A comparison of radiation exposure between diagnostic CTA and DSA examinations of cerebral and cervicocerebral vessels

Anatomical variations of the intracranial arteries and their association with intracranial aneurysms: Insights from digital subtraction angiographies

The purpose of this study was to identify the anatomical variants (AVs) in the intracranial arterial circulation of patients who underwent neuro-interventional procedures (NIPs) and to describe their relationship with intracranial aneurysms (IA). We performed a cross-sectional analysis of angiographic images from patients who underwent NIP at the Interventional Neuroradiology Department of the National Institute of Neurology and Neurosurgery in México between July 1, 2020, and January 1, 2022. After reviewing images from 150 NIPs, we found 144 AVs., yielding a prevalence of 81%. Of these, 49 AVs (34%) were located in the anterior circulation (AC) and 95 (66%) in the posterior circulation (PC); 23 NIPs (16%) showed AVs in both the AC and PC. The most frequent AVs were the fetal pattern of the posterior cerebral artery (19%) and hypoplasia of the A1 segment (12%). AVs were significantly more common in patients with neurovascular disorders than those without (80% vs 49%, p = .003) and in patients with IA compared to those without (68% vs 47%, p = .048). In the studied population, AVs were predominantly located in the PC and are significantly more frequent in patients with neurovascular disorders, particularly those with IA.

Thomas A, S. Vadakkedam S, K. P, M. A. Bow Hunter's Syndrome with Rotational Atlantoaxial Instability: A Rare Association

Bow Hunter's syndrome (BHS) is a very rare condition in which there is rotational vertebral artery (VA) insufficiency. The association of BHS with rotational atlantoaxial instability is extremely rare. We are reporting a case of pediatric BHS who presented with features of VA insufficiency on neck rotation. Careful evaluation revealed rotational C1-C2 instability. Provocative digital subtraction angiography and dynamic neck computed tomography were the mainstay of our diagnostic armamentarium. Our case emphasizes the fact that VA abnormalities need special consideration in young patients with craniovertebral junction instability and a high degree of suspicion is necessary in most instances for accurate diagnosis.

Effective and organ doses in patient undergoing interventional neuroradiology procedures: A multicentre study

PURPOSE

Radiation doses to adult patients submitted to cerebral angiography and intracranial aneurysms treatments were assessed by using DICOM Radiation Dose Structured Reports (RDSR) and Monte Carlo simulations. Conversion factors to estimate effective and organ doses from Kerma-Area Product (PKA) values were determined.

METHODS

77 cerebral procedures performed with five angiographic equipment installed in three Italian centres were analyzed. Local settings and acquisition protocols were considered. The geometrical, technical and dosimetric data of 16,244 irradiation events (13305 fluoroscopy, 2811 digital subtraction angiography, 128 cone-beam CT) were extracted from RDSRs by local dose monitoring systems and were input in MonteCarlo PCXMC software to calculate effective and organ doses. Finally, conversion factors to determine effective and organ doses from PKA were determined. Differences between centres were assessed through statistical analysis and accuracy of dose calculation method based on conversion factors was assessed through Bland-Altman analysis.

RESULTS

Large variations in PKA (14-561 Gycm2) and effective dose (1.2-73.5 mSv) were observed due to different degrees of complexity in the procedures and angiographic system technology. The most exposed organs were brain, salivary glands, oral mucosa, thyroid and skeleton. The study highlights the importance of recent technology in reducing patient exposure (about fourfold, even more in DSA). No statistically significant difference was observed in conversion factors between centres, except for some organs. A conversion factor of 0.09 ± 0.02 mSv/Gycm2 was obtained for effective dose.

CONCLUSIONS

Organ and effective doses were assessed for neuro-interventional procedures. Conversion factors for calculating effective and organ doses from PKA were provided.

Semi-automatic computed tomography angiography quantification assessment is an alternative method to digital subtraction angiography in intracranial stenosis: a multicenter study

Background

The recent randomized controlled trials studying intracranial atherosclerotic stenosis (ICAS) have used digital subtraction angiography (DSA) to quantify stenosis and enroll patients. However, some disadvantages of DSA such as invasive features, contrast agent overuse, and X-ray radiation overexposure, were not considered in these studies. This study aimed to explore whether computed tomography angiography (CTA) with semi-automatic analysis could be an alternative method to DSA in quantifying the absolute stenotic degree in clinical trials.

Methods

Patients with 50-99% ICAS were consecutively screened, prospectively enrolled, and underwent CTA and DSA between March 2021 and December 2021 at 6 centers. This study was registered at www.chictr.org.cn (ChiCTR2100052925). The absolute stenotic degree of ICAS on CTA with semi-automatic analysis was calculated by several protocols using minimal/maximum/mean diameters of stenosis and reference site from a semi-automatic analysis software. Intraclass correlation coefficient (ICC) was used to evaluate the reliabilities of quantifying stenotic degree on CTA. The optimal protocol for quantifying ICAS on CTA was explored. The agreements of quantifying ICAS in calcified or non-calcified lesions and 50-69% or 70-99% stenosis on CTA and DSA were assessed.

Results

A total of 191 participants (58.8±10.7 years; 148 men) with 202 lesions were enrolled. The optimal protocol for quantifying ICAS on CTA was calculated as (1 - the minimal diameter of stenosis/the mean diameter of reference) × 100% for its highest agreement with DSA [ICC, 0.955, 95% confidence interval (CI): 0.944-0.966, P<0.001]. Among the 202 lesions, 80.2% (162/202) exhibited severe stenosis on DSA. The accuracy of CTA in detecting severe ICAS was excellent (sensitivity =95.1%, positive predictive value =98.1%). The agreements between DSA and CTA in non-calcified lesions (ICC, 0.960 vs. 0.849) and severe stenosis (ICC, 0.918 vs. 0.841) were higher than those in calcified lesions and moderate stenosis.

Conclusions

CTA with semi-automatic analysis demonstrated an excellent agreement with DSA in quantifying ICAS, making it promising to replace DSA for the measurement of absolute stenotic degree in clinical trials.

Spiral time-of-flight magnetic resonance angiography for intracranial vascular imaging: performance compared to conventional Cartesian angiogram

Background

Computed tomography angiography (CTA) and digital subtraction angiography (DSA) usually raise the risk of potential malignancies with cumulative radiation doses. Current time-of-flight magnetic resonance angiography (TOF-MRA) (dubbed as cTOF), which is based on Cartesian sampling mode, may show limited diagnostic conspicuity at sinuous or branching regions. It is also prone to relatively high false positive diagnoses and undesirable display of distal intracranial vessels. This study aimed to use spiral TOF-MRA (sTOF) as a noninvasive alternative to explore possible improvement, such that the application of magnetic resonance angiography (MRA) can be extended to facilitate clinical examination or cerebrovascular disease diagnosis and follow-up studies.

Methods

Initially, 37 patients with symptoms of dizziness or transient ischemic attack were consecutively recruited for suspected intracranial vascular disease examination from Zhongshan Hospital of Xiamen University between July 2020 and April 2021 in this cross-sectional prospective study. After excluding 1 patient with severe scanning artifacts, 1 patient whose scanning scope did not meet the requirement, and 1 patient with confounding tumor lesions, a total of 34 participants were included according to the inclusion and exclusion criteria. Each participant underwent intracranial vascular imaging with both sTOF and cTOF sequences on a 3.0 T MR scanner with a conventional head-neck coil of 16 channels. Contrast CTA or DSA was also performed for 15 patients showing pathology. Qualitative comparisons in terms of image quality and diagnostic efficacy ratings, quantitative comparisons in terms of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel length, and sharpness were evaluated. Pair-wise Wilcoxon test was performed to evaluate the imaging quality derived from cTOF and sTOF acquisitions and weighted Cohen's Kappa was conducted to assess the rating consistency between different physicians.

Results

Compared to cTOF, sTOF showed better performance with fewer artifacts. It can effectively alleviate false positives of normal vessels being misdiagnosed as aneurysm or stenosis. Improved conspicuity was observed in cerebral distal regions with more clearly identifiable vasculature at finer scales. Quantitative comparisons in selected regions revealed significant improvement of sTOF in SNR (P<0.01 or P<0.001), CNR (P<0.001), vessel length (P<0.001), and sharpness (P<0.001) as compared to cTOF. Besides, sTOF can depict details of M1 and M2 segments of middle cerebral artery (MCA) at metallic implant region, showing its resistance to magnetic susceptibility.

Conclusions

The sTOF shows higher imaging quality and lesion detectability with reduced artifacts and false positives, representing a potentially feasible surrogate in intracranial vascular imaging for future clinic routines.

