Radiologist evaluation of a multispectral image compression algorithm for magnetic resonance images.

With the advent of teleradiology and picture archiving and communication systems (PACS), the expense and time required for image transmission and long term image archiving become important. The use of validated image compression algorithms can greatly reduce these costs. A lossy, multispectral image compression scheme at compression ratios (CR) of 25:1 and 32:1 was used for a set of 26 different patient MR exams. The original and compressed/decompressed (CD) images sets were evaluated in a blinded fashion by four radiologists in two phases. The main objective was to determine whether radiologic interpretation would vary between the two types of CD image sets and the corresponding originals. In general, the compression algorithm caused a slight decrease in image quality; however, the interpretation of pathology did not change between the original and CD image sets. In only one case at the maximum CR = 32 did one of four radiologists change the interpretation of pathology after CD. In this study, lossy multispectral image compression of MR images at CR = 25 maintained diagnostic integrity. This could play a significant role in image storage and communications.

Adenosine-sensitive ventricular tachycardia: right ventricular abnormalities delineated by magnetic resonance imaging.

BACKGROUND: Adenosine-sensitive ventricular tachycardia (VT) is thought to be due to cAMP-mediated triggered activity. It typically originates from the RVOT and occurs in patients with apparently normal hearts. Using magnetic resonance imaging (MRI), we tested the hypothesis that adenosine-sensitive VT occurs in patients without structural heart disease. METHODS AND RESULTS: Fourteen patients (9 women; age, 47+/-19 years) presented with sustained VT (n=3), repetitive monomorphic VT (n=7), or both (n=4). VT terminated with adenosine in each patient and was sensitive to vagal maneuvers in 9 of 11 and verapamil in 10 of 12. VT originated from the right ventricular outflow tract in 10 patients, the right ventricular apex in 1, and the left ventricular septum in 3. Conventional studies included normal signal-averaged ECGs in 9 of 9, normal right ventricular echocardiography in 10 of 10, and normal left ventriculography and coronary angiography in 6 of 7. In contrast, MRI scans were abnormal in 10 of 14 patients. These abnormalities included focal thinning (6), fatty infiltration (4), and wall motion abnormalities (4) of the right ventricle. The most common site of MRI abnormalities was the right ventricular free wall, but there was a poor correlation between the site of MRI abnormalities and the origin of VT. Among 18 control patients without clinical heart disease, thinning of the right ventricular wall was noted in only 1 patient (patients versus control subjects, P=.0001). CONCLUSIONS: Patients with idiopathic adenosine-sensitive VT comprise a heterogeneous group as assessed by MRI, with 70% demonstrating mild structural abnormalities. However, it is unlikely that these findings are causally related to tachycardia, and the functional significance of these anatomic abnormalities is uncertain.

Pulmonary artery sarcoma: diagnosis and postoperative follow-up with gadolinium-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging.

Pulmonary artery sarcomas are infrequently encountered and are often misdiagnosed before surgical exploration or autopsy. On clinical examination and conventional imaging studies, they are frequently mistaken for pulmonary emboli. To our knowledge, this case report is the first to describe the postoperative magnetic resonance imaging (MRI) appearance of residual disease of a pulmonary artery sarcoma and to assess the potential usefulness of MRI for monitoring such lesions postoperatively. Contrast-enhanced MRI, a relatively noninvasive method, seems well suited for postsurgical follow-up of pulmonary artery sarcomas.

MRI evaluation of dexamethasone acetate therapy for osteoarthritis in the hand.

A patient with clinically diagnosed Stage I primary idiopathic osteoarthritis of the first metacarpal trapezium joint of the left hand received intra-articular administration of dexamethasone acetate. Compared to pretreatment T2- weighted MR images, greatly decreased MR signal intensity was observed in the affected joint space and adjacent soft tissues 2 days after dexamethasone acetate therapy. This was representative of reduced edema in the metacarpal trapezium joint and demonstrated the ability of MRI to follow pharmacological treatment for arthritis.

MR imaging in the diagnosis of a retroperitoneal schwannoma.

