Impact of 80 kVp with iterative reconstruction algorithm and low-dose contrast medium on the image quality of craniocervical CT angiography.

PURPOSE: To assess the image quality of 80-kVp craniocervical CT angiography (CCCTA) protocol combined with adaptive statistical iterative reconstruction-V (ASIR-V) and low-dose contrast medium (CM). METHODS: A total of 119 patients were randomly divided into three groups. For group A, 120-kVp protocol was followed with 60 ml CM and filtered back projection; for group B, 80-kVp protocol with 60 ml CM and ASIR-V; and for group C, 80-kVp protocol with 45 ml CM and ASIR-V. Both subjective and objective image quality and radiation doses were evaluated. RESULTS: Arterial attenuation, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the head, neck, and shoulder regions were significantly higher in groups B and C compared with group A. Group C yielded significantly better subjective image quality than that observed in groups A and B (both p < .05). As compared with group A, effective radiation dose and the iodine load of group C were reduced by 51.4% and 25%, respectively. CONCLUSIONS: The CCCTA protocol with 80 kVp, ASIR-V, and 45 ml of CM injected at 3 ml/s significantly reduced the radiation dose, iodine load, and iodine delivery rate while providing better subjective and objective image quality, including higher arterial enhancement and a higher SNR and CNR compared with the 120-kVp protocol.

Susceptibility-weighted imaging provides complementary value to diffusion-weighted imaging in the differentiation between pyogenic brain abscesses, necrotic glioblastomas, and necrotic metastatic brain tumors.

PURPOSE: The purpose of this retrospective study was to investigate the differentiation of abscess and necrotic tumors, using susceptibility-weighted imaging (SWI) and apparent diffusion coefficients (ADC) either separated or combined. METHODS: Imaging was performed on 26 patients with pyogenic brain abscesses, 31 patients with rim-enhancing glioblastomas, and 21 patients with rim-enhancing metastases. The degree of intralesional susceptibility signal (ILSS) was independently assessed by three observers. Average ADC in the lesion core was calculated. After receiver operating characteristic (ROC) analysis, the area under the ROC curve was compared using three different analytical models (ILSS, ADC, and ILSS-ADC combined) to differentiate abscess from the two rim-enhancing necrotic tumors. RESULTS: The ILSS-ADC combined model had greater area under the ROC curves than ILSS or ADC used alone. In this study, the ILSS-ADC combined model showed 100% diagnostic accuracy differentiating abscesses from glioblastoma. The ADC model and the ILSS-ADC combined model performed equally well in distinguishing abscesses from metastases. CONCLUSION: It is concluded that SWI and ADC are complementary, and the combination of SWI and ADC may improve results compared with the use of only one model. Validation by an independent cohort is the next necessary step to broaden its applicability in routine clinical settings.

Coexistence of intracranial solitary fibrous tumor/hemangiopericytoma and right middle cerebral artery aneurysm.

Intracranial solitary fibrous tumors are rare mesenchymal neoplasms originating in the meninges and constitute a heterogeneous group of rare spindle cell tumors that include benign and malignant neoplasms of which hemangiopericytoma is nowadays considered a cellular phenotypic variant. From literatures, the incidence of coexistence of brain tumors and intracranial aneurysms is ~0.7-5.4%. Meningioma is the most frequent tumor coexisted with intracranial aneurysms, followed by pituitary adenoma, neuroepithelial tumor, and metastatic tumor. We would like to report a case of 74-year-old man harboring a rare intracranial solitary fibrous tumor/hemangiopericytoma and an unruptured aneurysm of the right middle cerebral artery which probably the first report of these combinations in the English literature. Both lesions were treated surgically in one session with favorable outcome. Magnetic resonance angiography should be performed in patients with brain tumor preoperatively not only to visualize neoplastic vascularization but also to pick up incidental aneurysm.

Combination of Adaptive Statistical Iterative Reconstruction-V and Lower Tube Voltage During Craniocervical Computed Tomographic Angiography Yields Better Image Quality with a Reduced Radiation Dose.

