenous and oral administration. Intra-arterial administration is believed to offer increasing drug responses by primary and metastatic brain tumors, and to be associated with better median overall survival. By directly injecting therapeutic agents into carotid or vertebral artery, intra-arterial administration rapidly increases intra-tumoral drug concentration but lowers systemic exposure. However, unexpected vascular or neural toxicity has questioned the therapeutic safety of intra-arterial drug administration and limits its widespread clinical application. Therefore, improving targeting and accuracy of intra-arterial administration has become a major research focus. This systematic review categorizes strategies for optimizing intra-arterial administration into five categories: (1) transient blood-brain barrier (BBB)/blood-tumor barrier (BTB) disruption, (2) regional cerebral hypoperfusion for peritumoral hemodynamic changes, (3) superselective endovascular intervention, (4) high-resolution imaging techniques, and (5) others such as cell and gene therapy. We summarize and discuss both preclinical and clinical research, focusing on advantages and disadvantages of different treatment strategies for a variety of cerebral tumor types.

Consecutive acquisition of time-resolved contrast-enhanced MR angiography and perfusion MR imaging with added dose of gadolinium-based contrast agent aids diagnosis of suspected brain metastasis

PURPOSE

Time-resolved contrast-enhanced magnetic resonance (MR) angiography (TCMRA) and perfusion MR imaging (PWI) have been used to assess the hemodynamics of brain tumors. We assessed the feasibility and value of consecutive performance of these techniques to evaluate suspected brain metastasis following supplementary injection of gadolinium-based contrast medium.

METHODS

In 69 patients with suspected brain metastasis, we obtained precontrast MR images followed by TCMRA and postcontrast T1-weighted images after administration of 0.1 mmol/kg gadoteridol. When findings were negative or equivocal, we injected an additional 0.1-mmol/kg dose of gadoteridol and obtained PWI and second postcontrast T1-weighted images. We used a 3-point scale to grade perfusion maps and TCMRA and assessed whether these techniques added information to conventional MR imaging in the differential diagnosis. We also evaluated whether the second contrast injection improved the conspicuity and/or number of enhancing lesions and used a 4-point scoring system to quantitatively analyze diagnostic yield of TCMRA and PWI.

RESULTS

We could assess tumor hemodynamics on PWI maps and TCMRA images in all 69 patients. In 14 cases (20%), PWI and/or TCMRA added information to conventional MR findings. After second injection of contrast medium, lesion conspicuity improved in 58 of the 69 cases (84%), and the number of detected lesions increased in 11 of 31 cases diagnosed with metastatic disease (36%). Quantitative analysis revealed TCMRA and PWI provided significant additional diagnostic information (Kruskal-Wallis test, P<0.0001).

CONCLUSION

Consecutive acquisition of TCMRA and PWI using supplementary contrast injection can facilitate differential diagnosis of suspected brain metastasis and improve the number and conspicuity of detected lesions.

Quality-evaluation scheme for cerebral time-resolved 3D contrast-enhanced MR angiography techniques

BACKGROUND AND PURPOSE

No practical tool has been reported in the literature to evaluate the quality of cerebral TR-3D-CE-MRA techniques. Our study assessed a large list of parameters used to propose a quality-evaluation scheme for TR-3D-CE-MRA.

MATERIALS AND METHODS

A large list of visual and quantitative parameters used to study the quality of images was collected from the literature and evaluated in 19 healthy patients and 11 patients with arteriovenous shunts who had undergone both CENTRA keyhole TR-3D-CE-MRA at 3T and CCA. Several observers evaluated the visual parameters, such as the diagnostic confidence index, artifacts, maximum vascular signal intensity, arterial-to-venous separation, and visibility of 17 arteries and 7 veins; and quantitative parameters, such as maximum arterial SI, arteriovenous transit time, arteriovenous contrast curve, and ADW. A statistical analysis was used to determine interobserver reproducibility of the visual parameters, to calculate the sensitivity of TR-3D-CE-MRA for detecting each vessel (with CCA as standard of reference), and to compare the results of the visual and quantitative evaluations.

