A new reference line for the brain CT: the tuberculum sellae-occipital protuberance line is parallel to the anterior/posterior commissure line

Retrosigmoid versus Retrolabyrinthine Posterior Petrosal Route to the Petroclival Area: Quantitative Assessment of Endoscope-Assisted Approaches and Correlations with Morphometric Features

OBJECTIVE

Using a cadaveric model, we compared endoscope-assisted retrosigmoid (EAR) and endoscope-assisted retrolabyrinthine posterior petrosal (EARPP) approaches towards the petroclival area, regarding surgical exposure and instrument maneuverability, also verifying how some petroclival morphometric parameters correlate with these variables.

METHODS

In five cadaver heads, EAR approach was performed on one side and EARPP on the other (10 approaches). Under endoscopic view, neuronavigation coordinates were acquired to compute areas of exposure (petroclival and pontomedullary) and maneuverability at Dorello's canal entrance to run the comparison. Correlations of these variables with petroclival angle and clival depth were also analyzed.

RESULTS

EAR and EARPP showed equivalence regarding surgical exposure (petroclival: 365.85 ± 133.12 mm² and 320.62 ± 103.44 mm², respectively, P = 0.69; pontomedullary: 255.83 ± 88.26 mm² and 229.80 ± 74.39 mm², respectively, P = 0.83), but EAR afforded greater maneuverability at Dorello's canal (1155.88 ± 134.35 mm², P = 0.03). The petroclival angle and clival depth showed different strong correlations with maneuverability depending upon the route, but not with surgical exposure in both approaches.

CONCLUSIONS

Endoscopic techniques can spare the need for additional steps of greater morbidity when approaching the petroclival area in both routes. A simpler and faster approach as EAR was favored over EARPP in this standardized quantitative assessment. The petroclival angle and clival depth may interfere with maneuverability, but not with surgical exposure in both endoscope-assisted approaches.

Toward automatic reformation at the orbitomeatal line in head computed tomography using object detection algorithm

Consistent cross-sectional imaging is desirable to accurately detect lesions and facilitate follow-up in head computed tomography (CT). However, manual reformation causes image variations among technologists and requires additional time. We therefore developed a system that reformats head CT images at the orbitomeatal (OM) line and evaluated the system performance using real-world clinical data. Retrospective data were obtained for 681 consecutive patients who underwent non-contrast head CT. The datasets were randomly divided into one of three sets for training, validation, or testing. Four landmarks (bilateral eyes and external auditory canal) were detected with the trained You Look Only Once (YOLO)v5 model, and the head CT images were reformatted at the OM line. The precision, recall, and mean average precision at the intersection over union threshold of 0.5 were computed in the validation sets. The reformation quality in testing sets was evaluated by three radiological technologists on a qualitative 4-point scale. The precision, recall, and mean average precision of the trained YOLOv5 model for all categories were 0.688, 0.949, and 0.827, respectively. In our environment, the mean implementation time was 23.5 ± 2.4 s for each case. The qualitative evaluation in the testing sets showed that post-processed images of automatic reformation had clinically useful quality with scores 3 and 4 in 86.8%, 91.2%, and 94.1% for observers 1, 2, and 3, respectively. Our system demonstrated acceptable quality in reformatting the head CT images at the OM line using an object detection algorithm and was highly time efficient.

Correlation of the external occipital protuberance with venous sinuses: a magnetic resonance imaging study

PURPOSE

To date, no study has explored the external occipital protuberance (EOP) using neuroimaging modalities. This study aims to characterize them using magnetic resonance imaging (MRI).

METHODS

A total of 96 patients underwent thin-sliced, post-contrast MRI. The sagittal images were analyzed.

RESULTS

In 97%, the EOPs were delineated as a focal external protrusion of the midline region of the occiput with varying morphologies. In 89% of 93 patients with identifiable EOPs, parts of the intracranial dural sinuses were found to lie just below the inion, the most prominent point of the EOP. The most frequently targeted dural sinus was the confluence of sinuses that was found in 57%, followed by the superior sagittal sinus. In 16%, a bony foramen and transmitting vessel were detected in the EOP, connecting between the diploic channels and the subcutaneous veins. Furthermore, in 33%, bony foramina and transmitting venous structures were identified in the region just below the EOPs, connecting between the diploic channels and the subcutaneous veins.

