MRI venous architecture of insula

PURPOSE

The purpose of this paper is to describe the venous anatomy of the insula using conventional MR brain imaging and confocal reconstructions in cases with glioma induced venous dilatation (venous gliography).

METHODS

Routine clinical MRI brain scans that included thin cut (1.5-2 mm) post contrast T1 weighted imaging were retrospectively reviewed to assess the insular venous anatomy in 19 cases (11 males and 8 females) with insular gliomas. Reconstruction techniques (Anatom-e and Osirix) were used to improve understanding of the venous anatomy.

RESULTS

We identified the following insular and peri-insular veins on MRI: the superficial middle cerebral vein (SMCV), peri-insular sulcus vein, vein of the anterior limiting sulcus, the precentral, central, and posterior sulcus veins of the insula, the communicating veins and deep MCV.

CONCLUSIONS

We concluded that venous anatomy of insula is complicated and is often overlooked by radiologists on MR brain imaging. Use of confocal imaging in different planes helped us to identify the superficial and deep middle cerebral veins and their relationship to the insula. The understanding of the insular venous architecture is also useful to distinguish these vessels from insular arteries. This knowledge may be helpful for presurgical planning prior to insular glioma resection.

Use of reconstructed sagittal computed tomography images to plan middle cranial fossa surgery

OBJECTIVE

To facilitate planning in temporal bone surgery for the middle cranial fossa approach by using sagittal reconstructed temporal bone computed tomography images.

STUDY DESIGN

Comparison of anatomic measurements on random high-resolution, reformatted computed tomography scans of the temporal bone.

METHODS

High-resolution computed tomography of 10 normal temporal bones in the axial and coronal planes was obtained, and two-dimensional sagittal reconstructions were performed using a commercial software program. Eight anatomical relationships between neural and/or vascular structures were measured. Representative images were inverted to recreate the plane of the middle cranial fossa approach.

RESULTS

Anatomical relationships among the vestibule, superior semicircular canal, internal auditory canal, internal carotid artery, and middle cranial fossa exhibited a high SD in the 10 subjects. The sample size and the large range for the eight anatomical relationships precluded the detection of a significant difference between right and left temporal bones or sex and age of the patient.

CONCLUSION

The present report presents a novel, practical measurement protocol for rapidly evaluating important individual anatomical differences in patients before middle cranial fossa surgery. Inverted sagittal reconstructions facilitate presurgical planning for the middle cranial fossa approach by 1) assessing critical anatomical relationships before surgery and 2) providing customized measurements between vital landmarks and the first in vivo measurements. This decreases the likelihood of surgical mishaps and improves teaching by providing the first in vivo measurements of practical anatomical relationships in the sagittal plane.

Sectional imaging anatomy: pelvic ring ligaments

The purpose of this article is to describe the complex anatomy of the pelvic ligaments. It uses schematics to display 10 color-coded ligaments in relation to the bony architecture. This atlas and the accompanying summary of the classification of pelvic ligamentous injuries is designed to encourage the use of magnetic resonance imaging in cases of pelvic ring trauma.

Surgical anatomy of the temporal bone: an atlas

This atlas demonstrates the usefulness of reconstructed high-resolution CT for planning temporal bone surgery. The first part focuses on a sagittal plane, the second on a rotated longitudinal plane, and the third on a rotated transverse plane. We believe knowledge of temporal bone anatomy in these planes facilitates surgical planning by showing anatomic relationships and providing a customized map for each patient. This decreases the likelihood of surgical mishap and improves teaching.

Sectional neuroanatomy of the lower limb II: leg and foot

The authors have produced a pair of articles that can be used to rapidly identify back, hip, and lower limb muscles and their innervation(s). This article presents the motor and sensory innervation of the lower limb by color-coding structures to match their peripheral nerves. It provides a companion summary table that allows prediction of unique patterns of denervation from 12 lesions sites.

