Normal CT anatomy of the spine

Summary To analyse the anatomo-radiological correlation of the spine and spinal cord, 22 formalized, frozen anatomical specimens corresponding to different regions of the spinal column (8 cervical, 5 dorsal, and 9 lumbar) were studied by CT scans on axial, sagittal and coronal planes and by contact radiography after they were cut into anatomical slices in order to clarify the normal CT anatomical spinal column. The results obtained from CT patient scans, performed exclusively on the axial plane, were compared with those obtained from the anatomical specimens (both CT and contrast radiography). High resolution CT programs were used, enabling us to obtain better individualization of the normal structures contained in the spinal column. Direct sagittal and coronal sections were performed on the specimens in order to get further anatomo-radiological information. Enhanced CT studies of the specimens were also available because of the air already present in the subarachnoid spaces. Excellent visualization was obtained of bone structures, soft tissue and the spinal cord. High CT resolution of the spine appears to be an excellent neuroradiological procedure to study the spine and spinal cord. A metrizamide CT scan is, however, necessary when a normal unenhanced CT scan is insufficient for diagnosis and when the spinal cord is not clearly visible, as often happens at the cervical level. Clinical findings are certainly very useful to ascertain the exact CT level and to limit the radiation exposure.     

Normal and pathologic radiographic anatomy of the motor innervation of the face

Facial motor disorders, including facial paralysis, myokymia, dyskinesia, and hemifacial spasm, are common clinical problems in which radiographic evaluation plays a crucial role. Since every segment of the motor innervation of the face from the brain to the parotid gland can now be seen radiographically, radiologists must understand the normal anatomy, the common pathologic lesions at each level, and the clinical findings that help localize the abnormality so that the most sensitive and accurate radiographic approach can be planned. Though computed tomography alone allows for visualization of every segment, other methods such as cisternography, angiography, polytomography, sialography, and magnetic resonance imaging are complementary in specific disorders.     

Prediction of transitional lumbosacral anatomy on magnetic resonance imaging of the lumbar spine

AIM:To evaluate two simple angle measurements for predicting lumbosacral transitional vertebra(LSTV) in magnetic resonance imaging(MRI) studies of the spine.METHODS:The lumbar spine MRI studies of 50 subjects with LSTV and 50 subjects with normal lumbosacral anatomy were retrospectively evaluated.In each study,the mid-sagittal T2-weighted image was used to measure the angle formed by a line parallel to the superior surface of the sacrum and a line perpendicular to the axis of the scan table(A-angle),as well as the angle formed by a line parallel to the superior endplate of the L3 vertebra and a line parallel to the superior surface of the sacrum(B-angle).RESULTS:The total study population consisted of 100 subjects(46 males,54 females,51 ± 16 years old).There were no differences in age and sex between the two groups.Both A-angle and B-angle were significantly increased in subjects with LSTV compared to controls(P < 0.05).The optimal cut-off values of A-angle and B-angle for the prediction of LSTV were 39.8°(sensitivity = 80%,specificity = 80%,accuracy = 83%;95% confidence interval = 74%-89%,P = 0.0001) and 35.9°(sensitivity = 80%,specificity = 54%,accuracy = 69%;95% confidence interval = 59%-78%,P = 0.0005),respectively.CONCLUSION:On sagittal MR images of the lumbar spine,an increased A-angle and/or B-angle should alert the radiologist to the presence of LSTV.     

Bone SPECT of the spine: a comparison of attenuation correction techniques.

Image artifacts from variable self-attenuation are recognized as major sources of diagnostic uncertainty in SPECT. For myocardial perfusion studies, an attenuation map is often obtained from a separate transmission study. However, for many applications such as bone SPECT, it has been believed to be unnecessary to obtain a transmission study to correct for the effects of attenuation. We have had significant success in clinical management of lower spine pain using bone SPECT. This success has led us to consider SPECT for the management of cervical spine pain. Cervical spine reconstructions without attenuation correction are difficult to interpret, because the high attenuation in the mandible and skull tends to decrease estimates of activity of the upper cervical spine, and the lower cervical/upper thoracic vertebrae are obscured by the shoulders. We present a technique that uses downscatter to provide attenuation correction for these acquisitions and compare it with other recognized attenuation correction techniques. METHODS: An emission study is acquired using two windows: one for obtaining the photopeak data and another for obtaining the downscattered photons. A body outline is estimated from these datasets using a projection data thresholding method. From this outline, a uniform attenuation map is created using attenuation coefficients appropriate for 99mTc in water (0.154 cm(-1)). These maps are used in SPECT reconstruction using ordered-subset expectation maximization (OSEM). This method is compared with (a) no attenuation correction (NC), (b) conventional Chang attenuation correction based on the interactive determination of the body outline from the 99mTc emission photopeak data (ChangAC) and (c) OSEM correction using attenuation maps estimated with a line source and fanbeam collimators (transAC). RESULTS: Patient studies using scatterAC demonstrated a significant improvement in the uniformity of estimated cervical spine uptake in normal patients, compared with either NC or ChangAC. Results using scatterAC were similar to those of transAC. We also observed significant improvement in uniformity using scatterAC in SPECT of the lower back in obese patients, as well as the relative limitations of scatterAC versus nonuniform, transmission-based attenuation correction. CONCLUSION: Comparisons with reconstructions using transmission data for estimating attenuation demonstrate that reasonable quantitative accuracy can be obtained in SPECT of the cervical spine using this simple attenuation estimate. Both scatterAC and transAC appear to provide consistent and expected uniform spine uptake in the cervical spines of normal patients.     