RATIONALE AND OBJECTIVES: To evaluate image quality and radiation exposure when using the adaptive statistical iterative reconstruction-V (ASIR-V) algorithm for reconstructing craniocervical computed tomographic angiography images acquired at 100 kVp. MATERIALS AND METHODS: We randomly divided 121 patients into three groups: group A (conventional protocol), 120 kVp with filtered back projection; group B, 120 kVp with 50% ASIR-V; and group C, 100 kVp with 50% ASIR-V. All patients underwent scans in a 256-slice computed tomography (CT) scanner. Radiation dose (volume CT dose index), dose-length product, and effective dose, objective parameters such as arterial attenuation value, signal-to-noise ratio, contrast-to-noise ratio, and noise obtained at head, neck, and shoulder levels were compared among the groups. Subjective image quality was independently assessed by two radiologists, and interobserver reliability was assessed using kappa analysis. RESULTS: The radiation dose in group C was the lowest (p < 0.01) with a 40% reduction in volume CT dose index, dose-length product, and effective dose values compared to group A, and group C showed higher arterial attenuation than either group A or B (p < 0.01). Additionally, signal-to-noise ratio and contrast-to-noise ratio were higher and noise was lower in groups B and C than group A. Group C had better subjective image quality than groups A and B (p < 0.05), and the interobserver reliability between the two radiologists was high (k = 0.783). CONCLUSION: Compared to the conventional protocol, using 50% ASIR-V and the 100 kVp protocol during craniocervical computed tomographic angiography yields better objective and subjective image quality at lower radiation doses.

Discriminating pyogenic brain abscesses, necrotic glioblastomas, and necrotic metastatic brain tumors by means of susceptibility-weighted imaging.

OBJECTIVES: To investigate the feasibility of using susceptibility-weighted imaging (SWI) to discriminate abscesses and necrotic tumours. METHODS: Twenty-one patients with pyogenic abscesses, 21 patients with rim-enhancing glioblastomas and 23 patients with rim-enhancing metastases underwent SWI. Intralesional susceptibility signal (ILSS) was analyzed employing both qualitative (QL) and semi-quantitative (SQ) methods. Logistic regression models and receiver operating characteristic analysis were used to demonstrate the discriminating power. RESULTS: In QL analysis, ILSSs were seen in 12 of 21 abscesses, in 20 of 21 glioblastomas, and in 16 of 23 metastases. In SQ analysis, a low degree of ILSS (85.8 %) was in the majority of abscesses and a high degree of ILSS (76.2 %) was in the majority of glioblastomas. SQ model was significantly better than QL model in distinguishing abscesses from glioblastomas (P < .001). A derived ILSS cutoff grade of 1 or less was quantified as having a sensitivity of 85.7 %, specificity of 90.5 %, accuracy of 88.1 %, PPV of 90.0 %, and NPV of 86.4 % in distinguishing abscesses from glioblastomas. CONCLUSIONS: A high-grade ILSS may help distinguish glioblastomas from abscesses and necrotic metastatic brain tumours. The lack of ILSS or low-grade ILSS can be a more specific sign in the imaging diagnosis of abscesses. KEY POINTS: • ILSS of SWI can contribute to differential diagnosis of rim-enhanced mass. • Low-grade ILSS can be a more specific sign in abscesses. • High-grade ILSS may help distinguish necrotic glioblastomas from abscesses. • ILSS spreads across the four ILSS categories in metastases.

Endovascular salvage of immature autogenous hemodialysis fistulas.

PURPOSE: To report the technical success and long-term clinical outcomes of immature arteriovenous fistula (AVF) after percutaneous angioplasty (PTA). MATERIALS AND METHODS: Patients with 58 immature AVF underwent PTA treatment in our institute during the past 9 years. Based on pretreatment ultrasound findings, the immature AVFs were categorized as stenosed, thrombosed, and obliterated type. An optimal entry site was punctured under ultrasound guidance followed by conventional fluoroscopy-guided PTA technique. Technical and clinical success as well as complications were recorded. Patency after angioplasty was estimated using Kaplan-Meier analysis. Predictors of patency were estimated using log-rank test. RESULTS: In our series, 50 % (29 of 58), 20.7 % (12 of 58), and 29.3 % (17 of 58) of immature AVF were stenosed, thrombosed, and obliterated, respectively. Technical and clinical success was achieved in 96.6 % (56 of 58) of cases with 100 % success in both the stenosed and thrombosed lesions and 88.2 % (15 of 17) success in the obliterated lesions. Vascular ruptures occurred in 12.1 % (7 of 58) of lesions. The overall primary and secondary patency rates of the 58 lesions were 45.4 and 84.2 % at 12 months and 36.5 and 80.1 % at 36 months. There were no significant differences of patency between the three types of lesions (p = 0.075 and 0.093) and the two groups of patients with or without residual side branches after intervention (p = 0.527 and 0.644). There was a significant difference of primary patency in patients with vascular rupture (p = 0.012) with a hazard ratio of 3.236. CONCLUSION: PTA could effectively prolong the lifetime of immature AVFs with high technical success. Vessel rupture was predictive of shorter primary patency, and long-term secondary patency was acceptable.

