Postoperative neuroimaging of high-grade gliomas: comparison of transcranial sonography, magnetic resonance imaging, and computed tomography

Transcranial ultrasonography to detect intracranial pathology: A systematic review and meta-analysis

BACKGROUND AND PURPOSE

Transcranial ultrasonography (TCU) can be a useful diagnostic tool in evaluating intracranial pathology in patients with limited or delayed access to routine neuroimaging in critical care or austere settings. We reviewed available literature investigating the diagnostic utility of TCU for detecting pediatric and adult patient's intracranial pathology in patients with intact skulls and reported diagnostic accuracy measures.

METHODS

We performed a systematic review of PubMed^® , Cochrane Library, Embase^® , Scopus^® , Web of Science™, and Cumulative Index to Nursing and Allied Health Literature databases to identify articles evaluating ultrasound-based detection of intracranial pathology in comparison to routine imaging using broad Medical Subject Heading sets. Two independent reviewers reviewed the retrieved articles for bias using the Quality Assessment of Diagnostic Accuracy Studies tools and extracted measures of diagnostic accuracy and ultrasound parameters. Data were pooled using meta-analysis implementing a random-effects approach to examine the sensitivity, specificity, and accuracy of ultrasound-based diagnosis.

RESULTS

A total of 44 studies out of the 3432 articles screened met the eligibility criteria, totaling 2426 patients (Mean age: 60.1 ± 14.52 years). We found tumors, intracranial hemorrhage (ICH), and neurodegenerative diseases in the eligible studies. Sensitivity, specificity, and accuracy of TCU and their 95% confidence intervals were 0.80 (0.72, 0.89), 0.71 (0.59, 0.82), and 0.76 (0.71, 0.82) for neurodegenerative diseases; 0.88 (0.74, 1.02), 0.81 (0.50, 1.12), and 0.94 (0.92, 0.96) for ICH; and 0.97 (0.92, 1.03), 0.99 (0.96, 1.01), and 0.99 (0.97, 1.01) for intracranial masses. No studies reported ultrasound presets.

CONCLUSIONS

TCU has a reasonable sensitivity and specificity for detecting intracranial pathology involving ICH and tumors with clinical applications in remote locations or where standard imaging is unavailable. Future studies should investigate ultrasound parameters to enhance diagnostic accuracy in diagnosing intracranial pathology.

Brain topography on adult ultrasound images: Techniques, interpretation, and image library

BACKGROUND AND PURPOSE

Many studies have explored the possibility of using cranial ultrasound for discerning intracranial pathologies like tumors, hemorrhagic stroke, or subdural hemorrhage in clinical scenarios where computer tomography may not be accessible or feasible. The visualization of intracranial anatomy on B-mode ultrasound is challenging due to the presence of the skull that limits insonation to a few segments on the temporal bone that are thin enough to allow transcranial transmission of sound. Several artifacts are produced by hyperechoic signals inherent in brain and skull anatomy when images are created using temporal windows.

METHODS

While the literature has investigated the accuracy of diagnosis of intracranial pathology with ultrasound, we lack a reference source for images acquired on cranial topography on B-mode ultrasound to illustrate the appearance of normal and abnormal structures of the brain and skull. Two investigators underwent hands-on training in Cranial point-of-care ultrasound (c-POCUS) and acquired multiple images from each patient to obtain the most in-depth images of brain to investigate all visible anatomical structures and pathology within 24 hours of any CT/MRI imaging done.

RESULTS

Most reproducible structures visible on c-POCUS included bony parts and parenchymal structures. Transcranial and abdominal presets were equivalent in elucidating anatomical structures. Brain pathology like parenchymal hemorrhage, cerebral edema, and hydrocephalus were also visualized.

CONCLUSIONS

We present an illustrated anatomical atlas of cranial ultrasound B-mode images acquired in various pathologies in a critical care environment and compare our findings with published literature by performing a scoping review of literature on the subject.

Neuroimaging classification of progression patterns in glioblastoma: a systematic review

BACKGROUND

Our primary objective was to report the current neuroimaging classification systems of spatial patterns of progression in glioblastoma. In addition, we aimed to report the terminology used to describe 'progression' and to assess the compliance with the Response Assessment in Neuro-Oncology (RANO) Criteria.

