Oblique Axial Planes Research Articles

Magnetic resonance sialography using CISS and HASTE sequences in inflammatory salivary gland diseases: Comparison with digital sialography

Inflammatory conditions are the most common pathology affecting the salivary glands. Magnetic resonance (MR) sialography has emerged as an alternative to conventional sialography for evaluation of inflammatory salivary gland diseases. To prospectively evaluate the role and diagnostic accuracy of MR sialography in the diagnosis of inflammatory salivary gland disease. Thirty-seven glands in 28 patients (19 males and nine females; mean age 31 years, range 3-65 years) presenting with inflammatory salivary gland disorders underwent MR sialography. Conventional sialography was used as the gold standard and was performed in 26 patients (34 glands). Thus, comparative evaluation was done in 26 patients (34 glands). Axial T1-weighted (T1W) and fat-suppressed T2W sequences, a constructive interference in steady state (CISS) sequence in the axial plane with maximum intensity projection (MIP)/multiplanar reformation (MPR) done in the axial and sagittal oblique planes, and a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence in the sagittal oblique direction were performed. Main salivary gland duct was visualized in 32 glands (94.1%) with MR sialography, and in all 34 (100%) glands with conventional sialography. Calculus and strictures were well demonstrated by MR sialography. MR sialography was superior for demonstration of the ductal system proximal to calculus/strictures. Sensitivity and specificity for diagnosis of specific pathology were 87% and 100% with CISS sequence and 90% and 75% with HASTE sequence, respectively. On using a combination of CISS and HASTE sequences, the sensitivity, specificity, and positive and negative predictive values in the diagnosis of specific pathology were 93%, 100%, 100%, and 64%, respectively. MR sialography using CISS and HASTE sequences is a promising technique and has the potential to replace conventional sialography in patients with inflammatory salivary gland disorders.

Magnetic Resonance Cisternographic Evaluation of Glossopharyngeal, Vagus, and Accessory Nerves

Purpose The individual visualization of the glossopharyngeal, vagus, and accessory nerves has been a troublesome issue. After the recent developments in the microsurgical field, the detailed knowledge of the relationship of these nerves and the tumour has gained importance. The purpose of this study is to compare the visibility of each of these nerves. Methods Thirty patients (M/F: 14/16; mean age 52.46 years) with complaints of vertigo, tinnitus, and hearing loss were examined with routine temporal magnetic resonance imaging (MRI) study. The imaging protocol consisted of 3-dimensional fast imaging with steady state acquisition in axial and sagittal oblique planes in addition to routine sequences. These images were transferred to a workstation and reformatted. Visibility of the nerves was evaluated by consensus of 2 radiologists who used an evaluation scale of 2 (excellently visible), 1 (partially visible), to 0 (not visible). Results In 26 patients, both sides were scanned; in 4 patients, only one side was scanned. A total of 168 nerves were investigated. The rates for visualization for each nerve were as follows: glossopharyngeal nerve, 100% and 100%; vagus nerve, 67.9% and 100%; and accessory nerve, 10.8% and 83.85% on axial and sagittal oblique 3-dimensional fast imaging with steady state acquisition, respectively. Conclusions Glossopharyngeal, vagus, and accessory nerve assessment improved when images were obtained in the sagittal oblique plane to the jugular foramen.

Accessory left atrial diverticulae: contractile properties depicted with 64-slice cine-cardiac CT

