Santanu Chakraborty

Evolution of Computed Tomography Angiography Spot Sign Is Consistent With a Site of Active Hemorrhage in Acute Intracerebral Hemorrhage

Background and Purpose— CT angiography spot sign predicts hematoma expansion in patients with acute intracerebral hemorrhage (ICH). The spot sign may represent a site of active extravasation, a locus of arrested hemorrhage forming fibrin globes, or represent associated epiphenomena such as hypertensive microaneurysms. We sought to describe the evolution of spot signs over 60 seconds in acute ICH using dynamic CT angiography and determine whether they grow and diffuse into the hematoma as would be expected with active extravasation. Methods— We prospectively identified consecutive patients presenting with spontaneous ICH <6 hours from symptom onset that completed dynamic CT angiography imaging over a 60-second acquisition protocol. We determined spot positivity, quantified spot volumes, and then used repeated-measures ANOVA to assess changes in spot volume over time. Results— We collected data on 35 patients; 13 of 35 (37%) patients were spot-positive. Spot-positive patients had larger median ICH volume compared with spot-negative patients (median 10.7 versus 49.2 mL; P=0.007). Maximal spot sign volumes ranged from 0.02 to 2.8 mL (median 0.17 mL). Spot sign volumes increased significantly with time (P<0.001) and seemed to disperse into the hematoma in all cases. Three of 13 (23%) spot-positive patients presented with 2 distinct spot signs, but the remaining patients either had only 1 spot sign or different contiguous components of an irregularly shaped spot sign. Conclusions— In this dynamic CT angiography study of ICH, spot signs evolve consistent with sites of active extravasation.

Vertebral Artery Dissection with a Normal-Appearing Lumen at Multisection CT Angiography: The Importance of Identifying Wall Hematoma

BACKGROUND AND PURPOSE: CT angiography (CTA) is widely used and may be the only vascular imaging technique ordered for emergent evaluation of neurovascular disease. With thin-section multisection CTA, the resolution of vessel wall imaging has improved. We describe cases of acute vertebral artery dissection (VAD) in which the only abnormality on CTA was a characteristic thickening of the wall of the V3 portion of the vertebral artery (VA). The arterial lumen at the dissection site was normal in caliber. This type of dissection is easily overlooked if only lumen-opacifying studies such as contrast MR angiography (MRA) or conventional angiography are performed. We highlight the importance of recognizing this finding, the “suboccipital rind” sign, in the V3 portion, a segment commonly affected in VAD. The purpose of our study was to review the CTA imaging characteristics of patients with VAD in the V3 portion compared with normal controls. MATERIALS AND METHODS: Our imaging data base was reviewed for cases of acute VAD and the presence of a “suboccipital rind” sign. A control group of 50 patients was randomly recruited from a group of patients undergoing CTA. The VA luminal diameter, the wall thickness (total diameter−luminal diameter), and the ratio of luminal diameter/total diameter were measured along 5 adjacent V3 segments and were compared between the 2 groups. RESULTS: There was no evidence of luminal tapering or narrowing in the dissected VAs compared with controls (P = .1). The average wall thickness of the dissection group was 2.96 mm greater than that for the control group (P < .001; 95% confidence interval, 2.6–3.3). There was a significant difference in the ratio of lumen diameter/lumen+wall diameter in dissected segments compared with controls (P < .001). CONCLUSIONS: Cross-sectional vascular imaging is often performed with multisection helical CTA for a variety of concerns, some without neurologic symptoms. Our study confirms that in cases of the “suboccipital rind” sign, the lumen appears normal in caliber, with wall thickening as the only imaging sign of VAD. In our center, this clinically occult VAD would influence management, with patients usually treated with antiplatelet agents. We caution against using only luminal-opacifying techniques such as contrast-enhanced MRA or conventional angiography to exclude VAD because they are limited in the evaluation of mural hematoma.

Diagnostic Accuracy of Dynamic Contrast-Enhanced MR Imaging Using a Phase-Derived Vascular Input Function in the Preoperative Grading of Gliomas