A comparative study of low voltage, low contrast cerebral computed tomography angiography with iterative reconstruction and conventional cerebral computed tomography angiography

BACKGROUND

Cerebral computed tomography angiography (CTA) has revolutionized the diagnosis of neurovascular emergencies. Strategies to reduce radiation, a concern for cancer, involve tube voltage and current reduction but with increased noise and inferior image quality. Hence, the objective of the study was to evaluate the quality of images obtained through low-dose radiation and low-contrast volume CTA with an iterative reconstruction (IR) technique versus standard CTA without IR.

METHODS

This prospective trial involved 100 adults requiring cerebral CTA for cerebrovascular diseases. They were split into two groups: one with 120 kVp tube voltage and 80 mL contrast using filtered back projection, and the other with 80 kVp and 30 mL contrast with IR. Evaluation criteria included attenuation values, signal-to-noise ratio, contrast-to-noise ratio, and subjective assessments.

RESULTS

Compared to 120 kVp, 80 kVp showed higher vessel attenuation in the internal (272.91 ± 30.59 vs 405.52 ± 53.08; p < .001) and middle cerebral artery (247.55 ± 29.84 vs 372.55 ± 49.02; p < .001) regions. Brain parenchymal attenuation at the centrum semiovale was lower with 80 kVp (29.12 ± 1.87 vs 24.78 ± 2.94; p < .001), accompanied by higher noise. Signal-to-noise ratio (p < .001) and contrast-to-noise ratio (p < .05) were lower at 80 kVp. Image quality didn't significantly differ, and radiation exposure reduced significantly by 70% in the 80 kVp group, suggesting its diagnostic feasibility.

CONCLUSIONS

The 80 kVp protocol for CTA of the cerebral vessels combined with lower contrast volume produces images with similar image quality with significant radiation effective dose and total iodine dose reduction. The 80 kVp protocol holds significant promise for replacing the standard 120 kVp protocol in cerebral CTA.

Seeing Is Believing: Photon Counting Computed Tomography Clearly Images Directional Deep Brain Stimulation Lead Segments and Markers After Implantation

BACKGROUND AND OBJECTIVES

Directional deep brain stimulation (DBS) electrodes are increasingly used, but conventional computed tomography (CT) is unable to directly image segmented contacts owing to physics-based resolution constraints. Postoperative electrode segment orientation assessment is necessary because of the possibility of significant deviation during or immediately after insertion. Photon-counting detector (PCD) CT is a relatively novel technology that enables high resolution imaging while addressing several limitations intrinsic to CT. We show how PCD CT can enable clear in vivo imaging of DBS electrodes, including segmented contacts and markers for all major lead manufacturers.

MATERIALS AND METHODS

We describe postoperative imaging and reconstruction protocols we have developed to enable optimal lead visualization. PCD CT images were obtained of directional leads from the three major manufacturers and fused with preoperative 3T magnetic resonance imaging (MRI). Radiation dosimetry also was evaluated and compared with conventional imaging controls. Orientation estimates from directly imaged leads were compared with validated software-based reconstructions (derived from standard CT imaging artifact analysis) to quantify congruence in alignment and directional orientation.

RESULTS

High-fidelity images were obtained for 15 patients, clearly indicating the segmented contacts and directional markers both on CT alone and when fused to MRI. Our routine imaging protocol is described. Ionizing radiation doses were significantly lower than with conventional CT. For most leads, the directly imaged lead orientations and depths corresponded closely to those predicted by CT artifact-based reconstructions. However, unlike direct imaging, the software reconstructions were susceptible to 180° error in orientation assessment.

CONCLUSIONS

High-resolution photon-counting CT can very clearly image segmented DBS electrode contacts and directional markers and unambiguously determine lead orientation, with lower radiation than in conventional imaging. This obviates the need for further imaging and may facilitate anatomically tailored directional programming.

Synthetic interpolated DSA for radiation exposure reduction via gamma variate contrast flow modeling: a retrospective cohort study

BACKGROUND

Digital subtraction angiography (DSA) yields high cumulative radiation dosages (RD) delivered to patients. We present a temporal interpolation of low frame rate angiograms as a method to reduce cumulative RDs.

METHODS

Patients undergoing interventional evaluation and treatment of cerebrovascular vasospasm following subarachnoid hemorrhage were retrospectively identified. DSAs containing pre- and post-intervention runs capturing the full arterial, capillary, and venous phases with at least 16 frames each were selected. Frame rate reduction (FRR) of the original DSAs was performed to 50%, 66%, and 75% of the original frame rate. Missing frames were regenerated by sampling a gamma variate model (GVM) fit to the contrast response curves to the reduced data. A formal reader study was performed to assess the diagnostic accuracy of the "synthetic" studies (sDSA) compared to the original DSA.

RESULTS

Thirty-eight studies met inclusion criteria (average RD 1,361.9 mGy). Seven were excluded for differing views, magnifications, or motion. GVMs fit to 50%, 66%, and 75% FRR studies demonstrated average voxel errors of 2.0 ± 2.5% (mean ± standard deviation), 6.5 ± 1.5%, and 27 ± 2%, respectively for anteroposterior projections, 2.0 ± 2.2%, 15.0 ± 3.1%, and 14.8 ± 13.0% for lateral projections, respectively. Reconstructions took 0.51 s/study. Reader studies demonstrated an average rating of 12.8 (95% CI 12.3-13.3) for 75% FRR, 12.7 (12.2-13.2) for 66% FRR and 12.0 (11.5-12.5) for 50% FRR using Subjective Image Grading Scale. Kendall's coefficient of concordance resulted in W = 0.506.

CONCLUSION

FRR by 75% combined with GVM reconstruction does not compromise diagnostic quality for the assessment of cerebral vasculature.

RELEVANCE STATEMENT

Using this novel algorithm, it is possible to reduce the frame rate of DSA by as much as 75%, with a proportional reduction in radiation exposure, without degrading imaging quality.

KEY POINTS

• DSA delivers some of the highest doses of radiation to patients. • Frame rate reduction (FRR) was combined with bolus tracking to interpolate intermediate frames. • This technique provided a 75% FRR with preservation of diagnostic utility as graded by a formal reader study for cerebral angiography performed for the evaluation of cerebral vasospasm. • This approach can be applied to other types of angiography studies.

Hemodynamic assessments of unilateral pulsatile tinnitus with jugular bulb wall dehiscence using 4D flow magnetic resonance imaging

Background

Pulsatile tinnitus (PT) is a type of tinnitus characterized by a rhythmic sound that is synchronous with the heartbeat. One of the possible causes of PT is the jugular bulb wall dehiscence (JBWD). However, the hemodynamics of this condition are not well understood. To elucidate this issue, the present study aimed to compare the blood flow of PT patients with JBWD, PT patients with sigmoid sinus wall dehiscence (SSWD), and volunteers.

Methods

A retrospective case-control study was conducted, which enrolled patients with unilateral PT who had undergone both computed tomography angiography (CTA) and four-dimensional (4D) flow magnetic resonance imaging (MRI) examinations at the Department of Otolaryngology-Head and Neck Surgery of Beijing Friendship Hospital affiliated to Capital Medical University between January 2019 and July 2023. After excluding the possible causes of PT, the patients were divided into the JBWD group and SSWD group according to the presence or absence of JBWD and/or SSWD. Finally, 11 female unilateral PT patients with JBWD (JBWD group, 11sides), 22 age- and side-matched female patients with SSWD (SSWD group, 22 sides), and 22 age-matched female volunteers (volunteer group, 36 sides) were enrolled. The area, maximum voxel velocity (Vv-max), maximum velocity (Vmax), average velocity (Vavg), and average blood flow rate (Q) were measured in the transverse sinuses (TSs), sigmoid sinuses (SSs), and jugular bulb (JB). The vortex flow pattern was also assessed. Fisher's exact test and Bonferroni correction were used for count data, with P<0.017 was considered statistically significant. Shapiro-Wilk test, one-way analysis of variance (ANOVA), Kruskal-Wallis H test, paired-samples t-test, and Wilcoxon matched-pairs signed-rank test were used for continuous variables depending on the distribution and variance of the data. The P<0.05 and corrected P<0.05 was considered statistically significant.

Results

The area and Q of TSs and JB on the symptomatic side were higher than those on the contralateral side in the JBWD group (TSs: Parea=0.004, Pflow=0.002; JB: Parea=0.034, Pflow=0.018). The area was larger and velocities were lower in the JBWD group at the TSs than the SSWD group (Parea=0.004, PVv-max=0.009, PVmax=0.021, PVavg=0.026), and velocities were higher at the distal TSs and SSs than the volunteer group (TSs: PVv-max=0.042, PVmax=0.046, PVavg=0.040; SSs: PVv-max=0.007, PVmax=0.001, PVavg=0.001). At the JB, the JBWD group also had higher Vv-max than the volunteer group (P=0.012). The occurrence rate of vortex at JB in the JBWD group was higher than both the JBWD and the volunteer groups (P=0.002<0.017 and P=0.009<0.017, respectively).

