Intravenous Magnetic Resonance Arthrography of the Knee

PURPOSE: Knee IVIR images were repeatedly obtained after intravenous administration of gadopentetate dimeglumine to evaluate the arthrographic effect and to determine the optimal scan timing and technique. MATERIALS AND METHODS: Sagittal Tl-weighted (650/15) sequences were repeated before and after intravenous gadolinium enhancement in 26 patients who were divided into exercise (14/26) and nonexercise (12/26) groups. Fourteen patients in exercise group were allowed to move the affected knee joint actively for 10 minutes immediately after the first post-enhancement scan and before repeating scans. The signal intensities in central and peripheral portions of the joint were measured and compared between these two groups. RESULTS: In all cases, enhancement of joint fluid began at peripheral portion and progressed toward central portion. The diffusion rate in exercise group was far faster than that in nonexercise group and homogeneous arthrographic image was revealed within 10 minutes after completion of joint movement. The arthrographic effect continued and the rate of signal decrease was quite slow. CONCLUSION: MR arthrographic image of knee joint can be obtained within 10 minutes after completion of a few minute exercise following intravenous injection of gadopentetate dimeglumine. Intravenous MR arthrography is expected to become an useful method as a convenient alternative to direct MR arthrography.

Anatomic Variations on PNS CT

PURPOSE: To illustrate frequently encountered anatomic variations on PNS computed tomography(CT) and to assess their clinical significance. MATERIALS AND METHODS: CT findings of 1523 patients, who underwent PNS CT with no history of sinus surgery, were reviewed, and prevalence of each anatomic variation and its relationship with mucociliary clearance pathway was evaluated. RESULTS: Two categories of anatomic variations were encountered. The first group included variations of the turbinates, such as concha bullosa(28.6% ), paradoxical middle turbinate(31.5%), of the uncinate process, such as medially bent or folded(36.3%), laterally bent(3.7%) or uncinate bulla(0.5%), of the ethmoidal sinus, such as Haller's ce11(28.2%), large agger nasi ce11(9.6%) or large ethmoidal bulla(23.5%) and nasal septal deviation(24. 1%), which might cause obstruction of mucociliary clearance pathway and thus give rise to secondary obstructive sinusitis. The second group included Onodi ce11(1.4%) and medial depression of the lamina papyracea (3.5%), which were not related with obstructive sinusitis. 87 cases of large agger nasi cell were associated with obstruction of nasofrontal recess. Large ethmoidal bulla(452 cases), Haller's ce11(245 cases) and true concha bullosa (25 cases) contributed to narrowing of the infundibulum. Medially bent uncinate process(220 cases), concha bullosa(157 cases), paradoxical middle turbinate(126 cases) and nasal septal deviation(93 cases) were observed in middle meatal obstruction and supreme concha (3 cases) accompanied sphenoethmoidal recess obstruction. CONCLUSION: Recognition of anatomic variations on PNS CT is important to build a treatment plan in patients with obstructive sinusitis as they may represent causes of the disease, and to avoid critical complications during functional endoscopic sinus surgery.

CT Evaluation of Nasal Cavity Masses: Differential Diagnosis between Nasal Polyps and Their Mimics

PURPOSE: The purposes of this article are to identify CT findings distinguishing nasal polyps, that are the most common cause of the nasal polypiod lesions, from other nasal cavity masses and to identify differential points between benign and malignant masses of nasal cavity. MATERIALS AND METHODS: We classified 567 cases of pathologically proved nasal cavity masses into 4 different groups on CT according to the sites of origin and surrounding bone changes. RESULT: The nasal polyps were the most common cause of nasal cavity masses(515/567). Group I had a high diagnostic specificity for the nasal polyps (513/515, 99.6%) although inverted papilloma (8/522) and malignant melanoma(1/522) showed similar CT appearances. The representitive nasal mass of Group Ila was the inverted papilloma (15/24, 66.5% of the inverted papilloma). Group III pattern was seen in 3 cases of benign minor salivary gland tumor and 2 cases of pyogenic granuloma. Group IV suggested malignancy and thus was mostly observed in malignant tumors except I case of inverted papilloma and 1 case of granulomatous necrosis. CONCLUSION: The differential diagnosis between nasal polyps and the other nasal cavity masses is possible by characteristic bone changes and their sites of origin revealed on CT. In addition, it is possible to differentiate malignant masses from benign in most cases.