Lateral Scout Image Research Articles

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

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. 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. 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). 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.

Scout-guided needle placement-a technical approach for dose reduction in CT-guided periradicular infiltration.

To develop and evaluate a technical approach for CT-guided periradicular infiltration using quantitative needle access and guidance parameters extracted from CT scout images. Five 3D-printed phantoms of the abdomen mimicking different patients were used to develop a technical approach for scout-guided periradicular infiltration. The needle access point, puncture depth, and needle angulation were calculated using measurements extracted from anterior-posterior and lateral CT scout images. Fifty needle placements were performed with the technique thus developed. Dose exposure and number of image acquisitions were compared with ten procedures performed using a conventional free-hand technique. Data were analyzed with the Mann-Whitney U test. Parameters derived solely from scout images provided adequate guidance for successful and reliable needle placement. Needle guidance was performed with the same equipment as the standard periradicular infiltration. Two scout images and 3.5 ± 2.3 (mean ± SD) single-shot images for needle positioning were acquired. Mean DLP ± SD was 3.8 ± 2.5mGycm. The number of single-shot acquisitions was reduced by 68% and the overall dose was reduced by 84% in comparison with the conventional free-hand technique (p < 0.0001). Scout-guided needle placement for periradicular infiltration is feasible and reduces radiation exposure significantly.

The turricephaly index: A validated method for recording turricephaly and its natural history in Apert syndrome

IntroductionWe present the CT scan-derived turricephaly index (TI) as a quotient of the maximal occipito-frontal length of the skull to the distance from the centre of the sella to the highest point on the vertex as a validated tool for assessing turricephaly and evaluating surgical techniques aimed at reducing it. Materials and methodsMeasurements taken from CTs of non-operated children with Apert syndrome and age-matched controls were analysed using Centricity PACS system (from the lateral scout image) and the thick-sliced Osirix tool. CTs from non-operated children with Apert syndrome were used to investigate the natural history of their turricephaly both as a group and individually. ResultsThere was statistically significant agreement between measurements taken from the CT scout and Osirix for 42 control children (R2 = 0.97) and 42 children with Apert syndrome (R2 = 0.98) and between two separate observers. There was a statistically significant difference (p < 0.001) between CT scout-derived TI value between controls (1.73 ± 0.12, range 1.46–1.99) and Apert children (1.42 ± 0.15, range 1.13–1.73). Analysis of 113 CTs of 65 non-operated children with Apert syndrome showed a decrease in turricephaly with age (positive spearman correlation: r = 0.50, p < 0.001). Analysis of 37 CTs of those with multiple (>2) CT's showed a similar decrease in turricephaly in the individual child (p < 0.001). ConclusionsTI derived from the CT scout view provides a simple, objective and validated method for assessing turricephaly. We recommend it for monitoring and for the prospective evaluation of reconstructive techniques in children with complex/syndromic craniosynostosis.

EFFECTS OF THE SCAN RANGE ON RADIATION DOSE IN THE COMPUTED TOMOGRAPHY COMPONENT OF ONCOLOGY POSITRON EMISSION TOMOGRAPHY/COMPUTED TOMOGRAPHY.

We performed phantom experiments to investigate radiation dose in the computed tomography component of oncology positron emission tomography/computed tomography in relation to the scan range. Computed tomography images of an anthropomorphic whole-body phantom were obtained from the head top to the feet, from the head top to the proximal thigh or from the skull base to the proximal thigh. Automatic exposure control using the posteroanterior and lateral scout images offered reasonable tube current modulation corresponding to the body thickness. However, when the posteroanterior scout alone was used, unexpectedly high current was applied in the head and upper chest. When effective dose was calculated on a region-by-region basis, it did not differ greatly irrespective of the scan range. In contrary, when effective dose was estimated simply by multiplying the scanner-derived dose-length product by a single conversion factor, estimates increased definitely with the scan range, indicating severe overestimation in whole-body imaging.

Clinical evaluation of CT radiation dose in whole-body 18F-FDG PET/CT in relation to scout imaging direction and arm position.

