New applications of MR contrast agents in neuroradiology

Residual tumor volume versus extent of resection: predictors of survival after surgery for glioblastoma

Object

The impact of extent of resection (EOR) on survival for patients with glioblastoma (GBM) continues to be a point of debate despite multiple studies demonstrating that increasing EOR likely extends survival for these patients. In addition, contrast-enhancing residual tumor volume (CE-RTV) alone has rarely been analyzed quantitatively to determine if it is a predictor of outcome. The purpose of this study was to evaluate the effect of CE-RTV and T2/FLAIR residual volume (T2/F-RV) on overall survival.

Methods

A retrospective review of 128 patients who underwent primary resection of supratentorial GBM followed by standard radiation/chemotherapy was undertaken utilizing quantitative, volumetric analysis of pre- and postoperative MR images. The results were compared with clinical data obtained from the patients' medical records.

Results

At analysis, 8% of patients were alive, and no patients were lost to follow-up. The overall median survival was 13.8 months, with a median Karnofsky Performance Scale (KPS) score of 90 at presentation. The median contrast-enhancing preoperative tumor volume (CE-PTV) was 29.0 cm3, and CE-RTV was 1.2 cm3, equating to a 95.8% median EOR. The median T2/F-RV was 36.8 cm3. CE-PTV, CE-RTV, T2/F-RV, and EOR were all statistically significant predictors of survival when controlling for age and KPS score. A statistically significant benefit in survival was seen with a CE-RTV less than 2 cm3 or an EOR greater than 98%. Evaluation of the volumetric analysis methodology was performed by observers of varying degrees of experience—an attending neurosurgeon, a fellow, and a medical student. Both the medical student and fellow recorded correlation coefficients of 0.98 when compared with the attending surgeon's measured volumes of CE-PTV, while for CE-RTV, correlation coefficients of 0.67 and 0.71 (medical student and fellow, respectively) were obtained.

Conclusions

CE-RTV and EOR were found to be significant predictors of survival after GBM resection. CERTV was the more significant predictor of survival compared with EOR, suggesting that the volume of residual contrast-enhancing tumor may be a more accurate and meaningful reflection of the pathobiology of GBM.

Evaluating the prognostic factors effective on the outcome of patients with glioblastoma multiformis: does maximal resection of the tumor lengthen the median survival?

BACKGROUND

The ETR that should be undertaken in patients with GBM remains controversial. This study aims to reiterate some independent predicting factors and to underscore the role and the ETR in increasing the survival of patients in the situation of developing countries, that is, without preoperative MRI or tractography. The authors submit additional information to be added to the list of CTRs in the management of malignant brain tumors.

METHODS

The authors prospectively analyzed a cohort of 35 consecutive patients with histologically proven GBM who underwent tumor resection in surgically amenable areas for the first time at Sina Hospital, Tehran, between 2003 and 2005. Demographic data, volumetric measurements, and other characteristics identified on preoperative and immediate postoperative MR imaging as well as intraoperative and postoperative clinical data were collectively analyzed by SPSS for Windows, version 11.5 (SPSS, Chicago, Ill).

RESULTS

Cox proportional hazards model multivariate analysis identified the following independent predictors of survival: Karnofsky performance scale ≥80 (P = .01), ETR (P = .01), tumor location in functionally silent prefrontal area (P = .002) vs tumor location in corpus callosum (P = .001), postoperative RT (P = .004), and postoperative chemotherapy (P = .001)

CONCLUSION

Maximal resection of the tumor volume is an independent variable associated with longer survival times in patient with GBM. Gross total resection should be performed whenever possible, although not at the expense of increased morbidity.

Collagen-only biomatrix as a novel dural substitute. Examination of the efficacy, safety and outcome: clinical experience on a series of 208 patients

OBJECTIVES

Dural replacement materials and other measures can provide an effective barrier between the subarachnoid compartment and the extradural space when a watertight closure of the patient's own dura is not possible.

PATIENTS AND METHODS

We evaluated the efficacy and safety of a novel collagen-derived dural substitute on a series of 208 patients undergoing a variety of neurosurgical procedures.