Nerves of the thorax: atlas of normal and pathologic findings

An anatomic and imaging atlas was created to provide detailed information about the six pairs of thoracic nerves (phrenic nerves, vagus nerves, recurrent laryngeal nerves, sympathetic trunks, costal nerves, long thoracic nerves). Serial axial computed tomographic (CT) scans of the normal thorax were obtained and included in the atlas, along with drawings showing the proper location of each nerve relative to adjacent anatomic structures. CT scans obtained in both symptomatic and asymptomatic patients with various thoracic diseases were paired with appropriate drawings and normal CT scans in the atlas. This format was designed to help determine the presence and severity of related disease, including injury from surgery, trauma, or penetrating injury, metastatic disease involvement, and, rarely, primary tumor. Although the nerves of the thorax are rarely identified at cross-sectional imaging, their location can be inferred by localizing easily identified anatomic landmarks. Familiarity with the functional anatomy and clinical significance of the nerves of the thorax is important for the correct interpretation of thoracic images.

Sectional neuroanatomy of the lower limb I: lower back and hip

This series of two articles is structured to provide anatomically accurate functional schematics of the motor and sensory innervation of the lower back, hip, and lower limb. This first paper provides radiographically oriented schematic axial sections of the lower back and hip in which the muscles are appropriately color-coded to match the peripheral nerves. A companion color-coded summary table allows prediction of unique patterns of denervation from 25 lesion sites. These are divided into three categories (roots T12 to S4, four plexal quadrants, and 11 sectional levels). Correlation between an imaging abnormality at one of these lesion sites and the predicted denervation pattern ensures the lesion is, in fact, clinically significant. The next article will continue this color-coded approach into the lower limb.

Reconciliation of the Anatomic, Surgical, and Radiographic Classifications of the Mediastinum

The mediastinum is a complex region that is variously subdivided by radiologists, surgeons and anatomists. This paper describes the most popular of these classifications and color-codes the radiologic and surgical divisions on 22 labeled axial sections of the chest. This allows the reader to quickly name the appropriate location of a lesion on any section.

Sectional neuroanatomy of the upper limb III: forearm and hand

This paper is the last of three articles that describe the functional anatomy of the upper limb. It extends the series by presenting the axial anatomy of the forearm and hand. In addition, it provides a table that defines the patterns of muscle denervation specific to six representative sites. This set of articles is clinically useful because it can be used to rapidly identify and describe the innervation of the muscles and skin of the upper limb.

Sectional neuroanatomy of the upper limb II: shoulder and upper arm

This article is the second in a series of three that presents an anatomic functional guide to the peripheral innervation of the shoulder and upper limb. It illustrates the axial anatomy of the shoulder and upper arm. The next article continues this format for the lower arm and hand. Together, all three papers can be used to rapidly identify each upper limb muscle and its innervation(s). They can also be used to locate the peripheral nerve trunks, and correlate lesions with the classic pattern(s) of muscle denervation and altered sensation.

Sectional neuroanatomy of the upper limb I: brachial plexus

This series of three articles is structured to provide anatomically accurate functional schematics of the motor and sensory innervation of the shoulder and upper limb. This first paper provides radiographically oriented sagittal sections through the brachial plexus to assist in directly identifying a plexal lesion. A coronal schematic of the brachial plexus and summary table allows prediction of unique patterns of denervation from 19 lesion sites. Correlation between the lesion and the denervation pattern ensures the lesion is, in fact, clinically significant. The next two articles will present a color-coded atlas that allows the radiologist to quickly assess patterns of denervated muscles and thereby indirectly localize the lesion site. Thus, the three articles can be used together to predict the clinical picture for a given nerve lesion or extrapolate lesion location when a constellation of denervated muscles are seen on an upper limb magnetic resonance imaging or electromyographic study.

Neuroimaging contrast agents in ophthalmology

Magnetic resonance (MR) imaging and computed tomography (CT) are routinely performed with the use of contrast materials in the diagnosis of neuro-ophthalmologic disease. Iodinated agents are commonly used in CT scanning and femoral contrast arteriography, and gadolinium is used in MR imaging. While contrast materials contribute greatly to diagnostic accuracy, they may also be responsible for adverse effects, ranging in severity from mild discomfort to death. The most frequent and severe side effects are associated with ionic iodinated contrast agents, while the rate of adverse reactions is less with use of nonionic iodinated contrast agents. Side effects and adverse reactions to gadolinium are uncommon, but they do occur. In neuro-ophthalmologic diagnosis, MR imaging is generally preferred over CT scanning, partly because of its greater ability to delineate soft tissue intracranial structures, but also because of the relative safety of gadolinium as a contrast agent. Properties of contrast agents are discussed in the context of specific imaging techniques and tissues investigated. Types and severity of adverse effects as well as risk factors for incurring such effects are summarized.