The computerized tomography (CT) and ultrasound characteristics of many of the primary retroperitoneal tumors are nonspecific, and thus preoperative diagnosis of these tumors is difficult. We describe a case of a retroperitoneal schwannoma in which the multiplanar capability of magnetic resonance imaging (MRI) provided anatomic information not obtainable by other modalities and helped to suggest the neural origin of the tumor.

Prostate visualization studies in males homozygous and heterozygous for 5 alpha-reductase deficiency.

Male pseudohermaphrodites with 5 alpha-reductase deficiency have ambiguous genitalia and nonpalpable prostates on rectal examination, suggesting the dihydrotestosterone dependency of these structures. To clearly delineate the status of the prostate, male pseudohermaphrodites with 5 alpha-reductase deficiency had transrectal sonography of the prostate performed, and the results were compared to that of age-matched male controls. In six male pseudohermaphrodites, magnetic resonance imaging studies of the prostate were also performed. Heterozygote fathers also had transrectal sonography of the prostate performed and the results compared to age-matched controls. The prostates of the male pseudohermaphrodites appeared as platelike soft tissue structures posterior to the urethra on both prostatic ultrasound and magnetic resonance imaging. Prostatic volume, as determined on prostatic ultrasound by two different methods, was significantly smaller (approximately one-tenth) than the volume of age-matched controls. Transurethral ultrasound guided biopsy of the prostate in two affected subjects revealed stromal tissue. These results correlate with undetectable prostate-specific antigen in affected subjects, suggesting atrophic epithelium or lack of epithelial differentiation. This study demonstrates the dihydrotestosterone dependence of the prostate for normal differentiation and growth. The presence of some prostatic tissue in the male pseudohermaphrodites may be due to the fact that there is a decrease and not an absence of 5 alpha-reductase activity, and/or that the increased level of testosterone in subjects with this condition partially compensates for the decreased level of dihydrotestosterone. There was no difference, however, in prostate size between heterozygous fathers and age-matched control males. The heterozygote fathers had dihydrotestosterone production sufficient for normal prostate growth and development.

Retroperitoneal germ cell neoplasm: MR and CT.

A case of germ cell neoplasm in an undescended retroperitoneal testicle is reported. CT revealed a large mass most consistent with a chronic hematoma. MRI demonstrated findings typical for neoplasm, and this was confirmed on biopsy.

MRI characteristics of two cases of adrenal ganglioneuromas.

Two cases of the magnetic resonance imaging (MRI) of adrenal ganglioneuromas are presented. The appearance on spin-echo sequences is that of a heterogeneous mass, increasing in signal intensity in T2-weighted images, with associated areas of decreased signal, consistent with findings in the one previously reported case. The diagnosis of adrenal ganglioneuroma should be considered in the differential diagnosis of heterogeneous adrenal masses.

Magnetic resonance imaging of an esophageal duplication cyst.

A confirmed case of an esophageal duplication is reported. We review the clinical and pathologic features of this rare anomaly, and describe its appearance on magnetic resonance imaging (MRI). The potential advantages of utilizing MRI in the diagnosis of suspected esophageal duplications, and in the detection of any associated lesions, are outlined.

MR imaging of cardiac mass in Wegener granulomatosis.

Wegener granulomatosis is a disorder of unknown etiology characterized by a necrotizing granulomatous vasculitis that primarily affects the paranasal sinuses, lungs, and kidneys. It is usually a disease of adults with infrequent cardiac involvement. We report the unusual presentation of this disorder in an adolescent with a cardiac mass. The findings on two-dimensional echocardiography and MR imaging are discussed.

Cadaver correlation of peroneal tendon changes with magnetic resonance imaging.

Magnetic resonance imaging (MRI) is used to show the soft tissues of the body. The presence of anomalous tendons and muscles can be detected. Chronic lateral ankle pain and instability can be associated with peroneal tendon pathology and MRI may be used to assess both longitudinal attrition of the peroneus brevis tendon, as well as the presence of the peroneus quartus which may be useful in lateral ankle reconstruction. Tenography can occasionally present technical difficulties and can lead to patient dissatisfaction.

Xanthogranulomatous pyelonephritis in an infant.