Radiation exposure in CT is modulated by automatic exposure control (AEC) mainly based on scout images. We evaluated CT radiation dose in whole-body PET/CT in relation to scout imaging direction and arm position, and investigated the behavior of AEC. Eighty adult patients who underwent whole-body 18F-FDG PET/CT were divided into groups A, B, C, and D. The posteroanterior scout image alone (PA scout) was used for AEC-based dose modulation in groups A and B, while the posteroanterior and lateral scout images (PA + Lat scout) were used in groups C and D. Patients in groups A and C were imaged with their arms beside the head, while those in groups B and D were imaged with their arms at the sides of the trunk. Dose-length product provided by the scanner was recorded. The tube current value, a determinant of radiation dose, for each slice was plotted against slice location to produce a tube current modulation curve. The scan range was divided into seven anatomical regions, and regional tube current was defined as average tube current for each region. Effective dose was calculated for each region and then summed together. Regional tube current was higher in the body trunk and proximal thigh using the PA scout than using the PA + Lat scout, resulting in higher dose-length product and effective dose using the PA scout. A marked dose increase was shown in the shoulder especially using the PA scout. Spike-like high current at the top of the head was often observed in tube current modulation curves using the PA scout but not using the PA + Lat scout. Raising the arms increased tube current in the head and neck and decreased it in the chest and abdomen. Although dose-length product did not differ significantly depending on arm position, raising the arms decreased effective dose significantly. AEC-based CT dose modulation in whole-body PET/CT is affected by scout imaging direction and arm position, which should be considered to determine an optimal imaging protocol for whole-body PET/CT.

Upper Airway Areas, Volumes, and Linear Measurements Determined on Computed Tomography During Different Phases of Respiration Predict the Presence of Severe Obstructive Sleep Apnea

The objective of this study was to analyze the potential of using low-dose volumetric computed tomography (CT) during different phases of respiration for identifying patients likely to have severe obstructive sleep apnea (OSA), defined as a respiratory disturbance index (RDI) higher than30. A prospective study was undertaken at the Ramathibodi Hospital (Bangkok, Thailand). Patients with diagnosed OSA (N=82) were recruited and separated into group 1 (RDI, ≤30; n=36) and group 2 (RDI, >30; n=46). The 2 groups were scanned by low-dose volumetric CT while they were 1) breathing quietly, 2) at the end of inspiration, and 3) at the end of expiration. Values for CT variables were obtained from linear measurements on lateral scout images during quiet breathing and from the upper airway area and volume measurements were obtained on axial cross-sections during different phases of respiration. All CT variables were compared between study groups. A logistic regression model was constructed to calculate a patient's likelihood of having an RDI higher than 30 and the predictive value of each variable and of the final model. The minimum cross-sectional area (MCA) measured at the end of inspiration (cutoff point, ≤0.33cm2) was the most predictive variable for the identification of patients likely to have an RDI higher than 30 (adjusted odds ratio [OR]=5.50; 95% confidence interval [CI], 1.76-17.20; sensitivity, 74%; specificity, 72%,), followed by the MCA measured at the end of expiration (cutoff point, ≤0.21cm2; adjusted OR=3.28; 95% CI, 1.05-10.24; sensitivity, 70%; specificity, 68%). CT scanning at the ends of inspiration and expiration helped identify patients with an RDI higher than 30 based on measurement of the MCA. Low-dose volumetric CT can be a useful tool to help the clinician rapidly identify patients with severe OSA and decide on the urgency to obtain a full-night polysomnographic study and to start treatment.

