Adult CT Scans Research Articles

Reappraising the surface anatomy of the pterion and its relationship to the middle meningeal artery

Despite its clinical importance, the surface anatomy of the pterion is inconsistently reported. This study reappraises the surface marking of the pterion and its relationship to the middle meningeal artery (MMA). The position and morphology of the pterion were analyzed in the Frankfurt plane in 76 adult skulls and 50 adult cranial cone beam CT scans. Relationship to the anterior branch of the MMA was examined in the skulls. Measurement reproducibility was assessed in a 20% randomly selected sample. In the skulls, the majority of pteria were sphenoparietal (78%), followed by epipteric (16%) and frontotemporal (5%). The center of the pterion was a mean of 26 ± 4 mm behind and 11 ± 4 mm above the posterolateral margin of the frontozygomatic suture; measurements were reproducible and consistent between sides and genders. Distances from the frontozygomatic suture were slightly greater (29 and 16 mm, respectively) in cranial CTs. A one centimeter circle centered on the midpoint of the pterion overlapped the anterior branch of the MMA in 68% of skulls; the artery was a few millimeters posterior in the remainder. Mean skull thickness at the midpoint of the pterion was 4.4 mm compared to 1 mm at its thinnest point in the squamous temporal bone. In conclusion, in most adults, the pterion lies within a one centimeter diameter circle 2.6 cm behind and 1.3 cm above the posterolateral margin of the frontozygomatic suture (which is easily palpable in vivo). This region overlaps the anterior branch of the MMA in two-thirds of cases.

TH-E-211-09: X-Ray Air Kerma at the Eye, Thyroid, and Scalp in CT Stroke Imaging Protocol Studies

Purpose: To determine air KERMA (Ka) at the scalp, orbit, and thyroid in patients undergoing a strokeimaging protocol that includes CT cerebral perfusion, pre‐ and post‐contrast head CT, and CTangiography scans. Method and Materials: IRB exemption was obtained to retrospectively review patient dosimetry information for 81 patients who were imaged under a strokeimaging protocol. Patients had OSL dosimeter chips placed on the head above the ear, at the lateral canthus, and approximately one inch above the sternal notch to measure Ka at the scalp, eye lens, and thyroid, respectively. To account for the different response of the chips exposed at both 80 and 120 kVp, experiments were performed to determine a correction factor to apply to the OSL Ka values, which were all read using a 120 kVp calibration. Results: A 5.5% reduction was used to correct the measured Ka. Ka at the thyroid ranged from 1.8 to 92.6 mGy, with a mean of 13.6 mGy and standard deviation of 18.3 mGy. Ka at the canthus was 22.7 to 393.3 mGy with mean of 185.8 mGy and standard deviation of 61.4 mGy. Ka at the scalp showed a bi‐modal distribution, as patients receiving Diamox therapy received two CT perfusion scans. Overall mean was 289 mGy, with peaks at 190 and 380 mGy. The range was 67.8 mGy to 575 mGy. Conclusions: Although the scan parameters (kVp, mA, rotation speed, etc.) show little variation for adult head CT scans, doses to patients undergoing strokeimaging protocols span a large range due to differences in the number of scans in each patient, and to some extent differences in patient size. Doses for a single study were below the threshold for deterministic effects, however for repeat studies the potential exists to exceed thresholds for erythema and epilation.

ESTIMATION OF THE NUMBER OF CT PROCEDURES BASED ON A NATIONWIDE SURVEY IN JAPAN

In 2007, a nationwide survey was conducted to determine the frequency of CT procedures in Japan in order to compare the current use of CT among developed countries. The frequency of adult and pediatric CT scans was estimated using a model based on the results of the survey. Survey questionnaires were sent to 2,266 CT facilities: 1,068 government hospitals and 1,198 other hospitals and non-hospital medical centers. The questionnaire requested information including the number of beds, outpatients per day, type of CT scanner, various body regions scanned, and the number of scans performed. The results of the study indicate that the number of CT procedures was closely correlated with the number of hospital beds. The authors estimate that approximately 20.5 million procedures were performed in 2005 and 21.2 million in 2006. The number of pediatric CT procedures was calculated by multiplying the total number of CT procedures by the estimated fraction of pediatric (0-15 y) CT procedures. Annual pediatric CT procedures were estimated to have been approximately 580,000 in 2005 and 600,000 in 2006. The present study indicates that the number of procedures per thousand of population, 166 for total CT and 32-34 for pediatric CT, is lower in Japan than in the U.S.