The nomenclature and sectional imaging anatomy III: capsular membranes and minor spinal ligaments

This paper is the third in a series of three that organizes the complex anatomy of the cervical, thoracic, and lumbar spinal ligaments. It describes and color-codes the anatomy and nomenclature of the capsular membranes and minor spinal ligaments. The first two articles describe the dorsal and ventral ligaments, respectively.

In vivo measurements of temporal bone on reconstructed clinical high-resolution computed tomography scans

PURPOSE

To retrospectively assess the accuracy of measurements of temporal bone anatomy made from reconstructed clinical high-resolution computed tomography (HRCT) scans.

METHODS

Nine HRCT scans were performed on unselected clinical cases in which the subjects had a temporal bone study judged to be normal. The orbitomeatal line was prescribed for the direct axial sections. Variations in head position (rotation at the neck and lateral bending of the neck) were corrected by using the software supplied by the manufacturer. All measurements were done on standard 1-mm axial sections and axial reconstructions obtained from 1-mm coronal slices. The images were viewed at 4000 Hounsfield units (HU) window width and 1000 HU window level. Measurements (n = 3) made on 1-mm direct axial HRCT scans were compared with the measurements made on reconstructed axial HRCT images from the same nine patients. These values were also compared with published cadaver data.

RESULTS

The measurements obtained from axial reconstructed and direct HRCT series approximated each other in each of the nine individual studies and also fell within the range of published cadaver values. They demonstrated the expected normal temporal bone variability between individuals.

CONCLUSION

Useful anatomic approximations can be measured in vivo from reconstructed clinical HRCT images. Pitfalls are improper window settings, head tilt, and rotation. This protocol is widely available and can be implemented retrospectively from clinical HRCT scans.

The nomenclature and sectional imaging anatomy II: ventral spinal ligaments

This paper is the second in a series of three that organizes the complex anatomy of the cervical, thoracic, and lumbar spinal ligaments. It describes and colorcodes the anatomy and nomenclature of the ventral ligaments. A prior article has described the dorsal ligaments, and a future article will illustrate the capsular joints and minor spinal ligaments.

The nomenclature and sectional imaging anatomy I: dorsal spinal ligaments

This article is the first in a series of three that organizes the complex anatomy of the cervical, thoracic, and lumbar spinal ligaments. It describes and color-codes the anatomy and nomenclature of the dorsal ligaments. The following articles will describe the ventral ligaments, and the capsular membranes and minor ligaments.

Triple-dose contrast-enhanced images in neurologically symptomatic HIV-positive patients

Our purpose was to determine whether triple-dose delayed contrast-enhanced images would improve lesion detection in patients with symptomatic human immunodeficiency virus (HIV) infection. We reviewed 33 MRI studies on 29 patients. Single-dose immediate T1-weighted spin-echo (1x-T1) images were compared with delayed triple-dose images (D3x-T1). Two neuroradiologists decided which technique showed more lesions, increased lesion conspicuity and/or altered the radiologic diagnosis. The D3x-T1 technique improved lesion detection in 14 of 29 patients (48%). In two patients (7%), the improvement changed the radiologic diagnosis by showing new meningeal lesions.

Functional neuroanatomy of the frontal lobe circuits

This article summarizes the current theories regarding the locations and functions of the three primary frontal lobe circuits. It forms the framework for structuring functional magnetic resonance imaging investigations. It can be used to assist in (a) detecting subtle lesions of the frontal circuits and (b) applying the current theories of neuropsychiatry to assess prognosis and to plan rehabilitation.