Normal and abnormal Ga-67 SPECT anatomy in patients with lymphoma

The appearance of normal Ga-67 SPECT images in the coronal, sagittal and transaxial planes is described. The normal tomographic appearance of bone, liver, spleen, and gut is shown and compared with disease involvement above and below the diaphragm.     

Normal anatomy of the neck with CT and MR imaging correlation

Knowledge of normal anatomy is the cornerstone for understanding pathologic processes. Often, the most difficult task for a radiologist is differentiating normal structures from pathology. There are many ways to organize a discussion of the normal anatomy in the neck. This article is organized by organ system, with an additional discussion of triangles, fascia, and spaces. Important normal variants are also discussed.     

The anatomy of the pelvis

The pelvis consists of the sacrum, the ossa coxae, and additionally the ligaments between these bones. According to mathematical calculations the bony structure as well as the arrangement of ligaments result in optimal engineering principles, i.e. maximal strength is achieved by minimal principles, i.e. maximal strength is achieved by minimal material. The muscles inside the pelvis are covered by a fascial layer. The latter represents a continuation of the abdominal transversal fascia which extends to the pelvic floor. The connective tissue fibres around the pelvic viscera interweave with those of the pelvic floor and laterally with the connective tissue around vessels and nerves. Connective tissue around the neurovascular sheaths is nearly transversely arranged and forms the lateral ligaments of bladder, uterus or prostate gland and the rectum. Several vertically arranged connective tissue ligaments accompany either the superior rectal artery and hypogastric nerves or the ureter and the ovarian vessels. Therefore, the lymphatic fluid of the pelvic organs passes the aortic lymph nodes and/or to the lateral pelvic wall along the branches of the internal iliac vessels.     

Normal anatomy and pathologic conditions of ankle tendons: current imaging techniques.

Radiologic assessment of tendon injuries requires familiarity with normal anatomy and the capabilities of available imaging modalities. Tenography, less commonly used nowadays, does not allow direct visualization of tendons, so that partial ruptures and longitudinal splits may go undetected. Ultrasonography can depict tenosynovitis, tendinitis, and complete tendon rupture of the Achilles tendon, but the other tendons are difficult to visualize with this technique. Magnetic resonance (MR) imaging is superior to computed tomography (CT) in the depiction of tenosynovitis and peritendinitis, tendinitis, tendon rupture, and tendon dislocation and subluxation. CT can demonstrate these abnormalities, but accompanying scar tissue or edema, early changes of tendon degeneration, and small amounts of inflammatory fluid are difficult to differentiate with this technique. CT is superior for demonstrating calcifications, convex retromalleolar groove, bone fragments, or spurs that complicate tendon dislocation and rupture. Although the authors prefer MR imaging, they caution that all of the modalities are not always specific and that differentiation between closely related processes such as tendinitis and early tendon rupture is difficult.     

CT evaluation of the lumbosacral spine

The biologic cost-effectiveness of computed tomography (CT) versus myelography is so favorable to CT that it is now the method of choice for evaluating patients with less clear-cut clinical findings. CT is now used to detect lesions formerly difficult to diagnose, such as subluxation, arthrosis, facet osteophytes, and stenosis of the vertebral canal, as well as herniated disks and lateral disks. The findings in over 1,000 patients examined by CT for lumbosacral spinal pathology are documented. Associated or multiple abnormalities were present in about 60% of cases, with bulging or herniated disks occurring in 45% and 44%, respectively. Postsurgical arachnoiditis was seen in 43% of 64 patients studied for recurrence of symptoms after surgery.     