METHODS

We conducted a systematic review to identify all neuroimaging studies of glioblastoma that have employed a categorical classification system of spatial progression patterns. Our review was registered with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) registry.

RESULTS

From the included 157 results, we identified 129 studies that used labels of spatial progression patterns that were not based on radiation volumes (Group 1) and 50 studies that used labels that were based on radiation volumes (Group 2). In Group 1, we found 113 individual labels and the most frequent were: local/localised (58%), distant/distal (51%), diffuse (20%), multifocal (15%) and subependymal/subventricular zone (15%). We identified 13 different labels used to refer to 'progression', of which the most frequent were 'recurrence' (99%) and 'progression' (92%). We identified that 37% (n = 33/90) of the studies published following the release of the RANO classification were adherent compliant with the RANO criteria.

CONCLUSIONS

Our review reports significant heterogeneity in the published systems used to classify glioblastoma spatial progression patterns. Standardization of terminology and classification systems used in studying progression would increase the efficiency of our research in our attempts to more successfully treat glioblastoma.

Diagnostic ability of intraoperative ultrasound for identifying tumor residual in glioma surgery operation

Achieving total glioma resection represents a major challenge to neurosurgeons with no distinct margin between tumor and surrounding brain tissue. Many imaging methods are employed in surgery visualization and resection control. We performed this meta-analysis to assess the diagnosis value of intraoperative ultrasound and judged whether ultrasound is a suitable tool in detecting glioma residual. The databases including PubMed, Embase, Web of Science, China National Knowledge Infrastructure (CNKI), Wanfang and Weipu were systematically searched to find out relevant studies and published up to May 5, 2017. A total of 14 studies involving 542 participants met the selection criteria and bivariate mixed effects models were used for analysis. The parameters and their corresponding 95% confidence interval (CI) were computed on Stata 12.0 software. The pooled sensitivity was 0.75 (95%CI: 0.62-0.84), specificity was 0.88 (95%CI: 0.79-0.94), positive likelihood ratios was 6.27 (95%CI: 3.76-10.47), negative likelihood ratios was 0.29 (95%CI: 0.20-0.42), diagnostic odds ratios was 21.83 (95%CI: 14.20-33.55) and area under the curve of summary receiver operator characteristic was 0.89. Stratified meta-analysis showed sensitivity and area under the curve in low-grade glioma were both higher than high-grade glioma. The Deek's plot showed no significant publication bias (t = -1.03, P = 0.33). Intraoperative ultrasound has high overall diagnostic value to identify glioma remnants, especially in low-grade glioma, which shows a benefit for prognosis and life quality of patients. In general, Intraoperative ultrasound is an effective tool for maximizing the extent of glioma resection.

Brain tissue echogenicity--implications for substantia nigra studies in parkinsonian patients

The aim of the present study was to assess the origin of the substantia nigra hyperechogenicity in Parkinson disease patients. The cause of hyperechogenicity was tested on an animal model. Fresh porcine brains were injected consecutively with ferritin, apoferritin and water. Then, glioma samples were inserted into animal model. The echogenicity of the region of interest was assessed before and after experimental procedures. We observed the same echogenicity of porcine brain before and after injections of iron-loaded ferritin, apoferritin and water. Increased echogenicity of glioma samples compared to surrounding porcine brain tissue could be clearly seen. We postulate that the relative gliosis might be, at least partially, responsible for the increased echogenicity of the substantia nigra in Parkinson disease patients. Keeping in mind all limitations and inaccuracies of animal model used, it seems that hyperechogenicity of substantia nigra is caused rather by structural changes within the brain tissue than by increased iron concentration.

Multiphoton excitation of autofluorescence for microscopy of glioma tissue

OBJECTIVE

Intraoperative detection of residual tumor tissue in glioma surgery remains an important challenge because the extent of tumor removal is related to the prognosis of the disease. Multiphoton excited fluorescence tomography of living tissues provides high-resolution structural and photochemical imaging at a subcellular level. In this conceptual study, we have used multiphoton microscopy and fluorescence lifetime imaging (4D microscopy) to image cultured glioma cell lines, solid tumor, and invasive tumor cells in an experimental mouse glioma model and human glioma biopsy specimens.