Conclusions

The blood flow of the intracranial venous sinus was different between the JBWD group and the SSWD group. The indicators that can differentiate include Vv-max, Vmax, Vavg, vortex, and TSs cross-sectional area.

Endovascular Treatment and Peri-interventional Management of Ruptured Cerebrovascular Lesions During Pregnancy : Case Series and Case-based Systematic Review

PURPOSE

Hemorrhagic stroke, particularly occurring from ruptured cerebrovascular malformations, is responsible for 5-12% of all maternal deaths during pregnancy and the puerperium. Whether endovascular treatment is feasible and safe for both the mother and the fetus, is still a matter of debate. The main objective of this case series and systematic review was to share our multi-institutional experience and to assess the feasibility and safety of endovascular treatment during pregnancy, as well as the corresponding maternal and fetal outcomes based on currently available evidence.

METHODS

We report a case series of 12 pregnant women presenting with hemorrhagic stroke from ruptured cerebrovascular arteriovenous malformations or aneurysms who underwent endovascular treatment prior to delivery. A systematic literature review of pregnant patients with endovascular treated cerebrovascular malformations, published between 1995 and 2022, was performed. Clinical patient information, detailed treatment strategies, maternal and fetal outcomes as well as information on the delivery were collected and assessed.

RESULTS

In most patients the course was uneventful and an excellent outcome without significant neurological deficits (mRS ≤ 1) was achieved. Furthermore, the maternal outcome was not worse compared to the general population who underwent endovascular treatment of ruptured vascular brain lesions. Also, in most cases a healthy fetus was born.

CONCLUSION

Endovascular treatment of ruptured cerebrovascular malformations during pregnancy is safe and feasible regarding both aspects, the maternal and fetal outcomes. Still, a stronger knowledge base is needed to correctly approach future cases of intracranial hemorrhage in the pregnant population.

[Morphological study on the transverse branch of lateral femoral circumflex artery based on digital subtraction angiography]

Objective: To summarize the morphological characteristics of the transverse branch of lateral femoral circumflex artery (LFCA) using digital subtraction angiography (DSA) and explore its clinical significance. Methods: A retrospective observational study was conducted. From October 2020 to May 2021, 62 patients with soft tissue injuries in the extremities were hospitalized in Suzhou Ruihua Orthopedic Hospital, including 40 males and 22 females, aged from 20 to 72 years. DSA was performed in the lateral femoral region of patients before the anterolateral thigh flap transplantation, and in combination with imaging scale to observe and measure the general condition of the blood vessels and the occurrence (with the occurrence rate being calculated), source artery, location of the origin point, direction of course, and the location of the perforating point of the cutaneous perforator of the transverse branch of LFCA, and in addition to classify the morphological characteristics of the transverse branch. Results: DSA detection showed that the femoral artery, the deep femoral artery, and the branches of LFCA were clearly distinguishable in 62 patients. Transverse branches of LFCA were observed in 59 patients, including 52 cases with a single transverse branch, and 7 cases with double transverse branches. The occurrence rate of transverse branches was 95.2% (59/62). A total of 66 transverse branches of LFCA were observed, of which 3 originated from the deep femoral artery, and 63 originated from the LFCA. The origin point of the transverse branch was 6.5-12.7 cm away from the anterior superior iliac spine. The transverse branch which was approximately perpendicular to the long axis of the body, originated outwards, ran between the ascending branch of LFCA and the oblique branch of LFCA, and branched along the way, with the trunk running under the greater trochanter. The perforating point of the cutaneous perforator of the transverse branch was 8.0-18.0 cm away from the anterior superior iliac spine. In the classification of morphological characteristics of the transverse branch of LFCA, the most common type was the one that originated from the same trunk with other branches of LFCA, accounting for 50.0% (31/62), followed by the one that originated from the singular trunk of LFCA (12 cases) or deep femoral artery (3 cases), accounting for 24.2% (15/62); the special type accounted for 21.0% (13/62), including 7 cases of double transverse branches and 6 cases of the transverse branch originated from the same trunk with multiple other branches of LFCA; those with small/absent transverse branch only accounted for 4.8% (3/62). Among the above-mentioned common trunk relationship of two branches, those with shared trunk of ascending and transverse branches were most frequently observed, accounting for 77.4% (24/31); those with shared trunks of the transverse and oblique branches (5 cases) and the transverse and descending branches (2 cases) accounted for 22.6% (7/31) altogether. Conclusions: A high incidence rate of the transverse branch of LFCA is observed through DSA. The transverse branch originates from the lateral femoral artery approximately perpendicular to the long axis of the body, mainly from the same trunk with another main branch of LFCA, especially the ascending branch. This positioning analysis can provide an important reference for the design and resection of anterolateral femoral flaps.

Improving the diagnostic performance of computed tomography angiography for intracranial large arterial stenosis by a novel super-resolution algorithm based on multi-scale residual denoising generative adversarial network

BACKGROUND

Computed tomography angiography (CTA) is very popular because it is characterized by rapidity and accessibility. However, CTA is inferior to digital subtraction angiography (DSA) in the diagnosis of intracranial artery stenosis or occlusion. DSA is an invasive examination, so we optimized the quality of cephalic CTA images.

METHODS

We used 5000 CTA images to train multi-scale residual denoising generative adversarial network (MRDGAN). And then 71 CTA images with intracranial large arterial stenosis were treated by Super-Resolution based on Generative Adversarial Network (SRGAN), Enhanced Super-Resolution based on Generative Adversarial Network (ESRGAN) and post-trained MRDGAN, respectively. Peak signal-to-noise ratio (PSNR) and structural similarity index measurement (SSIM) of the SRGAN, ESRGAN, MRDGAN and original CTA images were measured respectively. The qualities of MRDGAN and original images were visually assessed using a 4-point scale. The diagnostic coherence of digital subtraction angiography (DSA) with MRDGAN and original images was analyzed.

RESULTS

The PSNR was significantly higher in the MRDGAN CTA images (35.96 ± 1.51) than in the original (31.51 ± 1.43), SRGAN (25.75 ± 1.18) and ESRGAN (30.36 ± 1.05) CTA images (all P < 0.001). The SSIM was significantly higher in the MRDGAN CTA images (0.95 ± 0.02) than in the SRGAN (0.88 ± 0.03) and ESRGAN (0.90 ± 0.02) CTA images (all P < 0.01). The visual assessment was significantly higher in the MRDGAN CTA images (3.52 ± 0.58) than in the original CTA images (2.39 ± 0.69) (P < 0.05). The diagnostic coherence between MRDGAN and DSA (κ = 0.89) was superior to that between original images and DSA (κ = 0.62).

CONCLUSION

Our MRDGAN can effectively optimize original CTA images and improve its clinical diagnostic value for intracranial large artery stenosis.

Comparing Radiation Dose of Cerebral Angiography Using Conventional and High kV Techniques: A Retrospective Study on Intracranial Aneurysm Patients and a Phantom Study

Evaluation of patient radiation dose after the implementation of a high kV technique during a cerebral angiographic procedure is an important issue. This study aimed to determine and compare the patient radiation dose of intracranial aneurysm patients undergoing cerebral angiography using the conventional and high kV techniques in a retrospective study and a phantom study. A total of 122 cases (61 cases with conventional technique and 61 cases with high kV technique) of intracranial aneurysm patients, who underwent cerebral angiographic procedure and met the inclusion criteria, were recruited. The radiation dose and the angiographic exposure parameters were reviewed retrospectively. The radiation dose in the phantom study was conducted using nanoDot^TM optically stimulating luminescence (OSLD), which were placed on the scalp of the head phantom, the back of the neck, and the phantom skin at the position of the eyes. The standard cerebral angiographic procedure using the conventional and high kV techniques was performed following the standard protocol. The results showed that the high kV technique significantly reduced patient radiation dose and phantom skin dose. This study confirms that the implementation of a high kV technique in routine cerebral angiography for aneurysm diagnosis provides an effective reduction in radiation dose. Further investigation of radiation dose in other interventional neuroradiology procedures, particularly embolization procedure, should be performed.

Low-dose CT Perfusion with Sparse-view Filtered Back Projection in Acute Ischemic Stroke

RATIONALE AND OBJECTIVES

Radiation dose associated with computed tomography (CT) perfusion (CTP) may discourage its use despite its added diagnostic benefit in quantifying ischemic lesion volume. Sparse-view CT reduces scan dose by acquiring fewer X-ray projections per gantry rotation but is contaminated by streaking artifacts using filtered back projection (FBP). We investigated the achievable dose reduction by sparse-view CTP with FBP without affecting CTP lesion volume estimations.

