Orbitomeatal Line Research Articles

Artifact Assessment in the Skull Base Region of Head CT Images with Various Tilt Angles Relative to the Orbitomeatal Line

The aim of this study was to evaluate artifacts in the skull base region of head computed tomography (CT) images with various tilt angles relative to the orbitomeatal line. CT images of a head phantom acquired by helical and non-helical scanning with the tilt angles set from 0 to 20 degrees in 5-degree increments were evaluated in this study. Regions of interest (ROIs) were set at the cerebellum, temporal lobe, frontal lobe, and basal ganglia in the phantom images. Artifacts were evaluated by the coefficient of variation (CV) of the mean CT value between ROIs and the location parameter (β) of the Gumbel method. The CV and β values increased with increasing tilt angle for both helical and nonhelical images in the frontal lobes, but both decreased in the cerebellar region. In the temporal lobe and basal ganglia, there was no trend of change with tilt angle. Increasing the tilt angle relative to the OM line increased artifacts at the frontal lobes and decreased artifacts at the cerebellar region.

Usefulness of the superior orbitomeatal line without the lens included in the scan range at different tube voltage during pediatric head CT

Introduction and objectivesTo compare the real time skin dosimeter values at lens between with the lens included in the scan range (orbitomeatal base line [OML]) or without the lens included in the scan range (superior orbitomeatal line [SOML]) at different tube voltages. Materials and methodsWe used three pediatric anthropomorphic phantoms with a 64 detector-row computed tomography (CT) scanner with the OML- or SOML-protocol at different tube voltages during the head CT. A real time skin dosimeter was inserted into the phantom center of the head, and surfaces of the lens. We compared the real time skin dosimeter values at lens between the OML- and SOML-protocol. ResultsThere were no significant differences in the real time skin dosimeter values for the head in the scan area for each phantom at different tube voltages between the OML- and SOML-protocol (p > 0.05 for all phantom). Compared with the OML protocol, it is possible to reduce the real time skin dosimeter values at lens by approximately 80% by using the SOML protocol (p < 0.05) at all tube voltages. Compared with the OML protocol, it is possible to reduce the real time skin dosimeter values at mammary gland by approximately 20% by using the SOML protocol (p < 0.05) at all tube voltages. ConclusionsDuring the pediatric head CT examination, SOML protocol was possible to reduce the real time skin dosimeter values at lens by approximately 80% compared with OML protocol at all tube voltages.

Utilidad de la línea orbitomeatal superior sin incluir los cristalinos en la exploración con diferentes voltajes del tubo en la TC craneal pediátrica

Introduction and objectivesTo compare the real time skin dosimeter values at lens between with the lens included in the scan range (orbitomeatal base line [OML]) or without the lens included in the scan range (superior orbitomeatal line [SOML]) at different tube voltages. Materials and methodsWe used three pediatric anthropomorphic phantoms with a 64 detector-row computed tomography (CT) scanner with the OML- or SOML-protocol at different tube voltages during the head CT. A real time skin dosimeter was inserted into the phantom center of the head, and surfaces of the lens. We compared the real time skin dosimeter values at lens between the OML- and SOML-protocol. ResultsThere were no significant differences in the real time skin dosimeter values for the head in the scan area for each phantom at different tube voltages between the OML- and SOML-protocol (P>.05 for all phantom). Compared with the OML protocol, it is possible to reduce the real time skin dosimeter values at lens by approximately 80% by using the SOML protocol (P<.05) at all tube voltages. Compared with the OML protocol, it is possible to reduce the real time skin dosimeter values at mammary gland by approximately 20% by using the SOML protocol (P<.05) at all tube voltages. ConclusionsDuring the pediatric head CT examination, SOML protocol was possible to reduce the real time skin dosimeter values at lens by approximately 80% compared with OML protocol at all tube voltages.