MATERIAL AND METHODS

A laser imaging system containing a mode-locked 80 MHz titanium:sapphire laser with a tuning range of 710 to 920 nm, a scan unit, and a time correlated single photon counting board was used to generate autofluorescence intensity images and fluorescence lifetime images of cultured cell lines, experimental intracranial gliomas in mouse brain, and biopsies of human gliomas.

RESULTS

Multiphoton microscopy of native tumor bearing brain provided structural images of the normal brain anatomy at a subcellular resolution. Solid tumor, the tumor-brain interface, and single invasive tumor cells could be visualized. Fluorescence lifetime imaging demonstrated significantly different decay of the fluorescent signal in tumor versus normal brain, allowing a clear definition of the tumor-brain interface based on this parameter. Distinct fluorescence lifetimes of endogenous fluorophores were found in different cellular compartments in cultured glioma cells. The analysis of the relationship between the laser excitation wavelength and the lifetime of excitable fluorophores demonstrated distinct profiles for cells of different histotypes.

CONCLUSION

Multiphoton excited fluorescence of endogenous fluorophores allows structural imaging of tumor and central nervous system histo-architecture at a subcellular level. The analysis of the decay of the fluorescent signal within specific excitation volumes by fluorescent lifetime imaging discriminates glioma cells and normal brain, and the excitation/lifetime profiles may further allow differentiation of cellular histotypes. This technology provides a noninvasive optical tissue analysis that may potentially be applied to an intraoperative analysis of resection plains in tumor surgery.

Ultrasound guidance in intracranial tumor resection: correlation with postoperative magnetic resonance findings

PURPOSE

To determine the inter-method agreement between intraoperative ultrasonography and postoperative contrast-enhanced magnetic resonance imaging (MRI) in detecting tumor residue.

MATERIAL AND METHODS

After resection was completed, the cavity borders of 32 tumors were examined with a 7 MHz intraoperative probe. Any echogenic region >5 mm in thickness extending from the surgical cavity into the brain substance was taken as the sonographic criterion for residual tumor. A continuous echogenic rim< 5 mm was considered normal. Results were correlated with gadolinium-enhanced MRI obtained within 48 h after surgery.

RESULTS

The kappa value for inter-method agreement was 0.72. There were four cases in whom MRI showed residue despite a negative sonography: extensive edema or Surgicel along the cavity borders (three cases with glioblastoma multiforme) and the cystic component in the vicinity of cerebrospinal fluid (a case with pituitary macroadenoma) may be the reason for the residue going undetected. In a case with glioblastoma multiforme, residual enhancement was < 5 mm in thickness.

CONCLUSION

Intraoperative ultrasound is an effective tool for maximizing the extent of intracranial tumor resection. Surgical use has to be minimized if intraoperative ultrasound is to be used as an adjunct to surgery. Tumors with preoperatively detected cystic components in the proximity of CSF-containing spaces have to be carefully evaluated with intraoperative ultrasound if residual cystic components are to be detected. A low-thickness echogenic rim should not be considered a reliable sign of the absence of residue.

Correlation of factors predicting intraoperative brain shift with successful resection of malignant brain tumors using image-guided techniques

BACKGROUND

Intraoperative brain shift may cause inaccuracy of stereotactic image guidance on the basis of preoperatively acquired imaging data. The purpose of our study was to determine whether factors predicting brain shift affect the success of image-guided resection of malignant brain tumors.

METHODS

We retrospectively studied 54 patients who underwent image-guided resections of histopathologically confirmed malignant brain tumors (9 metastases, 45 high-grade gliomas). Precautions were taken during surgery to minimize brain shift, but intraoperative imaging was not performed. The following factors predictive of intraoperative brain shift were assessed: tumor size, periventricular location, patient age, prior surgery or radiation therapy, patient positioning, use of mannitol, and length of operative time. Postoperative magnetic resonance imaging was obtained in all cases within 48 hours of surgery to assess extent of resection.