Conservative management of extra-axial hematomas diagnosed by CT

Our purpose was to assess the role of serial CT in recently traumatized patients with clinically stable extra-axial intracranial hematomas (EACH) and a midline shift of less than 0.5 cm. A retrospective review of 91 imaging studies in 41 patients (with 45 EACH) was done to assess the time between trauma and CT; the presence and type of skull fracture; the volume, type, and location of the EACH; the presence of associated edema and/or contusion. Over a 19-day follow-up, 11% of the dense EACH increased in volume and 27% decreased. An adjacent skull fracture was seen most frequently in patients with a decrease in EACH volume. Clinical data remain the key to determining the need for neurosurgical intervention in patients with EACH. Follow-up CT afforded no data which altered the medical management of these patients. However, it may be said to have alerted the clinician to an increase in the size of the EACH in 11% of cases, which could mandate close observation of this group.

Hyperechoic foci in the thalamic region imaged via the posterior fontanelle: a potential mimic of thalamic pathology

BACKGROUND

We have incidentally noted foci of increased thalamic echogenicity (FITE) on cranial sonographic images obtained via the posterior fontanelle (PF) that were not confirmed on images obtained while scanning through the anterior fontanelle (AF). Therefore, we postulated that this is a normal variant of PF imaging rather than true thalamic pathology.

OBJECTIVE

The purpose of this study was to determine the incidence of FITE detected on posterior and anterior fontanelle images.

MATERIALS AND METHODS

Parasagittal images were obtained bilaterally through the trigone of the lateral ventricles (including the thalami) via both the anterior and posterior fontanelles in 15 consecutive neonates (30 thalami) and evaluated independently by two pediatric radiologists for the presence or absence of FITE. Thalami were graded as grade 0 (no FITE), grade 1 (possible FITE), or grade 2 (definite FITE). Follow-up CT (n = 3) and MR (n = 1) were reviewed.

RESULTS

FITE were absent in 87 % of thalami imaged via the AF, and possible FITE were present in 13 % of these cases. No cases of definite FITE were identified via the AF. However, possible FITE were identified in 33-40 % of thalami and definite FITE were seen in 33 % of thalami imaged via the PF.

CONCLUSIONS

FITE seen only on images obtained through the PF on cranial sonography are a normal finding and should not be attributed to thalamic hemorrhage or ischemia.

Intradural-extramedullary spinal cysticercosis: MR imaging findings

A rare case with intradural-extramedullary cysticercosis is presented here. MR imaging with and without gd-DTPA were performed. There were multiple cysts in the basal cistern, cisterna magna, and cervical subarachnoid space which were isointense with cerebrospinal fluid both on T2- and T1-weighted images. Swelling and increased signal intensity in the cord parenchyma were detected on T2-weighted images. Gadolinium enhanced studies showed rim-shaped enhancement in the cysts and irregular, diffuse enhancement in the meninges.

Spinal disease in neurologically symptomatic HIV-positive patients

We review the MRI findings of human immunodeficiency virus (HIV)-positive patients with "spinal" symptoms and review the literature. In 23 consecutive HIV-positive patients presenting with acute neurologic complaints thought to be referable to the spine, we reviewed spinal MRI, medical charts, and laboratory, pathologic, and autopsy data. In the early stages of HIV infection, the common causes of spinal complaints (i. e., degenerative spine and disc disease) predominated. However, pathology may be missed without contrast-enhanced MRI of the spine. In more advanced cases, the differential diagnosis includes one or more neoplastic and/or infectious causes which require contrast-enhanced MRI for detection. In these cases, normal cerebrospinal fluid findings should not preclude contrast-enhanced MRI of the spine. Imaging of the brain may also be indicated in cases when the spinal study is negative.

Vital sign changes during infant magnetic resonance examinations

Heart rate (HR) and blood oxygen saturation (SaO2) were monitored before and during clinically indicated MR examinations of newborns to (a) identify any temporal relationship between MR scanning and vital sign fluctuations and (b) assess the reliability of SaO2 monitoring of dynamic changes. Fluctuations in HR (but not in SaO2) that are temporally linked to the MR image acquisition occur in most neonates during routine clinical MR examinations.