BACKGROUND AND PURPOSE: The accuracy of tumor plasma volume and Ktrans estimates obtained with DCE MR imaging may have inaccuracies introduced by a poor estimation of the VIF. In this study, we evaluated the diagnostic accuracy of a novel technique by using a phase-derived VIF and “bookend” T1 measurements in the preoperative grading of patients with suspected gliomas. MATERIALS AND METHODS: This prospective study included 46 patients with a new pathologically confirmed diagnosis of glioma. Both magnitude and phase images were acquired during DCE MR imaging for estimates of Ktrans_ϕ and Vp_ϕ (calculated from a phase-derived VIF and bookend T1 measurements) as well as Ktrans_SI and Vp_SI (calculated from a magnitude-derived VIF without T1 measurements). RESULTS: Median Ktrans_ϕ values were 0.0041 minutes−1 (95 CI, 0.00062–0.033), 0.031 minutes−1 (0.011–0.150), and 0.088 minutes−1 (0.069–0.110) for grade II, III, and IV gliomas, respectively (P ≤ .05 for each). Median Vp_ϕ values were 0.64 mL/100 g (0.06–1.40), 0.98 mL/100 g (0.34–2.20), and 2.16 mL/100 g (1.8–3.1) with P = .15 between grade II and III gliomas and P = .015 between grade III and IV gliomas. In differentiating low-grade from high-grade gliomas, AUCs for Ktrans_ϕ, Vp_ϕ, Ktrans_SI, and Vp_SI were 0.87 (0.73–1), 0.84 (0.69–0.98), 0.81 (0.59–1), and 0.84 (0.66–0.91). The differences between the AUCs were not statistically significant. CONCLUSIONS: Ktrans_ϕ and Vp_ϕ are parameters that can help in differentiating low-grade from high-grade gliomas.

Preoperative Prognostic Value of Dynamic Contrast-Enhanced MRI–Derived Contrast Transfer Coefficient and Plasma Volume in Patients with Cerebral Gliomas

BACKGROUND AND PURPOSE: The prognostic value of dynamic contrast-enhanced MR imaging–derived plasma volume obtained in tumor and the contrast transfer coefficient has not been well-established in patients with gliomas. We determined whether plasma volume and contrast transfer coefficient in tumor correlated with survival in patients with gliomas in addition to other factors such as age, type of surgery, preoperative Karnofsky score, contrast enhancement, and histopathologic grade. MATERIALS AND METHODS: This prospective study included 46 patients with a new pathologically confirmed diagnosis of glioma. The contrast transfer coefficient and plasma volume obtained in tumor maps were calculated directly from the signal-intensity curve without T1 measurements, and values were obtained from multiple small ROIs placed within tumors. Survival curve analysis was performed by dichotomizing patients into groups of high and low contrast transfer coefficient and plasma volume. Univariate analysis was performed by using dynamic contrast-enhanced parameters and clinical factors. Factors that were significant on univariate analysis were entered into multivariate analysis. RESULTS: For all patients with gliomas, survival was worse for groups of patients with high contrast transfer coefficient and plasma volume obtained in tumor (P < .05). In subgroups of high- and low-grade gliomas, survival was worse for groups of patients with high contrast transfer coefficient and plasma volume obtained in tumor (P < .05). Univariate analysis showed that factors associated with lower survival were age older than 50 years, low Karnofsky score, biopsy-only versus resection, marked contrast enhancement versus no/mild enhancement, high contrast transfer coefficient, and high plasma volume obtained in tumor (P < .05). In multivariate analysis, a low Karnofsky score, biopsy versus resection in combination with marked contrast enhancement, and a high contrast transfer coefficient were associated with lower survival rates (P < .05). CONCLUSIONS: In patients with glioma, those with a high contrast transfer coefficient have lower survival than those with low parameters.

Comparison of the Diagnostic Accuracy of DSC- and Dynamic Contrast-Enhanced MRI in the Preoperative Grading of Astrocytomas

BACKGROUND AND PURPOSE: Dynamic contrast-enhanced MR imaging parameters can be biased by poor measurement of the vascular input function. We have compared the diagnostic accuracy of dynamic contrast-enhanced MR imaging by using a phase-derived vascular input function and “bookend” T1 measurements with DSC MR imaging for preoperative grading of astrocytomas. MATERIALS AND METHODS: This prospective study included 48 patients with a new pathologic diagnosis of an astrocytoma. Preoperative MR imaging was performed at 3T, which included 2 injections of 5-mL gadobutrol for dynamic contrast-enhanced and DSC MR imaging. During dynamic contrast-enhanced MR imaging, both magnitude and phase images were acquired to estimate plasma volume obtained from phase-derived vascular input function (Vp_Φ) and volume transfer constant obtained from phase-derived vascular input function (Ktrans_Φ) as well as plasma volume obtained from magnitude-derived vascular input function (Vp_SI) and volume transfer constant obtained from magnitude-derived vascular input function (Ktrans_SI). From DSC MR imaging, corrected relative CBV was computed. Four ROIs were placed over the solid part of the tumor, and the highest value among the ROIs was recorded. A Mann-Whitney U test was used to test for difference between grades. Diagnostic accuracy was assessed by using receiver operating characteristic analysis. RESULTS: Vp_ Φ and Ktrans_Φ values were lower for grade II compared with grade III astrocytomas (P < .05). Vp_SI and Ktrans_SI were not significantly different between grade II and grade III astrocytomas (P = .08–0.15). Relative CBV and dynamic contrast-enhanced MR imaging parameters except for Ktrans_SI were lower for grade III compared with grade IV (P ≤ .05). In differentiating low- and high-grade astrocytomas, we found no statistically significant difference in diagnostic accuracy between relative CBV and dynamic contrast-enhanced MR imaging parameters. CONCLUSIONS: In the preoperative grading of astrocytomas, the diagnostic accuracy of dynamic contrast-enhanced MR imaging parameters is similar to that of relative CBV.

