Magnetic resonance characteristics of intrapelvic haematomas

Evolution of intramural duodenal hematomas on magnetic resonance imaging

BACKGROUND

The magnetic resonance imaging (MRI) characteristics of evolving duodenal hematomas in children are unknown.

OBJECTIVE

To describe the MRI changes exhibited by evolving duodenal hematomas and the likely mechanisms behind these changes.

MATERIALS AND METHODS

We retrospectively reviewed the MR features of intramural duodenal hematomas (6 lesions, 10 examinations) studied on a 1.5-T MR unit. All patients had clinical histories of blunt abdominal trauma or endoscopic procedures and we were able to determine the time interval between the onset and MR imaging. We evaluated and analyzed the appearance and signal intensity patterns of hematomas of varying ages and we compared the results with those in previously reported intracranial hematomas.

RESULTS

The imaging appearances on five examinations were consistent with presence of deoxyhemoglobin. Two of these lesions were hypointense on T2-weighted images and iso- to hyperintense on T1-weighted images. Three had heterogeneous appearances on both T1- and T2-weighted images, and the bulk of the hematoma progressively increased in size and signal intensity on T2-weighted images. On the remaining five examinations, one lesion was hyperintense on T1-weighted images and iso- to hyperintense on T2-weighted images, consistent with intracellular methemoglobin, and four lesions were hyperintense on both T1- and T2-weighted images, consistent with the presence of extracellular methemoglobin. Duodenal hematoma stages were slower than those of intracranial hematomas; the acute stage spanned 2-7 days, and early and late subacute stages occurred 10-17 days after the injury.

CONCLUSION

Duodenal hematomas evolve like intracranial hematomas, but slower. Signal heterogeneity is common in the acute stage.

Magnetic Resonance Imaging Signal Characteristics of Medishield: Early Postoperative Profile in a Rabbit Interlaminotomy Model

OBJECTIVE

Application of Medishield to the nerve root is common during spinal surgery to create a mechanical barrier from pain mediators and reduce scar formation. However, Medishield's signal characteristics on magnetic resonance imaging (MRI) have not yet been examined.

METHODS

Microsurgical interlaminotomy was performed on 2 lower lumbar segments in 17 adult New Zealand white rabbits. After dural exposure, applications of 1 mL (autologous blood clot or Medishield) were randomized for each level. On postoperative days 1 through 3, various MRI sequences in 1.5T were performed including T1-weighted, T2-w, T1-gadolinium-weighted, susceptibility-weighted and turbo inversion recovery magnitude (TIRM) sequence. Signaling characteristics were analyzed by 3 blinded observers. Inter-rater agreement was calculated using Fleiss's kappa coefficient (κ). Positive and negative likelihood ratios in detecting Medishield by MRI were determined.

RESULTS

Of 24 MRIs performed, TIRM sequence identified Medishield with the highest likelihood ratio. Medishield's positive likelihood ratio was highest (5.8) on postoperative day 1 with interobserver agreement of 93% (κ = 0.75); these rates declined to 2.5 and 1.4 on postoperative days 2 and 3 with interobserver agreements of 71% (κ = 0.43) and 83% (κ = 0.67), respectively. Medishield adherence was confirmed in each rabbit by histologic examinations.

CONCLUSION

Understanding that radiologic detection of Medishield diminished over time as its signal characteristics became less distinguishable from a blood clot is essential in clinical practice. Medishield was detected on postoperative day 1 but not 2 days later after hemodynamic changes had occurred. These results may provide a guide for postoperative findings, such as differential diagnosis of hematoma.

Hemorrhage in the atherosclerotic carotid plaque: a high-resolution MRI study

BACKGROUND AND PURPOSE

High-resolution, multicontrast magnetic resonance imaging (MRI) has developed into an effective tool for the identification of carotid atherosclerotic plaque components, such as necrotic core, fibrous matrix, and hemorrhage/thrombus. Factors that may lead to plaque instability are lipid content, thin fibrous cap, and intraplaque hemorrhage. Determining the age of intraplaque hemorrhage can give insight to the history and current condition of the biologically active plaque. The aim of this study was to develop criteria for the identification of the stages of intraplaque hemorrhage using high-resolution MRI.

METHODS

Twenty-seven patients, scheduled for carotid endarterectomy (CEA), were imaged on a 1.5-T GE SIGNA scanner (sequences: 3-dimensional time of flight, double-inversion recovery, T1-weighted (T1W), PDW and T2W). Two readers, blinded to histology, reviewed MR images and grouped hemorrhage into fresh, recent, and old categories using a modified cerebral hemorrhage criteria. The CEA specimens were serially sectioned and graded as to presence and stage of hemorrhage.