Pitfalls and artifacts encountered in clinical MR imaging of the spine

Magnetic resonance (MR) imaging of the spine has become widely accepted as a valuable diagnostic tool. However, there are a number of artifacts and pitfalls associated with spinal MR imaging. Chemical shift artifacts may be induced by bone marrow, epidural fat, or intradural fat. Motion artifacts arise from several sources, which include respiration, flow of fluids, and swallowing. Artifacts due to a nonuniform magnetic field are particularly noticeable within trabecular bone or at bone-soft tissue interfaces but may also be caused by incomplete fat saturation or the presence of metal near the spine. Protocol errors may cause artifacts such as saturation, phase wraparound, truncation, radio-frequency interference, shading, and partial volume averaging. Use of fat saturation, use of motion and flow compensation, and careful screening of patients for metal in clothing can help reduce the occurrence of artifacts. In addition, use of an optimal imaging technique is essential and should include use of the proper surface coil, field of view, and pulse sequence.

The hippocampus: normal anatomy and pathology

The hippocampus is a complex and fascinating region of the brain that has enormous clinical significance. Specifically, small imaging abnormalities may cause major symptoms. We believe that the detection of these lesions will be improved if imaging clinicians have an organized reference that facilitates identification of the cellular zones that comprise the hippocampus.

Klüver-Bucy syndrome after bilateral selective damage of amygdala and its cortical connections

Isolated symmetric damage to the amygdala and their cortical connections occurred in an individual following cancer treatment. The lesions were imaged after reversal of hyponatremia. The patient displayed marked behavioral changes including visual agnosia, hypersexuality, hyperorality, a tendency to react to every visual stimulus, and memory deficits. The cluster of neurobehavioral symptoms is similar to previously reported accounts of Klüver-Bucy syndrome and suggests the importance of bilateral amygdala involvement in these behavioral changes.

Postnatal maturation of the sacrum and coccyx: MR imaging, helical CT, and conventional radiography

OBJECTIVE

The purpose of this paper is to provide a detailed radiologic description of the postnatal developmental anatomy of the sacrum and coccyx as revealed by MR imaging, helical CT, and conventional radiography.

MATERIALS AND METHODS

One hundred ten imaging examinations of the sacrococcygeal spine were performed in patients who were newborn to 30 years old. Imaging included conventional radiography (n = 63), three-dimensional gradient-recalled echo MR imaging (n = 10), and helical CT with sagittal and angled coronal reformations (n = 37). A detailed analysis was performed of the ossification and fusion of the primary and secondary ossification centers.

RESULTS

The sacrum and coccyx were noted to develop from 58 to 60 sacral ossification centers and eight coccygeal centers, respectively. These centers were noted to ossify and fuse in an organized temporal pattern from the fetal period to the age of 30.

CONCLUSION

The sacrum and coccyx are formed by a complex process that fuses primary and secondary ossification centers. Because the maturation process can be asymmetric, an understanding of this process may prove useful for distinguishing physeal plates from fracture lines.

In vivo CT and MR appearance of prosthetic intraocular lens

PURPOSE

We present the first in vivo CT and MR imaging description of intraocular lenses (IOLs), which are commonly encountered in elderly patients who have undergone cataract surgery.

METHODS

A retrospective review was done of the imaging studies of 20 patients (22 eyes) with IOLs and of three patients (four eyes) with aphakia. CT and MR studies were performed with standard clinical protocols.

RESULTS

Sixteen patients with 18 posterior IOLs underwent six CT and 43 MR studies. Four patients with four anterior IOLs had one CT and eight MR studies. The exact position of the optic portion of the IOL could be optimally determined on CT scans with 1-mm-thick sections and on fat-saturated fast T2-weighted MR orbital coil studies performed on a 1.5-T imager. The haptics could not be distinguished from the ciliary body. Three patients with aphakia had eight MR and two CT studies. Aphakia was difficult to identify if the image thickness was greater than the diameter of the pupil (2.5 to 4.0 mm).

CONCLUSION

The optic portion of an IOL is visible on either high-quality CT or MR studies. However, the haptic portion is not visible on clinical in vivo images.