Cephalalgia heterotopica: a case series of lower half face migraine

Introduction Migraine is a common and very disabling neurological disease. It typically causes severe throbbing pain or a pulsing sensation, usually on one side of the head. It's often accompanied by nausea, vomiting, and extreme sensitivity to light and sound. According to the definition of headache, the pain should be located in the head or in the face above the orbitomeatal line. Beyond this classical view, recent evidence has shown that it could be an arbitrary boundary, and other clinical features can prevail during the diagnosis process. Objective This consecutive case series study aimed to report clinical features, treatment, and outcome of 5 patients with a lower-half facial presentation of migraine. Materials and Methods Case series of our Headache Clinic. Data disclosure was authorized by the patients through an informed consent form. Results Of the 5 patients, 3 were women and 2 were men. Mean age was 34, 6 (13-56 years). The mean age of symptoms onset was 15,2 (11-29 years). All patients described a throbbing, moderate to severe pain in the malar area. Four patients reported frequent phonophobia and photophobia accompanying pain attacks. One patient reported great relief of pain with rizatriptan and another with sumatriptan. Preventive treatment with pizotifen, propranolol, flunarizine, amitriptyline, divalproex sodium, and pregabalin was useful. All patients underwent extensive dental and otolaryngological evaluation and treatment, which were worthless. Conclusion Migraine orofacial presentation is a diagnostic challenge. Proper recognition of these cases not only prevents unnecessary examination and treatment trials but directly benefits the patients since effective treatment is already available. A proper case definition of this rare clinical presentation may provide new insight into our understanding of the migraine mechanisms. Keywords: Facial pain, Migraine, Lower half-face migraine.

COMPARISON OF PEDIATRIC LENS DOSE MEASUREMENTS BETWEEN AXIAL SCAN MODE WITHOUT ACTIVE COLLIMATOR AND HELICAL SCAN MODE WITH ACTIVE COLLIMATOR BY USING A 64 DETECTOR-ROW COMPUTED TOMOGRAPHY SCANNER.

To investigate the pediatric eye lens entrance surface dose for both axial scan modes without an active collimator and helical scan modes with an active collimator on 64 detector-row computed tomography (CT) scanner. We used three pediatric anthropomorphic phantoms with axial and helical scan modes from the superior orbitomeatal line to the crown of the head. We compared the measured dose values of the real-time skin dosemeter at the surfaces of the lens and the image noise at different scan modes. The median measured dose values for the lens of newborn, 1-year-old and the 5-year-old phantom were 31.3, 0.97 and 0.65mGy, respectively, in the axial scan mode and 0.89, 1.21 and 0.71mGy, respectively, in the helical scan mode. Compared with helical scans with an active collimators, axial scans can reduce the lens dose by ∼10% during head CT on 64 detector-row CT scanner without deterioration of image noise.

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 ± 2.4s 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.

Using a Carpenter’s Square to Localize Narrow or Multilayered Chronic Subdural Hematomas Diagnosed on Computed Tomography

Chronic subdural hematomas (CSDHs) with narrow or multilayered hematomas must be accurately localized for burr hole drainage. We present a simple alternative localization method using conventional computed tomography (CT) scans acquired for the initial diagnosis and a commercially available carpenter's square (CS). Using our novel method, we localized 77 narrow or multilayered CSDHs. A single burr hole site on the thickest portion of narrow hematomas or on the site allowing access to both the isolated superficial layer and the deep layer of multilayered hematomas was identified on axial CT images; the image was parallel to the orbitomeatal line (OML). On the target CT slice, the level from the OML and from the surface of the forehead to the intended burr hole (sagittal distance) was measured. The OML and the level of the CT target slice were marked using the CS. Then, the CS was placed at the marked target level; the 2 edges of the CS were situated on the frontal and temporal scalp and parallel to the OML and the sagittal line. The sagittal distance was then marked. All burr holes reached the CSDHs. The mean deviation of the burr holes was 4.7 mm inferior and 1.4 mm anterior to the intended site. In 65 instances (84.4%), a deviation within 10 mm was observed in both the superoinferior and the anteroposterior directions. Our simple and inexpensive method can localize narrow or multilayered CSDHs with acceptable accuracy and increases the efficiency of routine clinical work.

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

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. 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). 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.

Idiopathic Facial Pain Syndromes–An Overview and Clinical Implications.

Idiopathic facial pain syndromes are relatively rare. A uniform classification system for facial pain became available only recently, and many physicians and dentists are still unfamiliar with these conditions. As a result, patients frequently do not receive appropriate treatment. This article is based on pertinent publications retrieved by a selective search in PubMed, focusing on current international guidelines and the International Classification of Orofacial Pain (ICOP). The ICOP subdivides orofacial pain syndromes into six major groups, the first three of which consist of diseases of the teeth, the periodontium, and the temporomandibular joint. The remaining three groups (non-dental facial pain) are discussed in the present review. Attack-like facial pain syndromes most closely resemble the well-known primary headache syndromes, such as migraine, but with pain located below the orbitomeatal line. These syndromes are treated in accordance with the guidelines for the corresponding types of headache. Persistent idiopathic facial pain (PIFP) is a chronic pain disorder with persistent, undulating pain in the face and/or teeth, without any structural correlate. Since this type of pain tends to become chronified after invasive procedures, no dental procedures should be performed to treat it if the teeth are healthy; rather, the treatmentis similar to that of neuropathic pain, e.g., with antidepressant and anticonvulsive drugs. Neuropathic facial pain is also undulating and persistent. It is often described as a burning sensation, and neuralgiform attacks may additionally be present. Trigeminal neuralgia is a distinct condition involving short-lasting, lancinating pain of high intensity with a maximum duration of two minutes. The first line of treatment is with medications; invasive treatment options should be considered only if pharmacotherapy is ineffective or poorly tolerated. With the aid of this pragmatic classification system, the clinician can distinguish persistent and attack-like primary facial pain syndromes rather easily and treat each syndrome appropriately.