To assess the contractility of accessory left atrial appendages (LAAs) using multiphasic cardiac CT. We retrospectively analyzed the presence, location, size and contractile properties of accessory LAAs using multiphasic cardiac 64-slice CT in 102 consecutive patients (63 males, 39 females, mean age 57). Multiplanar reformats were used to create image planes in axial oblique, sagittal oblique and coronal oblique planes. For all appendages with an orifice diameter >or= 10 mm, axial and sagittal diameters and appendage volumes were recorded in atrial diastole and systole. Regression analysis was performed to assess which imaging appearances best predicted accessory appendage contractility. Twenty-three (23%) patients demonstrated an accessory LAA, all identified along the anterior LA wall. Dimensions for axial oblique (AOD) and sagittal oblique (SOD) diameters and sagittal oblique length (SOL) were 6.3-19, 3.4-20 and 5-21 mm, respectively. All appendages (>or=10 mm) demonstrated significant contraction during atrial systole (greatest diameter reduction was AOD [3.8 mm, 27%]). Significant correlations were noted between AOD-contraction and AOD (R = 0.57, P < 0.05) and SOD-contraction and AOD, SOD and SOL (R = 0.6, P < 0.05). Mean diverticulum volume in atrial diastole was 468.4 +/- 493 mm(3) and in systole was 171.2 +/- 122 mm(3), indicating a mean change in volume of 297.2 +/- 390 mm(3), P < 0.0001. Stepwise multiple regression analysis revealed SOL to be the strongest independent predictor of appendage contractility (R(2) = 0.86, P < 0.0001) followed by SOD (R(2) = 0.91, P < 0.0001). Accessory LAAs show significant contractile properties on cardiac CT. Those accessory LAAs with a large sagittal height or depth should be evaluated for contractile properties, and if present should be examined for ectopic activity during electrophysiological studies.

Correlation between Pancreatic Microcirculation and Type 2 Diabetes in Patients with Coronary Artery Disease: Dynamic Contrast-enhanced MR Imaging

To evaluate pancreatic perfusion by using dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging with pharmacokinetic modeling in coronary artery disease (CAD) patients with and those without type 2 diabetes to determine which perfusion parameter alterations might be associated with type 2 diabetes. This prospective study was approved by the responsible institutional review board. Written informed consent was obtained from all patients. All patients studied had CAD documented at conventional angiography. DCE MR with a two-dimensional T1-weighted fast low-angle shot sequence in oblique axial planes was used to assess pancreatic microcirculation in patients with and those without type 2 diabetes (age +/- standard deviation, 60.8 years +/- 11.2 and 61.8 years +/- 11.2, respectively; 20 men and five women in each group). Microcirculatory quantitative parameters, including volume transfer constant (K(trans), in min(-1)), extravascular extracellular space volume per unit volume of tissue (v(e)), and plasma volume per unit volume of tissue (v(p)) were compared between groups by using independent-sample t tests. Patients with diabetes had a significantly higher K(trans) (0.977 vs 0.696, P = .031) and a lower v(p) (0.057 vs 0.084, P = .005) compared with patients without diabetes. A borderline difference in v(e) was found between the diabetes and nondiabetes groups (0.141 vs 0.103, P = .05). Among the 25 patients with diabetes, those who had the condition for more than 10 years (n = 11) had significantly higher K(trans) and v(e) than did those who had diabetes for less than 10 years (n = 14) (1.145 vs 0.783 and 0.174 vs 0.108; P = .04 and .02, respectively). DCE MR imaging demonstrated increased endothelial permeability and decreased plasma volume in the pancreas in CAD patients with type 2 diabetes; patients with a history of diabetes for more than 10 years showed further increase in endothelial permeability.

Comparison of Standard Hip MR Arthrographic Imaging Planes and Sequences for Detection of Arthroscopically Proven Labral Tear

The purpose of this study was to compare multiple imaging planes and two pulse sequences for detection of arthroscopically proven labral tears. From March 2004 through June 2007, acetabular labral tear was diagnosed at hip arthroscopy of 189 patients. Preoperative MR arthrography of the affected hip was performed on 144 patients at our institution. These MR arthrograms were retrospectively reviewed by a musculoskeletal fellow and two musculoskeletal radiologists. The sequences used were coronal T1-weighted with fat saturation, coronal T2-weighted with fat saturation, sagittal T1-weighted with fat saturation, axial oblique T1-weighted with fat saturation, sagittal oblique T1-weighted with fat saturation, and axial T1-weighted. Using consensus, the reviewers evaluated images obtained with each sequence for the presence of a tear, number of slices on which a tear was seen, and the signal intensity of the tear. Among the 144 tears, 97.2% were identified as definitely present on images obtained with at least one of the sequences. The axial oblique sequence had the highest individual detection rate (85.0%). The detection rates for the sagittal T1-weighted (74.6%), coronal T1-weighted (67.4%), and coronal T2-weighted (63.6%) sequences were intermediate. Detection rates with the axial T1-weighted (29.9%) and sagittal oblique (18.2%) sequences were low. With the combination of three sequences (coronal T2-weighted with fat saturation, axial oblique T1-weighted with fat saturation, and sagittal T1-weighted with fat saturation), 95.8% of the 144 tears were identified as definitely present. Twenty-eight percent of tears had a signal intensity less than that of gadolinium or fluid. Imaging in the axial oblique plane has the highest rate of detection of acetabular labral tears. More than 95% of tears were identified with the use of three imaging planes. Signal intensity within a tear does not have to be equal to that of gadolinium or fluid to confirm the diagnosis of labral tear.