MATERIALS AND METHODS

Thirty-eight consecutive patients with acute ischemic stroke and CTP were included in this simulation study. CTP projection data was simulated by forward projecting original reconstructions with 984 views and adding Gaussian noise. Full-view (984 views) and sparse-view (492, 328, 246, and 164 views) CTP studies were simulated by FBP of simulated projection data. Cerebral blood flow (CBF) and time-to-maximum of the impulse residue function (Tmax) maps were generated by deconvolution for each simulated CTP study. Ischemic volumes were measured by CBF<30% relative to the contralateral hemisphere and Tmax > 6 s. Volume accuracy was evaluated with respect to the full-view CTP study by the Friedman test with post hoc multiplicity-adjusted pairwise tests and Bland-Altman analysis.

RESULTS

Friedman and multiplicity-adjusted pairwise tests indicated that 164-view CBF < 30%, 246- and 164-view Tmax > 6 s volumes were significantly different to full-view volumes (p < 0.001). Mean difference ± standard deviation (sparse minus full-view lesion volume) ranged from -1.0 ± 2.8 ml to -4.1 ± 11.7 ml for CBF < 30% and -2.9 ± 3.8 ml to -12.5 ± 19.9 ml for Tmax > 6 s from 492 to 164 views, respectively.

CONCLUSION

By ischemic volume accuracy, our study indicates that sparse-view CTP may allow dose reduction by up to a factor of 3.

The value of whole-brain CT perfusion imaging combined with dynamic CT angiography in the evaluation of pial collateral circulation with middle cerebral artery occlusion

BACKGROUND

Middle cerebral artery (MCA) occlusion is extremely common, especially unilateral artery, which can result in a significant incidence of cerebral infarction.

OBJECTIVE

To assess the value of whole-brain computed tomography perfusion (CTP) imaging combined with dynamic CT angiography (dCTA) in the evaluation of pial collateral circulation in patients with MCA occlusion.

METHODS

Whole-brain CTP and dCTA images were acquired in 58 patients with unilateral MCA occlusion. All patients were divided into three groups according to the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) collateral score (by CTA). The CTP parameters were analysed, including relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), relative mean transit time (rMTT), and relative time to peak (rTTP). Patients were followed up with the modified Rankin scale (mRS). All cases in this study were confirmed by DSA.

RESULTS

The CTP parameters of the MCA blood supply area on the affected side of patients with different degrees of stenosis were significantly different from those on the unaffected side. There are significant differences in the CTP parameters and openings of the Willis circle in patients with different degrees of stenosis. Significant differences were found in the number of patients with good prognosis.

CONCLUSIONS

Whole-brain CT perfusion combined with dynamic CTA can structurally and functionally evaluate the establishment of pial collateral circulation and its effect on cerebral hemodynamic changes.

How Reliable Is the Intraoperative Computed Tomography Angiography in Assessing Complete Surgical Resection of Cerebral Arteriovenous Malformations?

BACKGROUND

Digital subtraction angiography (DSA) is still considered the gold standard test to evaluate arteriovenous malformation's (AVM) residual after microsurgical resection.

OBJECTIVE

To evaluate the safety and reliability of intraoperative computed tomography angiography (iCTA) as an immediate method of evaluating the surgical results of AVM resection.

METHODS

We performed a retrospective review for all cases of cerebral AVMs at our institute from January 2015 to April 2020 who underwent surgical resection of cerebral AVM and had iCTA. All included patients underwent a postoperative DSA, and the results were compared with iCTA.

RESULTS

Twenty-eight cases were included. All cases showed complete resection (100%) in the iCTA, and the results were consistent with the postoperative DSA results. The sensitivity of iCTA was 100%. The added operative time ranged from 25 to 30 min. There were no complications related to the use of iCTA.

CONCLUSION

Intraoperative assessment of AVMs surgical results with an iCTA is safe and reliable. The sensitivity of iCTA following AVM resection merits further investigations.

Feasibility of Ultra-High Resolution Supra-Aortic CT Angiography: An Assessment of Diagnostic Image Quality and Radiation Dose

(1) Background: To evaluate diagnostic image quality and radiation exposure of ultra-high resolution cerebral Computed-Tomography (CT) angiography (CTA) obtained on an ultra-high resolution computed tomography scanner (UHR-CT). (2) Methods: Fifty consecutive patients with UHR-CTA were enrolled. Image reconstruction was processed with a 1024 × 1024 matrix and a slice thickness of 0.25 mm. Quantitative analyses comprising CT values, contrast-noise ratio (CNR) and signal-to-noise ratio (SNR) were performed. Subjective assessment of image quality, vessel contrast, noise, artefacts and delineation of different sized vessels were assessed by two readers on a 4-point scale. Radiation exposure was determined. (3) Results: Hounsfield values (ACI: 461.8 ± 16.8 HU; MCA: 406.1 ± 24.2 HU; BA: 412.2 ± 22.3 HU), SNR (ACI: 35.4 ± 13.1; MCA: 20.8 ± 12.4; BA: 23.7 ± 12.9) and CNR (ACI: 48.7 ± 21; MCA: 63.9 ± 26.9; BA: 48.1 ± 21.4) were remarkably high in all segments. Subjective analysis by two raters (fair agreement, k = 0.26) indicated excellent image qualities (image quality = 4; contrast = 4; noise = 3; artefacts = 4).Our analysis revealed a notably high traceability of the cerebral perforators (3 Points). Radiation exposure was at moderate dose levels (effective dose = 2.5 ± 0.6mSv). (4) Conclusions: UHR-CTA generates highly valuable image qualities that allow the depiction of vessels including cerebral perforators at acceptable dose levels. The UHR-CTA may therefore enhance the detection of small cerebral pathologies and may improve interpretability, especially in settings where high image qualities are crucial for the diagnostic accuracy.

3D X-ray based visualization of directional deep brain stimulation lead orientation

Knowing the orientation of directional deep brain stimulation electrodes enables imaging-based adjustment of the stimulation settings. A rotational X-ray based examination was developed to determine the electrodes orientation. By identifying the patient´s 0° axis and the electrode´s rotation using the "iron sights"-sign, the exact orientation of the electrode in relation to the ACPC-line is given. The presented imaging approach offers a reliable diagnostic tool for visualization of the implanted DBS electrode orientation in clinical routine.

Neuroimaging of Acute Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) accounts for 10% to 20% of all strokes worldwide and is associated with high morbidity and mortality. Neuroimaging is clinically important for the rapid diagnosis of ICH and underlying etiologies, but also for identification of ICH expansion, often as-sociated with an increased risk for poor outcome. In this context, rapid assessment of early hema-toma expansion risk is both an opportunity for therapeutic intervention and a potential hazard for hematoma evacuation surgery. In this review, we provide an overview of the current literature surrounding the use of multimodal neuroimaging of ICH for etiological diagnosis, prediction of early hematoma expansion, and prognostication of neurological outcome. Specifically, we discuss standard imaging using computed tomography, the value of different vascular imaging modalities to identify underlying causes and present recent advances in magnetic resonance imaging and computed tomography perfusion.

Anatomical Variations in Circle of Willis in Patients Undergoing CT Cerebral Angiography in a Tertiary Hospital in Nepal: A Descriptive Cross-sectional Study

Introduction:

Variation in Circle of Willis is a commonly encountered entity in patients undergoing Computed Tomography angiography, identification of which is crucial in management of patients with vascular pathologies. The aim of the study was to find out the anatomical variations in Circle of Willis in patients undergoing Computed Tomography cerebral angiography in a tertiary hospital in Nepal.

Methods:

This is a descriptive cross-sectional study involving 95 patients using convenient sampling techniques who were sent to the Department of Radiology and Imaging, Tribhuvan University Teaching hospital, for further evaluation of suspected vascular pathologies in the brain from April 2017 to September 2017. Ethical approval was taken from the Institutional Review Committee of the Institute of Medicine with reference number 326 (6-11-E). CT angiographic images of these patients were evaluated for presence of variations in Circle of Willis, aneurysms and other vascular pathologies. Data were analysed using SPSS.

Results:

Among 95 subjects included in the study, the anatomical variations in the arteries of Circle of Willis was seen in 52 (54.7%) patients, hypoplastic posterior communicating artery being the most common variation 33 (34.7%). Aneurysm was seen in 22 (23.2%) of cases.

Conclusions:

CT Angiography is commonly performed imaging modality for suspected cases of cerebral aneurysms and various other vascular pathologies. Multidetector computed tomography can effectively detect variations in arteries of Circle of Willis, recognition of which is crucial in operative management of vascular pathologies.