Proton MR spectroscopy in patients with pyogenic brain abscess: MR spectroscopic imaging versus single-voxel spectroscopy.

PURPOSE: Single-voxel spectroscopy (SVS) has been the gold standard technique to diagnose the pyogenic abssess. Two-dimensional magnetic resonance spectroscopic imaging (MRSI) is able to provide spatial distribution of metabolic concentration, and is potentially more suitable for differential diagnosis between abscess and necrotic tumors. Therefore, the purpose of this study was to evaluate the equivalence of MRSI and SVS in the detection of the metabolites in pyogenic brain abscesses. MATERIALS AND METHODS: Forty-two patients with pyogenic abscesses were studied by using both SVS and MRSI methods. Two neuroradiologists reviewed the MRS data independently. A κ value was calculated to express inter-reader agreement of the abscesses metabolites, and a correlation coefficient was calculated to show the similarity of two spectra. After consensus judgment of two readers, the binary value of metabolites of pyogenic abscesses (presence or absence) was compared between SVS and MRSI. RESULTS: The consistency of spectral interpretation of the two readers was very good (κ ranged from 0.95 to 1), and the similarity of two spectra was also very high (cc=0.9±0.05). After consensus judgment of two readers, the sensitivities of MRSI ranged from 91% (acetate) to 100% (amino acids, succinate, lactate, lipid), and the specificities of MRSI were 100% for detecting all metabolites with SVS as reference. CONCLUSION: SVS and MRSI provide similar metabolites in the cavity of pyogenic brain abscess. With additional metabolic information of cavity wall and contralateral normal-appearing brain tissue, MRSI would be a more suitable technique to differentiate abscesses from necrotic tumors.

Multilayer appearance on contrast-enhanced susceptibility-weighted images on patients with brain abscesses: Possible origins and effects of postprocessing.

PURPOSE: To demonstrate the presence of a multilayer appearance of the capsule on contrast-enhanced (CE) susceptibility-weighted imaging (SWI) in patients with pyogenic brain abscesses. Possible origins for the appearance and effects of postprocessing settings are discussed. MATERIALS AND METHODS: Fourteen patients with pyogenic brain abscesses underwent post gadolinium-enhanced SWI at 1.5 T. All SWI images were postprocessed with various filter and mask settings to compare the image appearance. Computer simulations using a paramagnetic spherical shell model were performed to verify the clinical findings. RESULTS: Pyogenic brain abscesses demonstrated a multilayer appearance with a darkened ring within the enhanced capsule on CE-SWI in all patients. The multilayer appearance was slice-orientation-dependent, decreased with larger widths of the high-pass filter, and increased with larger numbers of phase mask multiplication operations, consistently on both simulation results and the clinical images. CONCLUSION: CE-SWI shows the multilayer appearance of the capsule in pyogenic brain abscesses, which may arise from postprocessing procedures originally designed to enhance susceptibility contrast. Although SWI may provide additional information valuable in the diagnosis of pyogenic brain abscesses, image interpretation should be exercised with caution, particularly for CE-SWI.

Comparison of real-time three-dimensional gadolinium-enhanced elliptic centric-ordered MR venography and two-dimensional time-of-flight MR venography of the intracranial venous system.

BACKGROUND: To compare 3-dimensional gadolinium-enhanced elliptic centric-ordered (3D GEC) magnetic resonance venography (MRV) with traditional 2-dimensional time-of-flight (2D TOF) MRV for imaging of the intracranial venous system. METHODS: Fifty-three patients underwent 2D and 3D MRV, whereby venous structures were evaluated by 2 neuroradiologists. RESULTS: Of the 53 patients, 10 were diagnosed with dural venous sinus thrombosis and 12 with intracranial tumors. 3D GEC MRV displayed superior sensitivity/specificity (90.9%/96.8%) compared to 2D TOF MRV (63.6%/48.4%). Analysis of the areas under the receiver operating characteristic curves also showed superiority of 3D GEC (0.91) versus 2D TOF (0.53) MRV. Of the remaining 31 healthy patients, the rate of complete visibility of venous structures was also greater for 3D GEC (95.8%) than for 2D TOF (62.1%) MRV. CONCLUSION: 3D GEC MRV is superior to 2D TOF MRV for providing more detail of the intracranial venous system, and can lead to better diagnosis of venous conditions.

