Oblique Axial Views Research Articles

Pelvic CT in addition to MRI to differentiate between rectal and sigmoid cancer on imaging using the sigmoid take-off as a landmark.

The sigmoid take-off (STO) is a recently established landmark to discern rectal from sigmoid cancer on imaging. STO-assessment can be challenging on magnetic resonance imaging (MRI) due to varying axial planes. To establish the benefit of using computed tomography (CT; with consistent axial planes), in addition to MRI, to anatomically classify rectal versus sigmoid cancer using the STO. A senior and junior radiologist retrospectively classified 40 patients with rectal/rectosigmoid cancers using the STO, first on MRI-only (sagittal and oblique-axial views) and then using a combination of MRI and axial CT. Tumors were classified as rectal/rectosigmoid/sigmoid (according to published STO definitions) and then dichotomized into rectal versus sigmoid. Diagnostic confidence was documented using a 5-point scale. Adding CT resulted in a change in anatomical tumor classification in 4/40 cases (10%) for the junior reader and in 6/40 cases (15%) for the senior reader. Diagnostic confidence increased significantly after adding CT for the junior reader (mean score 3.85 vs. 4.27; P < 0.001); confidence of the senior reader was not affected (4.28 vs. 4.25; P = 0.80). Inter-observer agreement was similarly good for MRI only (κ=0.77) and MRI + CT (κ=0.76). Readers reached consensus on the classification of rectal versus sigmoid cancer in 78%-85% of cases. Availability of a consistent axial imaging plane - in the case of this study provided by CT - in addition to a standard MRI protocol with sagittal and oblique-axial imaging views can be helpful to more confidently localize tumors using the STO as a landmark, especially for more junior readers.

Evaluation of Cam Deformity on 3-Dimensional Computed Tomography With the Best-Fit Sphere Technique and the Alpha Angle Marking Method

Background: Three-dimensional computed tomography (3D-CT) is commonly used for the evaluation of cam deformity; however, it does not display the cam border directly. Purpose: To compare the efficacy of the best-fit sphere (BFS) method and the alpha angle marking (AAM) method in 3D-CT evaluation for the cam border. Study Design: Cohort study (Diagnosis); Level of evidence, 3. Methods: Twenty-six cases of cam deformity, confirmed during hip arthroscopy, were included in this study. All patients underwent a CT scan before surgery. Using multiplanar reconstruction, we obtained reformatted CT images of oblique axial, oblique coronal, and radial views. The alpha angle and femoral head-neck offset ratio (hnoR) were measured on the reformatted CT images. The cam area on 3D-CT was displayed in 4 different ways: by importing the markers from the reformatted CT images of the oblique axial view (cam-oa), the oblique coronal view (cam-oc), or the radial view (cam-r) using the AAM method, or by using the BFS method (cam-bfs). The sizes and locations of the displayed cams were compared. Results: All hips in this study had an alpha angle greater than 60° and an hnoR smaller than 0.17. The radial view measured a larger alpha angle and smaller hnoR than the oblique axial and coronal views (P < .05). The areas of cam-oa, cam-oc, cam-r, and cam-bfs were 161.47 ± 27.96, 89.78 ± 19.23, 241.73 ± 34.55, and 329.75 ± 42.73 mm2, respectively, and their medial-to-lateral ranges along the acetabulum (clockface referents) were 12:30 to 03:00, 11:30 to 01:30, 11:30 to 03:00, and 11:00 to 03:30, respectively. Among the 4 displays, cam-bfs had the largest area and medial-to-lateral range (P < .05), and cam-r had the second largest area and range (P < .05). No significant difference in the mean distances from the acetabular rim to the superior border was detected among the 4 displays (P > .05). Conclusion: The cam area displayed by the BFS method on 3D-CT was larger than those evaluated by the AAM method. In the reformatted CT, the sizes and locations of cam deformity differed among the oblique axial, oblique coronal, and radial views, with the radial view showing the greatest area.

"Anterior-shift sign": a novel MRI finding of adult hip dysplasia.