Fe3O4@M nanoparticles for MRI-targeted detection in the early lesions of atherosclerosis

Atherosclerosis can lead to most cardiovascular diseases. Although some biomimetic nanomaterials coated by macrophage membranes have been reported in previous studies of atherosclerosis, to our knowledge, no studies regarding the detection of early lesions of atherosclerosis (foam cells) using such a strategy have yet been reported. In the present study, Fe₃O₄ biomimetic nanoparticles coated with a macrophage membrane (Fe₃O₄@M) were prepared to investigate the imaging effect on the early lesions of atherosclerosis (foam cells). The results showed that the Fe₃O₄@M particles are spheres with average diameters of approximately 300 nm. T1 and T2 relaxation values showed that the ratio of r2 to r1 was 26.09. The protein content accounted for approximately 27% of the total weight in Fe₃O₄@M, and Fe₃O₄@M nanoparticles exhibited high biosafety. Further testing showed that Fe₃O₄@M effectively targets early atherosclerotic lesions by the specific recognition of integrin α4β1 to VCAM-1. Taken together, Fe₃O₄@M is a promising contrast agent for the diagnosis of early stage atherosclerosis.

On the Use of Digital Subtraction Angiography in Stereoelectroencephalography Surgical Planning to Prevent Collisions with Vessels

OBJECTIVE

Stereoelectroencephalography (SEEG) consists of the implantation of microelectrodes for the electrophysiological characterization of epileptogenic networks. To reduce a possible risk of intracranial bleeding by vessel rupture during the electrode implantation, the stereotactic trajectories must follow avascular corridors. The use of digital subtraction angiography (DSA) for vascular visualization during planning is controversial due to the additional risk related to this procedure. Here we evaluate the utility of this technique for planning when the neurosurgeon has it available together with gadolinium-enhanced T1-weighted magnetic resonance sequence (T1-Gd) and computed tomography angiography (CTA).

METHODS

Twenty-two implantation plans for SEEG were initially done using T1-Gd imaging (251 trajectories). DSA was only used later during the revision process. In 6 patients CTA was available at this point as well. We quantified the position of the closest vessel to the trajectory in each of the imaging modalities.

RESULTS

Two thirds of the trajectories that appeared vessel free in the T1-Gd or CTA presented vessels in their proximity, as shown by DSA. Those modifications only required small shifts of both the entry and target point, so the diagnostic aims were preserved.

CONCLUSIONS

T1-Gd and CTA, despite being the most commonly used techniques for SEEG planning, frequently fail to reveal vessels that are dangerously close to the trajectories. Higher-resolution vascular imaging techniques, such as DSA, can provide the neurosurgeon with crucial information about vascular anatomy, resulting in safer plans.

New ischemic lesions on brain magnetic resonance imaging in patients with blunt traumatic cerebrovascular injury

BACKGROUND

Patients with blunt cerebrovascular injuries are at risk of thromboembolic stroke. Although primary prevention with antithrombotic therapy is widely used in this setting, its effectiveness is not well defined and requires further investigation. The aim of this study was to evaluate the utility of magnetic resonance imaging (MRI)-detected ischemic brain lesions as a possible future outcome for randomized clinical trials in this patient population.

METHODS

This prospective observational study included 20 adult blunt trauma patients admitted to a level I trauma center with a screening neck CTA showing extracranial carotid or vertebral artery injury. All subjects lacked initial evidence of an ischemic stroke and were managed with antithrombotic therapy and observation and then underwent brain MRI within 30 days of the injury to assess for ischemic lesions. The MRI scans included diffusion, susceptibility, and Fluid-attenuated Inversion Recovery (FLAIR) sequences, and were reviewed by two neuroradiologists blinded to the computed tomography angiography (CTA) findings.

RESULTS

Eleven CTAs were done in the emergency department upon admission. There were 12 carotid artery dissections and 11 unilateral or bilateral vertebral artery injuries. Median interval between injury and MRI scan was 4 days (range, 0.1-14; interquartile range, 3-7 days). Diffusion-weighted imaging evidence of new ischemic lesions was present in 10 (43%) of 23 of the injured artery territories. In those injuries with ischemic lesions, the median number was 8 (range, 2-25; interquartile range, 5-8). None of the lesions were symptomatic. Blunt cerebrovascular injury was associated with a higher mean ischemic lesion count (mean count of 3.17 vs. 0.14, p < 0.0001), with the association remaining after adjusting for injury severity score (p < 0.0001).

CONCLUSION

In asymptomatic blunt trauma patients with CTA evidence of extracranial cerebrovascular injury and treated with antithrombotic therapy, nearly half of arterial injuries are associated with ischemic lesions on MRI.

LEVEL OF EVIDENCE

Therapeutic/care management, level IV.

Deep learning for cerebral angiography segmentation from non-contrast computed tomography

Cerebral computed tomography angiography is a widely available imaging technique that helps in the diagnosis of vascular pathologies. Contrast administration is needed to accurately assess the arteries. On non-contrast computed tomography, arteries are hardly distinguishable from the brain tissue, therefore, radiologists do not consider this imaging modality appropriate for the evaluation of vascular pathologies. There are known contraindications to administering iodinated contrast media, and in these cases, the patient has to undergo another examination to visualize cerebral arteries, such as magnetic resonance angiography. Deep learning for image segmentation has proven to perform well on medical data for a variety of tasks. The aim of this research was to apply deep learning methods to segment cerebral arteries on non-contrast computed tomography scans and consequently, generate angiographies without the need for contrast administration. The dataset for this research included 131 patients who underwent brain non-contrast computed tomography directly followed by computed tomography with contrast administration. Then, the segmentations of arteries were generated and aligned with non-contrast computed tomography scans. A deep learning model based on the U-net architecture was trained to perform the segmentation of blood vessels on non-contrast computed tomography. An evaluation was performed on separate test data, as well as using cross-validation, reaching Dice coefficients of 0.638 and 0.673, respectively. This study proves that deep learning methods can be leveraged to quickly solve problems that are difficult and time-consuming for a human observer, therefore providing physicians with additional information on the patient. To encourage the further development of similar tools, all code used for this research is publicly available.

Preoperative computed tomography perfusion in pediatric moyamoya disease: a single-institution experience

OBJECTIVE

Moyamoya disease is a progressive occlusive arteriopathy for which surgical revascularization is indicated. In this retrospective study, the authors investigated the use of preoperative CT perfusion with the aim of establishing pathological data references.

METHODS

The authors reviewed the medical records of children with moyamoya disease treated surgically at one institution between 2016 and 2019. Preoperative CT perfusion studies were used to quantify mean transit time (MTT), cerebral blood volume (CBV), cerebral blood flow (CBF), and time to peak (TTP) for the anterior, middle, and posterior cerebral artery vascular territories for each patient. CT perfusion parameter ratios (diseased/healthy hemispheres) and absolute differences were compared between diseased and normal vascular territories (defined by catheter angiography studies). Sensitivity, specificity, and positive (PPV) and negative (NPV) predictive values for CT perfusion parameters for severe angiographic moyamoya were calculated.

RESULTS

Nine children (89% female) had preoperative CT perfusion data; 5 of them had evidence of unilateral hemispheric disease and 4 had bilateral disease. The mean age at revascularization was 77 months (range 40-144 months). The etiology of disease was neurofibromatosis type 1 (3 patients), Down syndrome (2), primary moyamoya disease (2), cerebral proliferative angiopathy (1), and sickle cell disease (1). Five patients had undergone unilateral revascularization. Among these patients, pathological vascular territories demonstrated increased MTT in 66% of samples, increased TTP in 66%, decreased CBF in 47%, and increased CBV in 87%. Severe moyamoya (Suzuki stage ≥ 4) had diseased/healthy ratios ≥ 1 for MTT in 78% of cases, for TTP in 89%, for CBF in 67%, and for CBV in 89%. The MTT and TTP region of interest ratio ≥ 1 demonstrated 89% sensitivity, 67% specificity, 80% PPV, and 80% NPV for the prediction of severe angiographic moyamoya disease.

CONCLUSIONS

Pathological hemispheres in these children with moyamoya disease demonstrated increased MTT, TTP, and CBV and decreased CBF. The authors' results suggest that preoperative CT perfusion may, with high sensitivity, be useful in deciphering perfusion mismatch in brain tissue in children with moyamoya disease. More severe angiographic disease displays a more distinct correlation, allowing surgeons to recognize when to intervene in these patients.

Neuroimaging of Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) accounts for 10% to 20% of strokes worldwide and is associated with high morbidity and mortality rates. Neuroimaging is indispensable for rapid diagnosis of ICH and identification of the underlying etiology, thus facilitating triage and appropriate treatment of patients. The most common neuroimaging modalities include noncontrast computed tomography (CT), CT angiography (CTA), digital subtraction angiography, and magnetic resonance imaging (MRI). The strengths and disadvantages of each modality will be reviewed. Novel technologies such as dual-energy CT/CTA, rapid MRI techniques, near-infrared spectroscopy, and automated ICH detection hold promise for faster pre- and in-hospital ICH diagnosis that may impact patient management.