Effects of different scout images on radiation dose in CT scanning using automatic tube current modulation

Objective To investigate the influence of different scout image on the radiation dose of head and chest spiral scanning in CT using automatic tube current modulation(ATCM). Methods CT scanning was performed on the head-neck and chest phantom with ATCM.Five different scout images through the five various positions that include anteroposterior(AP),posteroanterior(PA),lateral,AP, lateral,PA and lateral.The phantom was scanned three times for each position.Then each scout image was scanned by spiral technique once more. ROI in orbital center and C5 upper edge level were selected for Head and neck phantom, ROI in the apical and tracheal bifurcation level were selected for chest phantom. The contrast to noise ratio (CNR) was measured and recorded. The organ dose of eye lens and mammary glands were measured by thermoluminescent dosimeters (TLD) in every scanning(the average of 3 measurements), The cumulative value of scout image and spiral scanning were calculated.The volume CT dose index (CTDIvol) of each scan was recorded, and the cumulative value of CTDIvol was calculated. Results In the five scout images of the head-neck phantom mode, the maximum value of accumulated radiation dose of eye lens and CTDIvol appear on PA scout image(18.354 and 26.43 mGy respectively),while the minimum value appear on the lateral scout image(11.847 and 18.20 mGy respectively). In the chest phantom mode, the maximum value of the accumulated radiation dose of the mammary gland and CTDIvol emerge from the AP scout image(6.873 and 9.42 mGy respectively), while the minimum value of the mammary accumulated radiation dose appear on lateral scout image(4.592 mGy), the minimum value of CTDIvol appear on AP plus lateral scout images(3.94 mGy).The accumulated radiation dose of eye lens and CTDIvol value in PA scout image mode were 54.9%(6.507/11.847) and 45.2%(8.23/18.20) higher than those of the lateral scout image mode. The accumulated radiation dose of mammary gland and CTDIvol value in AP scout image mode were 42.5%(2.051/4.822) and 136.7% (5.44/3.98) higher than that of PA plus lateral scout images mode. In the head-neck phantom mode, the CNR value of orbital center and C5 upper edge level were 102.55 to 115.89, 161.01 to 204.52 respectively. In the chest phantom mode, the CNR value of the apical and tracheal bifurcation level were 82.74 to 164.00, 83.12 to 121.49 respectively. Conclusion The choice of the scout image had significant effect on the radiation dose and the sensitive organ dose in CT. Key words: Tomography,X-ray computed; Radiation dosage; Scout image

The clinical value of anteroposterior and lateral scout image combined with Care Dose 4D and Care kV in reducing radiation dose of chest CT scanning

Objective To investigate the feasibility and clinical value of anteroposterior and lateral scout scan combined with Care Dose 4D and Care kV in chest CT scan. Methods A total of 60 patients of clinical diagnosis with lung tumor were enrolled. Those patients were randomly divided into test group and control group. Control group underwent a scan protocol with lateral scout scan combined with Care Dose 4D and Care kV, while anteroposterior and lateral scout scan combined with Care Dose 4D and Care kV were performed in test group. The signal-to-noise ration (SNR) , contrast-to-noise ratio (CNR) , and overall image quality of two groups of images and diseased tissues were analyzed and evaluated by two high-grade radiologists using double-blind method. Effective doses (E) were also calculated. Results All the 60 patients had successfully completed the chest CT scans. Test group overall image quality (4.57±0.45) and control group overall image quality (4.73±0.45) had no statistically significant difference (P>0.05) . The control group image SNR, CNR and diseased tissue SNR, CNR compared with test group had no statistical significance difference (P>0.05) . The difference of the volume CT dose index (CTDIvol) , dose-length product (DLP) and effective dose (E) of test group and control group was statistically significant (t=8.514, 8.464, 8.464, P<0.001) . Compared with control group, the effective dose of test group decreased by 33.3%. Conclusions Compared with lateral scout scan, the technology of anteroposterior and lateral scout scan combined with Care Dose 4D and Care kV can decrease radiation dose without reducing the image quality. This technology can therefore be considered as a regular imaging modality for chest CT scan. Key words: Chest; Radiation dose; Care Dose 4D; Care kV; Scout image

Effect of patient centering on patient dose and image noise in chest CT.