In adult hip dysplasia, methods for direct evaluation of hip instability have not been established. The present study aimed to determine findings suggestive of hip instability on magnetic resonance imaging (MRI) and to evaluate their correlations with clinical and radiological factors. We retrospectively reviewed 72 hips in 50 patients with hip dysplasia (45 females, 5 males; mean age: 40.0years; age range: 15-59years; Kellgren-Lawrence grade: ≤ 2). Hip dysplasia was defined as a lateral center-edge angle < 25°. Among the hips, 50 had pain (symptomatic dysplasia group) and 22 were asymptomatic (asymptomatic dysplasia group). As controls, 12 normal hips in 12 patients who underwent screening for asymptomatic osteonecrosis of the femoral head by MRI were evaluated. Using an oblique axial view on fat-suppressed T2-weighted images, we evaluated the presence of a gap between the posterior part of the femoral head and the corresponding acetabular surface, indicating hip instability (anterior-shift sign). The correlations of anterior-shift sign with clinical and radiographical factors were examined. Anterior-shift sign was observed in 92.0% in the symptomatic dysplasia group, 9.1% in the asymptomatic dysplasia group, and 0% in the control group. In adult hip dysplasia, cases with anterior-shift sign had significantly more pain and labrum tear occurrence than cases without anterior-shift sign. Anterior-shift sign was correlated with Kellgren-Lawrence grade and degree of acetabular coverage. This study suggested that hip instability can be observed as the anterior-shift sign on MRI. This sign is useful when considering indications for periacetabular osteotomy in adult hip dysplasia.

Posterior fossa assessment in the axial view of the head at 11-14 weeks of gestation in normal and aneuploid fetuses.

Posterior fossa ultrasound appearance may offer clues for brain anomalies as early as the first trimester. The purpose of the study was to find an easy, reproducible method to examine the posterior fossa. From January 2017 to March 2018, 132 consecutive pregnancies presenting for first-trimester screening, were selected at 11-14 weeks' gestation. An oblique axial view of the fetal head was routinely achieved with visualization of the posterior fossa, wherein the cisterna magna (CM) and the fourth ventricle (V4) anteroposterior diameter was measured. Moreover, 81 patients had a follow-up scan at 19-24 weeks, and the CM and transverse cerebellar diameter (TCD) were measured. Normal ranges were established at 11-14 weeks for CM and V4 according to crown-rump length (CRL). The 50th centile for CM ranges from 1.2 mm to 2.3 mm at a CRL between 45 and 85 mm. The V4 50th centile ranges from 1.8 to 2.4 mm. A positive correlation was found between the first-trimester and second-trimester CM diameter and between the first-trimester V4 and second-trimester TCD. There is an inverse correlation between the first-trimester CM and second-trimester TCD. The measurements of different components of the posterior fossa in the first trimester cannot predict the size of CM and TCD in the second trimester. The presence of the three hypoechoic structures (cerebral peduncles, V4, and CM) separated by two hyperechoic lines is easy to see and measure.

Effects of Remnant Tissue Preservation on Tunnel Enlargement After Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction Using the Hamstring Tendon.

Background:The effects of remnant tissue preservation on tunnel enlargement after anatomic double-bundle anterior cruciate ligament (ACL) reconstruction have not yet been established.Hypothesis:The preservation of ACL remnant tissue may significantly reduce the degree and incidence of tunnel enlargement after anatomic double-bundle ACL reconstruction, while the remnant-preserving procedure may not significantly increase the incidence of tunnel coalition after surgery.Study Design:Cohort study; Level of evidence, 2.Methods:A total of 79 patients underwent anatomic double-bundle ACL reconstruction. Based on the Crain classification of ACL remnant tissue, 40 patients underwent the remnant-preserving procedure (group P), and the remaining 39 patients underwent the remnant-resecting procedure (group R). There were no differences between the 2 groups concerning all background factors, including preoperative knee instability and intraoperative tunnel positions. All patients were examined using computed tomography and a standard physical examination at 2 weeks and 1 year after surgery.Results:During surgery, the femoral and tibial anteromedial (AM) tunnel sizes in both groups averaged 6.6 and 6.5 mm, respectively. The femoral and tibial posterolateral (PL) tunnel sizes in both groups averaged 6 and 6 mm, respectively. There were no differences in the intraoperative tunnel positions and tunnel sizes between groups. Concerning the femoral AM tunnel, the degree of tunnel enlargement in the oblique coronal and oblique axial views in group P was significantly less than that in group R (P = .0068 and .0323, respectively). Regarding the femoral AM tunnel cross-sectional area, the degree and incidence of tunnel enlargement in group P were significantly less than those in group R (P = .0086 and .0278, respectively). There were no significant differences in tunnel coalition between groups. In each group, there were no significant relationships between tunnel enlargement and each clinical outcome.Conclusion:Remnant preservation in anatomic double-bundle ACL reconstruction reduced enlargement of the femoral AM tunnel and did not increase the incidence of tunnel coalition. This is one of the advantages of remnant-preserving ACL reconstruction.