Radiological and Pathological Features Associated with IDH1-R132H Mutation Status and Early Mortality in Newly Diagnosed Anaplastic Astrocytic Tumours

Background Glioblastoma can occur either de novo or by the transformation of a low grade tumour; the majority of which harbor a mutation in isocitrate dehydrogenase (IDH1). Anaplastic tumours are high-grade gliomas that may represent the final step in the evolution of a secondary glioblastoma or the initial presentation of an early primary glioblastoma. We sought to determine whether pathological and/or radiological variables exist that can reliably distinguish IDH1-R132H-positive from IDH1-R132H-negative tumours and to identify variables associated with early mortality. Methods Patients diagnosed with anaplastic astrocytic tumours were included. Magnetic resonance imaging was performed and immunohistochemistry was used to identify tumours with the IDH1-R132H mutation. Survival was assessed 12 months after diagnosis. Variables associated with IDH1-R132H status were identified by univariate and ROC analysis. Results 37 gliomas were studied; 18 were positive for the IDH1-R132H mutation. No tumours demonstrated a combined loss of chromosomes 1p/19q. Patients with IDH1-R132H-positive tumours were less likely to die within 12 months of diagnosis (17% vs. 47%; p=0.046), more likely to have tumours located in the frontal lobe (55% vs. 16%; p=0.015), and have a higher minimum apparent diffusion coefficient (1.115 x 10-3 mm2/sec vs. 0.838 x 10-3 mm2/sec; p=0.016), however, these variables demonstrated only moderate strength for predicting the IDH1-R132H mutation status (AUC=0.735 and 0.711, respectively). The Ki-67 index was significantly lower in IDH1-R132H-positive tumours (0.13 vs. 0.21; p=0.034). An increased risk of death was associated with contrast-enhancement ≥ 5 cm3 in patients with IDH1-R132H-positive tumours while edema ≥ 1 cm beyond the tumour margin and < 5 mitoses/mm2 were associated with an increased risk of death in patients with IDH1-R132H-negative tumours. Conclusions IDH1-R132H-positive and -negative anaplastic tumours demonstrate unique features. Factors associated with early mortality are also dependent on IDH1-R132H status and can be used to identify patients at high risk for death.

Canadian Expert Panel Recommendations for MRI Use in MS Diagnosis and Monitoring

Background: A definitive diagnosis of multiple sclerosis (MS), as distinct from a clinically isolated syndrome, requires one of two conditions: a second clinical attack or particular magnetic resonance imaging (MRI) findings as defined by the McDonald criteria. MRI is also important after a diagnosis is made as a means of monitoring subclinical disease activity. While a standardized protocol for diagnostic and follow-up MRI has been developed by the Consortium of Multiple Sclerosis Centres, acceptance and implementation in Canada have been suboptimal. Methods: To improve diagnosis, monitoring, and management of a clinically isolated syndrome and MS, a Canadian expert panel created consensus recommendations about the appropriate application of the 2010 McDonald criteria in routine practice, strategies to improve adherence to the standardized Consortium of Multiple Sclerosis Centres MRI protocol, and methods for ensuring effective communication among health care practitioners, in particular referring physicians, neurologists, and radiologists. Results: This article presents eight consensus statements developed by the expert panel, along with the rationale underlying the recommendations and commentaries on how to prioritize resource use within the Canadian healthcare system. Conclusions: The expert panel calls on neurologists and radiologists in Canada to incorporate the McDonald criteria, the Consortium of Multiple Sclerosis Centres MRI protocol, and other guidance given in this consensus presentation into their practices. By improving communication and general awareness of best practices for MRI use in MS diagnosis and monitoring, we can improve patient care across Canada by providing timely diagnosis, informed management decisions, and better continuity of care.