The objective of our study was to evaluate the effect of vertical centering on dose and image noise in chest MDCT of different-sized patients using anthropomorphic phantoms and retrospectively studying examinations of clinical patients. Three different anthropomorphic phantoms were scanned using different vertical centering (offset ± 6 cm) and were assessed with radiation dose-monitoring software. The effect of vertical positioning on the radiation dose was studied using the volume CT dose index, dose-length product, and size-specific dose estimates for different-sized phantoms. Image noise was determined from CT number histograms. Vertical positioning for chest CT examinations of 112 patients ranging from neonates to adults were retrospectively assessed. Radiation doses were highest when using the posteroanterior scout image for automatic exposure control (AEC) and when phantoms were set in the lowest table position, and radiation doses were lowest when phantoms were set in the uppermost table position. For the adult phantom, relative doses increased by 38% in the lowest table position and decreased by 23% in the highest table position. Similarly, doses for pediatric 5-year-old and newborn phantoms were 21% and 12% higher in the lowest table position and 12% and 8% lower in the highest table position, respectively. The effect decreased when a lateral scout image was used for AEC. The relative noise was lowest when the phantoms were properly centered and increased with vertical offset. In clinical patients, we observed offset with a median value varying from 25 to 35 mm below the isocenter. Regardless of patient size, most patients in this study were positioned too low, which negatively affected both patient dose and image noise. Miscentering was more pronounced in smaller pediatric patients.

Automatic heart positioning method in computed tomography scout images.

Computed tomography (CT) radiation dose can be reduced significantly by region of interest (ROI) CT scan. Automatically positioning the heart in CT scout images is an essential step to realize the ROI CT scan of the heart. This paper proposed a fully automatic heart positioning method in CT scout image, including the anteroposterior (A-P) scout image and lateral scout image. The key steps were to determine the feature points of the heart and obtaining part of the heart boundary on the A-P scout image, and then transform the part of the boundary into polar coordinate system and obtain the whole boundary of the heart using slant elliptic equation curve fitting. For heart positioning on the lateral image, the top and bottom boundary obtained from A-P image can be inherited. The proposed method was tested on a clinical routine dataset of 30 cases (30 A-P scout images and 30 lateral scout images). Experimental results show that 26 cases of the dataset have achieved a very good positioning result of the heart both in the A-P scout image and the lateral scout image. The method may be helpful for ROI CT scan of the heart.

Quantitative analysis of factors affecting cobalt alloy clip artifacts in computed tomography.

ObjectiveClip artifacts limit the visualization of intracranial structures in CT scans from patients after aneurysmal clipping with cobalt alloy clips. This study is to analyze the parameters influencing the degree of clip artifacts.MethodsPostoperative CT scans of 60 patients with straight cobalt alloy-clipped aneurysms were analyzed for the maximal diameter of white artifacts and the angle and number of streak artifacts in axial images, and the maximal diameter of artifacts in three-dimensional (3-D) volume-rendered images. The correlation coefficient (CC) was determined between each clip artifact type and the clip blade length and clip orientation to the CT scan (angle a, lateral clip inclination in axial images; angle b, clip gradient to scan plane in lateral scout images).ResultsAngle b correlated negatively with white artifacts (r=-0.589, p<0.001) and positively with the angle (r=0.636, p<0.001) and number (r=0.505, p<0.001) of streak artifacts. Artifacts in 3-D images correlated with clip blade length (r=0.454, p=0.004). Multiple linear regression analysis revealed that angle b was the major parameter influencing white artifacts and the angle and number of streak artifacts in axial images (p<0.001), whereas clip blade length was a major factor in 3-D images (p=0.034).ConclusionUse of a clip orientation perpendicular to the scan gantry angle decreased the amount of white artifacts and allowed better visualization of the clip site.