Optimal imaging protocol after intraocular silicone oil tamponade

PURPOSE

Our purpose was to define the optimal protocol for imaging of the orbits after vitreous humor replacement with silicone oil.

METHODS

Eleven eyes in 10 patients with tractional and/or rhegmatogenous retinal detachment were studied. Five CT scans and 18 high-field (1.5 T) MR images were obtained. Standard T1-weighted, T1-weighted with fat and silicone saturation, fast spin density-weighted, and T2-weighted orbital MR sequences were performed. Unique pulse sequences included fast spin density-weighted and T2-weighted imaging with and without fat saturation or silicone saturation, gradient-echo imaging, and short-tau inversion recovery imaging.

RESULTS

The T1-weighted MR and CT studies were comparable in displaying the silicone. However, the fat- or silicone-saturated fast T2-weighted sequences always showed the fibrous bands and subretinal fluid to best advantage. In one case, the eye also contained inadvertently retained perfluorocarbon liquid, which blended with silicone oil on both saturated images, requiring companion T1-weighted sequences without saturation to demonstrate its presence.

CONCLUSION

Simple, commonly available fat-saturated fast T2-weighted MR images supplemented by standard T1-weighted images are all that are needed to evaluate the eye efficiently after vitrectomy and tamponade.

Neuro-ophthalmologic manifestations of adenoid cystic carcinoma

Intracranial adenoid cystic carcinoma is uncommon. We report two unusual cases of intracranial adenoid cystic carcinoma. The first patient presented with a steroid-responsive optic neuropathy from an orbital mass that simulated orbital pseudotumor, and subsequently developed intracranial involvement, presumably by contiguous perineural spread. The second patient presented with proptosis of the left eye, right facial weakness and numbness, and an intracranial mass, presumably from hematogenous metastatic spread.

A guide to the isolated dilated pupil

The poorly reactive and dilated pupil observed in a comatose patient is often thought to represent an acute third nerve palsy owing to brain herniation or aneurysm. In the well patient, however, the isolated dilated pupil is unlikely to be owing to a third nerve palsy. It is more commonly owing to other benign causes such as local iris sphincter abnormalities, pharmacologic dilation, tonic pupil syndrome, or sympathetic irritation. This article presents a diagnostic flowchart to help the primary care physician analyze this problem and prevent costly and unnecessary imaging of these patients.

Artifacts and pitfalls in MR imaging of the orbit: a clinical review

High-resolution magnetic resonance (MR) imaging of the orbit has become widely accepted as a valuable diagnostic technique. However, there are a number of artifacts and pitfalls associated with orbital MR imaging. Chemical shift artifacts may be induced by orbital fat or silicone oil used to treat retinal detachment. Motion artifacts are caused primarily by unavoidable globe motion during imaging. Artifacts due to a nonuniform magnetic field are particularly noticeable at air-tissue interfaces but may also be caused by incomplete fat saturation or highly magnetic materials near the orbit. Protocol errors may cause artifacts such as saturation, phase wraparound, truncation, shading, and partial-volume artifacts. This information can be used to improve orbital image quality and avoid misinterpretation of image artifacts. Use of fat saturation, silicone saturation, and careful patient screening for metal near the eyes and instruction to reduce motion can help reduce the occurrence of artifacts. In addition, optimal imaging technique is essential and should include use of proper surface coils, plane of section, and pulse sequences.

Imaging the temporal fossa

OBJECTIVE

The purpose of our study was to delineate the interconnections in the temporal fossa that are visible on high-resolution clinical images.

SUBJECTS AND METHODS

Thin-section MR images and CT scans of the temporal fossa in two normal volunteers were obtained in coronal and axial sections. MR images, CT scans, or both of 20 patients with demonstrable spread of disease were reviewed.

RESULTS

The imaging studies of patients with disease proved more informative than images of the normal subject or the published anatomic and surgical descriptions of the temporal fossa. We recognized five discrete radiographically defined regions: the connective tissue layer, compartment of the superficial fat pad, compartment of the deep fat pad, compartment of the temporal muscle (superior recess of the suprazygomatic masticator), and subperiosteal zone. Important, tortuous, and to our knowledge undescribed interconnections between the scalp, posterior neck, eyelid, face, and the suprazygomatic masticator were delineated.