Canadian Association of Radiologists Radiation Protection Working Group: Review of Radiation Units and the Use of Computed Tomography Dose Indicators in Canada

Radiation has played a vital role in health care for overa century now. Since Roentgen’s first radiograph in 1895, themedical imaging community has made tremendous advanceswith imaging technology, leading to earlier detectionof disease, minimally invasive approaches to diagnosisand therapy, and, most importantly, improved patientoutcome.Ionizing radiation can directly damage tissue and isrecognized by multiple national and international bodies asa weak carcinogen [1e3]. Direct tissue damage is referred toas the deterministic effect of radiation and will occur afterthe patient receives a radiation dose that exceeds a threshold,whereas the risk of cancer is referred to as a random orstochastic effect, with the probability of developing cancerincreasing with increasing radiation dose to the patient. Bothdeterministic and stochastic effects are a function ofradiation dose, a concept with multiple terminologies thathas led to significant confusion in practice. With an increasedreliance on medical imaging for patient care, both the short-and long-term risks associated with each imaging proceduremust be understood by all practitioners. The CanadianAssociation of Radiologists (CAR) has formed the RadiationProtection Working Group (RPWG) to provide leadership ondose education in Canada. This group aims to developstandards on diagnostic medical radiation protection todecrease patient risk and provide the CAR membership withinformation, online dose-calculating tools, and a forum todiscuss medical radiation dose in Canada.In this first essay, 3 important concepts will be discussed:radiation risk models, radiation units and the dose deliveredby medical imaging systems, and the estimated radiationdose received by the patient. Because computed tomographic(CT) examinations account for the majority of total radiationreceived by patients, especially when considering thedisproportionately lower examination frequency comparedwith other medical imaging examinations [4,5], theseconcepts will be discussed with a specific emphasize on dosefrom common CT examinations.

The evaluation of MRI diffusion values of active demyelinating lesions in multiple sclerosis

BACKGROUND Gadolinium (Gd) enhancement of lesions is the main radiologic marker for detection of activity in Multiple Sclerosis (MS). This study compares Diffusion weighted imaging (DWI) characteristics and enhancement to determine whether DWI can be used as an alternative to Gd administration. METHODS A retrospective study of 72 patients who had MRI with Gd and DWI. Visual assessment and comparison of the Apparent Diffusion Coefficient (ADC) values on Gd+ lesions, all lesions showing restricted diffusion, 2 Gd- lesions and 1 area of normal-appearing white matter (NAWM) in each MRI were performed. RESULTS DWI values were measured on 275 T2 lesions, 68 Gd+ and 207 Gd- lesions, as well as 104 NAWM. 34 Gd+ lesions showed restricted diffusion. The median ADC-minimum of Gd+ lesions was significantly lower than NAWM and even lower than Gd- lesions. Most DWI restricted lesions were also Gd+(specificity≥94%), however many Gd+ lesions did not show visually detectable restriction in DWI (sensitivity≤34%). The median ADC-minimum of symptomatic lesions was lower than asymptomatic lesions. CONCLUSION While Gd+ lesions have lower ADC-minimum, visual DWI assessment cannot replace Gd administration for identifying active lesions. Gd+ lesions showing restricted diffusion are clinically important as they are more likely associated with neurological symptoms.

Evolving role of MRI in optimizing the treatment of multiple sclerosis: Canadian Consensus recommendations

Background Magnetic resonance imaging (MRI) is increasingly important for the early detection of suboptimal responders to disease-modifying therapy for relapsing–remitting multiple sclerosis. Treatment response criteria are becoming more stringent with the use of composite measures, such as no evidence of disease activity (NEDA), which combines clinical and radiological measures, and NEDA-4, which includes the evaluation of brain atrophy. Methods The Canadian MRI Working Group of neurologists and radiologists convened to discuss the use of brain and spinal cord imaging in the assessment of relapsing–remitting multiple sclerosis patients during the treatment course. Results Nine key recommendations were developed based on published sources and expert opinion. Recommendations addressed image acquisition, use of gadolinium, MRI requisitioning by clinicians, and reporting of lesions and brain atrophy by radiologists. Routine MRI follow-ups are recommended beginning at three to six months after treatment initiation, at six to 12 months after the reference scan, and annually thereafter. The interval between scans may be altered according to clinical circumstances. Conclusions The Canadian recommendations update the 2006 Consortium of MS Centers Consensus revised guidelines to assist physicians in their management of MS patients and to aid in treatment decision making.