An unusual case of xanthogranulomatous pyelonephritis (XGP) in an infant is presented. Findings on magnetic resonance imaging, computerized tomography, ultrasound, and intravenous urography in our patient are contrasted with others reported in the literature. Absent were such commonly seen findings as nonfunctioning kidney, hydronephrosis, urinary calculi, and calcifications.

Urachal carcinoma: the role of magnetic resonance imaging.

Urachal carcinoma is a very rare tumor that occurs primarily in middle-aged and elderly men. Most are mucinous adenocarcinomas. The lesion's poor prognosis primarily reflects its clinically silent behavior in its early stages. Therefore, aids to preoperative diagnosis and tumor staging may be of benefit. Conventional radiographic techniques have not proved very effective at diagnosing urachal lesions. Magnetic resonance imaging (MRI) may be particularly useful in this regard, mainly due to its multiplanar imaging capability. We review the clinical, pathological, and radiological features of urachal carcinoma, and include a description of the MRI appearance of two cases.

MR appearance of cervical pregnancy.

Cervical pregnancy is a rare type of ectopic pregnancy, although its incidence appears to be increasing. Prompt recognition is important since it can be the cause of catastrophic hemorrhage. Yet the diagnosis is rarely made prior to surgery due to the rarity of cervical pregnancy and the emergent nature of its complications. This report describes the magnetic resonance (MR) appearance of a cervical gestation and discusses the potential advantages of MR in making the diagnosis.

Magnetic resonance imaging evaluation of spontaneous portosystemic collaterals.

Three patients, two of whom had histories of episodic hepatic encephalopathy, were shown by magnetic resonance imaging (MRI) to have occult spontaneous portosystemic shunts. The multiplanar imaging capabilities of MRI provided an optimal, noninvasive method of visualization of collateral anatomy in each case.

MRI of primary amyloidosis.

In a patient with primary amyloidosis, we compared T2 values and relative signal intensity ratios of involved organs to those of normal patients. T2 was significantly decreased in the spleen and adrenals, while significantly increased in the pancreas. T2 values were insignificantly changed in the liver, subcutaneous fat, bone marrow, or kidney. Ratios may facilitate detection of relative changes in T2 values.

Adrenal hemorrhage and renal vein thrombosis in the newborn: MR imaging.

Three newborn infants with flank masses underwent magnetic resonance (MR) imaging after ultrasound (US) indicated adrenal hemorrhage and/or renal vein and inferior vena cava thrombosis. MR imaging was valuable in defining the hemorrhagic nature of echogenic and hypoechoic suprarenal masses and in delineating thrombi within the renal veins and inferior vena cava. Two infants with renal parenchymal damage had abnormal radionuclide scans and abnormal corticomedullary distinction on MR images. The major role of MR imaging may be in the early course of these conditions, when added diagnostic specificity is likely to affect patient management. In most instances, size of hemorrhage and intravenous clots, as well as renal size, may be accurately followed with US, while radionuclide scanning remains necessary for evaluation of renal functional impairment.

MR imaging of portal venous thrombosis: correlation with CT and sonography.

Fourteen patients with portal venous thrombosis (PVT) diagnosed by CT and/or sonography were studied with MR. Three of the 14 had portal hypertension. The MR findings were compared with those of eight patients with portal hypertension, but without CT or sonographic evidence of PVT. MR imaging showed portal venous thrombosis in all 14 PVT cases. Intraluminal thrombi of less than 5 weeks duration appeared markedly hyperintense relative to liver and muscle on both T1- and T2-weighted images. Older thrombi appeared hyperintense relative to liver and muscle in eight of 11 cases, but only on T2-weighted images. MR showed thrombi in 11% more portal vessels than did CT (MR = 30, CT = 27) and in 28% more vessels than did sonography (MR = 32, sonography = 25). MR also showed 24% more collateral vessels than did CT (MR = 31, CT = 25) and 50% more vessels than did sonography (MR = 33, sonography = 22). Third-echo images (echo time = 96 msec, repetition time = 1500-2150 msec) verified the presence of venous thrombi in 28 (93%) of 30 PVT vessels, and they differentiated flow-related intravascular signal from true thrombi in six (17%) of 36 portal hypertension vessels. We conclude that MR is a valuable tool for imaging portal vein thrombosis. MR is a good substitute for CT and can be more informative than sonography.