RESULTS

No patients experienced any local or systemic complications nor toxicity related to the dural patch. No patients experienced post-operative CSF fistula except for one. Post-operative MRIs showed signs of moderate inflammatory response in only one patient, who did not present any post-operative clinical symptom nor neurological deficits. Three patients underwent reoperation for bone flap repositioning after decompressive craniectomy: in these cases, the dural substitute appeared to have promoted a satisfactory dural regeneration, as confirmed by the histological studies. Furthermore, in such cases no or minimal adherences with the other tissues and the brain cortex was observed.

CONCLUSIONS

The new collagen-only biomatrix is a safe and effective dural substitute for routine neurosurgical procedures. The absence of local and systemic toxicity or complications, and the scarce promotion of adherences and inflammation, make this material appealing for its use as dural substitute even in cases when a needed re-operation is anticipated.

Contrast Enhancement of Central Nervous System Lesions: Multicenter Intraindividual Crossover Comparative Study of Two MR Contrast Agents

PURPOSE

To prospectively compare gadobenate dimeglumine with gadopentetate dimeglumine (0.1 mmol per kilogram body weight) for enhanced magnetic resonance (MR) imaging of central nervous system (CNS) lesions.

MATERIALS AND METHODS

This study was HIPAA-compliant at U.S. centers and was conducted at all centers according to the Good Clinical Practice standard. Institutional review board and regulatory approval were granted; written informed consent was obtained. Seventy-nine men and 78 women (mean age, 50.5 years +/- 14.4 [standard deviation]) were randomized to group A (n = 78) or B (n = 79). Patients underwent two temporally separated 1.5-T MR imaging examinations. In randomized order, gadobenate followed by gadopentetate was administered in group A; order of administration was reversed in group B. Contrast agent administration (volume, speed of injection), imaging parameters before and after injection, and time between injections and postinjection acquisitions were identical for both examinations. Three blinded neuroradiologists evaluated images by using objective image interpretation criteria for diagnostic information end points (lesion border delineation, definition of disease extent, visualization of internal morphologic features of the lesion, enhancement of the lesion) and quantitative parameters (percentage of lesion enhancement, contrast-to-noise ratio [CNR]). Overall diagnostic preference in terms of lesion conspicuity, detectability, and diagnostic confidence was assessed. Between-group comparisons were performed with Wilcoxon signed rank test.

RESULTS

Readers 1, 2, and 3 demonstrated overall preference for gadobenate in 75, 89, and 103 patients, compared with that for gadopentetate in seven, 10, and six patients, respectively (P < .0001). Significant (P < .0001) preference for gadobenate was demonstrated for diagnostic information end points, percentage of lesion enhancement, and CNR. Superiority of gadobenate was significant (P < .001) in patients with intraaxial and extraaxial lesions.

CONCLUSION

Gadobenate compared with gadopentetate at an equivalent dose provides significantly better enhancement and diagnostic information for CNS MR imaging.

Early-postoperative magnetic resonance imaging in glial tumors: prediction of tumor regrowth and recurrence

OBJECTIVE

This study investigated the value of early-postoperative magnetic resonance (EPMR) imaging in the detection of residual glial tumor and investigated the role of EPMR for the prediction of tumor regrowth and recurrence.

METHODS AND MATERIALS

We retrospectively analyzed pre- and post-operative magnetic resonance imaging results from 50 adult patients who underwent surgical treatment for supratentorial glial tumor. There were glioblastoma multiforme in 25 patients, astrocytoma (grades II and III) in 11 patients, oligodendroglioma (grades II and III) in 9 patients, and oligoastrocytoma (grades II and III) in 5 patients. EPMR imaging was performed within 24 h after surgery. EPMR findings were compared with the neurosurgeon's intraoperative estimation of gross tumor removal. Patterns of contrast enhancement at the resection site, in residual and developing tumor tissue and blood at the resection site were evaluated on EPMR and in follow-up studies. 'Residual tumor' was defined as contrast enhancing mass at the operative site on EPMR. 'Regrowth' was defined as contrast enhancing mass detected on follow-up in the same location as the primary tumor. 'Recurrence' was defined as appearance of a mass lesion in the brain parenchyma distant from the resection bed during follow-up.