RESULTS

Perioperative mortality was 0% in our series; perioperative morbidity was 3 of 54 patients (5.5%); 1 patient required reoperation for a hematoma, and 2 had transient neurological deficits. Successful resection was accomplished in 93% of tumors less than 30 cm(3) compared with 63.6% of tumors greater than 30 cm(3) (P = .026, Fisher exact test). This difference was more pronounced for patients with malignant gliomas. However, other factors predictive of intraoperative brain shift were not associated with unsuccessful resection.

CONCLUSIONS

Intraoperative brain shift does not significantly affect the likelihood of successful resection of malignant brain tumors smaller than 30 cm(3). Larger tumors are less likely to be successfully resected, although factors other than brain shift can contribute to unsuccessful resection.

Perfusion imaging of high-grade gliomas: a comparison between contrast harmonic and magnetic resonance imaging

✓ Transcranial contrast harmonic (CH) imaging is emerging as a promising tool for the evaluation of brain perfusion. The authors report on two cases of histologically proven high-grade gliomas evaluated using CH imaging in comparison to perfusion magnetic resonance (pMR) imaging. In both cases, pMR imaging results demonstrated a massive decrease in signal intensity and an elevated regional cerebral blood volume (rCBV) in the tumor region; however, signal decrease was less prominent and rCBV was lower in healthy brain tissue. In one patient, the rCBV ratio of tumor/brain was 5.0 and the maximal signal decay occurred 3.1 times deeper in the tumor than in the healthy brain tissue. Results of an ultrasonography examination using CH imaging revealed similar data: the tumor/brain ratio for the area under the curve, a parameter corresponding to rCBV, was 4.1. The maximal signal intensity in the tumor was 3.3 times greater than in adjacent healthy brain. Comparable data were obtained in a second patient. Taken together, these findings indicate that CH imaging may be a valuable alternative to pMR imaging. This new, cost-effective bedside ultrasonic technique could be helpful not only as a means of noninvasive staging of gliomas but also as a follow-up imaging modality to evaluate postoperative tumor recurrence or response to antiangiogenic therapy.

Clinical results in MR-guided therapy for malignant gliomas

The prognostic impact of the extent of tumour resection in surgery of malignant glioma patients remains controversial. We report the results of cumulative survival of malignant glioma patients operated with MR-guidance. Patients with complete tumour removal were compared with a population of patients with incomplete tumour removal. A 0.5 T scanner was used to criticize the extent of resection during surgery. In total no significant difference could be found, however there is a tendency that complete tumour removal seems to be associated with a slightly increased median survival time.

Second harmonic imaging: a new ultrasound technique to assess human brain tumour perfusion

BACKGROUND

Second harmonic imaging is a new ultrasound technique that allows evaluation of brain tissue perfusion after application of an ultrasound contrast agent.

OBJECTIVE

To evaluate the potential of this technique for the assessment of abnormal echo contrast characteristics of different brain tumours.

METHODS

27 patients with brain tumours were studied. These were divided into four groups: gliomas, WHO grade III-IV (n = 6); meningiomas (n = 9); metastases (n = 5); and others (n = 7). Patients were examined by second harmonic imaging in a transverse axial insonation plane using the transtemporal approach. Following intravenous administration of 4 g (400 mg/ml) of a galactose based echo contrast agent, 62 time triggered images (one image per 2.5 seconds) were recorded and analysed off-line. Time-intensity curves of two regions of interest (tumour tissue and healthy brain tissue), including peak intensity (PI) (dB), time to peak intensity (TP) (s), and positive gradient (PG) (dB/s), as well as ratios of the peak intensities of the two regions of interest, were derived from the data and compared intraindividually and interindividually.

RESULTS

After administration of the contrast agent a marked enhancement of echo contrast was visible in the tumour tissue in all patients. Mean PI and PG were significantly higher in tumour tissue than in healthy brain parenchyma (11.8 v 5.1 dB and 0.69 v 0.16 dB/s; p < 0.001). TP did not differ significantly (37.1 v 50.2 s; p = 0.14). A tendency towards higher PI and PG as well as shorter TP was apparent in malignant gliomas. When comparing different tumour types, however, none of these variables reached significance, nor were there significant differences between malignant and benign tumours in general.