Alpha Angle Measurements in Healthy Adult Volunteers Vary Depending on the MRI Plane Acquisition Used

Background: It has been shown that cam deformities are located at a more anterosuperior location than was previously described. Purpose: To establish, in a large group of asymptomatic participants, the normative range of the alpha angle in the anterosuperior location in both the oblique axial and radial views of magnetic resonance imaging (MRI). Study Design: Cross-sectional study; Level of evidence, 3. Methods: In 197 asymptomatic participants (394 asymptomatic hips) with a mean age of 29.4 years (range, 21.4-50.6 years), T1-weighted MRI scans were studied. The anterosuperior alpha angle measurement was performed by 2 observers using a previously described methodology and also using the radial view. The intraclass correlation coefficient (ICC) was determined for interobserver and intraobserver reliability. Descriptive statistics, the Student t test, correlation studies, and the Bland-Altman technique were used for data analysis. Results: The ICC for interobserver and intraobserver reproducibility was 0.74 (good agreement) and 0.84 (very good agreement), respectively. Anterosuperiorly, the mean (±SD) alpha angles in the oblique axial and radial views were 45.11° ± 8.52° and 50.30° ± 7.91°, respectively (P < .0001). The upper limits of the 95% reference interval for the oblique axial and radial views were 63° and 66°, respectively. In the oblique axial view, the mean (±SD) alpha angle for male participants was 48.3° ± 7.5° compared with 42.6° ± 6.2° for female participants (P < .0001), and in the radial view, it was 53.0° ± 7.1° compared with 48.1° ± 5.6°, respectively (P < .0001). Linear regression analysis demonstrated an insignificant relationship between age and alpha angle, regardless of the imaging plane (r2 = 0.06). Conclusion: We suggest using a higher threshold of 63° (in the oblique axial view) and 66° (in the radial view) at the 1:30 clockface position for the diagnosis of a cam-type deformity. This is significantly higher than 50° to 55° at the 3-o’clock position traditionally used based on the oblique axial view that has been initially described.

Shared Morphology of Slipped Capital Femoral Epiphysis and Femoroacetabular Impingement in Early-onset Arthritis

A subclinical form of slipped capital femoral epiphysis (SCFE) can lead to subtle morphologic abnormalities, such as cam-type femoroacetabular impingement (FAI). Femoroacetabular impingement is a mechanical hip abnormality that typically affects young populations and leads to hip pain and premature osteoarthritis. Imaging is critical to diagnosis, whether by radiograph, magnetic resonance imaging, or computed tomography. The authors investigated the use of imaging to detect characteristics of subclinical SCFE and cam-type FAI in patients undergoing hip resurfacing. They retrospectively assessed computed tomography scans of 81 hips from 75 patients. Measurements were taken of the proximal femur and included the alpha angle, head-neck tilt, and anterior offset taken in both the conventional oblique axial plane and the radial plane. The cohort consisted of 68 men and 13 women with an average age of 52 years. Ninety percent of hips on the oblique axial view and 95% of hips on the radial view were found to have pathologically increased alpha angles. Negative correlations were found between the alpha angle and head-neck tilt and positive correlations between head-neck tilt and anterior offset ratio. Sixty percent and 68% of hips in the oblique axial and radial planes, respectively, were abnormal for the alpha angle, head-neck tilt, and anterior offset ratio, strongly suggesting SCFE morphology. This study's results show similarity in morphology between cam-type FAI and SCFE, known precursors to osteoarthritis, in an early arthritic patient population.

