A simple method for MRI-assisted radiotherapy planning in brain tumors

A simple method for radiation therapy planning of brain tumors is presented. Therapy portals of midline tumors can easily be determined by comparing sagittal MRI scans with the lateral simulator radiograph. By addition of appropriately processed MR-tomograms a similar planning is possible for parasagittal tumors. Digital data exchange between different operating systems is not necessary with our simple method, problems with varying input/output standards and expensive hardware requirements are thus avoided.     

A preliminary study of pediatric brain tumors using multi-component diffusion weighted imaging

目的:探讨多b值DWI在儿童脑肿瘤中的应用价值.方法:对31例脑肿瘤患儿行EPI-DWI扫描,采用0～4000 s/mm2之间的12个b值.按照单指数模型计算低b值ADC (ADClow)(b≤200 s/mm2)、高b值ADC( ADChigh,200 s/mm2 ＜b≤4000 s/mm2)和标准ADC( ADCstandard,0 s/mm2＜b≤4000 s/mm2);按照双指数模型计算快ADC(ADCfast)、慢ADC( ADCslow)和ADCfast所占比例;用传统的单指数衰减模型计算b=800 s/mm2时的ADC值.全部病例均经病理证实,分为低级别肿瘤组和高级别肿瘤组,比较这些参数在两组肿瘤中的鉴别诊断价值.结果:ADClow、ADChigh、ADCstandard、传统的ADC、ADCfast和ADCslow在儿童高、低级别脑肿瘤间的差异均具有显著性意义(P均＜0.05).ADCslow在高、低级别脑肿瘤间的差异最大.结论:当b值在较大范围取值时,双指数模型能反映更多儿童脑肿瘤的组织特征,代表细胞内水分子扩散的ADCslow值在儿童高、低级别脑肿瘤间差异最大,此结论尚需大样本进一步验证.     

多b值DWI在儿童脑肿瘤中的初步研究

目的:探讨多b值DWI在儿童脑肿瘤中的应用价值。方法:对31例脑肿瘤患儿行EPI-DWI扫描,采用0～4000s/mm2之间的12个b值。按照单指数模型计算低b值ADC(ADClow)(b≤200s/mm2)、高b值ADC(ADChigh,200s/mm2相似文献   

Computer‐aided detection of metastatic brain tumors using automated three‐dimensional template matching

Purpose:

To demonstrate the efficacy of an automated three‐dimensional (3D) template matching‐based algorithm in detecting brain metastases on conventional MR scans and the potential of our algorithm to be developed into a computer‐aided detection tool that will allow radiologists to maintain a high level of detection sensitivity while reducing image reading time.

Materials and Methods:

Spherical tumor appearance models were created to match the expected geometry of brain metastases while accounting for partial volume effects and offsets due to the cut of MRI sampling planes. A 3D normalized cross‐correlation coefficient was calculated between the brain volume and spherical templates of varying radii using a fast frequency domain algorithm to identify likely positions of brain metastases.

Results:

Algorithm parameters were optimized on training datasets, and then data were collected on 22 patient datasets containing 79 total brain metastases producing a sensitivity of 89.9% with a false positive rate of 0.22 per image slice when restricted to the brain mass.

Conclusion:

Study results demonstrate that the 3D template matching‐based method can be an effective, fast, and accurate approach that could serve as a useful tool for assisting radiologists in providing earlier and more definitive diagnoses of metastases within the brain. J. Magn. Reson. Imaging 2010;31:85–93. © 2009 Wiley‐Liss, Inc.     

A CT method to measure hemodynamics in brain tumors: validation and application of cerebral blood flow maps