Cerebral pilocytic astrocytoma with spontaneous intracranial hemorrhage in adults.

Pilocytic astrocytomas are found predominantly in the pediatric population; reports of these tumors are extremely rare in adults. We report 2 cases of adult pilocytic astrocytoma with intracranial hemorrhage. A 32-year-old male presented with neck stiffness and severe headache, and a 34-year-old male was referred for headache and double vision. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a well-enhanced and circumscribed cystic hemorrhagic tumor with mural nodule over the cerebral hemisphere region. Perfusion-weighted MRI (PWI) was also performed in both patients. The measured relative cerebral blood volume ratios of the mural nodules in these 2 cases were, respectively, 1.34 and 2.81 when compared with normal white matter. After surgical resection, microscopic examination of the lesions showed pilocytic astrocytomas. Since pilocytic astrocytoma and other cystic tumors with mural nodule (such as hemangioblastoma) have similar findings on conventional CT and MRI, PWI is helpful in the differential diagnosis. The literature on hemorrhagic pilocytic astrocytoma is also reviewed.

Proton magnetic resonance spectroscopy and diffusion-weighted imaging in intracranial cystic mass lesions.

BACKGROUND: The differential diagnosis of various intracranial cystic lesions is sometimes difficult on the basis of CT or MRI findings. Our objective was to evaluate (1)H MRS and DWI in the differential diagnosis of these lesions and in comparison with conventional MRI. METHODS: Fifty patients with intracranial cystic lesions (21 pyogenic abscesses, 23 tumor cysts, 3 epidermoid cysts, and 3 arachnoid cysts) were evaluated with conventional MRI, DWI, and in vivo (1)H MRS. Preoperative diagnosis of the lesions was based on the results of DWI and in vivo MRS. All DWI and (1)H MRS studies were performed with a clinical 1.5-T system. The DWI was performed using single-shot spin-echo echo-planar pulse sequence with b = 1000 s/mm(2). The ADC value was measured. Diagnostic accuracy of conventional MRI, DWI, and in vivo (1)H MRS was calculated with respect to a final diagnosis of brain abscess vs nonabscess cystic tumor. RESULTS: Lactate and cytosolic amino acids with/without succinate, acetate, and alanine were observed in 18 of 21 cases of abscesses on MRS. In 3 cases of epidermoid cysts, lactate was observed and could be differentiated from 3 cases of arachnoid cysts, which showed only minimal lactate. Only lactate was seen in 14 of 23 patients with tumor cysts, whereas both lipid/lactate and choline were visible in 9 patients with tumor cysts. Increased signal was seen in 20 of 21 patients with abscesses and 3 patients with epidermoid cysts on DWI. Decreased signal was observed in 22 of 23 patients with tumor cysts and 3 patients with arachnoid cyst on DWI. Diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of conventional MRI for the differentiation of brain abscess from nonabscess cystic tumor were 61.4%, 61.9%, 60.9%, 59.1%, and 63.6%, respectively, whereas they were 93.2%, 85.7%, 100%, 100%, and 88.5% with MRS; 95.5%, 95.2%, 95.7%, 95.2%, and 95.7% with DWI; and 97.7%, 95.2%, 100%, 100%, and 95.8% with MRS and DWI. Magnetic resonance imaging, when combined with in vivo MRS and DWI, accurately predicted the diagnosis in 47 (94%) of 50 and 48 (96%) of 50 of the cases, respectively. CONCLUSIONS: Proton MRS and DWI are useful as additional diagnostic modalities in differentiating intracranial cystic lesions. Combination of DWI with calculated ADC values and metabolite spectrum acquired by MRS add more information to MRI in the differentiation of intracranial cystic mass lesions.

Percutaneous endovascular repair of a ureteroarterial fistula with a stent graft.

Ureteroarterial fistula is a rare but life-threatening cause of hematuria. The predisposing factors of a ureteroarterial fistula includes pelvic exenteration, radiation therapy, infection, primary vascular disease, vascular reconstructive surgery, and indwelling ureteral catheters or stents. We report a case of ureteroarterial fistula between the right ureter and a pseudoaneurysm originating from the right proximal external iliac artery in a female patient presenting with intermittent massive hematuria. She had previously undergone an operation for cervical cancer, radiation therapy, and ureteral stent placement. She was treated successfully by percutaneous endovascular stent graft placement to exclude the pseudoaneurysm. Percutaneous stent graft placement appears to be an effective and safe therapeutic alternative in the treatment of ureteroarterial fistula.