RESULTS

Diagnostic confidence index, artifacts, arterial-to-venous separation, and 4 vessels-the PICA, ophthalmic and occipital arteries, and the ISS-demonstrated high reproducibility and sensitivity. The ADW was the most reliable dynamic quantitative parameter and was correlated with arterial-to-venous separation.

CONCLUSIONS

The image quality of TR-3D-CE-MRA can be effectively evaluated with a scheme of 1 quantitative and 7 visual parameters.

Diffusion-weighted imaging and ADC mapping of head-and-neck paragangliomas: initial experience

BACKGROUND

Paragangliomas are rare, hypervascularized benign tumors. In some cases a clear differentiation of paragangliomas and other entities is impossible.

PATIENTS AND METHODS

The authors evaluated ten patients with skull base lesions (paraganglioma n = 7, meningioma n = 1, giant cell tumor n = 1, and neurinoma n = 1) in addition to conventional magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI), and calculation of apparent diffusion coefficient (ADC).

RESULTS

Mean ADC values +/- standard deviation of the paragangliomas were 1.304 +/- 0.257 x 10(-3) mm(2)/s and differed from ADC values of the other jugular fossa tumors with 0.743 +/- 0.108 x 10(-3) mm(2)/s and measurement derived from the cerebellum with 0.802 +/- 0.075 x 10(-3) mm(2)/s.

CONCLUSION

Due to the difference of ADC values, the authors propose that DWI and ADC mapping could be a promising tool in the diagnostic work-up of paragangliomas.

Meningioma

Meningiomas are mostly benign tumours originating from the arachnoid cap cells, represent 13-26% of all intracranial tumours. They are more common in older age and in females. Deletion in NF2 gene and exposure to ionizing radiation are established risk factors, while the role of sex hormones is yet not clarified. Five-year survival for typical meningiomas exceeds 80%, but is poorer (5-year survival <60%) in malignant and atypical meningiomas. Papillary and haemangiopericytic morphology, large tumour size, high mitotic index, absence of progesterone receptors, deletions and loss of heterozygosity are poor prognostic factors. Complete surgical excision is the standard treatment. Radiotherapy is currently used in the clinical practice in atypical, malignant or recurrent meningioma at a total dose of 45-60Gy. However, the role of adjuvant irradiation is still controversial and has to be compared in a randomised prospective setting with a policy of watchful waiting. Radiosurgery has gained more and more importance in the management of meningiomas, especially in meningiomas that cannot be completely resected as for many skull base meningiomas. Medical therapy for patients with recurrent, progressive and symptomatic disease after repeated surgery, radiosurgery and radiotherapy is investigational. Hormonal therapy with progesterone antagonists has shown modest results, while chemotherapy with hydroxyurea appears moderately active.

Head and neck paragangliomas: value of contrast-enhanced 3D MR angiography

BACKGROUND AND PURPOSE

A rapid and accurate MR imaging technique would be beneficial to assess paragangliomas in the head and neck and to distinguish them from other lesions. The purpose of this study was to determine whether the combination of elliptic centric contrast-enhanced MR angiography (CE-MRA) and unenhanced and enhanced spin-echo imaging (conventional MR imaging) is more accurate than conventional MR imaging alone to assess paragangliomas in the head and neck.

MATERIALS AND METHODS

Three radiologists retrospectively and independently reviewed CE-MRA and conventional MR imaging in 27 patients with suspected paragangliomas. The overall image quality and the probability of paraganglioma were recorded. The results of each technique and their combination were analyzed for sensitivity and specificity. Receiver operating characteristic (ROC) analyses were performed by using histologic analysis, imaging, and/or clinical findings as the reference standard.

