Jürgen Mäurer

Biomechanical properties and vascularity of an anterior cruciate ligament graft can be predicted by contrast-enhanced magnetic resonance imaging. A two-year study in sheep.

Magnetic resonance imaging has been used to determine graft integrity and study the remodeling process of anterior cruciate ligament grafts morphologically in humans. The goal of the present study was to compare graft signal intensity and morphologic characteristics on magnetic resonance imaging with biomechanical and histologic parameters in a long-term animal model. Thirty sheep underwent anterior cruciate ligament reconstruction with an autologous Achilles tendon split graft and were sacrificed after 6, 12, 24, 52, or 104 weeks. Before sacrifice, all animals underwent plain and contrast-enhanced (gadolinium-diethylenetriamine pentacetic acid) magnetic resonance imaging (1.5 T, proton density weighted, 2-mm sections) of their operated knees. The signal/noise quotient was calculated and data were correlated to the maximum load to failure, tensile strength, and stiffness of the grafts. The vascularity of the grafts was determined immunohistochemically by staining for endothelial cells (factor VIII). We found that high signal intensity on magnetic resonance imaging reflects a decrease of mechanical properties of the graft during early remodeling. Correlation analyses revealed significant negative linear correlations between the signal/noise quotient and the load to failure, stiffness, and tensile strength. In general, correlations for contrast-enhanced measurements of signal intensity were stronger than those for plain magnetic resonance imaging. Immunohistochemistry confirmed that contrast medium enhancement reflects the vascular status of the graft tissue during remodeling. We conclude that quantitatively determined magnetic resonance imaging signal intensity may be a useful tool for following the graft remodeling process in a noninvasive manner.

Drug smuggling by ingested cocaine-filled packages: conventional x-ray and ultrasound.

PurposeTo evaluate the imaging characteristics and the diagnostic value of both abdominal ultrasound and conventional abdominal x-ray in identifying ingested drug packages in “body packers.”Materials and MethodsTwelve individuals were studied prospectively by abdominal ultrasound and by abdominal x-ray to rule out incorporated drug containers.ResultsBoth abdominal ultrasound and abdominal x-ray correctly identified the 7 of 12 individuals who had ingested multiple drug packages. In 5 of the 12 individuals, ultrasound as well as abdominal x-ray were correctly unremarkable with regard to abdominal foreign bodies.ConclusionsAbdominal ultrasound and abdominal x-ray both represent valuable diagnostic tools in the assessment of ingested drug packages. Abdominal x-ray is superior to ultrasound in differentiating ingested drug-filled condoms from “pseudocondoms.”

Evaluation of Metastases and Reactive Lymph Nodes in Doppler Sonography Using an Ultrasound Contrast Enhancer

RATIONALE AND OBJECTIVES The authors conducted a prospective study in D-galactose signal-enhanced Doppler sonography of lymph nodes to investigate new aspects in differentiating malignant from reactive lymph nodes of patients with suspected malignancy of the neck. METHODS Twenty-one patients with suspected squamous epithelial cell carcinoma metastases of the neck were examined by Doppler sonography before and after administration of an ultrasound signal-enhancing agent, consisting of D-galactose microbubbles. Qualitative sonomorphology, peak flow rates, and pulsatility and resistive indices were assessed. RESULTS Compared with conventional Doppler, enhanced Doppler sonography gave detailed additional information about vascularization of metastases or reactive lymph nodes. Signal-enhanced Doppler of metastases showed a relatively characteristic pattern of vascularity, therefore facilitating differential diagnoses and allowing better discrimination from surrounding tissue, demonstrated by the infiltration of neighboring vessels in the neck. Concerning reactive lymph nodes, vascularization could be stated and measured in many cases only after signal enhancement. Evaluating peak velocities and pulsatility and resistive indices could not differentiate significantly malignant from reactive lymph nodes. CONCLUSIONS Administration of a D-galactose-based signal-enhancer helps to differentiate malignant from reactive lymph nodes of the neck. It is superior to conventional Doppler by improving evaluation of the vascularity and could be of use for staging procedures.

