Amyloid-Related Imaging Abnormalities with Emerging Alzheimer Disease Therapeutics: Detection and Reporting Recommendations for Clinical Practice.

Monoclonal antibodies are emerging disease-modifying therapies for Alzheimer disease that require brain MR imaging for eligibility assessment as well as for monitoring for amyloid-related imaging abnormalities. Amyloid-related imaging abnormalities result from treatment-related loss of vascular integrity and may occur in 2 forms. Amyloid-related imaging abnormalities with edema or effusion are transient, treatment-induced edema or sulcal effusion, identified on T2-FLAIR. Amyloid-related imaging abnormalities with hemorrhage are treatment-induced microhemorrhages or superficial siderosis identified on T2* gradient recalled-echo. As monoclonal antibodies become more widely available, treatment screening and monitoring brain MR imaging examinations may greatly increase neuroradiology practice volumes. Radiologists must become familiar with the imaging appearance of amyloid-related imaging abnormalities, how to select an appropriate imaging protocol, and report findings in clinical practice. On the basis of clinical trial literature and expert experience from clinical trial imaging, we summarize imaging findings of amyloid-related imaging abnormalities, describe potential interpretation pitfalls, and provide recommendations for a standardized imaging protocol and an amyloid-related imaging abnormalities reporting template. Standardized imaging and reporting of these findings are important because an amyloid-related imaging abnormalities severity score, derived from the imaging findings, is used along with clinical status to determine patient management and eligibility for continued monoclonal antibody dosing.

Metabolic characteristics of cortical malformations causing epilepsy.

PURPOSE: Cortical malformations (CMs) are increasingly recognized as the epileptogenic substrate in patients with medically refractory neocortical epilepsy (NE). The aim of this study was to test the hypotheses that: 1. CMs are metabolically heterogeneous. 2. The structurally normal appearing perilesional zone is characterized by similar metabolic abnormalities as the CM. METHODS: Magnetic resonance spectroscopic imaging (MRSI) in combination with tissue segmentation was performed on eight patients with NE and CMs and 19 age matched controls. In controls, NAA, Cr, Cho,NAA/Cr and NAA/Cho of all voxels of a given lobe were expressed as a function of white matter content and thresholds for pathological values determined by calculating the 95% prediction intervals. These thresholds were used to identify metabolically abnormal voxels within the CM and in the perilesional zone. RESULTS: 30% of all voxels in the CMs were abnormal, most frequently because of decreases of NAA or increases of Cho. Abnormal voxels tended to form metabolically heterogeneous clusters interspersed in metabolically normal regions. Furthermore, 15% of all voxels in the perilesional zone were abnormal, the most frequent being decreases of NAA and Cr. CONCLUSION: In CMs metabolically normal regions are interspersed with metabolically heterogeneous abnormal regions. Metabolic abnormalities in the perilesional zone share several characteristics of CMs and might therefore represent areas with microscopic malformations and/or intrinsic epileptogenicity.

Advances in magnetic resonance imaging of the head and neck.

The head and neck encompass a tremendous spectrum of tissues in a compact space with almost every organ system represented, including the digestive and respiratory tracts, as well as the nervous, osseous, and vascular systems. Because of its anatomic complexity, this area tends to be approached with considerable trepidation. The high resolution of magnetic resonance imaging (MRI) and its outstanding definition of tissue contrast allow for an exquisite display of normal and pathologic anatomy. However, imaging of the head and neck, due to this intricate anatomy and the varied orientation of structures, demands much more attention to detail than do other areas of the body. This is underscored by the multitude of MRI sequences that can be employed. In this article I will review the application of various MRI techniques in the evaluation of the head and neck.

Magnetic resonance imaging of tuberculum sellae meningiomas: preventing preoperative misdiagnosis as pituitary macroadenoma.

Despite recent advances in neurodiagnostic imaging, it may be difficult to differentiate tuberculum sellae meningiomas from pituitary macroadenomas preoperatively. Magnetic resonance (MR) imaging has supplanted computed tomography as the imaging modality of choice for sellar and parasellar lesions, but unenhanced MR imaging does not reliably distinguish between all tuberculum sellae meningiomas and pituitary macroadenomas. Accurate differentiation between these alternative diagnoses of a suprasellar mass is important because a tuberculum sellae meningioma always requires a craniotomy, whereas a transsphenoidal route is preferred for removing most pituitary macroadenomas. The gadolinium-enhanced MR images of seven patients with tuberculum sellae meningioma and seven with pituitary macroadenoma were reviewed retrospectively. Although no specific radiological feature was pathognomonic, a combination of several features allowed the correct diagnosis in all cases. Three characteristics of tuberculum sellae meningiomas distinguish them from pituitary macroadenomas: 1) bright homogeneous enhancement with gadolinium, as opposed to heterogeneous, relatively poor enhancement; 2) a suprasellar rather than a sellar epicenter of tumor; and 3) tapered extension of an intracranial dural base. Each of these findings can be subtle, but careful examination of gadolinium-enhanced, high-quality, thin section coronal and sagittal MR images of the parasellar region for this constellation of findings will allow the correct preoperative diagnosis in patients with either of these tumors.