Optimal slice thickness of brain computed tomography using a hybrid iterative reconstruction algorithm for identifying hyperdense middle cerebral artery sign of acute ischemic stroke.

To determine the optimal slice thickness of brain non-contrast computed tomography using a hybrid iterative reconstruction algorithm to identify hyperdense middle cerebral artery sign in patients with acute ischemic stroke. We retrospectively enrolled 30 patients who had presented hyperdense middle cerebral artery sign and 30 patients who showed no acute ischemic change in acute magnetic resonance imaging. Reformatted axial images at an angle of the orbitomeatal line in slice thicknesses of 0.5, 1, 3, 5, and 7mm were generated. Optimal slice thickness for identifying hyperdense middle cerebral artery sign was evaluated by a receiver operating characteristics curve analysis and area under the curve (AUC). The mean AUC value of 0.5-mm slice (0.921; 95% confidence interval (95% CI), 0.868 to 0.975) was significantly higher than those of 3-mm (0.791; 95% CI, 0.686 to 0.895; p = 0.041), 5-mm (0.691; 95% CI, 0.583 to 0.799, p < 0.001), and 7-mm (0.695; 95% CI, 0.593 to 0.797, p < 0.001) slices, whereas it was equivalent to that of 1-mm slice (0.901; 95% CI, 0.837 to 0.965, p = 0.751). Thin slice thickness of ≤ 1mm has a better diagnostic performance for identifying hyperdense artery sign on brain non-contrast computed tomography with a hybrid iterative reconstruction algorithm in patients with acute ischemic stroke.

Use of the orbito-occipital line as an alternative to the Frankfort line.

Frankfort horizontal line, the line passing through the orbitale and porion, is one of the most widely used intracranial landmarks in cephalometric analysis. This study investigated the use of the orbito-occipital line extending from the orbitale to the external occipital protuberance as a novel horizontal line of the skull for substituting the Frankfort horizontal line. We evaluated the reproducibility of the new landmark and measured the angle between the orbito-occipital line and the Frankfort line. This study was conducted on 170 facial computed tomography (CT) scans of living adults from the Department of Plastic Surgery. After three-dimensionally reconstructed images were obtained from facial CT, the porion, orbitale, and external occipital protuberance were indicated by two observers twice. The angles between the orbito-meatal line (inferior orbital rim to porion; the Frankfort line) and the orbito-occipital line (inferior orbital rim to external occipital protuberance) were measured. There was no significant intraobserver or interobserver bias. The overall angle between the Frankfort line and orbito-occipital line was −0.5°±2.2° (mean±standard deviation). There was no statistically significant difference among side and sex. This study demonstrated good reproducibility of a new landmark—the external occipital protuberance—tested to replace the porion. The orbito-occipital line is a reliable, reproducible, and easily identifiable line, and has potential as a novel standard horizontal line to replace or at least supplement the Frankfort line in anthropological studies and certain clinical applications.

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.

Supratentorial Cerebral Arterial Territories for Computed Tomograms: A Mapping Study in 1160 Large Artery Infarcts