CONCLUSION

Imaging studies of the temporal fossa can be used to formulate a clinically useful approach that simplifies the complex anatomy of the temporal fossa.

A sellar misadventure--imaging considerations

This report describes a patient with a headache and a bitemporal hemianopsia immediately following endoscopic ethmoid and sphenoid sinus surgery. Computed tomographic imaging revealed tension pneumocephalus caused by surgical interruption of the boundaries between the sinus(es) and the anterior cranial cavity. The delineation of the central chiasmal injury required follow-up magnetic resonance imaging.

Importance of clot structure in gradient-echo magnetic resonance imaging of hematoma

The MR appearance of clots with different internal structures was compared on gradient-echo (GE) and spin-echo (SE) images. After MR imaging, clots were submitted for histological analysis to allow direct correlation of clot structure with MR image intensity. Normal heterogeneous clots (containing entrapped serum) were hypointense compared to both unclotted blood (Hct 45) and brain on GE MR images. Homogeneous (serum-poor) clots and settled blood were hyperintense to unclotted blood and isointense or hyperintense to brain. These results indicate that the GE technique is quite sensitive to the physical inhomogeneity created (at the voxel level) when blood forms an inhomogeneous clot containing relatively large islands of red blood cells (RBCs) surrounded by lakes of serum. The effect of the different possible clot structures on GE signal intensity thus provides an etiology for the previously unexplained observations of hemorrhage with high signal intensity on GE MR images.

Preliminary report: changes in vital signs of term newborns during MR

PURPOSE

To investigate the effect of the MR environment on vital signs of term neonates.

METHODS

We retrospectively analyzed physiological monitoring data obtained from seven term infants (20 to 22 days old) undergoing a clinically indicated MR examination. They were monitored for heart rate, blood pressure, and oxygen saturation while sedated and physically quiet. Six control infants were monitored while sedated and resting in the magnet.

RESULTS

All of the test infants exhibited substantial changes in blood pressure, heart rate, and/or oxygen saturation during the MR examination. No such changes were observed in the control infants.

CONCLUSION

These preliminary results suggest that undergoing an MR examination may alter the vital signs of term newborn infants.

Incidental asymptomatic orbital calcifications

OBJECTIVE

To use modern computed tomography (CT) imaging to quantify the incidence of asymptomatic incidental orbital calcifications and describe their histological features.

MATERIALS AND METHODS

One hundred orbital CT scans were reviewed. In addition, patients who had orbital calcification(s) detected on a brain CT scan were examined by the ophthalmology service.

RESULTS

Of the orbital CT scans, 2% had bilateral drusen of the optic nerve head, 3% had calcified scleral plaques anterior to the medial or lateral rectus muscles, and 3% had bilateral ossification of the trochlear apparatus. Routine brain CT scans detected asymptomatic calcifications of the sclera and dura surrounding the proximal optic nerves.

CONCLUSION

Incidental asymptomatic orbital calcifications are commonly encountered on modern high-resolution CT images of the brain and orbit. This article should help the clinician to confidently distinguish these densities from foreign bodies or pathological calcifications.

MR imaging of the eyelids: normal and pathologic findings

MR imaging is commonly used to evaluate orbital and facial soft-tissue disease. Although the eyelids are visible on these images, the radiographic appearance and the detailed anatomy of these structures has received little attention in the literature [1-4]. Anatomic correlation with MR images may be extremely helpful in the accurate interpretation and staging of eyelid malignancies and infections.

Sensitivity and specificity of fluid-blood levels for coagulopathy in acute intracerebral hematomas

PURPOSE

To characterize the imaging features of intracerebral hemorrhages in coagulopathies that alter prothrombin time or partial thromboplastin time.