Comparison of MRI Alpha Angle Measurement Planes in Femoroacetabular Impingement

Insufficient femoral head-neck offset is common in femoroacetabular impingement (FAI) and reflected by the alpha angle, a validated measurement for quantifying this anatomic deformity in patients with FAI. We compared the alpha angle determined on magnetic resonance imaging (MRI) oblique axial plane images with the maximal alpha angle value obtained using radial images. The MRIs of 41 subjects with clinically suspected FAI were reviewed and alpha angle measurements were performed on both oblique axial plane images parallel to the long axis of the femoral neck and radial images obtained using the center of the femoral neck as the axis of rotation. The mean oblique axial plane and mean maximal radial alpha angle values were 53.4 degrees and 70.5 degrees, respectively. In 54% of subjects, the alpha angle was less than 55 degrees on the conventional oblique axial plane image but 55 degrees or greater on the radial plane images. Radial images yielded higher alpha angle values than oblique axial images. Patients with clinically suspected FAI may have a substantial contour abnormality that can be underestimated or missed if only oblique axial plane images are reviewed. Radial plane imaging should be considered in the MRI investigation of FAI.

Inter-observer agreement in the identification of the two bundles of the anterior cruciate ligament using magnetic resonance imaging

Magnetic resonance imaging has become the method of choice to diagnose meniscal and ligament lesions of the knee. New approaches to the surgical treatment of partial anterior cruciate ligament tears led us to try to distinguish the two bundles of that ligament with MRI and to evaluate inter-observer agreement in different viewing planes. Images of 50 right and 50 left ligament-intact knees were examined in the coronal and axial viewing planes. Each sequence was independently read by a radiologist and a medical student to note, in each viewing plane, the number of images in which the two-bundle structure of the ligament was clearly seen. Cohen's Kappa coefficients were used to determine inter-observer agreements. The percentage of sequences in which the two bundles were distinguished by the radiologist and the student on one image at least were 82 versus 73% in the coronal plane and 90 versus 93% in the axial plane, respectively. The average number of successive images with clear bundles was higher in the axial (2.7 vs. 1.7) than in the coronal plane (2.2 vs. 1). There was a poor inter-observer agreement in the coronal plane (k=0.176) but an intermediate agreement in the axial plane (k=0.385 or 0.522 depending on number pooling). The axial viewing plane seems more favourable to distinguish the two bundles of the anterior cruciate ligament with the best possible reproducibility. An oblique-axial plane is deemed to insure a clearer diagnosis of partial tears.

P40.08: Posterior wall of the fetal palate: is it a reliable sign applicable in routine?