RESULTS

Forty-six lesions were found in 27 patients. In the assessment of paragangliomas, the combination of conventional MR imaging and CE-MRA was significantly superior to conventional MR imaging alone. Sensitivity and specificity respectively were the following: for CE-MRA, 100% and 94%; and for conventional MR imaging, 94% and 41%. The specificity of CE-MRA was significantly higher than that of conventional MR imaging (P = .004). There was good-to-excellent interobserver agreement for the paraganglioma probability with CE-MRA (nonweighted kappa, 0.67-0.77), whereas there was fair-to-good interobserver agreement with conventional MR imaging (nonweighted kappa, 0.50-0.65).

CONCLUSION

In combination with conventional MR imaging, CE-MRA yields an excellent diagnostic value for the assessment of head and neck paragangliomas; hence, the 2 techniques should be regarded as complementary.

Contrast-enhanced time-resolved 3-D MRA: applications in neurosurgery and interventional neuroradiology

PURPOSE

The decision-making process in the endovascular treatment of cranial dural AV fistulas and angiomas and their follow-up after treatment is usually based on conventional digital subtraction angiography (DSA). Likewise, acquiring the vascular and hemodynamic information needed for presurgical evaluation of meningiomas may necessitate DSA or different MR-based angiographic methods to assess the arterial displacement, the location of bridging veins and tumor feeders, and the degree of vascularization. New techniques of contrast-enhanced MR angiography (MRA) permit the acquisition of images with high temporal and spatial resolution. The purpose of this study was to evaluate the applicability and clinical use of a newly developed contrast-enhanced 3-D dynamic MRA protocol for neurointerventional and neurosurgical planning and decision making.

METHODS

With a 3-T whole-body scanner (Philips Achieva), a 3-D dynamic contrast-enhanced (MultiHance, Bracco) MRA sequence with parallel imaging, and intelligent k-space readout (keyhole and "CENTRA" k-space filling) was added to structural MRI in patients with meningiomas, dural arteriovenous fistulas and pial arteriovenous malformations. The sequence had a temporal resolution of 1.3 s per 3-D volume with a spatial resolution of 0.566x0.566x1.5 mm per voxel in each 3-D volume and lasted 25.2 s. DSA was performed in selected patients following MRI.

RESULTS

In patients with arteriovenous fistulas and malformations, MRA allowed the vascular shunt to be identified and correctly classified. Hemodynamic characteristics and venous architecture were clearly demonstrated. Larger feeding arteries could be identified in all patients. In meningiomas, MRA enabled assessment of the displacement of the cerebral arteries, depiction of the tumor feeding vessels, and evaluation of the anatomy of the venous system. The extent of tumor vascularization could be assessed in all patients and correlated with the histopathological findings that indicated hypervascularization.

CONCLUSION

High temporal and spatial resolution 3-D MRA may allow correct identification and classification of fistulas and angiomas and help to reduce the number of pre-or postinterventional invasive diagnostic angiograms. This sequence is also helpful for characterizing the degree of vascularization in preoperative evaluation of meningiomas and to select meningiomas suitable for embolization. Displacement of normal arteries and depiction of the venous anatomy can be achieved cost-effectively in a short period of time. The high spatial resolution also permits improved demonstration of the major feeding arteries, which helps to reduce the number of conventional angiograms required for meningioma evaluation.

Time Resolved 3D MRA. Applications for Interventional Neuroradiology

SUMMARY

The decision for endovascular treatment of cranial dural AV fistulae and angiomas and their follow-up after treatment is usually based on conventional DSA. New techniques of magnetic resonance angiography (MRA) facilitate high temporal and spatial resolution images.The purpose of this study was to evaluate the applicability and clinical use of a newly developed 3D dynamic MRA protocol on a 3T scanner for neurointerventional planning and decisionmaking. Using a 3T whole body scanner, a three-dimensional dynamic contrast enhanced MRA sequence with parallel imaging, and intelligent kspace readout (Keyhole and "CENTRA" kspace filling) was added to structural MRI and time-of-flight MRA in seven patients. DSA was performed in each patient following MR examination. In all patients MRA allowed the identification and correct classification of the vascular lesion. Hemodynamic characteristics and venous architecture were clearly demonstrated. Larger feeding arteries could be identified in all cases. Smaller feeding vessels were overlooked in dynamic MRA and only depicted in conventional DSA High temporal and spatial resolution 3D MRA may correctly identify and classify fistulae and angiomas and help to reduce the number of pre- or post-interventional invasive diagnostic angiograms.