Can Experienced CT Radiologists Use Technique Parameters to Predict Excessive Patient Dose? An Analysis of the ACR CT Accreditation Database

The aim of this study was to determine, for 3 basic clinical examinations, whether blinded, experienced CT radiologists participating in the ACR's CT Accreditation Program could use scan parameters such as tube current-time product (mAs), tube voltage (kVp), and pitch to predict scanner output settings, expressed as weighted CT dose index (CTDIw) and volume CT dose index (CTDIvol), exceeding CTDIw diagnostic reference levels (DRLs) set by the ACR in 2002 and CTDIvol DRLs adopted by the ACR in 2008. CT sites with 829 scanners submitted examinations to the ACR between 2002 and 2004, yielding 518 eligible examinations for analysis (138 adult head CT scans, 333 adult abdominal CT scans, and 47 pediatric abdominal CT scans). The sites' measured CTDIw values for each type of examination were compared with the ACR's CTDIw DRLs in effect from 2002 to 2004 and compared with comments regarding excessively high mAs or kVp made by radiologist clinical reviewers to determine if excessively high-dose index measurements could be predicted. The same analysis was repeated using CTDIvol DRLs adopted by the ACR in 2008 and compared with excessively high mAs or kVp and excessively low-pitch comments. Excessively high mAs or kVp comments yielded sensitivity of only 21.2% in predicting examinations above the CTDIw DRLs, with specificity of 87.6%. Using the 2008 CTDIvol DRLs, the corresponding sensitivity was 13.1% and specificity was 86.2%. Significance was not achieved for use of clinical parameters in predicting either the CTDIw or CTDIvol. Experienced CT radiologists cannot reliably use scan parameters to predict examinations that exceed CTDIw or CTDIvol DRLs.

Acetabular orientation variability and symmetry based on CT scans of adults

Understanding acetabular orientation is important in many orthopaedic procedures. Acetabular orientation, usually described by anteversion and abduction angles, has uncertain measurement variability in adult patients. The goals of this study are threefold: (1) to describe a new method for computing patient-specific abduction/anteversion angles from a single CT study based on the identification of anatomical landmarks and acetabular rim points; (2) to quantify the inaccuracies associated with landmark selection in computing the acetabular angles; and (3) to quantify the variability and symmetry of acetabular orientation. A total of 25 CT studies from adult patients scanned for non-orthopaedic indications were retrospectively reviewed. The patients were randomly selected from the hospital's database. Inclusion criteria were adults 20-65 years of age. Acetabular landmark coordinates were identified by expert observers and tabulated in a spreadsheet. Two sets of calculations were done using the data: (1) computation of the abduction and anteversion for each patient, and (2) evaluation of the variability of measurements in the same individual by the same surgeon. The results were tabulated and summary statistics computed. This retrospective study showed that acetabular abduction and anteversion angles averaged 54 degrees and 17 degrees, respectively, in adults. A clinically significant intra-patient variability of >20 degrees was found. We also found that the right and left side rim plane orientation were significantly correlated, but were not always symmetric. A new method of computing patient-specific abduction and anteversion angles from a CT study of the anterior pelvic plane and the left and right acetabular rim planes was reliable and accurate. We found that the acetabular rim plane can be reliably and accurately computed from identified points on the rim. The novelty of this work is that angular measurements are performed between planes on a 3-D model rather than lines on 2-D projections, as was done in the past.

１６列ＭＤＣＴにおける小児体幹部撮影条件の基礎的検討

In infant CT scans, it is important to minimize radiation exposure without lowering the quality of the diagnosis. Therefore, appropriate parameters for infant CT scan should be considered at each institute. In order to determine parameters for infant body CT, we measured the physical characteristics of our current CT machine and evaluated scan parameters as S.D. below 10 on the basis of literature recommendations, which say that we should adopt S.D. of the liver when treated with a radiation exposure dose in an adult abdominal CT scan. As a result, the ideal parameters were 90 kV tube voltage, ultra fast detail resolution, B kernel, and Eff.mAs value calculated from patient body width. Infant body CT scans with the mentioned parameters resulted in an S.D. below 10, and this is thought to be applicable to further examinations.

