The ability to identify the intraparotid facial nerve for locating parotid gland lesions in comparison to other indirect landmark methods: evaluation by 3.0 T MR imaging with surface coils.

INTRODUCTION: It is important to know whether a parotid gland lesion is in the superficial or deep lobe for preoperative planning. We aimed to investigate the ability of 3.0 T magnetic resonance (MR) imaging with surface coils to identify the intraparotid facial nerve and locate parotid gland lesions, in comparison to other indirect landmark methods. METHODS: We retrospectively evaluated 50 consecutive patients with primary parotid gland lesions. The position of the facial nerve was determined by tracing the nerve in the stylomastoid foramen and then following it on sequential MR sections through the parotid gland. The retromandibular vein and the facial nerve line (FN line) were also identified. For each radiologist and each method, we determined the diagnostic ability for deep lobe lesions and superficial lobe lesions, as well as accuracy. These abilities were compared among the three methods using the Chi-square test with Yates' correction. RESULTS: Mean diagnostic ability for deep lobe lesions, the diagnostic ability for superficial lobe lesions, and accuracy were 92%, 86%, 87%, respectively, for the direct identification method; 67%, 89%, 86%, respectively, for the retromandibular vein method; and 25%, 99%, 90% , respectively, for the FN line method. The direct identification method had significantly higher diagnostic ability for deep lesions than the FN line method (P < 0.01), but significantly lower diagnostic ability for superficial lobe lesions than the FN line method (P < 0.01). CONCLUSION: Direct identification of the intraparotid facial nerve enables parotid gland lesions to be correctly located, particularly those in the deep lobes.

Capsule of parotid gland tumor: evaluation by 3.0 T magnetic resonance imaging using surface coils.

BACKGROUND: magnetic resonance (MR) imaging of parotid gland tumors has been widely reported, although few reports have evaluated the capsule of parotid gland tumors in detail. PURPOSE: to evaluate the diagnostic usefulness of 3.0 T MR imaging with surface coils for detection of the parotid gland tumor capsule, and to clarify the characteristics of the capsules. MATERIAL AND METHODS: seventy-eight patients with parotid gland tumors (63 benign and 15 malignant) were evaluated. Axial and coronal T2-weighted and contrast-enhanced T1-weighted images were obtained using a 3.0 T MR scanner with 70 mm surface coils. It was retrospectively assessed whether each parotid gland tumor was completely surrounded by a capsule. The capsule was classified as regular or irregular in terms of capsular thickness, and as none, mildly, or strongly enhancing in terms of contrast enhancement. Visual interpretations were compared with histopathological findings to evaluate the diagnostic ability of MR imaging to detect parotid gland tumor capsules. Statistical evaluation was conducted concerning the presence of capsules, capsular irregularity, and the difference in contrast enhancement between benign and malignant tumors, and that between pleomorphic adenomas and Warthin's tumors. RESULTS: capsules completely surrounding the tumor on MR imaging yielded a sensitivity of 87.7% (50/57), specificity of 90.5% (19/21), and accuracy of 88.5% (69/78). Benign tumors had a capsule completely surrounding the tumor significantly more often than malignant tumors (P = 0.009). Concerning capsular irregularity, malignant tumors tended to have more irregular capsules than benign tumors, although there were no significant differences. The capsules of malignant tumors enhanced significantly more strongly than those of benign tumors (P = 0.018). CONCLUSION: 3.0 T MR imaging using surface coils could correctly depict parotid gland tumor capsules in most cases. Most benign and some malignant tumors had capsules completely surrounding the tumors. Malignancy should be considered in tumors with irregular and strongly enhancing capsules.

Clinical feasibility of pulmonary perfusion analysis using dynamic computed tomography and a gamma residue function.

PURPOSE: To create and determine the clinical feasibility of a model based on dynamic computed tomography (CT) and a bolus injection of iodine contrast medium for evaluation of pulmonary perfusion for healthy individuals and for patients with lung diseases. MATERIALS AND METHODS: We analyzed pulmonary perfusion by means of dynamic 16-row multidetector CT scanning with a gamma residue function with adding a linear component (extended gamma function model) for 20 healthy individuals and in five patients. RESULTS: Four types of the time-attenuation curve (TAC) were identified for the peripheral lung. Although the TACs of most pixels for the peripheral lung comprised a single peak or a single-peak followed by another increase, no peak was observed for a small proportion of pixels, which either increased linearly or resulted in a delayed peak for healthy subjects. The ratios of these linearly increasing or delayed peak types of lung fields increased for pathological lungs. The analytical results for pathological cases showed that changes in lung perfusion, difficult to identify using only CT imaging, could be detected. CONCLUSIONS: The extended gamma function model adequately evaluated pulmonary perfusion not only for normal regions, but also for structurally abnormal regions. Regional changes in perfusion could be evaluated by use of our model, and we confirmed its clinical feasibility for pulmonary perfusion analysis.

Evaluation of a noise reduction procedure for chest radiography.