The magnetic resonance Matas test: Feasibility and comparison with the conventional intraarterial balloon test occlusion with SPECT perfusion imaging

PURPOSE

To evaluate a new MR Matas test that uses a form of contrast-enhanced MR angiography (MRA) with temporary manual occlusion of the common carotid artery whose internal carotid artery (ICA) is to be permanently sacrificed.

MATERIALS AND METHODS

The MR Matas test was performed on eight patients using an open type MR imager (Signa Profile 0.2 Tesla ver. 7.5, GE-YMS, Tokyo, Japan). Conventional balloon occlusion Matas test and single-photon emission computed tomography (SPECT) of the brain were performed in all cases within a week before or after the MR Matas test.

RESULTS

The MR Matas test was successful in all eight patients without any complications. The image quality of the MR Matas test was generally sufficient to confirm cross-flow from the patent side to the occluded side in comparison with selective intraarterial digital subtraction angiography (IADSA) except in one case.

CONCLUSION

Brain perfusion information using MR Matas test is comparable to brain SPECT.

High temporal and spatial resolution 4D MRA using spiral data sampling and sliding window reconstruction

Contrast-enhanced magnetic resonance angiography (CE-MRA) requires high spatial resolution to demonstrate detailed vasculature and high temporal resolution to capture the contrast bolus. Sparse bright voxels in MRA permit substantial undersampling in MRI data acquisition, allowing simultaneous high temporal and spatial resolution. We developed a time-resolved 3D MRA technique using the efficient spiral sampling trajectory, and performed off-resonance corrections using inhomogeneity field maps. View sharing and sliding window reconstruction were utilized to generate high temporal resolution. High-resolution 3D angiograms were generated at 1-2 s per frame, with a 5-8 ml gadolinium dose, in patients with vascular disease.

Three-dimensional MR digital subtraction angiography using parallel imaging and keyhole data sampling in cerebrovascular diseases: initial experience

We assessed the feasibility of MR digital subtraction angiography (DSA) using parallel imaging and keyhole data sampling in the diagnosis of cerebrovascular diseases (CVDs) in 11 patients. Their diseases included arterial trunk stenosis/occlusion ( n=4), aneurysm ( n=3), arteriovenous malformation ( n=2), venous angioma ( n=1), and sinus thrombosis ( n=1). The technique depicted not only anatomical features, comparably to MR angiography ( n=10/11), but also hemodynamics such as collateral flow at a temporal resolution of 1.68 s/frame. When compared with conventional angiograms ( n=7), details were missed in four patients (incomplete demonstration of aneurysmal neck in two and poor separation of AVM components in two). Although inferior to conventional angiography, this technique can provide both anatomical and hemodynamic information of CVDs.

MR digital subtraction angiography with three-dimensional data acquisition in the diagnosis of brain tumors: preliminary experience

MR digital subtraction angiography (DSA) visualizes intracranial vasculature using a rapid T1-weighted sequence and a bolus injection of gadolinium. Although two-dimensional sequences are most frequently used, we applied a three-dimensional technique in combination with a fast method of k-space filling to improve both the temporal and spatial resolutions. In this preliminary study, we assessed the feasibility of using this technique for the diagnosis of brain tumors in 21 patients by reviewing the obtained images and, in 10 patients, comparing the images with conventional angiograms. MR DSA visualized a tumor stain in 11 patients, a tumor mass effect in 9, and tumor-related vessels in 5. In 9 of the 10 patients for whom conventional angiograms were available, the two kinds of angiograms corresponded well. Three-dimensional MR DSA using our technique is a useful adjunct to conventional MR imaging for the visualization of tumor hemodynamics and, in some cases, tumor-related vessels and mass effects.