4D-CT angiography versus 3D-rotational angiography as the imaging modality for computational fluid dynamics of cerebral aneurysms

Background and purpose

Computational fluid dynamics (CFD) can provide valuable information regarding intracranial hemodynamics. Patient-specific models can be segmented from various imaging modalities, which may influence the geometric output and thus hemodynamic results. This study aims to compare CFD results from aneurysm models segmented from three-dimensional rotational angiography (3D-RA) versus novel four-dimensional CT angiography (4D-CTA).

Methods

Fourteen patients with 16 cerebral aneurysms underwent novel 4D-CTA followed by 3D-RA. Endoluminal geometries were segmented from each modality using an identical workflow, blinded to the other modality, to produce 28 'original' models. Each was then minimally edited a second time to match length of branches, producing 28 additional 'matched' models. CFD simulations were performed using estimated flow rates for 'original' models (representing real-world experience) and patient-specific flow rates from 4D-CTA for 'matched' models (to control for influence of modality alone).

Results

Overall, geometric and hemodynamic results were consistent between models segmented from 3D-RA and 4D-CTA, with correlations improving after matching to control for operator-introduced variability. Despite smaller 4D-CTA parent artery diameters (3.49±0.97 mm vs 3.78±0.92 mm for 3D-RA; p=0.005) and sac volumes (157 (37–750 mm3) vs 173 (53–770 mm3) for 3D-RA; p=0.0002), sac averages of time-averaged wall shear stress (TAWSS), oscillatory shear (OSI), and high frequency fluctuations (measured by spectral power index, SPI) were well correlated between 3D-RA and 4D-CTA 'matched' control models (TAWSS, R2=0.91; OSI, R2=0.79; SPI, R2=0.90).

Conclusions

Our study shows that CFD performed using 4D-CTA models produces reliable geometric and hemodynamic information in the intracranial circulation. 4D-CTA may be considered as a follow-up imaging tool for hemodynamic assessment of cerebral aneurysms.

Ferumoxytol-enhanced MRI for surveillance of pediatric cerebral arteriovenous malformations

OBJECTIVE

Children with intracranial arteriovenous malformations (AVMs) undergo digital DSA for lesion surveillance following their initial diagnosis. However, DSA carries risks of radiation exposure, particularly for the growing pediatric brain and over lifetime. The authors evaluated whether MRI enhanced with a blood pool ferumoxytol (Fe) contrast agent (Fe-MRI) can be used for surveillance of residual or recurrent AVMs.

METHODS

A retrospective cohort was assembled of children with an established AVM diagnosis who underwent surveillance by both DSA and 3-T Fe-MRI from 2014 to 2016. Two neuroradiologists blinded to the DSA results independently assessed Fe-enhanced T1-weighted spoiled gradient recalled acquisition in steady state (Fe-SPGR) scans and, if available, arterial spin labeling (ASL) perfusion scans for residual or recurrent AVMs. Diagnostic confidence was examined using a Likert scale. Sensitivity, specificity, and intermodality reliability were determined using DSA studies as the gold standard. Radiation exposure related to DSA was calculated as total dose area product (TDAP) and effective dose.

RESULTS

Fifteen patients were included in this study (mean age 10 years, range 3-15 years). The mean time between the first surveillance DSA and Fe-MRI studies was 17 days (SD 47). Intermodality agreement was excellent between Fe-SPGR and DSA (κ = 1.00) but poor between ASL and DSA (κ = 0.53; 95% CI 0.18-0.89). The sensitivity and specificity for detecting residual AVMs using Fe-SPGR were 100% and 100%, and using ASL they were 72% and 100%, respectively. Radiologists reported overall high diagnostic confidence using Fe-SPGR. On average, patients received two surveillance DSA studies over the study period, which on average equated to a TDAP of 117.2 Gy×cm2 (95% CI 77.2-157.4 Gy×cm2) and an effective dose of 7.8 mSv (95% CI 4.4-8.8 mSv).

CONCLUSIONS

Fe-MRI performed similarly to DSA for the surveillance of residual AVMs. Future multicenter studies could further investigate the efficacy of Fe-MRI as a noninvasive alternative to DSA for monitoring AVMs in children.

Comparison of Subtracted Computed Tomography from Computed Tomography Perfusion and Digital Subtraction Angiography in Residue Evaluation of Treated Intracranial Aneurysms

BACKGROUND

Assessing clipped intracranial aneurysms for residues or incomplete occlusions is critical. Digital subtraction angiography (DSA) has been the gold standard for this. Previously, we presented subtracted computed tomography angiography (sub-CTA) from computed tomography perfusion as a more effective noninvasive technique for clipped aneurysms. The aim of this study was to compare effectiveness of sub-CTA with DSA in residue evaluation.

METHODS

A retrospective study of 17 patients with aneurysmal subarachnoid hemorrhage operated on at our institution between November 1, 2016, and December 31, 2018, was performed. Residue aneurysms were evaluated with both sub-CTA and DSA. Positive predictive value and negative predictive value were calculated. Correlation between techniques was determined by the McNemar test and κ value.

RESULTS

Sensitivity of sub-CTA in residue evaluation was low in aneurysms ≤3 mm (positive predictive value = 60%). DSA detected residue aneurysm in 29% (5/17) of patients, whereas sub-CTA detected residue aneurysm in 11% (2/17). Only 40% of aneurysms (2/5) were demonstrated by sub-CTA, all >3 mm; 60% (3/5) were missed, all ≤3 mm.

CONCLUSIONS

This is the first study comparing the effectiveness of sub-CTA from computed tomography perfusion with DSA in residue aneurysm evaluation. Our results were suggestive, but not conclusive. DSA is still the gold standard in residue evaluation. Sub-CTA from computed tomography perfusion can be a reliable method in evaluation of residual aneurysm >3 mm.

Learning-based automatic segmentation of arteriovenous malformations on contrast CT images in brain stereotactic radiosurgery

PURPOSE

Stereotactic radiosurgery (SRS) is widely used to obliterate arteriovenous malformations (AVMs). Its performance relies on the accuracy of delineating the target AVM. Manual segmentation during a framed SRS procedure is time consuming and subject to inter- and intraobserver variation. To address these drawbacks, we proposed a deep learning-based method to automatically segment AVMs on CT simulation image sets.

METHODS

We developed a deep learning-based method using a deeply supervised three-dimensional (3D) V-Net with a compound loss function. A 3D supervision mechanism was integrated into a residual network, V-Net, to deal with the optimization difficulties when training deep networks with limited training data. The proposed compound loss function including logistic and Dice losses encouraged similarity and penalized discrepancy simultaneously between prediction and training dataset; this was utilized to supervise the 3D V-Net at different stages. To evaluate the accuracy of segmentation, we retrospectively investigated 80 AVM patients who had CT simulation and digital subtraction angiography (DSA) acquired prior to treatment. The AVM target volume was segmented by our proposed method. They were compared with clinical contours approved by physicians with regard to Dice overlapping, difference in volume and centroid, and dose coverage changes on original plan.

RESULTS

Contours created by the proposed method demonstrated very good visual agreement to the ground truth contours. The mean Dice similarity coefficient (DSC), sensitivity and specificity of the contours delineated by our method were >0.85 among all patients. The mean centroid distance between our results and ground truth was 0.675 ± 0.401 mm, and was not significantly different in any of the three orthogonal directions. The correlation coefficient between ground truth and AVM volume resulting from the proposed method was 0.992 with statistical significance. The mean volume difference among all patients was 0.076 ± 0.728 cc; there was no statistically significant difference. The average differences in dose metrics were all less than 0.2 Gy, with standard deviation less than 1 Gy. No statistically significant differences were observed in any of the dose metrics.

CONCLUSION

We developed a novel, deeply supervised, deep learning-based approach to automatically segment the AVM volume on CT images. We demonstrated its clinical feasibility by validating the shape and positional accuracy, and dose coverage of the automatic volume. These results demonstrate the potential of a learning-based segmentation method for delineating AVMs in the clinical setting.

Implementation of Intraoperative Computed Tomography for Deep Brain Stimulation: Pitfalls and Optimization of Workflow, Accuracy, and Radiation Exposure

OBJECTIVE

Deep brain stimulation (DBS) is an effective treatment for movement disorders. Stereotactic electrode placement can be guided by intraoperative imaging, which also allows for immediate intraoperative quality control. This article is about implementation and refining a workflow applying intraoperative computed tomography (iCT) for DBS.

METHODS

Eighteen patients underwent DBS with bilateral implantation of directional electrodes applying a 32-slice movable computed tomography scanner in combination with microelectrode recording.