OP02.04: Oblique axial view of the brain to evaluate posterior brain: should be considered part of the routine 11–13 week scan?

OP02.04: Oblique axial view of the brain to evaluate posterior brain: should be considered part of the routine 11–13 week scan?

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) in a newborn

A 5-day-old child was referred to the department of cardiology for bradycardia without any other cardiac symptoms. ECG was normal. Cardiac echography demonstrated a reverse flow inside the interventricular branch of the left coronary artery suggesting ALCAPA. ECG-gated multidetector CT angiography, with oblique axial view (a) and 3-D volume-rendered images (b), confirmed the diagnosis of ALCAPA (DLP=99 mGy-cm) (Fig. 1). Reimplantation of the left coronary artery into the aorta was performed promptly and with success. ALCAPA is a rare congenital anomaly but is one of the most common causes of myocardial ischemia in children [1]. Usually, symptoms occur around 8 weeks of life. If untreated, most patients will die within the first year of life. Cardiac echography alone permits the diagnosis of ALCAPA. Nevertheless, ECG-gated multidetector CT angiography can be used instead of conventional angiography to clarify the anatomy or confirm an unclear diagnosis [2]. In neonates, early surgical correction allows improvement of ventricular function.

Improved Divergence Angles With Femoral Interference Screw Placement Through the Tibial Tunnel as Measured by Multiplanar Reconstruction Computed Tomography

A modified technique for anterior cruciate ligament (ACL) reconstruction without graft injury by femoral interference screw insertion directly through the tibial tunnel is reported. This study evaluated femur bioabsorbable interference screw divergence and obliquity of the graft and tunnel positions as measured by multiplanar reconstruction computed tomography (MPR-CT) after endoscopic ACL reconstruction. Twenty-five patients who underwent single-incision arthroscopically assisted ACL reconstruction using hamstring tendon autografts were enrolled in this prospective study. All procedures were performed using the same technique: femoral bioabsorbable interference screw insertion directly through the tibial tunnel. Divergence angles of oblique sagittal and oblique axial views of the graft and tunnel positions using MPR-CT evaluation were obtained. CT images were evaluated in a blinded manner by 3 experienced radiologists. The average divergence angles in oblique sagittal and oblique axial views were 0.88 +/- 1.06 and 1.44 +/- 1.17, respectively. Sagittal, axial, and coronal obliquity of the graft in reconstructed patients averaged 64 degrees (range, 46 degrees to 69 degrees ), 19 degrees (range, 17 degrees to 22.5 degrees ), and 73.6 degrees (range, 70 degrees to 77.6 degrees ), respectively. Radiologic analysis of the femoral insertion according to the quadrant technique showed that the femoral center of the anteromedial (grafted) bundle was 18.6% and 23.6% of the depth of Blumensaat's line and the height of the femoral condyle. At the tibia, the tibial ACL attachment at the center of the anteromedial bundle was at 41.1% of the maximal tibial diameter. Our study showed that MPR-CT is a useful diagnostic tool for evaluation of the femoral interference screw divergence, obliquity of the graft, and the exact femoral and tibial insertion site of the graft. The screw will have little or no divergence using this novel technique as measured by the very accurate MPR-CT. Level IV, therapeutic case series.

MR orthogonal views of the femoral neck: oblique-axial view from the oblique-coronal plane.

The authors describe a simple technique for imaging femoral neck lesions in two orthogonal views. Oblique-coronal imaging was performed in planes parallel to the femoral neck from an axial localizer. Subsequently, oblique-axial imaging was performed perpendicular to the oblique-coronal images. This technique localizes the lesion to either the cortex or the medullary space. Precise location of the femoral neck lesion refines the differential diagnosis and assists the clinicians in therapeutic planning.

A RADIOLOGICAL APPROACH TO THE SUBTALAR JOINT

The subtalar joint is not easy to visualise by standard radiographic methods. Several projections are described including medial and lateral oblique axial views to demonstrate the three compartments of the joint. It is suggested that when visualisation of the subtalar joint is required these views should be routine. Various conditions affecting the subtalar joint and their demonstration by these oblique axial views are discussed.