We recently generated a high-resolution supratentorial vascular topographic atlas using diffusion-weighed MRI in a population of large artery infarcts. These MRI-based topographic maps are not easily applicable to CT scans, because the standard-reference-lines for axial image orientation (i.e., anterior-posterior commissure line versus orbito-meatal line, respectively) are ‘not parallel’ to each other. Moreover, current, widely-used CT-based vascular topographic diagrams omit demarcation of the inter-territorial border-zones. Thus, we aimed to generate a CT-specific high-resolution atlas, showing the supratentorial cerebrovascular territories and the inter-territorial border-zones in a statistically rigorous way. The diffusion-weighted MRI lesion atlas is based on 1160 patients (67.0 ± 13.3 years old, 53.7% men) with acute (<1-week) cerebral infarction due to significant (>50%) stenosis or occlusion of a single large cerebral artery: anterior, middle, or posterior cerebral artery. We developed a software package enabling the transformation of our MR-based atlas into a re-oriented CT space corresponding to the axial slice orientations used in clinical practice. Infarct volumes are individually mapped to the three vascular territories on the CT template-set, generating brain maps showing the voxelwise frequency of infarct by the affected parent vessel. We then mapped the three vascular territories collectively, generating a dataset of Certainty-Index (CI) maps to reflect the likelihood of a voxel being a member of a specific vascular territory. Border-zones could be defined by using either relative infarct frequencies or CI differences. The topographic vascular territory atlas, revised for CT, will allow for easier and more accurate delineation of arterial territories and borders on CT images.

Assessment of the relationship of the Frankfort horizontal plane and the orbitomeatal line with attainment of the natural head position

Background: The diagnosis of dentofacial deformities and the choice of ortho-surgical treatment depend on the correct positioning of the head at the time of registration in 2D or 3D, called the natural head position (NHP).

Best zero level for external ICP transducer

BackgroundContinuous monitoring of intracranial pressure (ICP) was introduced in the 1950s. For correct ICP recordings, the zero-reference point for the external pressure gauge must be placed next to a head anatomical structure. We evaluated different anatomical points as zero reference for the ICP device at different head positions and their relation to brain centre (BC), foramen of Monro (Monro), and brain surface.MethodsPatients referred for neuroimaging due to e.g. headache all having normal 3D MRI scans were selected. Monro, BC, Orbit(O), external auditory meatus (EAM), and orbito-meatal (OM) line were identified and projected to mid-sagittal, or axial images. Each scan was evaluated like lying supine, 45° head elevations, upright, and 45° lateral position. Distances from skin to brain surface, BC, and Monro were measured. All values are presented as mean ± SD and/or range in millimetre. For conversion to mmHg, millimetre was multiplied by 0.074.ResultsTwenty MRI scans were examined. A zero reference at EAM or glabella was ideal at BC when head was strict supine or in the lateral position. At 45° head elevation, an overestimation of the BC-ICP by 4.8 ± 0.8 and in upright 5.6 ± 0.5 mmHg was found, and 45° lateral underestimated ICP-BC by 6.3 ± 1.0 mmHg. Monro was situated 45 ± 5 mm rostral to the mid-OM line and 24 (18–31) mm inferior and 13 (8–17) mm in front of BC. A zero-reference point aligned with the highest point of the head underestimated BC-ICP and Monro-ICP. If the ICP reading was added 5.9 or 6.3 mmHg, respectively, a deviation from BC-ICP was ≤ 1.8 mmHg and Monro-ICP was ≤ 0.9 mmHg in all head positions.ConclusionsEAM and glabella are defined anatomical structures representing BC when strict supine or lateral but with 12 mmHg variation with different head positions used in clinical practice. The OM line follows Monro at head elevation, but not when the head is turned. When the highest external point on the head is used, ICP values at brain surface as well as Monro and BC are underestimated. This underestimation is fairly constant and, when corrected for, provides the most exact ICP reading.

A simple method for semi-automatic readjustment for positioning in post-mortem head computed tomography imaging

Abstract The purpose of this study is to evaluate the usefulness of a simple method for readjustment of positioning in post-mortem (PM) head computed tomography (CT) imaging. Two hundred and twenty-five autopsied cases were used to test our proposed method. The coordinates of 5 landmarks on axial planes in PM head CT images were determined manually to calculate Yaw, Pitch, and Roll angles for the sake of readjustment. A radiologist and a forensic pathologist evaluated the readjustment by mutual agreement. Intraclass correlation coefficients (ICCs) for Yaw, Pitch, and Roll angles were measured for 3 operators. Similarity in AM and PM images after the readjustment was tested for 18 cases to evaluate the usefulness of the readjustment in personal identification for forensic cases. If similarity of the same person showed the highest value among all combinations in 18 cases, it was regarded as the correct identification. The processing time of our readjustment was limited to within 2 min per case. The orbitomeatal line (OML) was included in a single axial plane in 96.4% (217/225) of the cases after the readjustment. Reproducibility for determining landmarks showed acceptable ICC. Moreover, rank-one identification rate before and after readjustment were 16.7% (3/18) and 88.9% (16/18), respectively. Thus, our method for semi-automated readjustment exhibited potential usefulness in forensic cases. A simple method for semi-automatic readjustment would be a useful tool for post-mortem CT imaging with high reproducibility and a short processing time.