Objectives: To evaluate the assessment methods for fetal lip/palate on 3D ultrasound with various techniques and examination planes. Methods: Stored 3D volumes of fetuses with postnatal confirmation of cleft lip and/or palate were reviewed. The abnormalities at birth were compared with the antenatal 3D ultrasound findings in the following planes obtained on techniques previously described: 1. The axial plane 2. The sagittal plane 3. The coronal plane 4. Oblique axial plane 5. Oblique sagittal plane 6. Targeted reverse face view Results: There were limitations to each technique or examination plane in antenatal assessment of fetal lip/palate on 3D ultrasound. Different parts of the fetal lip and palate could be visualized with each of the above planes. The anterior part of the palate and the fetal lips are better seen in the axial, sagittal and coronal planes. The oblique axial, oblique sagittal planes and the targeted reverse face view allowed better visualization of the hard and the soft palates. The presence of facial cleft led to a distortion of the anatomy. The use of a combination of these planes allowed a more complete assessment of fetal lip and palate from various angles. Conclusions: The use of a combination of planes and techniques provides more information than the use of a single one in evaluation of fetal cleft lip/palate on 3D ultrasound.

Evaluation of radial-sequence imaging in detecting acetabular labral tears at hip MR arthrography

In recent years, radial imaging has been advocated for improved visualization of the acetabular labrum in magnetic resonance arthrography of the hip. The purpose of this study was to investigate whether radial imaging demonstrates labral tears not visible on standard imaging planes. Fifty-four consecutive magnetic resonance (MR) arthrograms of the hip that included radial imaging over 2 years were retrospectively analyzed by two radiologists. Standard imaging planes and radial imaging were reviewed for identification of labral tears in four specific areas of the labrum: anterosuperior, posterosuperior, anteroinferior, and posteroinferior. The standard imaging sequences include fat-saturated spin-echo T1-weighted images in the coronal and oblique axial planes, non-fat-saturated T1-weighted images in the coronal and sagittal planes, and T2-weighted sequence in the axial plane. Radial imaging was performed as previously described using fat-saturated T1-weighted sequences. Using standard imaging planes, 50 anterosuperior, 31 posterosuperior, 10 anteroinferior, and 9 posteroinferior labral tears were detected in 54 MR arthrograms of the hip. Using radial sequences alone, 44 anterosuperior, 25 posterosuperior, 9 anteroinferior, and 5 posteroinferior labral tears were detected. In all four areas of the labrum, the radial imaging did not show any labral tear not seen on standard imaging planes. In MR arthrography of the hip, radial imaging did not reveal any additional labral tears. Standard imaging planes sufficiently demonstrate all acetabular labral tears.

Pelvimetría por resonancia magnética

Objectives To describe the usefulness of magnetic resonance imaging (MRI) pelvimetry in the evaluation of fetal-pelvic disproportion. Material and methods MRI pelvimetry was performed in 29 women at 36-38 weeks’ gestation in a 1T system and a phased-array coil, in the sagittal and oblique axial planes. Results Pelvic diameters were calculated according to the modified parameters at our institution. The anatomic reference points were identified and images were added when these points were in different planes. The results were similar to those of radiopelvimetry except for the sacral angle, because of the different positioning of the patient in the 2 techniques. Conclusion MRI is a useful technique for the performance of pelvimetry because it allows pelvicdiameters to be measured quickly and directly without the use of ionizing radiation.

Abnormalities of the Oculomotor Nerve in Congenital Fibrosis of the Extraocular Muscles and Congenital Oculomotor Palsy

High-resolution magnetic resonance imaging (MRI) can now directly demonstrate innervation to extraocular muscles and quantify optic nerve size. A quantitative MRI technique was developed to study the oculomotor nerve (CN3) and applied to congenital fibrosis of extraocular muscles (CFEOM) and congenital oculomotor palsy. The subarachnoid portions of the CN3s were imaged with a 1.5-T MRI scanner and conventional head coils, acquiring heavily T(2)-weighted oblique axial planes 1-mm thick and parallel to the optic chiasm. Thirteen normal subjects, 14 with CFEOM, and 3 with congenital CN3 palsy were included. Digital image analysis was used to measure CN3 diameter, which was correlated with motility findings. In CFEOM, CN3 diameter was bilaterally subnormal in eight subjects, unilaterally subnormal in three subjects, and normal in three subjects. Mean +/- SD CN3 diameter in CFEOM was 1.14 +/- 0.61 mm, significantly smaller than the diameter in normal subjects, which measured 2.01 +/- 0.36 mm (P < 0.001). CN3 diameter variably correlated with clinical function. One subject with congenital CN3 palsy showed bilateral CN3 hypoplasia, but CN3 diameter was normal in two other subjects with congenital CN3 palsy. Unilateral or bilateral hypoplasia of CN3 is quantitatively demonstrable using MRI in many cases of CFEOM and occasionally in congenital CN3 palsy. Variations in CN3 diameter in CFEOM and congenital CN3 palsy suggest mechanistic heterogeneity of these disorders that may be clarified by further imaging and genetic studies.