CONCLUSIONS

Second harmonic imaging not only allows identification of brain tumours, but may also help in distinguishing between different tumour types. It gives additional and alternative information about tumour perfusion. Further studies are needed to evaluate the clinical potential of this technique in investigating brain tumours-for example in follow up investigations of patients undergoing radiation or chemotherapy-especially in comparison with neuroradiological and neuropathological findings.

Evaluation of factors predicting accurate resection of high-grade gliomas by using frameless image-guided stereotactic guidance

Object

Frameless image-guided stereotaxy is often used in the resection of high-grade gliomas. The authors of several studies, however, have suggested that brain shift may occur intraoperatively and result in inaccurate resection. To determine the usefulness of frameless stereotactic image-guided surgery of high-grade gliomas, the authors correlated factors predictive of brain shift, such as tumor size, periventricular location, and patient age (as an indicator of brain atrophy) with the extent of resection.

Methods

Inclusion criteria included the following: 1) stereotactic volumetric craniotomy for resection of tumor; 2) histologically proven high-grade glioma; 3) preoperative magnetic resonance (MR) imaging demonstration of an enhancing portion of tumor; 4) postoperative MR imaging within 48 hours to assess the extent of resection; and 5) preoperative intention to perform gross-total resection of the enhancing tumor. Fifty-four patients met these criteria between September 1997 and November 2002. Accurate resection was considered to be indicated by a lack of nodular enhancement on postoperative Gd-enhanced MR images obtained within 48 hours of surgery.

Frameless stereotactic image-guided surgery resulted in the successful resection of 46 (85%) of 54 high-grade gliomas. Accurate resection was significantly more likely with tumors less than 30 ml in volume than with those greater than 30 ml (93 and 58%, respectively [p < 0.05]). In addition, small periventricular tumors were associated with significant less successful resection compared with nonperiventricular tumor (77 and 96%, respectively [p = 0.5]). Patient age did not affect the likelihood of successful resection.

Conclusions

Frameless image-guided stereotactic techniques can be reliably used for accurate resection of high-grade gliomas when the tumor is less than 30 ml in volume and not adjacent to the ventricular system. In cases involving tumors larger in volume or located near the ventricles, intraoperative ultrasonography or MR imaging updates should be considered.

Perspectives of B-mode transcranial ultrasound

Transcranial color coded sonography has proved valuable in the diagnostic work-up of cerebrovascular disorders in adults. More recently, evidences have converged that transcranial sonography is also useful in the diagnosis of brain parenchymal disorders. Here, a new field of application is the visualization of signal intensity shift in specific brain areas in some neurodegenerative disorders (Parkinson's disease, idiopathic dystonia, and depression). Findings obtained by transcranial ultrasound complement information from other neuroimaging data in these disorders and have led to the generation of new pathophysiological concepts. In this review we summarize the application fields of transcranial sonography with special emphasis on recent findings in neurodegenerative disorders and their implications for future research. As new application and processing techniques are being developed transcranial color coded sonography will gain increasing impact on both diagnosis and research of neurological disorders.

Transcranial sonography of brain tumors in the adult: an in vitro and in vivo study

BACKGROUND

Few reports indicate the potential of transcranial sonography (TCS) in detecting human brain tumors.

METHODS

With an Agilent Sonos 2500 ultrasound device, the authors studied 4 brain tumor phantoms and compared the findings with magnetic resonance imaging (MRI). TCS was performed on 40 patients with intracranial tumors in a follow-up design. Sonographic tumor volume and affection of the ventricular system were compared with MRI findings.

RESULTS

The authors found a good correlation between TCS and MRI volumetry in the in vitro study. TCS showed good intraobserver and interobserver reliability. A new volumetric formula for TCS measurement was determined. TCS detection rate of brain tumors in vivo was 40%. When the investigators were given access to radiological findings, the rate of tumor identification was 80%. Despite a sufficient acoustic window, 40% of gliomas grade II and III were not detected. One glioblastoma was not identified owing to an insufficient temporal acoustic window. Tumor volumes measured with MRI and TCS correlated well. MRI volumes exceeded TCS volumes by 41%. In the postoperative examinations (mean = 8 days postoperative, n = 15), the resection cavity was displayed as hyperechogenic. It appeared impossible to differentiate between residual tumor tissue and normal repair mechanisms or blood. In the follow-up examination (mean = 99 days postoperative, n = 15) in 5 patients, neither MRI nor TCS showed tumor regrowth. Ten patients had residual tumors that were detected by sonography.