Setting Method of the Optimal Slab of Brain MRA for Detective Unruptured Cerebral Aneurysm

Generally, the imaging range of the brain magnetic resonance angiography (MRA) is determined in the subjectivity by the operator used by the plan image that a blood vessel is not depicted. However, a necessary blood vessel may not be often depicted by an error of the setting of the imaging area. Therefore, optimal slab angle, thickness, distance, and image contrast for depiction of the unruptured cerebral aneurysm were examined. The brain MRA of 14 subjects was imaged in a wide area parallel to an orbitomeatal line (OM) line. The line which linked the arteria vertebral (the first cervical vertebrae curved section) to anterior cerebral artery (A3) was determined with an optimal slab base line, and the angle with the OM line was evaluated. Moreover, slavic range including the unruptured aneurysm was calculated. In addition, the distance from the inferior margin of pons to the slavic bottom end was measured. Furthermore, the cerebrovascular contrast by the slave angle was compared. As a result, the slave setting of the range was recommended in brain-MRA as an angle was 34.3 degrees, and the thickness was 56.4 mm, and, as the distance from the inferior margin of pons was 27.6 mm. The cerebrovascular contrast of the optimal slab base line angle did not have a significant difference for an OM line.

A guide to identification and selection of axial planes in magnetic resonance imaging of the brain.

For brain magnetic resonance (MR) examination, three-dimensional imaging is commonly performed. Radiologists need to know the appropriate imaging angle for viewing. We present six imaging angles for the axial images. Each angle is determined by the reference line. The landmarks on the midsagittal MR image to determine the angle of the reference lines are as follows: the supraorbito-meatal line (the center of the mammillary body and the fastigium of the fourth ventricle), the orbito-meatal (OM) line (the center of the mammillary body and the most posterior point of the cerebellar tentorium), the Talairach anterior commissure (AC)-posterior commissure (PC) line (the superior edge of the AC and the inferior edge of the PC), the Schaltenbrand AC-PC line (the center of the AC and the center of the PC), the subcallosal line (the inferior border of the genu and the inferior border of the splenium of the corpus callosum), Reid's baseline (the center of the pituitary gland and the most posterior point of the cerebellar tentorium) and the brainstem vertical line (the line perpendicular to the posterior border of the brainstem). The AC-PC line is most commonly used in MR examination. The OM line is most commonly used in computed tomography examination. The supraorbito-meatal line is recommended for avoiding irradiation to the orbit. In cases of multiple sclerosis, the subcallosal line is recommended in the guidelines. For lesions in the orbital cavity, paranasal cavity or skull base, Reid's baseline is useful. For cases of brainstem lesions, the brainstem vertical line is useful.

Assessment of the Relationship of the Frankfort Horizontal Plane and the Orbitomeatal Line with Attainment of the Natural Head Position

The diagnosis of dentofacial deformities and the choice of ortho-surgical treatment depend on the correct positioning of the head at the time of registration in 2D or 3D, called the natural head position (NHP). We selected 32 subjects from Arnett class I and obtained their frontal and lateral photographs in NHP to evaluate the relationship and stability between the orbitomeatal line, the Frankfort horizontal plane and the face midline with the true vertical line (TVL) and the true horizontal line (THL). Mean and standard deviation of angulation were obtained for all cited variables, with the results leading to the conclusion that the orbitomeatal line and the Frankfort horizontal plane can be used to obtain the NHP in an individualized way.

Optimization of Reformatting Angle Using Orbitomeatal Base Line in Dopamine Transporter Scintigraphy.

Recently, dopamine transporter (DaT) scintigraphy, which contributes to the early diagnosis of Parkinson's disease and Lewy body dementia, has been widely spread. It has been revealed that analytical results can be affected by the image-reformatting angle, and a horizontal section is recommended for the anterior commissure-posterior commissure (AC-PC) line according to the clinical guidelines for ioflupane. However, it is difficult to identify AC-PC line visually, as there is no remarkable accumulation in the cerebral parenchyma in DaT scintigraphy with poor contrast resolution. The objective of this study was to establish and optimize an adjustment method for the image-reformatting angle by using orbitomeatal base line (OM line). Evaluations were made on items such as comparison of image reformatting angles by an analyst, comparison of measurement angles of OM line, the angle formed by the intersection of OM line and AC-PC line, and the change in specific biding ratio (SBR) according to the difference in the image-reformatting angle. Consequently, the difference in analytical results among technicians became smaller, and consistent results were obtained by adjusting the image-reformatting angle.