Scalar Localization of the Electrode Array After Cochlear Implantation

Improved resolution available with 64-slice multidetector computed tomography (MDCT) could potentially be used clinically to localize the cochlear implant (CI) electrode array within the basal turn. In CI surgery, the electrode array should be inserted into and remain within the scala tympani to avoid injury to Reissner's membrane and the scala media. Correlating the position of the electrode in the basal turn with surgical technique and implant design could be helpful in improving outcomes. After a standard left mastoid exposure of the round window niche through the facial recess performed on a cadaver head, an electrode array from a Nucleus Softip Contour CI was fully inserted through a cochleostomy. The head was then scanned axially on a 64-slice MDCT with 0.4-mm slice thickness and reconstructed into the oblique axial, oblique coronal, and oblique sagittal planes of the cochlea. The temporal bone was then harvested and imaged on a microcomputed tomographic scanner using 20-microm slice thickness. Identical reconstructions were made and compared with the 64-slice images to confirm exact location of the electrode array. The 64-slice MDCT accurately localized the electrode array to the scala tympani. This was best demonstrated in the oblique sagittal plane, identifying the electrode array in the posterior inferior portion of the basal turn, posterior to the spiral lamina. This ex vivo validation study suggests that 64-slice MDCT has the potential to allow accurate localization of the CI electrode array within the basal turn of the cochlea.

Arcuate ligament of the wrist: normal MR appearance and its relationship to palmar midcarpal instability: a cadaveric study

To describe the magnetic resonance (MR) imaging and gross anatomic appearance of the scaphocapitate (SC) ligament and triquetrohamocapitate (THC) ligament, which are the radial and ulnar limbs of the composite arcuate ligament, a critical volar midcarpal stabilizing ligament. T1 spin-echo and 3D gradient-echo MR imaging in the standard, coronal oblique, and axial oblique planes were performed both before and following midcarpal arthrography in seven cadaveric wrists. The seven specimens were then sectioned in selected planes to optimally visualize the SC and THC ligaments. These specimens were analyzed and correlated with their corresponding MR images. The SC and THC ligaments can be visualized in MR images as structures of low signal intensity that form an inverted "V" joining the proximal and distal carpal rows. The entire ligamentous complex is best visualized with coronal and axial oblique MR imaging but can also be seen in standard imaging planes. SC and THC ligaments together form the arcuate ligament of the wrist. Their function is crucial to the normal functioning of the wrist. Palmar midcarpal instability (PMCI) is a resulting condition when abnormalities of these ligaments occur. Dedicated MR imaging in the coronal and axial imaging planes can be performed in patients suspected of having PCMI.

Sonoanatomy Of The Brachial Plexus With Single Broad Band-High Frequency (L17-5 Mhz) Linear Transducer

Sonoanatomy Of The Brachial Plexus With Single Broad Band-High Frequency (L17-5 Mhz) Linear Transducer

Axial oblique MR imaging of the intrinsic ligaments of the wrist: initial experience