CONCLUSIONS

The value of TCS for the diagnostics of brain tumors is at present limited. Once the tumor has been identified, sonographic results match well with those of MRI.

Comparison of intraoperative MR imaging and 3D-navigated ultrasonography in the detection and resection control of lesions

Object

The authors undertook a study to compare two intraoperative imaging modalities, low-field magnetic resonance (MR) imaging and a prototype of a three-dimensional (3D)–navigated ultrasonography in terms of imaging quality in lesion detection and intraoperative resection control.

Methods

Low-field MR imaging was used for intraoperative resection control and update of navigational data in 101 patients with supratentorial gliomas. Thirty-five patients with different lesions underwent surgery in which the prototype of a 3D-navigated ultrasonography system was used. A prospective comparative study of both intraoperative imaging modalities was initiated with the first seven cases presented here.

In 35 patients (70%) in whom ultrasonography was performed, accurate tumor delineation was demonstrated prior to tumor resection. In the remaining 30% comparison of preoperative MR imaging data and ultrasonography data allowed sufficient anatomical localization to be achieved. Detection of metastases and high-grade gliomas and intra-operative delineation of tumor remnants were comparable between both imaging modalities. In one case of a low-grade glioma better visibility was achieved with ultrasonography. However, intraoperative findings after resection were still difficult to interpret with ultrasonography alone most likely due to the beginning of a learning curve.

Conclusions

Based on these preliminary results, intraoperative MR imaging remains superior to intraoperative ultrasonography in terms of resection control in glioma surgery. Nevertheless, the different features (different planes of slices, any-plane slicing, and creation of a 3D volume and matching of images) of this new ultrasonography system make this tool a very attractive alternative. The intended study of both imaging modalities will hopefully allow a comparison regarding sensitivity and specificity of intraoperative tumor remnant detection, as well as cost effectiveness.

Transcranial sonography: integration into target volume definition for glioblastoma multiforme

PURPOSE

Recent studies indicate that transcranial sonography (TCS) reliably displays the extension of malignant brain tumors. The effect of integrating TCS into radiotherapy planning for glioblastoma multiforme (GBM) was investigated herein.

METHODS AND MATERIALS

Thirteen patients subtotally resected for GBM underwent TCS during radiotherapy planning and were conventionally treated (54 to 60 Gy). Gross tumor volumes (GTVs) and stereotactic boost planning target volumes (PTVs, 3-mm margin) were created, based on contrast enhancement on computed tomography (CT) only (PTV(CT)) or the combined CT and TCS information (PTV(CT+TCS)). Noncoplonar conformal treatment plans for both PTVs were compared. Tumor progression patterns and preoperative magnetic resonance imaging (MRI) were related to both PTVs.

RESULTS

A sufficient temporal bone window for TCS was present in 11 of 13 patients. GTVs as defined by TCS were considerably larger than the respective CT volumes: Of the composite GTV(CT+TCS) (median volume 42 ml), 23%, 13%, and 66% (medians) were covered by the overlap of both methods, CT only and TCS only, respectively. Median sizes of PTV(CT) and PTV(CT+TCS) were 34 and 74 ml, respectively. Addition of TCS to CT information led to a median increase of the volume irradiated within the 80% isodose by 32 ml (median factor 1.51). PTV(CT+TCS) volume was at median 24% of a "conventional" MRI(T2)-based PTV. Of eight progressions analyzed, three and six occurred inside the 80% isodose of the plans for PTV(CT) and for PTV(CT+TCS), respectively.

CONCLUSION

Addition of TCS tumor volume to the contrast-enhancing CT volume in postoperative radiotherapy planning for GBM increases the treated volume by a median factor of 1.5. Since a high frequency of marginal recurrences is reported from dose-escalation trials of this disease, TCS may complement established methods in PTV definition.