RESULTS

Hemorrhage was histologically identified and staged in 145/189 (77%) of carotid artery plaque locations. MRI detected intraplaque hemorrhage with high sensitivity (90%) but moderate specificity (74%). Moderate agreement in classifying stages occurred between MRI and histology (Cohen kappa=0.7, 95% CI: 0.5 to 0.8 for reviewer 1 and 0.4, 95% CI: 0.2 to 0.6 for reviewer 2), with moderate agreement between the 2 MRI readers (kappa=0.4, 95% CI: 0.3 to 0.6).

CONCLUSIONS

Multicontrast MRI can detect and classify carotid intraplaque hemorrhage with high sensitivity and moderate specificity.

MR imaging for the noninvasive assessment of atherothrombotic plaques

Imaging methods to quantify the progression and regression of atherosclerosis could play a strong role in the management of patients. High-resolution, noninvasive MR imaging may provide exhaustive 3D anatomical information about the lumen and the vessel wall. Furthermore, MR imaging has the ability to characterize plaque composition and microanatomy and therefore to identify lesions vulnerable to rupture or erosion. The high resolution of MR imaging and the development of sophisticated contrast agents offer the promise of molecular in vivo molecular imaging of the plaque. This may aid early intervention (eg, lipid-lowering drug regiments) in both primary and secondary treatment of vascular disease in all arterial beds.

Atherothrombotic plaques and the need for imaging

The assessment of atherothrombotic plaques by imaging techniques is essential for the in vivo identification of vulnerable plaques. Several invasive and noninvasive imaging techniques are available to assess atherothrombotic disease. The use of some of the available imaging modalities for the study of regression and progression of atherothrombosis are described in more detail in the subsequent articles.

Clinical imaging of the high-risk or vulnerable atherosclerotic plaque

The study of atherosclerotic disease during its natural history and after therapeutic intervention will enhance our understanding of disease progression and regression and aid in selecting appropriate treatments. Several invasive and noninvasive imaging techniques are available to assess atherosclerotic vessels. Most of the standard techniques identify luminal diameter, stenosis, wall thickness, and plaque volume; however, none can characterize plaque composition and therefore identify the high-risk plaques. We will present the different imaging modalities that have been used for the direct assessment of the carotid, aortic, and coronary atherosclerotic plaques. We will review in detail the use of high-resolution, multicontrast magnetic resonance for the noninvasive imaging of vulnerable plaques and the characterization of plaques in terms of their various components (ie, lipid, fibrous, calcium, or thrombus).

Imaging evaluation of ovarian masses

Adnexal masses present a special diagnostic challenge, in part because benign adnexal masses greatly outnumber malignant ones. Determination of a degree of suspicion for malignancy is critical and is based largely on imaging appearance. Endovaginal ultrasonography (US) is the most practical modality for assessment of ovarian tumors because it is readily available and has a high negative predictive value. Morphologic analysis of adnexal masses is accurate for identifying masses as either low risk or high risk. The most important morphologic features are non-fatty solid (vascularized) tissue, thick septations, and papillary projections. Color Doppler US helps identify solid, vascularized components in a mass. Spectral Doppler waveform characteristics (eg, resistive index, pulsatility index) correlate well with malignancy but generally add little information to morphologic considerations. Computed tomography can help assess the extent of disease in patients before and after primary cytoreductive surgery. Magnetic resonance (MR) imaging is better reserved for problem solving when US findings are nondiagnostic or equivocal because, although it is more accurate for diagnosis, it is also more expensive. The signal intensity characteristics of ovarian masses make possible a systematic approach to diagnosis. Mature cystic teratomas, cysts, endometriomas, leiomyomas, fibromas, and other lesions can be accurately diagnosed on the basis of T1-weighted, T2-weighted, and fat-saturated T1-weighted MR imaging findings.

Tissue characterization in the female pelvis by means of MR imaging

Pelvic imaging techniques such as computed tomography and ultrasonography provide a limited capability for tissue characterization. Fat, fluid, and calcification, for example, can be identified on the basis of parameters such as x-ray attenuation, echogenicity, and sound attenuation. Because of the many tissue parameters, such as T1, T2, magnetic susceptibility, and chemical shift, that contribute to signal intensity, magnetic resonance (MR) imaging may afford an ability to identify a wider array of specific tissues. The purpose of this article is to review the ability of MR imaging to help identify various types of soft tissue and to provide an approach to interpretation of MR images of the female pelvis through tissue characterization. Lipid, fluid, hemorrhage, smooth muscle, fibrosis, solid malignant tissue, and hydrated soft tissue (including edema, mucin, and myxomatous tissue) have typical MR imaging properties, and their presence in a mass can often be established on MR images. Consideration of the tissue composition of various pathologic processes in the pelvis can result in more systematic approaches to image interpretation and thus narrow the differential diagnosis.