RADIATION EXPOSURE IN SPIRAL COMPUTED TOMOGRAPHY: DOSE DISTRIBUTION AND DOSE REDUCTION

RATIONALE AND OBJECTIVES The authors investigate the dose distribution of spiral and conventional computed tomography (CT) with film densitometry and to present a new method of evaluating the possibility of dose savings with spiral CT. METHODS Films were exposed in a cuboid polymethyl-methacrylate phantom in conventional and spiral scan technique. Axial density profiles were obtained by digitizing the films using a fluorescent light scanner. The ratio of the number of rotations in spiral CT to the number of slices in conventional CT was calculated. RESULTS In spiral CT with a pitch of 2, the densities in all points were lower than those in corresponding points in spiral CT with a pitch of 1 and in conventional CT with slice distance equal to slice thickness. A pitch of 1.5 in spiral CT led to a dose reduction of 14% to 30% compared with conventional CT. CONCLUSIONS Increasing the pitch in spiral CT leads to a reduction of both integral dose and absorbed doses within the examined body region. The reduction of the integral dose can be significant, especially in cases where slice overlapping is diagnostically advantageous.

The spectrum of imaging in Currarino triad.

Abstract. The aim of this study was to evaluate the spectrum of findings and the efficacy of different imaging modalities in order to formulate recommendations for diagnostic imaging of Currarino triad (ASP syndrome), including screening of relatives. The imaging films of five female patients (age range 6 weeks to 12 months) were analysed retrospectively. The studied material consisted of US and MRI of the lower spine (5 patients each), lumbosacral plain radiography (4 patients), contrast enema (4 patients), urinary US (2 patients), genitography (1 patient) and myelo-CT (1 patient). Depiction of pathological findings with different imaging modalities was reviewed and validated with special respect to their demonstrability by US. Ultrasonography detected the sacral bony defect as well as the presacral pathology (meningocele and/or tumour) and thereby gave the basic diagnosis in all of the cases. It also depicted tethered cord and urinary tract abnormalities correctly. Magnetic resonance imaging gave a more distinct visualization of pre- and intraspinal pathology with additional demonstration of intraspinal lipoma in two cases. Regarding anorectal and genital malformations, radiographic contrast agent studies had been used in all patients. Two blind-ending retrorectal fistulas, depicted by enema, were missed by MRI. Patients with congenital or early infancy obstipation, anorectal malformations and complex urinary tract malformations should have spinal and pelvic sonography first. A plain film of the sacrum is recommended in equivocal cases. The need for MRI and contrast agent studies depends on the individual pathology, whereas presently MRI has made further radiographic imaging increasingly dispensable. A screening program with lumbosacral US or plain radiography for families with Currarino triad should be obligatory.

A new ultrasound-based method for the assessment of torsional differences following closed intramedullary nailing of femoral fractures.

Abstract  Objective. A torsional difference of more than 15° is found in up to 30% of patients following closed intramedullary nailing of femoral fractures. The diagnosis is usually established postoperatively by computed tomography. A torsional deformity of more than 15° should be corrected by early derotation. In order to enable an intraoperative control and possible correction to avoid a second operation for the patient, a new ultrasound-based method suitable for the intraoperative setting has been developed, using the anterior condylar line as a distal reference line. Design and patients. In a prospective study the torsional difference after closed intramedullary nailing of femoral fractures was measured postoperatively by ultrasound in 32 patients and compared with standard CT readings. Results. Torsional differences measured by ultrasound and CT showed a high correlation (r=0.8) and a median difference of less than ±3°. Conclusions. By the introduction of the anterior condylar line as a distal reference line femoral torsion can accurately be assessed by ultrasound in a position required for intraoperative control and possible correction.

Keratinization and necrosis. Morphologic aspects of lymphatic metastases in ultrasound.