Lesions of the foramen ovale: CT-guided fine-needle aspiration.

To verify perineural spread of tumor along the mandibular division of the trigeminal nerve in four patients, the authors obtained cytologic specimens by means of a CT-guided transfacial fine-needle aspiration technique. Diagnoses were squamous cell carcinoma (n = 3) and meningioma (n = 1). The technique allows biopsy of deep lesions that would otherwise require open surgical biopsy.

Lateral tibial rim (Segond) fractures: MR imaging characteristics.

The magnetic resonance (MR) imaging characteristics of lateral tibial rim (Segond) fractures and their associated injuries were reviewed in 12 patients with radiographic evidence of this fracture. Bone marrow adjacent to the fracture emitted a focally abnormal MR signal, which indicated an injury of the lateral capsular junction. The Segond fragment, however, was seen on MR images in only four of 12 patients. Associated ligamentous and meniscal injuries identified with MR imaging and arthroscopy involved the anterior (n = 11) and medial (n = 7) cruciate ligaments and the lateral (n = 4) and medial (n = 1) menisci. Focal bone marrow edema was due to injury of the lateral capsular junction. MR imaging evidence of such edema should indicate the presence of a lateral capsular injury and fracture, if one has not already been demonstrated with conventional radiography. A high association of Segond fractures with tears of the anterior cruciate ligament was confirmed, and MR imaging signs of a Segond fracture may therefore be used as indirect evidence for tears of that ligament.

Orbit, skull base, and pharynx: contrast-enhanced fat suppression MR imaging.

The high signal intensity of fat on T1-weighted magnetic resonance images has limited the utility of gadopentetate dimeglumine in imaging of the extracranial head and neck. Enhancing lesions may be obscured either by proximity to fat or by chemical misregistration artifact. The authors evaluated the role of a gadolinium-enhanced fat suppression imaging technique in the detection of extracranial head and neck abnormalities in 29 patients. These studies were directly compared with conventional pre- and postcontrast T1- and T2-weighted SE sequences. In detecting and defining the extent of abnormalities, fat-suppressed images were superior to non-fat-suppressed gadolinium-enhanced T1-weighted images in the majority of cases (22 of 27 [81%]). Fat-suppressed images were particularly beneficial in the detection of perineural spread of tumor as well as in defining lesions situated within or adjacent to fat-containing areas such as the base of the skull. These findings demonstrate that fat suppression techniques in combination with gadolinium enhancement are of value in extracranial head and neck imaging and should replace conventional postcontrast T1-weighted SE imaging.

Imaging of the neck.

The neck encloses a tremendous spectrum of tissues in a compact space. The normal and pathologic anatomy of the neck can be exquisitely displayed with high-resolution CT and MR imaging. Accurate assessment of the neck requires a thorough knowledge of both its complex anatomy and the scope of pathologic entities that may affect the various cervical compartments. We review the advances in the past year that serve to improve our ability to identify and characterize pathology of the cervical soft tissues.

Comparison of computed tomography and magnetic resonance imaging in the evaluation of focal hepatic lesions.

Two combined magnetic resonance (MR) spin-echo pulse sequences at 0.35 T were compared with dynamic bolus contrast-enhanced computed tomography (CT) in the evaluation of focal hepatic lesions. Each combined MR sequence was performed in a separate group of patients. The first group consisted of 76 patients in whom a moderately T1-weighted sequence (spin echo [SE] 500/30 [repetition time/echo time]) was combined with a T2-weighted sequence (SE 2000/60). In the second group, consisting of 68 patients, a more heavily T1-weighted sequence (SE 250/15) was combined with the T2-weighted sequence. All studies were evaluated in a retrospective blinded fashion, with construction of receiver operating characteristic curves. We conclude that, in detection of patients with one or more focal hepatic lesions, either combined MR sequence was comparable to CT. In the detection of individual hepatic lesions, the sensitivity of the combined MR sequence with a moderately T1-weighted sequence (SE 500/30 and 2000/60) was essentially equivalent to CT (79 vs 77%, respectively). Additionally, a combined MR sequence with a heavily T1-weighted pulse sequence (SE 250/15 and 2000/60) was not statistically different than CT (86 vs 80%, respectively). These findings were supported by the receiver operating characteristic analysis.

MR imaging of acute transverse myelitis and AIDS myelopathy.