A distribution of submental artery, especially the relation between lingual foramen and a sublingual artery in the Japanese population

This study evaluates the mandibular lingual foramina (LF) using computed tomographic imaging data from a large Central European cohort, focusing on the most relevant anatomical parameters. We aimed to examine whether there are differences in key parameters between ethnic groups, or based on age and gender. Additionally, we analyze the potential effect of tooth loss on the LF and discuss risk management options before and during surgery.460 CT scans of adults (273 females and 186 males) were examined. The number, the location and the diameter of the median and lateral LF were assessed for each patient. The data was analyzed statistically, whereby a p-value lower than 0.05 was considered as significant.Median and lateral LF were present in 95,9%, and 38,9% of patients, respectively. Male patients had a greater number of LF than females. While the majority of median LF (62%) was located above the mental spine, the majority of lateral LF was located below (84%). The diameter of lateral LF (1,15 mm ± 0,33) was smaller than for median LF (1,22 mm ± 0,35), as well the lateral canals (4,8 mm ± 1,28) were shorter than the median canals (5,32 mm ± 1,74). Lateral LF were equidistant to the symphysis (13,89 ± 3,63 mm) on either side. Critical diameter size >1 mm was found in about 2/3 of our cases. The distance from the foramen to the residual ridge was ∼7 mm less in edentulous patients compared to dentulous patients.The median LF is a near-obligatory structure of the mandible, while the lateral LF is a frequently encountered structure. Age does not seem to affect the frequency of LF. Edentulous patients did not show differences regarding the presence of the LF, but their vertical osseous dimension was diminished by 7 mm and they may, therefore, be at an increased risk of adverse surgical incidents. The main findings of this study relate to the substantial variability in the anatomy and location of the LF and confirm with previous studies. As the LF can be reliably detected using CT/CBCT, the use of three-dimensional-imaging is recommended prior to conducting oral surgery. Careful pre-operative planning and accurate anatomical information may help to avoid surgical complications. To ascertain the potential significance of ethnicity on LF, more data need to be collected using standardized methodologies. A definitive conclusion on the impact of ethnicity on LF thus cannot currently be drawn based on the results of our study and those available from the published medical literature.

New findings on intermetacarpal fat pads: anatomy and imaging

Many studies have focused on the functional importance of the gliding structures of the hand. These structures are clinically important in reconstructive surgery and mechanically essential for an efficient hand grasp. The aims of this study were to first review the intermetacarpal space and then focus on its fatty tissue, the intermetacarpal fat pad. This study used dissections and histological analysis of fetal and adult hands and CT scans of adult hands. The intermetacarpal fat pads are well-defined adipose structures located between the heads of the second, third, fourth and fifth metacarpal bones. They are located in spaces defined by the palmar fascia and its deep expansions. These spaces are closed distally but open proximally into the tunnels surrounding the flexor tendons (Legueu and Juvara canals). The pads are composed of non-mobilizable fat; they protect the neurovascular pedicles of the fingers. They may act with the palmar skin to mitigate compressive and shear forces during gripping. Finally they may be involved in neurological symptoms if their size is increased by any trauma or inflammatory process.

Adult third ventricle width and infant behavioral arousal in groups at high and low risk for schizophrenia

Previous research has demonstrated: (1) Subjects who are at genetic high risk for schizophrenia and who suffer delivery complications are at increased risk to evidence a widened third ventricle. (2) A widened third ventricle is related to decreased ANS arousal and, among schizophrenics, is related to negative symptom schizophrenia. (3) Adult schizophrenics evidence behavioral analogues of negative symptom schizophrenia premorbidly. This study compared adult CT scans to ratings of infant behavior in 179 subjects (104 at high genetic risk for schizophrenia) with the hypothesis that widened third ventricles would be related to underaroused infant behavior. Results of an ANOVA suggest that subjects who are at genetic high risk for schizophrenia and who evidence a widened third ventricle are more likely to have shown signs of behavioral underarousal as infants. Possible explanations, implications and limitations of the study are discussed.

Leuko-araiosis: a reappraisal. I. CT studies

Leuko-araiosis is a purely descriptive term indicating images of bilateral, patchy or diffuse areas of decreased density frequently observable in the deep white matter on brain CT scans of adults and elderly subjects. While in earlier studies these images were considered as the "in vivo" expression of leukoencephalopathy associated with Binswanger disease, subsequently they have been reported in a rather broad spectrum of clinical conditions, including healthy aging and dementia of different types. Evidence of arterial hypertension and lacunar stroke is found in only two-thirds of subjects with leuko-araiosis. The results of pathological studies are conflicting about the nature of leukoencephalopathy, and the type and severity of medullary artery involvements. Probably several mechanisms underlie leuko-araiosis. They might act separately or be combined in different cases. Classification by physiopathological mechanism may be a suitable aim of future research in this field.