To evaluate two separate MR sequences acquired in the axial oblique plane, parallel to the long axis of the scapholunate (SL) and lunotriquetral (LT) ligaments, to determine whether the addition of these sequences to the standard MR wrist examination improves visualization of the intrinsic ligaments, and the evaluation of their integrity. To our knowledge, this plane has not been described in the literature previously. In total we evaluated 26 patients with chronic wrist pain or instability, referred for MR imaging following assessment by an orthopedic surgeon or physiatrist. All patients underwent initial conventional tri-compartment wrist arthrography, which served as the reference standard. This was immediately followed by MR arthrography, in the standard coronal and true axial planes, as well as in the axial oblique plane. The SL and LT ligaments were initially assessed for the presence or absence of tear, using the standard coronal and true axial sequences, and subsequently re-evaluated with the addition of the axial oblique planes. A total of ten intrinsic ligament tears were identified with conventional arthrography: six SL and four LT tears. Five of the six SL tears were identified on the standard sequences. All six were diagnosed with the addition of the oblique sequences. There were three false-positive SL tears identified using standard MR imaging, and two false-positives with the addition of the oblique sequences. No LT tear was identified on standard sequences, whereas all four were confidently seen with the addition of oblique images. No false-positives of the LT ligament were recorded with either standard or axial oblique sequences. The study suggests that the addition of axial oblique MR sequences helps identify tears to the intrinsic ligaments of the wrist, particularly the LT ligament. In addition, the axial oblique images assist in localization of the tear.

High-Resolution Magnetic Resonance Imaging (MRI) Quantifies Oculomotor Nerve (CN3) Size in Congenital Neuropathic Strabismus

Introduction: High-resolution MRI can now directly demonstrate innervation to extraocular muscles and quantify optic nerve size. We developed a quantitative MRI technique to study CN3 and applied it to congenital fibrosis of extraocular muscles (CFEOM), congenital oculomotor palsy, and Duanes retraction syndrome (DRS). Methods: Oculomotor nerves were imaged at the brainstem using a 1.5-T scanner and conventional head coils, acquiring heavily T2-weighted oblique axial MRI planes 1 mm thick parallel to the optic chiasm.

PATIENTS AT HIGH RISK FOR UPPER TRACT UROTHELIAL CANCER: EVALUATION OF HYDRONEPHROSIS USING HIGH RESOLUTION MAGNETIC RESONANCE UROGRAPHY

We assessed the potential of magnetic resonance urography (MRU) in the evaluation of hydronephrosis not explained by standard investigation in patients at high risk for upper tract urothelial cancer. A total of 23 consecutive patients in a specialist urological unit with unexplained hydronephrosis prospectively underwent MRU which comprised overview heavily T2-weighted MR urographic images followed by focused high resolution turbo spin echo T2-weighted sequences obtained in an axial and coronal oblique plane through the level of urinary obstruction. All were at high risk for urothelial cancer and had either contraindications to or problems with standard investigations including poor contrast excretion due to obstruction or renal failure, failed ureteral cannulation or contrast allergy. Clinical events and imaging followup, subsequent endoscopic/surgical findings and histopathology validated MR findings. In 23 patients with a high clinical suspicion of upper tract transitional cell tumors (TCC), 8 ureteral and 5 renal pelvic TCCs (2 bilateral) were diagnosed by MR, and confirmed histologically. In a further 5 patients benign causes for the hydronephrosis were found. No intrinsic or extrinsic pathology was demonstrable in 5 patients whose imaging findings were stable during 1 year of followup. MRU is a valuable noninvasive investigation for evaluating hydronephrosis in this group of patients with suspected urothelial cancer in which routine investigation had failed to provide clinically important information. Focused high resolution T2-weighted images were reliable in the diagnosis of ureteral and renal pelvic TCCs, and were valuable in excluding these and other mass lesions as the cause of hydronephrosis.

Radial head fractures: MRI evaluation of associated injuries

The purpose of this study was to evaluate the incidence of combined osteochondral and ligamentous injuries by magnetic resonance imaging (MRI) in 24 patients with an acute radial head fracture (Mason type II and III) without documented dislocation or tenderness at the distal radioulnar joint. Elbow radiographs (anteroposterior and lateral views) were obtained on all patients as well as magnetic resonance images in the sagittal, coronal, axial, axial oblique, and coronal oblique planes with the injured elbow in a splint. The incidence of associated injuries revealed by MRI was medial collateral ligament not intact in 13 of 24 (54.16%), lateral ulnar collateral ligament not intact in 18 of 24 (80.1%), both collateral ligaments not intact in 12 of 24 (50%), capitellar osteochondral defects in 7 of 24 (29.1%), capitellar bone bruises in 23 of 24 (95.83%), and loose bodies in 22 of 24 (91.67%). A high level of suspicion should be used when one is treating displaced or comminuted radial head fractures, because concurrent osteochondral injuries and/or ligamentous injuries may be present.