CONCLUSIONS

The intracranial dural venous sinus is located just below the EOP with a high probability. Most bony foramina in the EOP and midline suboccipital region may transmit veinous structures connecting to the diploic channel.

A Real-World Clinical Implementation of Automated Processing Using Intelligent Work Aid for Rapid Reformation at the Orbitomeatal Line in Head Computed Tomography

MATERIALS AND METHODS

We retrospectively reviewed 781 head CTs (median, 70 years; 441 men) collected by CT systems from 3 vendors. In addition to the orbitomeatal line image reformatted by a CT specialist as a reference, we obtained the fully automated orbitomeatal line image using the intelligent work aid. We calculated the offset angle from the reference of the automatically reformatted image. We defined the large offset angle groups as those with an offset angle greater than 3 degrees. Multivariate logistic regression was used to determine the independent factors for the large offset angle groups. We compared the postprocessing times measured using the intelligent work aid or by a CT specialist.

RESULTS

With the intelligent work aid, 99.7% of CTs were automatically reformatted to the orbitomeatal line without error. Furthermore, 88.1% of CTs were within the 3 degrees' offset angle when compared with the reference produced by a CT specialist. The median offset angle from the reference was 1.41 degrees. Multivariate analysis showed that the offset angle of the positioning plane was an independent factor (odds ratio, 1.045; P = 0.005) for predicting the large offset angle group. Furthermore, this technique was 4 times faster (6.4 ± 0.7 seconds) than a CT specialist (25.6 ± 6.4 seconds).

CONCLUSIONS

The intelligent work aid can generate a fast and precise head CT image aligned at the orbitomeatal line, even in real-world clinical CTs. However, precise positioning remains essential.

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.

Evaluation of anatomical landmark position differences for head computed tomography: A reliability study among technologists

INTRODUCTION

In computed tomography (CT) imaging protocols, lack of practice standards and variability in head positioning may all yield substantial inter-study image variance in the clinical setting which may limit the diagnostic and comparative value of subsequent scans. We aimed to evaluate repeatability of multiplanar reformatting of head CT based on the tuberculum sella (TS) to internal occipital protuberance (IOP) reference line and reduce variance.

METHODS

Reference lines that correspond to the TS-IOP plane on high-resolution CT scans were reviewed by technologists manually to calculate Yaw (z-rotation, rotation along the superoinferior direction), Pitch (x-rotation, rotation along the left-right direction), and Roll (y-rotation, rotation along the anteroposterior direction) angles in this pre-post design intervention study. The Yaw, Pitch, and Roll angles deviating from the reference TS-IOP in the head CT images before and after technologist training were measured with the technologists' actual graphical prescriptions, and their differences were calculated with t-tests. The intra-rater agreement was calculated using the intraclass correlation coefficient (ICC).

RESULTS

Mean pitch, yaw, and roll before technologist training was 6.7° ± 5.4°, 0.9° ± 1.5°, and 1.1° ± 1.2° and after training were 3.2° ± 2.6°, 0.6° ± 1.1°, and 0.6° ± 1.1°, respectively. Technologist training resulted in a significant decrease in pitch (p < 0.001) and roll (p = 0.001) inter-subject variability with respect to the TS-IOP line, however no significant difference for the yaw correction (p = 0.065) was noted. Intra-rater agreement regarding the reproducibility of TS-IOP reformation was excellent (ICC>0.950).

CONCLUSION

TS-IOP reference line corrected for direct roll, yaw, and pitch can be readily achieved by trained technologists.

IMPLICATIONS FOR PRACTICE

Adoption of the TS-IOP reference line should facilitate intra- and intermodality comparisons, leading to more reproducible and readily interpretable CT images.

A new reference line for coronal head CT to align with MRI: development of a standardised approach

BACKGROUND AND PURPOSE

There are great variations in how different technologists create the different imaging planes that can make a precise comparison of computed tomography and magnetic resonance imaging difficult. We aimed to identify a reference line for the coronal images on a computed tomography topography parallel to the posterior borderline of the brainstem (PB), matching standard coronal magnetic resonance imaging planes.

METHODS

We retrospectively reviewed computed tomography topography images of 80 consecutive patients to determine a computed tomography plane to match the PB on magnetic resonance imaging. These included the tuberculum sella (TS)-anterior arch of the C1 vertebra (C1), TS-tip of dens axis (D), dorsum sellae (DS)-C1 and DS-D. We compared these methods of prescribing the coronal computed tomography plane to coronal magnetic resonance imaging planes by measuring the angles between TS-C1 and PB, TS-M and PB, DS-C1 and PB, DS-D and PB on midsagittal brain magnetic resonance images. Bland-Altman plots were created to assess intra-observer reliability.