RESULTS

iCT led to a significant decrease in overall procedural time, despite performing multiple scans. In 3 of the initial 5 cases, iCT caused an adjustment of the final electrodes demonstrating the learning curve and the necessity to integrate road mapping for the exchange of microelectrode to final electrode. Implementation of low-dose computed tomography protocols added microelectrode iCT to the refined workflow, resulting in an intraoperative adjustment of a trajectory in 1 patient. Low-dose protocols lowered the total effective dose to 1.15 mSv, that is, a reduction by a factor of 3.5 compared to a standard non-iCT DBS procedure, despite repeated iCTs. Intraoperative lead detection based on final iCT revealed a radial error of 1.04 ± 0.58 mm and a vector error of 2.28 ± 0.97 mm compared to the preoperative planning, adjusted by the findings of microelectrode recording.

CONCLUSIONS

iCT can be easily integrated into the surgical workflow resulting in an overall efficient time-saving procedure. Repeated intraoperative scanning ensures reliable electrode placement, although low-dose scanning protocols prevent extensive radiation exposure. iCT of microelectrodes is feasible and led to the adjustment of 1 electrode.

Risk of Radiation-Induced Cancer From Computed Tomography Angiography Use in Imaging Surveillance for Unruptured Cerebral Aneurysms

Background and Purpose- Although computed tomography angiography (CTA) is an excellent, noninvasive imaging modality for surveillance of intracranial aneurysms, radiation concerns have been cited to restrict its use in surveillance imaging. The goal of this study was to estimate distributions of radiation-induced central nervous system cancer incidence from CTA surveillance for intracranial aneurysms, and the impact of frequency and duration of surveillance imaging using follow-up CTAs. Methods- Simulation-modeling approach was performed using data on CTA associated radiation risk. We used the Radiation Risk Assessment Tool, based on the data using the BEIR VII report (BEIR VII). Each CTA was assigned as a separate exposure event. Men and women, respectively, starting surveillance imaging at 30, 40, and 50 years and receiving annual CTAs were considered as separate subgroups. As a comparison, we also calculated the radiation-induced cancer risk in the same groups of patients but receiving CTAs every 2 and 5 years, respectively. Results- CTA-associated excess cancer risk per exposure increases relatively more rapidly with the first 10 exposures and plateaus after the 44th exposure. On average, per CTA incurs ≈0.0026% in excess lifetime cancer risk. Receiving CTA follow-up at a younger age, more frequent follow-up, longer surveillance period, and men are the major factors contributing to an elevated excess lifetime risk. In the highest risk group, male patient receiving annual CTA follow-ups from the age of 30 years, the excess lifetime risk is 0.115% at the age of 81 years. Conclusions- Radiation-induced brain cancer incidence associated with unruptured intracranial aneurysm surveillance strategies using CTA is low relative to the risk for aneurysmal rupture. Further cost-effectiveness/utility analyses might help assess this risk in the context of aneurysmal ruptures prevented by surveillance imaging.

Subtraction CTA: An Alternative Imaging Option for the Follow-Up of Flow-Diverter-Treated Aneurysms?

BACKGROUND AND PURPOSE

This was a pilot study to explore the diagnostic accuracy and safety of subtraction CTA combined with a single-energy metal artifact reduction algorithm (SEMAR) compared to DSA for the evaluation of intracranial aneurysm occlusion after flow diverter treatment.

MATERIALS AND METHODS

We included patients treated with a flow diverter for an unruptured intracranial aneurysm between November 2015 and November 2016. The patient cohort comprised 2 groups: those who underwent follow-up imaging 1 month after flow-diverter treatment and those with a known residual intracranial aneurysm after flow diverter treatment who underwent imaging at regular follow-ups. Full-brain subtraction CTA was performed on a 320-detector row CT system. A low-dose non-enhanced volume acquisition was followed by a contrast-enhanced volume CTA. Iterative and noise-reduction filters, SEMAR, and ^SURESubtraction algorithms were applied. DSA was performed on a flat panel C-arm angiography system. Standard posteroanterior, lateral, 3D, and detailed 2D acquisitions were performed. Imaging was independently scored by 2 clinicians. Aneurysm occlusion (Raymond scale) was our primary outcome parameter.

RESULTS

Thirteen intracranial aneurysms were evaluated with subtraction CTA and DSA. Nine aneurysm remnants were demonstrated by both subtraction CTA and DSA. The sensitivity and specificity of subtraction CTA for the detection of aneurysm occlusion were 100% (95% CI, 82.41%-100%) and 100% (95% CI, 67.55%-100%), respectively. Agreement between readers was perfect (κ = 1.0). The smallest neck remnant detected on subtraction CTA was 1.2 mm. No complications occurred.

CONCLUSIONS

Subtraction CTA with single-electron metal artifact reduction is effective in the reduction of metal artifacts of flow diverters and might therefore be a viable alternative in the assessment of intracranial aneurysm occlusion after flow diverter treatment.

High-resolution 3D volumetric contrast-enhanced MR angiography with a blood pool agent (ferumoxytol) for diagnostic evaluation of pediatric brain arteriovenous malformations

OBJECTIVE Patients with brain arteriovenous malformations (AVMs) often require repeat imaging with MRI or MR angiography (MRA), CT angiography (CTA), and digital subtraction angiography (DSA). The ideal imaging modality provides excellent vascular visualization without incurring added risks, such as radiation exposure. The purpose of this study is to evaluate the performance of ferumoxytol-enhanced MRA using a high-resolution 3D volumetric sequence (fe-SPGR) for visualizing and grading pediatric brain AVMs in comparison with CTA and DSA, which is the current imaging gold standard. METHODS In this retrospective cohort study, 21 patients with AVMs evaluated by fe-SPGR, CTA, and DSA between April 2014 and August 2017 were included. Two experienced raters graded AVMs using Spetzler-Martin criteria on all imaging studies. Lesion conspicuity (LC) and diagnostic confidence (DC) were assessed using a 5-point Likert scale, and interrater agreement was determined. The Kruskal-Wallis test was performed to assess the raters' grades and scores of LC and DC, with subsequent post hoc pairwise comparisons to assess for statistically significant differences between pairs of groups at p < 0.05. RESULTS Assigned Spetzler-Martin grades for AVMs on DSA, fe-SPGR, and CTA were not significantly different (p = 0.991). LC and DC scores were higher with fe-SPGR than with CTA (p < 0.05). A significant difference in LC scores was found between CTA and fe-SPGR (p < 0.001) and CTA and DSA (p < 0.001) but not between fe-SPGR and DSA (p = 0.146). A significant difference in DC scores was found among DSA, fe-SPGR, and CTA (p < 0.001) and between all pairs of the groups (p < 0.05). Interrater agreement was good to very good for all image groups (κ = 0.77-1.0, p < 0.001). CONCLUSIONS Fe-SPGR performed robustly in the diagnostic evaluation of brain AVMs, with improved visual depiction of AVMs compared with CTA and comparable Spetzler-Martin grading relative to CTA and DSA.

Vascular assessment after clipping surgery using four-dimensional CT angiography

Recent advances in computed tomography angiography (CTA) enable repeated imaging follow up for post-clipping surgery. The purpose of this study was to clarify the critical volume and configuration of the aneurysmal clip in the postoperative evaluation using volume rendering (VR) imaging, and present four-dimensional (4D)-CTA for these larger metal artifacts. A total of 44 patients with cerebral aneurysm, treated using clipping surgery, were included in this study. The metal artifact volume was assessed using CTA and the association between the type of clips and its metal artifact volume was analyzed. A VR image and a 4D-CTA were then produced, and the diagnostic accuracy of arteries around the clip or residual aneurysm on these images was evaluated. In the receiver operating characteristic (ROC) curve analysis, the cutoff value for metal artifacts was 2.32 mm³ as determined through a VR image. Patients were divided into two groups. Group 1 included patients with a simple and small clip, and group 2 included patients with multiple, large or fenestrated clips. The metal artifact volume was significantly larger in group 2, and the group incorporated the cutoff value. Post-clipping status on the VR image was significantly superior in group 1 compared with group 2. In group 2, the imaging quality of post-clipping status on 4D-CTA was superior in 92.9% of patients. The metal artifact volume was dependent on the number, size, or configuration of the clip used. In group 2, evaluation using a 4D-CTA eliminated the effect of the metal artifacts.

The effect of scan interval and bolus length on the quantitative accuracy of cerebral computed tomography perfusion analysis using a hollow-fiber phantom

The shuttle scan technique is expected to extend scan range in cerebral computed tomography (CT) perfusion by 16- or 64-row multidetector CT (MDCT), but it may affect quantitative accuracy. This study aims to evaluate the effect of long scan interval and bolus length on the quantitative accuracy of perfusion indices using an innovative hollow-fiber phantom.We used an originally developed hollow-fiber hemodialyzer covered with polyurethane resin as a perfusion phantom. We scanned the phantom during various scan intervals (1-13 s) and bolus injection lengths (5, 10, 15, and 20 s), and evaluated cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and time-to-peak (TTP). We verified the influence on measured values using a two-way analysis of variance (ANOVA). All measured CBF values were smaller than the theoretical CBF values, and all the measured MTT values were larger that the theoretical MTT values (95% confidence interval). Extended scan intervals resulted in more overestimation of MTT and more underestimation of CBF (p < 0.001). CBV is not affected by the change in scan interval (p < 0.001), and a longer bolus length improved the underestimation of CBV (p < 0.001). Extended scan intervals resulted in the loss of quantitative accuracy in MTT, even with longer bolus injection length, while quantitative CBF values were underestimated and TTP values overestimated. The CBV measurement was not affected by the change in scan interval, and a longer bolus injection improved the accuracy of these measurements.