BACKGROUND: The aim of this study was to evaluate the usefulness of noise reduction procedure (NRP), a function in the new image processing for chest radiography. METHODS: A CXDI-50G Portable Digital Radiography System (Canon) was used for X-ray detection. Image noise was analyzed with a noise power spectrum (NPS) and a burger phantom was used for evaluation of density resolution. The usefulness of NRP was evaluated by chest phantom images and clinical chest radiography. We employed the Bureau of Radiological Health Method for scoring chest images while carrying out our observations. RESULTS: NPS through the use of NRP was improved compared with conventional image processing (CIP). The results in image quality showed high-density resolution through the use of NRP, so that chest radiography examination can be performed with a low dose of radiation. Scores were significantly higher than for CIP. CONCLUSION: In this study, use of NRP led to a high evaluation in these so we are able to confirm the usefulness of NRP for clinical chest radiography.

Radiation-induced microbleeds after cranial irradiation: evaluation by phase-sensitive magnetic resonance imaging with 3.0 tesla.

BACKGROUND: Although there are many reports regarding radiation-induced microbleeds, its frequency, relation to dose and latency after radiation are not fully elucidated. The purpose of this study was to evaluate the frequency, latency, patient factors and dose relation of radiation-induced microbleeds after cranial irradiation using phase-sensitive magnetic resonance imaging (PSI) at 3.0 T. METHODS: Retrospective evaluation of 34 patients (age range, 13-78 years; mean, 49 years; follow-up period, 3-169 months; mean 29 months) who had undergone cranial irradiation using magnetic resonance (MR) imaging including PSI was performed. Twenty-three patients received high-dose irradiation (44-60 Gy), and 11 patients received 24-30 Gy whole brain irradiation. When microbleeds were detected on MR imaging in these high-dose irradiation patients, dose distribution maps were reproduced by reviewing the clinical records. Then the irradiated areas were divided into 6 radiation-dose classes: regions > 55 Gy, 45-55 Gy, 35-45 Gy, 25-35 Gy, 15-25 Gy and 5-15 Gy. The frequency of microbleeds in each radiation-dose class was analyzed. RESULTS: Microbleeds were detected in 7 (21%) of 34 patients on T2-weighted imaging, whereas they were detected in 16 (47%) of the 34 patients on PSIs. The frequency of microbleeds was higher than previously reported. The latency of radiation-induced microbleeds after radiation was 3 months to 9 years (mean, 33 months). In high-dose irradiation patients, the frequency of microbleeds significantly was associated with radiation dose. There were no foci that were observed in regions that had received < 25 Gy. CONCLUSION: Radiation-induced microbleeds occurred more frequently in the present study than has been previously reported. PSI can be used to detect these vascular changes earlier than other conventional MR imaging techniques.

Radiation-induced damage to microstructure of parotid gland: evaluation using high-resolution magnetic resonance imaging.

PURPOSE: To elucidate the radiation-induced damage to the microstructure of the parotid gland using high-resolution magnetic resonance imaging. METHODS AND MATERIALS: High-resolution magnetic resonance imaging of the parotid gland was performed before radiotherapy (RT) and during the RT period or < or =3 weeks after RT completion for 12 head-and-neck cancer patients using a 1.5-T scanner with a microscopy coil. The maximal cross-sectional area of the gland was evaluated, and changes in the internal architecture of the gland were assessed both visually and quantitatively. RESULTS: Magnetic resonance images were obtained at a median parotid gland dose of 36 Gy (range, 11-64). According to the quantitative analysis, the maximal cross-sectional area of the gland was reduced, the width of the main duct was narrowed, and the intensity ratio of the main duct lumen to background was significantly decreased after RT (p <.0001). According to the visual assessment, the width of the main duct tended to narrow and the contrast of the duct lumen tended to be decreased, but no significant differences were noted. The visibility of the duct branches was unclear in 10 patients (p = .039), and the septum became dense in 11 patients (p = .006) after RT. CONCLUSION: High-resolution magnetic resonance imaging is a noninvasive method of evaluating radiation-induced changes to the internal architecture of the parotid gland. Morphologic changes in the irradiated parotid gland were demonstrated during the RT course even when a relatively small dose was delivered to the gland.

[Evaluation of the results of radiotherapy for carcinoma involving the external auditory canal or middle ear].

PURPOSE: To evaluate the results and significance of radiotherapy for carcinoma involving the external auditory canal or middle ear. MATERIALS AND METHODS: Six patients underwent radiotherapy. Five patients had squamous cell carcinoma and one had ceruminous adenocarcinoma. In addition to radiotherapy, two patients underwent complete resection, and the other patient underwent incomplete resection. Total radiation doses ranged from 30 to 88 Gy (2 Gy/fraction, 5 fractions/week). RESULTS: The post-treatment survival period ranged from 8 months to 7 years (mean, 3 years, 11 months). Two patients treated by radiotherapy alone (doses of more than 60 Gy) lived for more than five years. CONCLUSION: The prognosis of patients with advanced cancer involving the external auditory canal and middle ear is generally poor. Based on even this limited clinical experience, a tumor dose of at least 70 Gy should be delivered for local control of advanced cancer. To avoid complications, several plans such as application of the shrinking field technique are recommended.