RESULTS

The angles between the PB line and each topogram-determined line are as follows: TS-C1, 10.40° ± 4.86°; TS-D, 22.46° ± 5.23°; DS-C1, 3.01° ± 3.16°; and DS-D, 11.53° ± 4.10°. The mean angles between the DS-C1 and the PB lines were significantly smaller than the mean angle between any other line (DS-D, TS-C1, or TS-D, all P < 0.001). Intra-observer agreement regarding the angular position of the reformatted coronal images on the lateral scout image was excellent (intraclass correlation coefficient >0.900, P < 0.05).

CONCLUSIONS

The DS-C1 is almost parallel to the PB and easily identifiable on the lateral scout topography of brain computed tomography. Utilising the DS-C1 line as the baseline for brain computed tomography could allow better corroboration with coronal magnetic resonance imaging angulation.

Automatic Alignment of Cranial CT Examinations to the Anterior Commissure/Posterior Commissure (ACPC) Reference Plane for Reliable Interpretation and Quality Assurance

Alignment of cranial CT scans (cCTs) to a common reference plane simplifies anatomical-landmark-based orientation and eases follow-up assessment of intracranial findings. We developed and open sourced a fully automated system, which aligns cCTs to the Anterior Commissure/Posterior Commissure (ACPC) line and exports the results to the PACS. FMRIB's Linear Image Registration Tool (FLIRT) with an ACPC-aligned atlas is used in the alignment step. Five mm mean slabs are generated with the top non-air slice as the starting point. For evaluation, 301 trauma cCTs from the CQ500 dataset were processed. In visual comparison with the respective ACPC-aligned atlas, all were successfully aligned. Image quality (IQ) and ease of identification of the central sulcus (CS) were rated on a Likert scale (5 = excellent IQ/immediate CS identification). The median IQ was 4 (range: 2-4) in the original series and 5 (range: 4-5) in the ACPC-aligned series (p < 0.0001). The CS was more easily identified after fatbACPC (original scans: 4 (range: 2-5); ACPC-aligned: 5 (range: 4-5); p < 0.0001). The mean rotation to achieve alignment was |X| = 6.4 ± 5.2° ([-X,+X] = -26.8°-24.2°), |Y| = 2.1 ± 1.7° ([-Y,+Y] = -8.7°-9.8°), and |Z| = 3.1 ± 2.4° ([-Z,+Z] = -14.3°-12.5°). The developed system can robustly and automatically align cCTs to the ACPC line. Degrees of deviation from the ideal alignment could be used for quality assurance. KEY POINTS:: · fatbACPC automatically aligns cranial CT scans to the Anterior Commissure/Posterior Commissure plane.. · ACPC-aligned images simplify anatomical-landmark-based orientation.. · fatbACPC does not impact image quality.. · fatbACPC is robust, fully PACS-integrated, and Open Source: https://github.com/BrainImAccs. CITATION FORMAT: · Rubbert C, Turowski B, Caspers J. Automatic Alignment of Cranial CT Examinations to the Anterior Commissure/Posterior Commissure (ACPC) Reference Plane for Reliable Interpretation and Quality Assurance. Fortschr Röntgenstr 2021; 193: 61 - 67.

A new brain CT reference line: the lower eyelid to the inner occipital base line closely parallels the Talairach-Tournoux line

Background

There is no standardized brain computed tomography (CT) reference line that can be determined on both scout and reformatted sagittal CT images. Here, a tangential line from the anterior edge of the lower eyelid to the inner table of the occipital base (LEL/O line) appears nearly parallel to the Talairach–Tournoux (T/T) line, which shows a consistent intracranial anatomical relationship among subjects, and acts as a standard reference line for magnetic resonance (MR) imaging.

Purpose

To quantitatively validate the LEL/O line as a new standard brain CT reference line.

Material and Methods

We measured: angle 1 = the LEL/O line on scout images from the LEL/O line on parasagittal CT images (n=93); and angle 2 = the LEL/O line on scout images from the T/T line on high resolution midsagittal MR images (n=97). Angles in a clockwise direction were defined as positive and were expressed as mean±SD with the 95% confidence interval (CI) of the SD. Angle 2 was measured independently by two observers and intraclass correlation coefficients (ICCs) were calculated.