RATIONALE AND OBJECTIVE The authors performed a retrospective study in ultrasound to investigate new aspects in the sonomorphology of lymph node metastases of the neck. In this study, it could be demonstrated the first time that the histologic characteristics of the metastases determine the sonographic appearance. In addition to criteria such as the longitudinal/ transversal quotient, sonomorphology could support a more precise differential diagnosis of neck lymph nodes. METHODS In 105 of 145 patients with histologically proved head and neck carcinomas, 187 lymph node metastases were detected by ultrasound. Sonomorphology was compared with the corresponding histology. RESULTS Five sonomorphologic groups could be differentiated. (1) Thirty-one percent of the metastases were homogenous. (2) Concerning the more complex morphology of lymph node metastases in ultrasound, echolucent forms could be differentiated from echogenic textures: low- or nondifferentiated and nonkeratinizing metastases appeared echolucent and cyst-like, with dorsal signal amplification. (3) Nonkeratinizing lymphomas with necrosis showed single or multiple echolucent intranodal lesions. (4) In correlation with an increasing keratinization, the echogenecity of the lymph nodes increased and intranodal echogenic inclusions appeared. (5) An extended keratinization correlated with a central echogenecity. CONCLUSIONS The morphologic assessment of lymph nodes in ultrasound allows for primary histologic and prognostic evaluation of lymph node metastases.

Magnetic resonance imaging of inflammatory bowel disease: Evaluation in a rabbit model

To correlate intestinal contrast enhancement and wall thickening with the degree of inflammation in an experimental model of inflammatory bowel disease.

Applications of specialized coils for high-resolution MRI on a whole-body scanner

To investigate the application of a mini-coil surface system for high-resolution MRI, 60 volunteers were examined in a 1.5-T whole-body scanner. Two replaceable probe heads were available: a circular 2.5-cm coil and a quadratic 5-cm coil, both of which were placed directly on the skin. The skin layers, Achilles tendon and finger joints were examined with the 2.5-cm coil and a FOV of 25 × 25 mm2. A matrix of 256 × 256 pixels resulted in a pixel size of 0.098 × 0.098 mm2. For imaging of the carpal tunnel, the 5-cm coil was used in transverse orientation. The FOV was 50 × 50 mm2 so that a matrix of 256 × 256 pixels led to a pixel size of 0.195 × 0.195 mm2. The resulting spatial resolution permitted visualization of the epidermis, dermis and subcutis, resulting in clear definition of anatomical detail of the musculoskeletal system. MRI measurement of skin-layer thickness did not correlate with histometric data (p<0.05). This discrepancy was due in part to shrinkage of the tumor specimen on histologic preparation. Other causes include the motion artifacts and the limited accuracy of determining thickness on the MRI display unit.

PULMONARY DISEASE IN LIVER TRANSPLANT RECIPIENTS: Spectrum of CT features

Purpose: To determine the features of pulmonary disease in liver transplant recipients by CT. Material and Methods: Of 792 patients, 102 were referred to thoracic CT 3-2093 days after the transplantation procedure (median 107 days). All CT studies were retrospectively analyzed and correlated with clinical, microbiological, serological and histopathological findings. Results: Eighty-eight of 102 patients (86%) had an abnormal CT. In 25 patients (25%), an elevated right hemidiaphragm, basal atelectasis and small effusions were the only abnormalities. Fourty-one patients (40%) displayed an infiltrate and 13 (13%) a mass lesion. Evidence of cytomegalovirus (CMV) infection was found in 20 patients. CMV pneumonia was suggested by an interstitial pattern of pneumonia on CT (n=13). Pneumocystis carinii pneumonia was highlighted by peribronchovascular infiltrates (n=5/8), bacterial pneumonia (n=24) including legionellosis (n=13) by bilateral effusions (n=14) and lobar consolidation (n=13). In 7/41 patients (17%) with both clinically apparent pulmonary disease and CT signs of pneumonia, no pathogen could be detected. Neoplastic disease was mostly due to tumor recurrence (n=6). Conclusion: Thoracic CT of liver transplant recipients aids in detecting and classifying both infectious and neoplastic complications.