RESULTS

Nineteen patients showed no evidence of residual tumor, regrowth, or recurrence on EPMR or any of the later follow-up radiological examinations. EPMR identified 20 cases of residual tumor. Follow-up showed tumor regrowth in 10 patients, and tumor recurrence in 1 case. EPMR showed contrast enhancement of the resection bed in 45 of the 50 patients. Four of the 20 residual tumors showed a thick linear enhancement pattern, and the other 16 cases exhibited thick linear-nodular enhancement. No thin linear enhancement was observed in the residual tumor group. Nine of the 10-regrowth tumors showed a thick linear-nodular enhancement pattern, and one exhibited thin linear enhancement in EPMR. For predicting regrowth tumor EPMR sensitivity was 91%, specificity was 100%, positive predictive value 1; negative predictive value was 0.9375.

CONCLUSION

EPMR, depending on the surgical site enhancement pattern, is a valuable means of demonstrating residual tumors, and can be used to predict possible regrowth after surgery.

Pachymeningeal gadolinium enhancement of the lumbar region secondary to neuraxis hypotension

STUDY DESIGN

A case of diffuse pachymeningeal gadolinium enhancement of the lumbar region secondary to neuraxis hypotension is presented.

OBJECTIVE

To report a case of diffuse pachymeningeal gadolinium enhancement of the lumbar region and to show the importance of considering neuraxis hypotension in the differential diagnosis of this type of enhancement so as to avoid excessive invasive and noninvasive diagnostic testing.

SUMMARY OF BACKGROUND DATA

Diffuse pachymeningeal gadolinium enhancement of the lumbar region secondary to neuraxis hypotension has not been reported previously.

METHODS

A case of diffuse pachymeningeal gadolinium enhancement of the lumbar region is presented in the context of clinical signs and symptoms replete with a history of cerebrospinal fluid diversion that strongly suggest neuraxis hypotension.

RESULTS

The patient's clinical presentation and history of shunting implicated neuraxis hypotension as a cause of the diffuse dural enhancement.

CONCLUSION

Proper attribution of the dural gadolinium enhancement to neuraxis hypotension helped avoid a dural biopsy with its potential attendant morbidity. It is important to consider neuraxis hypotension in the differential diagnosis of diffuse pachymeningeal enhancement occurring anywhere in the central neuraxis to avoid unnecessary diagnostic testing with its attendant morbidity and cost.

Dynamic imaging of intracranial lesions using fast spin-echo imaging: differentiation of brain tumors and treatment effects

The purpose of this study was to develop a technique for differentiating between recurrent brain tumors and treatment-related changes, such as radiation necrosis, using dynamic MRI. Ninety-five patients with intracranial mass lesions were evaluated using T1-weighted fast spin-echo (FSE) MRI at 1.5 T. Pathologies included treatment-related changes (n = 32), primary tumors (n = 41), metastatic tumors (n = 5), meningiomas (n = 4), and mixed primary/treatment related changes (n = 13). Signal enhancement-time curves were analyzed by fitting to a sigmoidal-exponential function. Maximal enhancement rates were calculated as the first derivative of the fitted curve. Based on the maximal enhancement rates, treatment-related changes could be differentiated from primary tumors, metastatic tumors, and meningiomas at the P < .05 confidence level. Lesions of mixed tumor and treatment-related change had intermediate values. Dynamic MRI can be used to differentiate treatment-related changes from primary tumors in previously treated patient populations based on maximal enhancement rates. Individual case studies demonstrate the clinical significance of these findings.

Syndrome of orthostatic headaches and diffuse pachymeningeal gadolinium enhancement

OBJECTIVE

To characterize clinical and imaging features, biopsy findings, etiologic factors, and outcome in the syndrome of intracranial hypotension, headaches, and diffuse pachymeningeal gadolinium enhancement on magnetic resonance imaging (MRI).

MATERIAL AND METHODS

We describe our experience with 26 consecutive patients with orthostatic headaches and diffuse pachymeningeal gadolinium enhancement, for all of whom clinical, imaging, and follow-up data were available. For 10 patients who had undergone meningeal biopsy, slide material was also reviewed.