Results

Angle 1 was –0.4°±1.2° (95% CI of SD 1.1°–1.5°); angle 2 was –0.4°±2.0° (95% CI of SD, 1.8°–2.4°). The ICC in the angle 2 measurement was 0.780 (P<0.001), which indicated high inter-observer reliability.

Conclusion

The LEL/O lines on scout and parasagittal CT images show practically the same gradient, and these LEL/O lines are almost parallel to the T/T line. Use of the LEL/O line either for direct scanning or reformation can minimize intra- and inter-subject variations on CT images and mismatch between CT and MR images.

Evaluation of Concomitant Orbital Floor Fractures in Patients with Head Trauma Using Conventional Head CT Scan: A Retrospective Study at a Level II Trauma Center

BACKGROUND

Patients with head trauma may have concomitant orbital floor fractures (OFFs). The objective of our study was to determine the specific CT findings and investigate the diagnostic performance of head CT in detecting OFFs.

METHODS

We analyzed 3534 head trauma patients undergoing simultaneous head and facial CT over a 3-year period. The clinical data and specific head CT findings between patients with and without OFFs were compared.

RESULTS

In our cohort, 198 patients (5.6%) had OFFs visible on CT. On head CT, orbital floor discontinuity, gas bubbles entrapped between floor fragments, inferior extraconal emphysema, and maxillary hemosinus (MHS) were more commonly observed among patients with OFFs (p < 0.001). The absence of MHS had a high negative predictive value (99.7%) for excluding OFFs. Among the different types of MHS, the pattern showing high-attenuation opacity mixed with mottled gas had the highest positive predictive value (69.5%) for OFFs and was the only independent predictor of OFFs after adjusting for the other CT variables in all patients with MHS.

CONCLUSION

Head CT may serve as a first-line screening tool to detect OFFs in head trauma patients. Hence, unnecessary facial CT and additional radiation exposure may be reduced.

Automatic Detection of a Standard Line for Brain Magnetic Resonance Imaging Using Deep Learning

Recently, deep learning technology has been applied to medical images. This study aimed to create a detector able to automatically detect an anatomical structure presented in a brain magnetic resonance imaging (MRI) scan to draw a standard line. A total of 1200 brain sagittal MRI scans were used for training and validation. Two sizes of regions of interest (ROIs) were drawn on each anatomical structure measuring 64 × 64 pixels and 32 × 32 pixels, respectively. Data augmentation was applied to these ROIs. The faster region-based convolutional neural network was used as the network model for training. The detectors created were validated to evaluate the precision of detection. Anatomical structures detected by the model created were processed to draw the standard line. The average precision of anatomical detection, detection rate of the standard line, and accuracy rate of achieving a correct drawing were evaluated. For the 64 × 64-pixel ROI, the mean average precision achieved a result of 0.76 ± 0.04, which was higher than the outcome achieved with the 32 × 32-pixel ROI. Moreover, the detection and accuracy rates of the angle of difference at 10 degrees for the orbitomeatal line were 93.3 ± 5.2 and 76.7 ± 11.0, respectively. The automatic detection of a reference line for brain MRI can help technologists improve this examination.

Comparative radiologic identification with standardized single CT images of the paranasal sinuses-Evaluation of inter-rater reliability

The aim of this study was to assess the reproducibility of a standardized image for personal identification (SIPI), used in the comparative analysis of paranasal sinuses, and test the effect of inaccurate reformation of the SIPI on suitability for comparative identification. Five raters with different professional backgrounds independently reformatted SIPIs from ten post-mortem head CTs. Inter-rater, intra-rater agreement as well angular deviations between reformatted SIPI images and reference SIPI images were calculated. Second, raters assessed the suitability of 70 accurately and inaccurately reformatted SIPIs for identification with a 4-point Likert scale. Inter-rater agreement as well as levels of significance regarding image suitability were calculated. Inter-rater agreement regarding reproducibility of SIPI reformation was excellent (inter-rater correlation coefficient (ICC) 0.9995, intra-rater ICC 0.9983). Deviation between the angular dimensions of the reformatted SIPIs and the reference SIPIs was ≤1° in 94% of all 300 measurements. Inter-rater agreement regarding the effect of inaccurate SIPI reformation on suitability for comparative identification was fair (ICC 0.6809). There was no statistically significant difference between raters' evaluation of image suitability (p=0.9755). This study shows that the standardized image for personal identification can be accurately reformatted by different raters with varying professional backgrounds. In addition, raters agree that inaccurately reformatted SIPIs are still suitable for comparative identification in the majority of cases.