METHODS

A fluid-blood level was defined as a horizontal interface between hypodense bloody serum layered above hyperdense settled blood. The prevalence of fluid-blood levels in acute intracerebral hemorrhages was determined on third-generation CT scans in 32 patients with elevation in prothrombin time or partial thromboplastin time. This was compared with the frequency of fluid-blood levels in 185 patients with intracerebral hemorrhage in which there was no laboratory evidence of coagulopathy.

RESULTS

The probability of finding a fluid-blood level in an intracerebral hemorrhage of a patient with abnormal prothrombin time or partial thromboplastin time was 59% (sensitivity). The probability that there will be no fluid-blood level in a patient with a normal prothrombin time and partial thromboplastin time was 98% (specificity).

CONCLUSION

Fluid-blood levels in acute intracerebral hemorrhage are moderately sensitive to the presence of coagulopathy (ie, abnormal prothrombin time and partial thromboplastin time) and highly specific for this condition. Thus, an intracerebral hemorrhage with a fluid-blood level should prompt a thorough search for coagulopathy because early treatment of this condition may improve the 40% mortality in these patients. Caution should be used to distinguish the horizontal interface of a fluid-blood level from a clot with a flat top. A decubitus CT is useful in these rare instances.

Acute intracranial hemorrhage secondary to thrombocytopenia: CT appearances unaffected by absence of clot retraction

PURPOSE

To describe the in vivo CT appearance of acute intracerebral blood clots formed from anemic platelet-depleted blood.

METHODS

Three patients with intracerebral hemorrhage secondary only to thrombocytopenia were examined with CT within 2 1/2 hours after the onset of clinical symptoms.

RESULTS

There were no unusual CT features found in the intracerebral hemorrhages of patients with only thrombocytopenia. Specifically, a hyperdense zone(s) surrounded by areas of decreased density was identified.

CONCLUSION

Clot retraction (which cannot occur in patients with severe thrombocytopenia) is not necessary for the CT appearance of acute intracerebral hemorrhage.

Chiasmal trauma: clinical and imaging considerations

This report presents a patient who sustained closed head injury with chiasmal trauma. This uncommon injury may not be apparent on routine imaging studies. It is significant, not only from the visual standpoint, but also because of the association with serious conditions, such as panhypopituitarism, traumatic carotid aneurysm, carotid cavernous fistulae, and meningitis associated with leakage of cerebrospinal fluid. This report demonstrates that magnetic resonance imaging (MRI) is the best method for identifying chiasmal abnormalities.

Invasive pressure monitoring of patients during magnetic resonance imaging

The purpose of this paper is to describe a system for monitoring patients who require general anaesthesia, profound sedation or intensive care while undergoing high field (> or = 1.5 T) magnetic resonance (MR) imaging. Continuous evaluation of invasive and noninvasive pressures, inspired and end-tidal respiratory gas concentrations, body temperature, heart rate, ECG and pulse oximetry were measured successfully during the MR examination. Diagnostic quality MR images were acquired on all 15 monitored patients. The calculated signal-to-noise ratios were not different between the control and monitored patients. Commonly encountered technical problems and their solutions are described. This study demonstrates that invasive monitoring can be safely performed in critically ill patients who are undergoing high field MR examinations.

MR appearance of extravasated gadolinium contrast medium

This case illustrates that a large zone of signal void can be produced on short relaxation time MR images when gadopentate dimeglumine is injected through an infiltrated intravenous catheter. The authors consider the physics behind this paradoxical decrease in signal intensity where there are high concentrations of gadopentate dimeglumine.

Change in red blood cell relaxation with hydration: application to MR imaging of hemorrhage

T1 and T2 were measured in unclotted blood samples with 0.24- and 4.7-T spectrometers. The fraction by weight of intracellular water in the red blood cells (RBCs) was varied by either osmotic manipulation or density separation in concentrated (packed RBCs) and dilute (RBCs suspended in buffer or serum) samples. Reducing the cell water content caused a moderate decrease in T1 and a profound decrease in T2 at both 0.24 and 4.7 T. Conversely, increasing the cell water content caused an increase in both T1 and T2. The authors conclude that dehydrated RBCs in an area of hemorrhage would cause a substantial decrease in signal intensity on long TR/TE (T2-weighted) images. Overhydration of RBCs would have the opposite effect.