BACKGROUND AND PURPOSE: CT is an imaging technique that is routinely used for evaluating brain tumors. Nonetheless, imaging often cannot show the distinction between radiation necrosis and neoplastic growth among patients with recurrent symptoms after radiation therapy. In such cases, a diagnostic tool that provides perfusion measurements with high anatomic detail would show the separation between necrotic areas, which are characterized by low perfusion, from neoplastic areas, which are characterized by elevated CBF. We attempted to validate a dynamic contrast-enhanced CT method for the measurement of regional CBF in brain tumors, and to apply this method by creating CBF maps. METHODS: We studied nine New Zealand White rabbits with implanted brain tumors. We obtained dynamic CT measurements of CBF, cerebral blood volume (CBV), and permeability surface (PS) from the tumor, peritumor, and contralateral normal tissue regions. In all nine rabbits (two studies per rabbit), we compared CT-derived CBF values with those simultaneously obtained by the standard of reference ex vivo microsphere technique. Using CT, we examined three rabbits to assess the variability of repeated CBF and CBV measurements; we examined the other six to evaluate regional CBF reactivity to arterial carbon dioxide tensions. Finally, CT CBF maps were obtained from a rabbit with a brain tumor during normocapnia and hypocapnia. RESULTS: We found a significant linear correlation (r = 0.847) between the regional CT-and microsphere-derived CBF values, with a slope not significantly different from unity (0.99+/-0.03, P>.01). The mean difference between regional CBF measurements obtained using both methods did not significantly deviate from zero (P>.10). During normocapnia, tumor had significantly higher CBF, CBV, and PS values (P<.05) than did peritumor and normal tissues. The variability in CT-derived CBF and CBV measurements in the repeated studies was 13% and 7%, respectively. CT revealed no significantly different CBF CO2 reactivity from that determined by the microsphere method (P>.10). The CBF map of tumor regions during normocapnia showed much higher flow than normal regions manifested, and this difference was reduced on the hypocapnia CBF map. CONCLUSION: The dynamic CT method presented herein provides absolute CBF measurements in brain tumors that are accurate and precise. Preliminary CBF maps derived with this method demonstrate their potential for depicting areas of different blood flow within tumors and surrounding tissue, indicating its possible use in the clinical setting.     

Evaluation of brain tumors using positron emission tomography]

The clinical application of positron emission tomography (PET) for the evaluation of brain tumours has proved clinically valuable. Amino acid and FDG-glucose PET provide information on the degree of malignancy and the prognosis during the initial evaluation. After therapy, the residual tumour can be visualized and recurrence can be differentiated from necrosis. Amino acids have advantages over FDG for these clinical applications. Blood flow, oxygen extraction and metabolism and blood-brain barrier permeability are of minor relevance in clinical situations. Comparison of PET with MRI and MRS will provide new data. The quantitative information of the unique information yielded by PET will lead to a more important clinical role, as will the extrapolation of this experience to the SPECT technique.     

A discrimination method for the detection of pneumonia using chest radiograph

This paper presents a statistical method for the detection of lobar pneumonia when using digitized chest X-ray films. Each region of interest was represented by a vector of wavelet texture measures which is then multiplied by the orthogonal matrix Q₂. The first two elements of the transformed vectors were shown to have a bivariate normal distribution. Misclassification probabilities were estimated using probability ellipsoids and discriminant functions. The result of this study recommends the detection of pneumonia by constructing probability ellipsoids or discriminant function using maximum energy and maximum column sum energy texture measures where misclassification probabilities were less than 0.15.     

Objective symmetry detector method for gammaencephalography. IV. Investigation of brain tumours.

Sixty-six cases with possible brain tumour were objectively classified as having normal or abnormal 99TcmO4 distribution in the skull recorded by the symmetry detector method for gammaencephalography. The diagnostic accuracy in 37 confirmed tumour cases was about 95 percent. Astrocytomas I-II were seperated from astrocytomas III-IV by the degree of abnormality, and meningiomas were seperated from astrocytomas by diverging time-dependent changes in the pathologic isotope accumulation. The high diagnostic accuracy was obtained in spite of low spatial resolution and simplicity of the method. The careful choice of evaluation parameters and the restriction of their normal variance were necessary and effective in optimizing the method.     