Localization of orofacial representation in the corona radiata, internal capsule and cerebral peduncle in Macaca mulatta

Subcortical white matter injury is often accompanied by orofacial motor dysfunction, but little is known about the structural substrates accounting for these common neurological deficits. We studied the trajectory of the corticobulbar projection from the orofacial region of the primary (M1), ventrolateral (LPMCv), supplementary (M2), rostral cingulate (M3) and caudal cingulate (M4) motor regions through the corona radiata (CR), internal capsule (IC) and crus cerebri of the cerebral peduncle (ccCP). In the CR each pathway was segregated. Medial motor area fibers (M2/M3/M4) arched over the caudate and lateral motor area fibers (M1/LPMCv) curved over the putamen. At superior IC levels, the pathways were widespread, involving the anterior limb, genu and posterior limb with the M3 projection located anteriorly, followed posteriorly by projections from M2, LPMCv, M4 and M1, respectively. Inferiorly, all pathways maintained this orientation but shifted posteriorly, with adjacent fiber bundles overlapping minimally. In the ccCP, M3 fibers were located medially and M1 fibers centromedially, with M2, LPMCv, and M4 pathways overlapping in between. Finally, at inferior ccCP levels, all pathways overlapped. Following CR and superior IC lesions, the dispersed pathway distribution may correlate with acute orofacial dysfunction with spared pathways contributing to orofacial motor recovery. In contrast, the gradually commixed nature of pathway representation inferiorly may enhance fiber vulnerability and correlate with severe, prolonged deficits following lower subcortical and midbrain injury. Additionally, in humans these findings may assist in interpreting orofacial movements evoked during deep brain stimulation, and neuroimaging tractography efforts to localize descending orofacial motor pathways.

[Comparison of Quantitative Value of Dopamine Transporter Scintigraphy Calculated from Different Analytical Software]

In the dopamine transporter scintigraphy there are two quantitative analysis softwares, DaTView and DaTQUANT. The quantitative value of both software has to be treated independently because there is a difference between them in the point of how to set the region of interest on the striatum and the background, calculation formula of quantitation. And also DaTQUANT has a capability of performing anatomical standardization which DaTView does not have. The aim of this study was to evaluate the accuracy of registration on DaTQUANT using a phantom, and to evaluate the correlation between the quantitative values between DaTView and DaTQUANT using clinical data. As a result, the accuracy of registration was acceptable. Regardless of the degree of accumulation in the striatum, there was a high correlation to each analysis software (r>0.85).

First stage in predicative measure for transnasal transsphenoidal approach to petrous apex cholesterol granuloma

OBJECTIVES/HYPOTHESIS

This study evaluates the feasibility of the transsphenoidal approach to petrous apex cholesterol granuloma based on the petrous angle. This is the angle centered at the vomer, extending between the medial aspect of the C3 segment of the internal carotid artery and the occipital protuberance. The aim of this study is to determine the average petrous angle in a population of normal computed tomography scans.

STUDY DESIGN

Retrospective review at the University of Cincinnati Medical Center.

METHODS

Two of the authors independently reviewed 400 consecutive normal temporal bone computed tomography scans obtained between September and December of 2009. All scans had slice thickness of 1.25 mm at 0.6-mm intervals. Axial images parallel to the orbitomeatal plane were analyzed, and the petrous angle was measured bilaterally. Interrater reliability was tested on 50 of the computed tomography scans.

RESULTS

A total of 400 temporal bones were reviewed. The mean and median petrous angle was 17.7 and 16.5 degrees, respectively. Eleven (2.8%) had an angle ≤ 10.0, 331 (82.8%) between 10.1 to 20.0, and 58 (14.5%) ≥ 20.1. The interrater variability was highly correlated (r = 0.912, P < .005).

CONCLUSIONS

Normative data on consistent petrous apex radiographic landmarks are important for assessing the feasibility of the transphenoidal approach to the petrous apex for cholesterol granuloma drainage. Based on a large population of normal computed tomography scans, the majority of temporal bones (82.8%) have a petrous angle ranging between 10.0 and 20.0 degrees.