An evaluation of reconstruction techniques and scatter correction in bone SPECT of the spine

A selection of commonly used reconstruction and filter techniques in the processing of 99mTc oxidronate (i.e., 99mTc hydroxymethane diphosphonate) single photon emission computed tomography (SPECT) of the spine was compared. The possible additional value of scatter correction on image contrast was also evaluated. Twenty-eight bone SPECT examinations of consecutive patients were studied retrospectively. The reconstruction techniques used were filtered back-projection and iterative reconstruction with the use of ordered subsets estimation maximization. Three-dimensional post-filtering with a Metz filter and a Butterworth filter was used. Each combination was evaluated with or without scatter correction. Each study was also processed with the department's standard technique of two-dimensional pre-filtering with a Metz filter followed by filtered back-projection (without scatter correction). Five observers evaluated the image quality of reconstructed coronal and sagittal slices, with special reference to the resolution of vertebrae, vertebral processes, the spinal canal and suspected abnormal uptakes. A grading scale from -2 to +2 was used with the standard technique as the reference. The best image quality was found with iterative reconstruction in combination with a contrast enhancing Metz filter or a noise reducing Butterworth filter. Scatter correction did not improve image quality.     

Computed tomography of the bony pelvis: a protocol for multiplanar imaging. Part I: Normal anatomy

The normal gross and computed tomographic anatomy of the bony pelvis is briefly reviewed, with special reference to the bony masses of greatest concern to a surgeon. Normal transverse computed tomography (CT) images are shown. I describe a unique, comprehensive protocol for multiplanar CT reformation of the osseous pelvis. This algorithm provides "direct-view" images that are considerably more reliable than "mental reformatting" from transverse images alone. The procedure is of particular value in assessing fractures and dislocations occurring separately or together.     

Comparing the supine and erect pelvis radiographic examinations: an evaluation of anatomy,image quality and radiation dose

Objectives:Pelvis radiographs are usually acquired supine despite standing imaging reflecting functional anatomy. We compared supine and erect radiographic examinations for anatomical features, radiation dose and image quality.Methods:60 patients underwent pelvis radiography in both supine and erect positions at the same examination appointment. Measures of body mass index and sagittal diameter were obtained. Images were evaluated using visual grading analysis and pelvic tilt was compared. Dose–area product values were recorded and inputted into the CalDose_X software to estimate effective dose (ED). The CalDose_X software allowed comparisons using data from the erect and supine sex-specific phantoms (MAX06 & FAX06).Results:Patient sagittal diameter was greater on standing with an average 20.6% increase at the iliac crest (median 30.0, interquartile range [26.0 to 34.0] cm), in comparison to the supine position [24.0 (22.3 to 28.0) cm; p < 0.001]. 57 (95%) patients had posterior pelvic tilt on weight-bearing. Erect image quality was significantly decreased with median image quality scores of 78% (69 to 85) compared to 87% for the supine position [81 to 91] (p < 0.001). In the erect position, the ED was 47% higher [0.17 (0.13 to 0.33) mSv vs 0.12 (0.08 to 0.18) mSv (p < 0.001)], influenced by the increased sagittal diameter. 42 (70%) patients preferred the standing examination.Conclusion:Patient diameter and pelvic tilt were altered on weightbearing. Erect images demonstrated an overall decrease in image quality with a higher radiation dose. Optimal acquisition parameters are required for erect pelvis radiography as the supine technique is not directly transferable.     

Evaluation of techniques for the elimination of "hot" bladder artifacts in SPECT of the pelvis

The purpose of this study was to validate the usefulness of two digital filtering techniques used to eliminate the artifacts caused by rapid bladder filling during SPECT of the pelvis. A dynamic phantom model was used containing two hips and a bladder. The phantom was studied under three conditions--bladder empty, filling, and full. The ability of the pixel truncation and interpolative background replacement techniques to eliminate bladder artifacts was assessed. Both techniques gave similar results and resulted in significant (but not complete) recovery of activity in the hips. Quantitative analysis of pixel counts over each hip shows that the measured activity was variable and approximately 20%-30% less than that seen in the empty bladder study. The use of left/right ratio to quantitate differences in hip activity was highly inaccurate despite the use of these filtering techniques. In summary, while these techniques significantly improve image quality, caution should be exercised, particularly in the evaluation of the medial aspects of the hips.     

Normal radiographic anatomy of thoracic structures: analysis of 316 lateral chest radiographs

PURPOSE: To study the frequency of visualization and characteristics of normal thoracic structures on lateral chest radiographs in the Japanese population. MATERIALS AND METHODS: We reviewed 316 lateral chest radiographs of men and women ranging in age from 20 to 90 years. The frequency of visualization and configuration of structures including major, minor, superior and inferior accessory fissures, and orifices of the right and left upper lobe bronchi were reviewed. RESULTS: On lateral chest radiographs, major fissure and minor fissure were visualized in 99.4% and 87.3%, respectively. Superior accessory fissure and inferior accessory fissure were visualized in 1.9% and 9.5%, respectively. Orifices of the right and left upper bronchi were seen in 92.4% and 98.4%, respectively. CONCLUSION: Frequency of visualization and characteristics of various normal anatomic structures on lateral chest radiographs in the Japanese population differ from those reported previously from the West. Familiarity with these normal thoracic structures and variations is important for daily image interpretation.