Parkes Weber or Klippel-Trenaunay syndrome? Non-invasive diagnosis with MR projection angiography

Klippel-Trenaunay and Parkes Weber (Klippel-Trenaunay-Weber) syndromes consist of vascular malformations of the capillary, venous and lymphatic systems combined with soft tissue and bone hypertrophy of the affected extremity. Klippel-Trenaunay syndrome is a pure low-flow condition, while Parkes Weber syndrome is characterized by significant arteriovenous fistulas. The distinction of both entities is relevant, since the prognosis and therapeutic strategies differ significantly. Our purpose is to demonstrate that thick-slice dynamic magnetic resonance projection angiography (MRPA) is a non-invasive tool to detect arteriovenous shunting in Parkes Weber syndrome. Four patients underwent MR imaging and MRPA. MRPA demonstrated arteriovenous shunting in three patients. Arteriovenous shunting was characterized by early appearing draining veins. The time of arrival between normal arteries and pathological veins varied between less than 0.5 and 1.0 s. Therefore, the diagnosis in these cases could be specified as Parkes Weber syndrome. In all these cases, arteriovenous shunting was confirmed by intraarterial digital subtraction angiography. One patient showed normal results in MRPA and could be diagnosed as having Klippel-Trenaunay syndrome.

Resolution improvement in thick-slab magnetic resonance digital subtraction angiography using SENSE at 3T

PURPOSE

To evaluate the use of parallel imaging (sensitivity encoding [SENSE]) to improve spatial resolution and achieve sub-second temporal resolution in fluoroscopic contrast-enhanced, magnetic resonance digital subtraction angiography (MR-DSA).

MATERIALS AND METHODS

A MR-DSA sequence was optimized on a 3-T scanner with respect to sampling bandwidth and SENSE acceleration factor subject to the constraints of half-second acquisition time and 0.6 x 1.2 mm in-plane resolution. MR-DSA with and without SENSE acceleration was then evaluated in patients with arterio-venous malformations (AVMs).

RESULTS

Consistent with previously reported results and theory, SENSE factors greater than two and increasing sampling bandwidth both led to increasing image noise. Compared to lower resolution MR-DSA images with similar temporal resolution, the SENSE accelerated sequence provided better spatial resolution without notable changes in the contrast enhancement of the vascular territories of the AVMs but was hampered somewhat in the late venous phases by a reconstruction artifact.

CONCLUSION

SENSE acceleration of MR-DSA by a factor of two allows improved temporal or spatial resolution without significant loss of image quality. Signal-to-noise degradation associated with higher SENSE acceleration factors are likely to necessitate other approaches to further improving resolution in MR-DSA. Clinically, SENSE accelerated MR-DSA improves the non-invasive pre- and postoperative depiction of AVM flow dynamics.

Head and neck vascular malformations: time-resolved MR projection angiography

Extracranial vascular anomalies can be divided into haemangiomas and vascular malformations. The latter can be subdivided on the basis of the predominant type of vascular channels. Separation of high- and low-flow vascular malformations is of clinical importance. We report preliminary observations on time-resolved magnetic resonance projection angiography (MRPA) of vascular malformations of the head and neck. We examined eight patients with vascular anomalies of the head and neck. On MRPA the time between the early arterial phase and enhancement of the malformation could be used to distinguish high- and low-flow lesions. High-flow arteriovenous malformations showed early, intense enhancement. Venous malformations were either not visible on MRPA or showed late enhancement of veins. One patient was examined after embolisation of an arteriovenous fistula of the mandible. Normal MRPA was taken to indicate absence of a residual lesion.

Development of intraarterial contrast-enhanced 2D MRDSA with a 0.3 tesla open MRI system

PURPOSE

The purpose of this study was to develop a new technique for a high temporal resolution two-dimensional MR digital subtraction angiography (2D MRDSA) sequence under intraarterial injection of contrast material to permit the visualization of vascular anatomy and hemodynamics.