Time resolved computed tomography angiography in the evaluation of brain arteriovenous malformation: a feasibility study

Background and purpose Digital subtraction angiography is the current gold standard for diagnosing as well as the follow-up of cerebral arteriovenous malformations. However, as it is invasive, relatively expensive and time-consuming, a non-invasive alternative is of interest. We aimed to evaluate the feasibility of time resolved computed tomography angiography (TR-CTA) in a series of five diagnosed cranial arteriovenous malformation patients, demonstrated by conventional digital subtraction angiography with respect to acquisition, depiction of angiographic phases and radiation exposure. Materials and methods Five patients demonstrating a cranial arteriovenous malformation on digital subtraction angiography were studied with TR-CTA. The TR-CTA imaging was done by using a 128-detector computed tomography scanner. Digital subtraction angiography and TR-CTA studies were independently read by two blinded observers, by using a standardised scoring sheet. TR-CTA results were analysed with digital subtraction angiography as the criterion standard. Results TR-CTA generated comparable angiographic phases. In all five cases, there was complete agreement between digital subtraction angiography and TR-CTA regarding the size, arterial feeders, nidal morphology and venous drainage of the arteriovenous malformation. Conclusions TR-CTA imaging as a technique is feasible, providing images with good temporal and spatial resolution at an acceptable radiation dose. It appears to be a promising non-invasive adjunct to digital subtraction angiography.

Cerebrovascular Imaging: Which Test is Best?

Optimal diagnosis and characterization of cerebrovascular disease requires selection of the appropriate imaging exam for each clinical situation. In this review, we focus on intracranial arterial disease and discuss the techniques in current clinical use for imaging the blood vessel lumen and blood vessel wall, and for mapping cerebral hemodynamic impairment at the tissue level. We then discuss specific strategies for imaging intracranial aneurysms, arteriovenous malformations, dural arterial venous fistulas, and arterial steno-occlusive disease.

Quantitative accuracy of computed tomography perfusion under low-dose conditions, measured using a hollow-fiber phantom

PURPOSE

The purpose of this study was to investigate the quantitative accuracy under low-dose conditions on computed tomography (CT) perfusion using a hollow-fiber phantom that had the theoretical absolute values of perfusion indices.

MATERIALS AND METHODS

Our phantom comprised two components, i.e., a hollow-fiber hemodialyzer to pump the diluted contrast material and a surrounding syringe-shaped X-ray-absorbing body to simulate the absorption of X-rays by a brain and cranium. We performed CTP scans on the phantom under various dose conditions ranging from 20 to 140 mA using a 64-row CT scanner, measuring experimental cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and time to peak (TTP) values using a deconvolution algorithm.

RESULTS

The theoretical value of the CBV was within the 95% confidence interval of CBV values measured under 80 mA. The CBV measured under low-dose settings and all CBF values measured were smaller than the theoretically calculated ones, and all MTT values measured were larger. All measured values of the CBV, CBF, MTT, and TTP decreased with an increase in image noise under lower dose conditions.

CONCLUSION

It is difficult to define a low-dose limit in clinical scan conditions because of the complex characteristics of perfusion indices.

4D-CT angiography with arterial- and venous-phase anatomical pre-surgical approaches in cases with head and neck neoplasms

PURPOSE

The relationship between neoplasm and its surrounding vascular structure is essential to the following clinical treatment plan. In this study, 4D computed tomography angiography (4D-CTA) with a wide scan range and dynamic phases of arteriography and venography was used to describe detailed anatomical information for pre-surgical approaches.

MATERIALS AND METHODS

From January 2011 to February 2012, we subjected 13 patients with head and neck neoplasms to 4D-CTA. 4D-CTA was performed by a multidetector computed tomography (MDCT) scanner of 320 detectors. The parameters were set to a 0.5 mm section thickness, at 0.5 second per rotation, 80 kV and 150 mA. The scan range was set depending on the tumor size, with a maximal setting of 16 cm. A 30 mL contrast medium with 60 mL saline was injected at the rate of 5-7 mL per second based on the vascular patency, scanning every 2 seconds from the 16th to the 28th second after contrast injection.

RESULTS

The vasculature surrounding the tumors was successfully illustrated in all cases. The 4D-CTA provided detailed vascular information that was compatible with the surgical and angiographic findings.

CONCLUSION

4D-CTA with a wide scan range and precise injection timing methods facilitated an anatomical approach to tumor-related vascular structures, providing detailed vascular information. This non-invasive technique may be useful for evaluating neoplasms and developing treatment plans, as an alternative to conventional angiography.

Contemporary Imaging of Cerebral Arteriovenous Malformations

OBJECTIVE

Brain arteriovenous malformation (AVM) rupture results in substantial morbidity and mortality. The goal of AVM treatment is eradication of the AVM, but the risk of treatment must be weighed against the risk of future hemorrhage.

CONCLUSION

Imaging plays a vital role by providing the information necessary for AVM management. Here, we discuss the background, natural history, clinical presentation, and imaging of AVMs. In addition, we explain advances in techniques for imaging AVMs.

Comparison of eye-lens doses imparted during interventional and non-interventional neuroimaging techniques for assessment of intracranial aneurysms

Background

A neurointerventional examination of intracranial aneurysms often involves the eye lens in the primary beam of radiation.

Objective

To assess and compare eye-lens doses imparted during interventional and non-interventional imaging techniques for the examination of intracranial aneurysms.

Methods

We performed a phantom study on an anthropomorphic phantom (ATOM dosimetry phantom 702-D; CIRS, Norfolk, Virginia, USA) and assessed eye-lens doses with thermoluminescent dosimeters (TLDs) type 100 (LiF:Mg, Ti) during (1) interventional (depiction of all cerebral arteries with triple 3D-rotational angiography and twice 2-plane DSA anteroposterior and lateral projections) and (2) non-interventional (CT angiography (CTA)) diagnosis of intracranial aneurysms. Eye-lens doses were calculated following recommendations of the ICRP 103. Image quality was analysed in retrospective by two experienced radiologists on the basis of non-interventional and interventional pan-angiography examinations of patients with incidental aneurysms (n=50) on a five-point Likert scale.

Results

The following eye-lens doses were assessed: (1) interventional setting (triple 3D-rotational angiography and twice 2-plane DSA anteroposterior and lateral projections) 12 mGy; (2) non-interventional setting (CTA) 4.1 mGy. Image quality for depiction of intracranial aneurysms (>3 mm) was evaluated as good by both readers for both imaging techniques.

Conclusions

Eye-lens doses are markedly higher during the interventional than during the non-interventional diagnosis of intracranial aneurysms. For the eye-lens dose, CTA offers considerable radiation dose savings in the diagnosis of intracranial aneurysms.

Imaging Carotid Atherosclerosis Plaque Ulceration: Comparison of Advanced Imaging Modalities and Recent Developments

Atherosclerosis remains the leading cause of long-term mortality and morbidity worldwide, despite remarkable advancement in its management. Vulnerable atherosclerotic plaques are principally responsible for thromboembolic events in various arterial territories such as carotid, coronary, and lower limb vessels. Carotid plaque ulceration is one of the key features associated with plaque vulnerability and is considered a notable indicator of previous plaque rupture and possible future cerebrovascular events. Multiple imaging modalities have been used to assess the degree of carotid plaque ulceration for diagnostic and research purposes. Early diagnosis and management of carotid artery disease could prevent further cerebrovascular events. In this review, we highlight the merits and limitations of various imaging techniques for identifying plaque ulceration.

Diagnosing Vasospasm After Subarachnoid Hemorrhage: CTA and CTP

Cerebral vasospasm is a potentially devastating complication in patients with aneurysmal subarachnoid hemorrhage. The purpose of this article is to review the use of computed tomogram (CT) angiography and CT perfusion in the diagnosis of cerebral vasospasm after aneurysmal subarachnoid hemorrhage and also assess their use in guiding treatment decisions. Both techniques are widely used for other indications but their use in cerebral vasospasm has not been well defined. Computed tomogram angiography can directly visualize arterial narrowing and CT perfusion is able to evaluate differences in perfusion parameters after aneurysmal subarachnoid hemorrhage with high sensitivity and specificity. CT perfusion is better at predicting which patients require endovascular treatment.