RESULTS

The 15 men and 11 women ranged from 24 to 76 years of age. All 26 patients had postural headaches; in 22 patients, the headaches were completely alleviated by recumbency. Nausea or emesis, neck pain, horizontal diplopia, changes in hearing, photophobia, upper limb pains or paresthesias, visual blurring, or dysgeusia was noted in some of the patients. Cardinal MRI features were diffuse pachymeningeal gadolinium enhancement (100%), subdural collections of fluid (69%), and evidence of descent of the brain (62%) that sometimes resembled type I Chiari malformation. Cerebrospinal fluid (CSF) opening pressures were 40 mm or less in only 46%. In three patients, CSF pressures were consistently no less than 90 and as high as 130 mm of water. A variable pleocytosis of 5 or more cells/mm3 was noted in 15 patients (more than 40 cells/mm3 in 4 patients). A variable increase in CSF protein was noted in at least one spinal tap in 23 patients. Six patients had overdraining CSF shunts; CSF leak was documented in another 11 patients. Shunt revision or ligation and surgical correction of the leak led to a resolution of the clinical and MRI abnormalities in all cases thus treated. Improvement occurred with epidural blood patch in four patients. Three of the 12 patients treated supportively have remained symptomatic. Histologically, a thin subdural zone of fibroblasts and thin-walled vessels was noted in an amorphous matrix. Two patients with prolonged symptoms had a more pronounced proliferative reaction.

CONCLUSION

The syndrome of low-pressure headaches and pachymeningeal gadolinium enhancement is being recognized with increasing frequency. The source of the CSF leak can be demonstrated in many patients. Meningeal abnormalities are likely attributable to decreased CSF volume and hydrostatic CSF pressure changes. The prognosis is typically good.

Quantitative magnetic resonance imaging of capillary water permeability and regional blood volume with an intravascular MR contrast agent

A novel method is presented to simultaneously measure the permeability surface area product of water (PS), also known as capillary diffusion capacity, and the regional blood volume (RBV). It is based on magnetic resonance imaging of the longitudinal relaxation times of tissue and blood at different concentrations of an intravascular MR contrast agent. PS and RBV were measured in vivo in different regions of the brain and the skeletal muscle of the rat. The average PS values (n = 5) obtained in cerebral cortex, corpus callosum, hippocampus, thalamus, jaw muscle, and tongue muscle were 3.31 +/- 0.20, 1.81 +/- 0.25, 3.37 +/- 0.36, 3.68 +/- 0.44, 10.6 +/- 1.1, and 14.1 +/- 2.51 ml x min(-1) x g(-1), respectively. The corresponding average RBV values were 1.63 +/- 0.18, 1.22 +/- 0.25, 3.30 +/- 0.37, 3.03 +/- 0.36, 1.66 +/- 0.30, and 1.38 +/- 0.33 ml x 100 g(-1). These results are in good agreement with previously reported literature values obtained by means of autoradiography.

Early postoperative magnetic resonance imaging following nonneoplastic cortical resection

Postcraniotomy residual tumor is often determined by magnetic resonance (MR) imaging. Magnetic resonance changes that occur in the postoperative setting must be defined to ensure both the optimum timing of postoperative image acquisition and the accurate assessment of images for residual tumor. Postoperative changes in nontumor parenchyma have previously been described for computerized tomography but not for MR imaging. In the present study, 11 patients without intracranial neoplastic disease (six females and five males with a median age of 36 years) submitted to MR imaging 17 to 28 hours after undergoing temporal lobectomies for epilepsy. Four of the operations were performed with the patients under general anesthesia and seven under local anesthesia. Postoperative MR images (T1-weighted, T1-weighted gadolinium enhanced, and T2-weighted) were reviewed. Extraaxial fluid, air, or blood was present in all cases. Enhancement of the resection bed parenchyma occurred in seven (64%) of 11 patients. In three of the remaining four patients, assessment of parenchymal enhancement was obscured by extraaxial fluid collections. Dural enhancement occurred adjacent to the resection site in all of the cases and remotely in 73%. Eight (73%) of 11 patients displayed enhancement of the pia-arachnoid of the ipsilateral cerebral convexity, two (18%) of the contralateral convexity, and four (36%) of the pia-arachnoid overlying the cerebellum. Contrary to previous reports, contrast enhancement of nonneoplastic human brain parenchyma can occur postoperatively within 17 hours. Benign parenchymal contrast enhancement is usually linear in appearance; nonneoplastic dural and leptomeningeal enhancement can occur both adjacent to and distant from the surgical site. Extraaxial fluid collections can hinder MR evaluation of the resection bed.

The calvarium

The calvarium is a crucial structure that can manifest a great deal of pathology. The plain film remains the main imaging modality, although CT and MRI are becoming increasingly important. We discuss its anatomy, normal variants, congenital and developmental anomalies, hematologic disease, idiopathic disorders, neoplasms, metabolic disease, trauma, and the postoperative skull. Whenever possible, we emphasize CT and MRI.