Multiplanar reconstructions of helical computed tomography in planning of atlanto-axial transarticular fixation

The objective of this study was to determine atlanto-axial bone morphometric measurements related to screw transarticular fixation technique. One hundred helical computerized tomography (helical CT) scans with volumetric acquisition, including the first and the second cervical vertebrae, were studied. The screw insertion axis according to the Magerl technique for C1-C2 transarticular fixation was the referential to select the correct oblique axial and oblique parasagittal planes obtained with multiplanar reconstruction (MPR) on helical CT. The selected measured parameters on each side of the vertebrae were C2 interarticular isthmus height and width, optimal screw length, optimal screw trajectory sagittal and axial angles, and the distance between the ideal screw trajectory and the vertebral artery groove. C2 interarticular isthmus height measured 7.75+/-1.27 mm, C2 interarticular isthmus width 7.94+/-1.72 mm, optimal screw length 39.03+/-2.81 mm, optimal screw trajectory sagittal angle 57.54+/-5.28 degrees , optimal screw trajectory medial angle 7.90+/-4.05 degrees. Isthmus narrowing under 5 mm (height and/or width) was seen in 5% of cases. In 30% of cases reconstructed parasagittal images showed the vertebral artery groove. In those cases, the distance between the vertebral artery groove and the ideal screw path was measured. This distance measured under 2.5 mm in 7% of C2 articular masses. A classification of C2 articular mass morfology was proposed. The C2 articular masses without anatomic variations predisposing to vertebral artery injury were considered type I. The C2 articular masses potentially associated with vascular injury (12%) were classified as type II. Potential risk was identified at the C2 isthmus only (3%), at the anterior portion of C2 articular mass only (7%) or at both regions (2%). According to selected criteria 18% of patients would have at least one side C2 articular mass with potential risk for the vertebral artery. In 6% of patients the potential risk was identified bilaterally. There is a great variation in the maximum and minimum values of the anatomic measurements. Therefore preoperative CT scans are very important to identify type II cases, such that the surgeon may preoperatively define the bony anatomy trough which the screws will pass.

Evaluation of Painful Hydronephrosis in Pregnancy:: Magnetic Resonance Urographic Patterns in Physiological Dilatation Versus Calculous Obstruction

We evaluated magnetic resonance urography (MRU) appearances in symptomatic hydronephrosis in pregnancy and compared urographic patterns in physiological and calculous disease. A total of 24 consecutive pregnant women with symptomatic hydronephrosis underwent MRU, comprising an overview fast T2-weighted examination of the abdomen and pelvis, and thick slab, heavily T2-weighted MRU images, followed by focused, high resolution T2-weighted sequences obtained in an axial and coronal oblique plane through the level of ureteral caliber change. Of these 24 pregnant women 15 were found to have physiological hydronephrosis, 7 had calculous disease and 2 had preexisting urinary anomalies. MRU findings in physiological hydronephrosis cases were extrinsic compression of the middle third of the ureter, no filling defect and a collapsed ureter below it. Obstruction by ureteral calculi was seen at points of ureteral narrowing in the ureter, that is at the vesicoureteral junction in 2 cases, in the compressed mid ureter in 3 and at the pelviureteral junction in 1. Nonobstructive renal calculi were seen in another patient. Calculi presented throughout pregnancy but physiological hydronephrosis presented only in the late second and third trimesters. With distal calculi the MRU appearance was the double kink sign with constriction at the pelvic brim and the vesicoureteral junction with a standing column of urine in the pelvic ureter. There was renal edema and perirenal extravasation. Small calculi were only identified using high resolution T2-weighted magnetic resonance imaging. MRU is a valuable and well tolerated investigation for evaluating painful hydronephrosis in pregnancy. There are characteristic and differing urographic appearances in physiological and calculous obstruction.