Correlation of Cross-Sectional Diameter With Image Quality and Radiation Exposure in MDCT Examinations of the Neck

The purpose of this study was to identify an optimal cross-sectional neck diameter that correlates with image quality and radiation exposure in MDCT examinations of the neck performed with automatic tube current modulation. Ninety-six adults underwent 64-MDCT of the neck with automatic tube current modulation at the same noise setting. On frontal and lateral scout images, maximal body diameters were measured in the transverse and anteroposterior planes at two levels: just below the mandible (upper neck) and at the lung apex (lower neck). Neck diameters were correlated with image quality on a subjective 4-point scale and with radiation exposure (volume CT dose index). As continuous variables, both anteroposterior and transverse diameters in the lower neck were associated with image quality (p ≤ 0.0012). Diameters in the upper neck were not associated with image quality. When diameters in the lower neck were categorized into small, medium, and large, image quality grades were higher for smaller patients (p < 0.001). Images of 81% of small patients (lower neck transverse diameter < 40 cm) had a high image quality grade, compared with images of 7-20% of large patients (diameter > 48 cm). Transverse diameter in the lower neck correlated best with radiation dose measured as volume CT dose index (r = 0.78). When transverse diameter in the lower neck was used to categorize patients' size, the mean volume CT dose index for small patients was 34.1 mSv and that for large patients was 63.5 mSv. Lower neck transverse diameter on the CT scout image best correlates with image quality and radiation exposure for neck MDCT examinations performed with automatic tube current modulation. Images of patients with a lower neck transverse diameter less than 40 cm are of higher quality than those of larger patients. Individualized dose reduction techniques therefore may be appropriate for smaller patients.

The computed tomographic enhancement pattern of the normal canine pituitary gland.

Dynamic computed tomography (CT) of the pituitary gland was performed on four healthy male dogs of similar size, weight and age. The pituitary gland region was first identified on lateral scout and transverse non-contrast images. After localization, water soluble iodinated contrast medium was administered intravenously as a bolus at a dose of 1 ml/lb using a pressure injector at an injection rate of 10 ml/sec and a total of 40 post contrast images of the pitutary gland were acquired. No images were made after 400 seconds. The same pituitary region was imaged in each slice. The slice thickness was 1.5 mm, with a two second scan time and an eight second delay between images (resulting in images every ten seconds). The contrast medium injection and initial image were acquired simultaneously, resulting in a non-contrast enhanced initial image. At the completion of the CT scan, a region of interest (ROI) was drawn around the pituitary gland and time density data were obtained. The mean pituitary Hounsfield number was plotted as a function of time. A bi-exponential least squares model was used to derive the best fitting line through the data. The mean relative peak increase in pituitary Hounsfield Units (HU) was 65.9% +/- 2.1%. After the initial increase there was a decrease in pituitary Hounsfield number with a half-time of 16.1 seconds, followed by a slower phase with a half-time of 16.5 minutes. The mean pituitary gland HU value during the period of gradual opacity decline was 35.0% +/- 4.4% above that of the pre-contrast image. Establishing the enhancement pattern in the canine pituitary gland is the precursor to the clinical application of dynamic CT of the pituitary gland to diagnose pituitary microadenomas and/or small macroadenomas before they become exceptionally large.

Relationship between atlanto-odontoid osteoarthritis and idiopathic suboccipital neck pain.

We discuss the relationship of atlanto-odontoid (AO) (anterior C1-C2 joint) osteoarthritis to suboccipital pain. A questionnaire regarding suboccipital neck pain was presented to 210 consecutive patients undergoing computed tomography (CT) of the brain or sinuses for a variety of indications. In all patients the AO joint and the lateral scout image of the cervical spine were studied. In 104 (49%) degenerative changes were seen at the AO joint. There were 89 patients (42%) who reported pain in the suboccipital region, although this was not the reason for CT in any patient. Statistical analysis of the prevalence of suboccipital neck pain in all patients showed the presence of AO osteoarthritis seen on CT to be associated with occurrence of these symptoms. This association remained significant in the same study population after excluding patients with a history of rheumatoid arthritis, migraine, stress and neck trauma and patients with signs of degenerative changes of C2-C7 on the computed lateral scout image.

Use of the Lateral Scout Image as an Adjunct to Computed Tomography-Guided Spinal Biopsy

Use of the Lateral Scout Image as an Adjunct to Computed Tomography-Guided Spinal Biopsy