METHODS

2D MRDSA was imaged on a 0.3T open MR scanner with a T(1)-weighted fast gradient echo sequence. The phantom study examined vials containing gadolinium (Gd) solutions ranging in concentration from 0.5 mmol/L to 100 mmol/L. Repetition time and echo time were fixed at minimal values in order to achieve high temporal resolution, and only the flip angle was changed in 10-degree increments between 10 and 90 degrees. The in vivo study examined a brachial artery of a human volunteer. MRDSA images were acquired continuously during intraarterial injections of Gd solutions ranging in concentration from 0.5 mmol/L to 100 mmol/L. The subtracted images were displayed on the monitor in real time at a frame rate of one frame per second and evaluated to determine the optimal concentration of contrast material.

RESULTS

In the phantom study, a 10-mmol/L Gd concentration with a flip angle of 50 degrees -90 degrees and a 25-mmol/L Gd concentration with a flip angle of 60 degrees -90 degrees showed high signal-to-noise ratios. In the human brachial artery experiment, the forearm arteries were well visualized when solutions of 5-50 mmol/L Gd concentration were used. The 10- and 25-mmol/L Gd concentrations were considered optimal. The palmar digital arteries were also visualized. Higher Gd concentrations showed a paradoxical signal increase when diluted by blood.

CONCLUSION

We successfully developed an intraarterial contrast-enhanced 2D MRDSA sequence. With appropriate settings of imaging parameters and Gd concentrations, we obtained acceptable vessel visualization in the human study. The low Gd concentration for optimal visualization permits repeated intraarterial injections. This technique can be a useful tool for investigating the vascular anatomy and hemodynamics required for MR-guided vascular interventions.

Dynamic contrast enhancement of paragangliomas of the head and neck: evaluation with time-resolved 2D MR projection angiography

Our objective was to evaluate tumor hemodynamics of paragangliomas of the head and neck. A 2D magnetic resonance projection angiography (MRPA) protocol was developed. Six patients with histologically proven paragangliomas were included in the study. The sequence protocol and data post-processing procedure were optimized in view of a high temporal resolution and maximum contrast-to-noise ratio. Image-time series of two freely orientated slabs could be obtained. Correlation analysis was performed to generate selective arterial and venous weighted angiographic images. Glomus tumors showed a rapid and intense homogeneous enhancement following the intravenous administration of contrast material. The smallest tumors investigated measured 10 mm and could be visualized clearly. Time-resolved analysis of the tumor enhancement revealed an early bolus arrival within the vascular bed of the tumor and prolonged incomplete washout indicating blood pooling. The dynamic contrast enhancement of glomus tumors can be evaluated non-invasively with MRPA providing a high temporal resolution and high image quality. The characteristic contrast enhancement of glomus tumors can be helpful in the diagnostic workup of lesions that may mimic glomus tumors.

MR digital subtraction angiography in the diagnosis of meningiomas

OBJECTIVE

MR digital subtraction angiography (DSA) is a technique for demonstrating the vasculature combining a rapid two-dimensional T1-weighted sequence with a bolus injection of gadolinium. We attempted to determine its contribution to the diagnosis of intracranial meningiomas.

METHODS AND PATIENTS

MR DSA was performed in 18 patients with meningioma as well as in 28 patients with other tumors. The findings were analyzed regarding demonstration of tumor stain and tumor-related vessels.

RESULTS

All meningiomas except one were visualized as a homogeneous and intense stain. Feeding arteries were visualized in 2 patients, and draining or abnormal veins in three. In 21 of the 28 patients with other tumors, tumor stains of varying degrees were demonstrated.

CONCLUSION

MR DSA can serve as an adjunct to routine MR imaging, because it enables assessment of the hemodynamics of meningiomas and facilitates its differential diagnosis from other tumors.