Early postoperative magnetic resonance imaging after resection of malignant glioma: objective evaluation of residual tumor and its influence on regrowth and prognosis

In the vast majority of studies that address the role of surgery in the management of high-grade gliomas, the degree of tumor removal accomplished is solely based on the intraoperative perception of the neurosurgeon. Despite its fundamental importance for a comparison of different treatment modalities, little systematic effort has been made to evaluate the residual gross tumor by neuroimaging methods immediately after surgery. We report the results of a prospective study using contrast-enhanced computed tomography and magnetic resonance imaging (MRI) to monitor 60 patients after the resection of a high-grade glioma. In each case, the first scans were obtained between Days 1 and 5 after surgery, followed by serial imaging every 2 to 3 months, usually until the condition of the patient deteriorated severely or the patient died. Gadolinium-enhanced MRI proved to be extremely valuable for assessing gross residual tumor when performed during Days 1 to 3 after the resection of a preoperatively enhancing high-grade glioma. This timing avoided surgically induced contrast enhancement and minimized interpretative difficulties. In delineating residual tumor, MRI was vastly superior to computed tomography. About 80% of tumor "recurrences" emerged from definitely enhancing remnants, as revealed by early postoperative MRI. The neurosurgeon's estimation of gross tumor burden reduction could be shown to be much less accurate (by a factor of 3) than the postoperative assessment by modern neuroimaging. In our series, residual tumor enhancement was the most predictive prognostic factor of survival in patients with glioblastoma, followed by radiotherapy. Patients with a residual tumor postoperatively had a 6.595-times higher risk of death in comparison to patients without a residual tumor. Patients undergoing radiotherapy had a 0.258-times lower risk of death in comparison to patients who were not treated with radiation. Concerning survival, the prognostic significance of both variables surpassed age and performance.

Measurement of capillary permeability from the Gd enhancement curve: a comparison of bolus and constant infusion injection methods

Dynamic imaging of Gd-DTPA uptake has been used by several groups to characterise the permeability of blood-brain barrier and blood-retina barrier lesions, using both bolus and constant infusion rate injections. However, no consensus on which injection protocol is most efficient has been reached. To address this problem, we extend our Simplified Early Enhancement (SEE) theory, applicable to retinal lesions, to cover infusion injections, and demonstrate its application to published data. The two injection methods are compared using computer simulation. We find that, first, an infusion cannot produce a constant plasma concentration in an acceptable time (although a hybrid injection, consisting of a combined bolus and infusion, is able to do this). Second, at any given time after the start of injection, a bolus achieves a higher tissue concentration, and hence enhancement, than does the same dose given as an infusion. Conversely, a bolus achieves any given tissue concentration in a shorter time than the same dose given as an infusion. Consequently, a bolus uses a smaller dose to achieve a given enhancement at a particular time. Third, if renal function is reduced, the error in calculating the permeability from a particular value of enhancement is lower for the bolus than for the infusion. And last, the SEE method is more accurate for a bolus than for an infusion. We conclude that a bolus is always more efficient than an infusion, as well as being easier to administer, and should always be used in preference to an infusion.

Gadodiamide injection as a contrast medium for MRI of the central nervous system: a comparison with gadolinium-DOTA

The tolerance and diagnostic efficacy of a new nonionic, intravenous MRI contrast medium, gadodiamide injection (Omniscan) are reported and compared with those of gadolinium-DOTA after completion of a double-blind, randomized, parallel study in 60 patients using a dose of 0.1 mmol/kg. Two patients were excluded from the statistical analysis after trial entrance since no contrast medium was injected. The indications for the MRI examination were known or suspected CNS lesions. Vital signs, chemical and haematological parameters were monitored. No significant abnormalities were observed, confirming the excellent tolerance of both contrast media. The usefulness of gadolinium-containing contrast media was again documented, since in 8.6% (5/58) of the patients the lesion(s) could be seen only after injection. Contrast enhancement was seen in 87.8% (43/49) of the patients with abnormal findings, and provided additional diagnostic information in 24.5% (12/49). Lack of contrast enhancement in 12.2% (6/49) of patients with abnormal findings was a significant negative finding.