Staging and managing lung tumors using F-18 FDG coincidence detection

PURPOSE: Fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomographic (PET) imaging can be a vital tool in the evaluation and preoperative staging of pulmonary neoplasms. Imaging studies on the gamma camera using coincidence PET (co-PET) were introduced recently into clinical practice. This prospective study assessed the efficacy of co-PET for identifying primary tumors, mediastinal lymph node involvement, the presence of distant spread, the effect on disease staging, and influence on disease management. PATIENTS AND METHODS: Sixty consecutive patients with 61 lung tumors were enrolled in the study (36 men, 24 women; age range, 32-87 years; mean age, 67 years). Histopathologic confirmation was obtained in 58 patients (59 tumors). RESULTS: In assessments of a primary lesion to establish its malignant or benign nature, the sensitivity rate of co-PET was 96% (53 of 55 lesions), the specificity rate was 83% (5 of 6 lesions), and the accuracy rate was 95% (58 of 61 lesions). In the co-PET assessment of lymph node involvement in which histopathologic confirmation was obtained (n = 32), the sensitivity rate was 89% (8 of 9 lesions), the specificity rate was 91% (21 of 23 lesions), and the accuracy rate was 91% (29 of 32 lesions). Previously unknown distant metastases were correctly identified in eight patients, but five false-positive lesions were detected in the brain. Disease staging was correctly altered in 20 patients (33%), and disease management plans were changed in 20 patients (33%) based on the co-PET findings. Unnecessary surgery was obviated in six patients (10%). One patient was given the chance for curative treatment based on the findings of the co-PET study. CONCLUSION: The evaluation of patients with lung neoplasms using F-18 FDG coincidence detection appears to be reliable.     

MR imaging of the brain: tumors

The radiologic modality that most likely provides the imaging information needed in a patient suspected of having a brain tumor is MR imaging. A brain tumor can be reliably ruled out if the MR examination is performed properly and experts interpret the results as negative. If there is a tumor, however, its exact location and topography must be determined. Important for therapy and prognosis are also tumor properties such as histologic type and grade, as well as effects on adjacent brain structures. Although potentially a noninvasive method of in vivo neuropathology, MR is still far from being sufficiently specific, as dissimilar lesions may look the same despite the use of refined imaging protocols. The evolution of MR imaging continues, however, making further methodologic improvement likely. Presently, advanced methods, such as diffusion- and perfusion-weighted MR imaging, functional MR imaging, neuronavigation based on MR imaging data, and the use of MR imaging during surgery (intraoperative MR imaging), influence the way patients are treated. Likewise, follow-up imaging (monitoring) of tumor patients by MR has become more effective, and experience has shown how to distinguish reactive changes from recurrent tumor. In the future, MR imaging may gain importance in the development of novel therapeutic concepts.     

Neonatal brain tumors: CT and MR findings

Twelve neonatal brain tumors, presenting within 60 days of birth, constituted 3.3% of pediatric brain tumors. Three-fourths were supratentorial. Two-thirds were benign. Forty-two percent were choroid plexus papilloma. Twenty-five percent were teratoma. Eight percent each were hypothalamic glioma, gliosarcoma, medulloblastoma, and primitive neuroectodermal tumor. Clinical symptoms were nonspecific. Signs of herniation were absent in all 12 patients. Forty-two percent of these patients died 1 day to 8 months after diagnosis. Ultrasound, CT, and magnetic resonance have all proved useful for displaying these lesions suitably for surgery.     

Thallium-201 imaging of brain tumors using single photon emission CT

Single photon emission CT using thallium-201 chloride, injected intravenously, was performed on 28 cases of cerebral lesions, among which were 16 gliomas, 2 meningiomas, 5 other brain tumors, 3 metastatic brain tumors and 2 cerebral radiation necroses. The degree of thallium-201 accumulation was evaluated by a new method called the thallium index (TLI); that is, TLI was expressed as (T-C)/C (T and C indicate relative counts in a pixel of a lesion and in non-affected normal brain tissue, respectively). Thallium-201 accumulation occurred in 86% (24) of the evaluated cases. In general, there was a tendency in high-grade or recurrent gliomas, as well as in metastatic brain tumors for the TLI values to be high. Moreover, high TLI values were noticed in cases of meningioma, radiation necrosis of cerebellum and in cases involving subacute stages of cerebral infarction. It is particularly noteworthy that the meningioma TLI values were about two times higher than those of the glioblastomas. The CT contrast-enhancement of lesions was clearly correlated with the TLI values, and the relationship between the TLI values and the number of vessels observed microscopically in the specimen was statistically significant. From the above results, it was concluded that thallium-201 accumulation in lesions might be strongly influenced by the development of vascularity in lesions, and/or the interference with the blood brain barrier due to the tumor itself. However, this malignancy diagnostic method is probably limited to the diagnosis of glioma.