Acute transverse myelitis (ATM) is a well recognized clinical entity, though its etiology remains obscure. Only a few reports of magnetic resonance imaging of ATM appear in the literature. These reports describe conflicting findings with respect to the signal intensity of the spinal cord on long repetition time (TR) sequences. The purpose of this study is to present our experience with five cases of ATM in which long TR sequences demonstrated abnormal increase in signal intensity of the cord. Magnetic resonance imaging also demonstrated extension of abnormal cord signal intensity over at least six spinal segments and above the clinically determined sensory level in four of five cases. Cord expansion was noted in two of five cases with normal myelograms. A case of acquired immunodeficiency syndrome (AIDS) myelopathy that demonstrated a similar high signal intensity of the cord is also presented. Our findings suggest that both ATM and AIDS myelopathy should be considered in the list of conditions that may result in a diffuse increase in the signal intensity of the cord on long TR sequences.

High signal intensity lesions of the chest in MR imaging.

The majority of pathologic lesions in the lung and mediastinum have relatively long T1 and T2 relaxation times and consequently yield medium to low signal intensity on T1-weighted images. Pulmonary lesions with high signal intensity on T1-weighted images are unusual and raise a special group of diagnostic considerations. In the current study, a mass with a lesion/fat signal intensity ratio of greater than 0.7 on a T1-weighted sequence was considered high signal intensity. The nature of these masses was ganglioneuroma or ganglioneuroblastoma (n = 3), atrial lipoma (lipomatous atrophy of the interatrial septum) (n = 3), pheochromocytoma (n = 2), bronchogenic cyst (n = 2), lymphangioma (n = 1), teratoma (n = 1), and a variety of primary and metastatic tumors of the mediastinum and lung. A single pathologic structure of these lesions was not present, but rather several underlying tissue compositions were noted, including fat, subacute hemorrhage, myxoid material, and cellular composition with high cytoplasmic/nuclear ratio. Thus, high signal intensity lesions of the thorax on T1-weighted images should suggest a number of differential diagnoses.

Magnetic resonance imaging of cardiac and paracardiac masses.

Magnetic resonance imaging (MRI) with ECG-gated acquisition displays the blood pool as a signal void and thereby provides high contrast differentiation between cardiovascular structures and soft-tissue masses. The role of MRI for the detection and definition of the extent of paracardiac and intracardiac masses is reviewed. The extension of mediastinal, lung, and upper abdominal tumors to the heart and pericardium is depicted favorably by MRI and this attribute is also demonstrated. It is anticipated that MRI will have an increasing role in the evaluation of primary and secondary masses of the heart and pericardium.

Hepatobiliary scintigraphy and scintiangiography in abdominal trauma.

Scintiangiography and hepatobiliary scintigraphy were performed in 45 patients with abdominal trauma. There were 18 gunshot wounds, six stab wounds, and 21 blunt injuries. Thirty-one of 45 patients showed abnormalities (69%). There were nine bilomas (4 with leaks), three leaks without biloma, (7 total leaks), five liver hematomas, three liver infarcts, one liver abscess, four renal injuries, one post-traumatic hepatic artery aneurysm, one acute acalculus cholecystitis, and four bowel injuries including one fistula, two obstructions, and one stricture. Two of the renal injuries and the hepatic artery aneurysm were identified only during scintiangiography. Eighteen of 38 gallbladders were not visualized despite normal bowel transit and delayed views to 4 hours (47%). Fourteen of 16 gallbladders were grossly normal at surgery, one had gallstones, and one had post-traumatic acalculus cholecystitis (6%). Hepatobiliary scintiangiography showed unique characteristics of vascular and renal lesions that were not seen on routine images. Sulfur colloid had no advantage over disofenin in evaluating liver injuries in nine cases. A high percentage of nonvisualized gallbladders (47%) were noted in acutely traumatized patients, and caution is recommended in diagnosing acute cholecystitis in the face of trauma.

Renal biopsy-related hemorrhage: frequency and comparison of CT and sonography.

To evaluate the frequency of retroperitoneal hemorrhage related to renal biopsy, we prospectively assessed 182 patients (200 biopsies) using state-of-the-art CT and ultrasound. Our study revealed definite CT evidence of hemorrhage after 90.9% of biopsies. In a blinded analysis of images obtained in biopsied patients and in unbiopsied control patients the overall accuracy of CT was 93.8 versus 76.4% for ultrasound. Our data suggest that detectable hemorrhage is virtually always seen after renal biopsy and its frequency is much higher than noted in earlier studies.

Kock continent ileal urinary reservoir. Anatomy and potential pitfalls of radionuclide imaging.

The Kock continent ileal urinary reservoir (Kock pouch) is a new form of urinary diversion that, due to its advantages over previous techniques of urinary bypass, will probably become widespread in urologic practice. When bone imaging is performed in the presence of the Kock pouch, the unusual configuration of the pouch may obscure or simulate osseous lesions. An understanding of the surgical anatomy as well as the planar and SPECT scintigraphic appearances of the Kock pouch is necessary to avoid errors during interpretation. This series of 51 bone images reports on the variable scintigraphic appearance of the Kock pouch. In addition, the incidence and type of potentially avoidable pitfalls in the interpretation of bone imaging when this form of urinary diversion is used are evaluated.