Image quality assessment of three cone beam CT machines using the SEDENTEXCT CT phantom.

OBJECTIVES: The SEDENTEXCT Project proposed quality assurance (QA) methods and introduced a QA image quality phantom. A new prototype was recently introduced that may be improved according to previous reports. The purpose of this study is to evaluate image quality in various protocols of three cone beam CT (CBCT) machines using the proposed QA phantom. METHODS: Using three CBCT machines, nine image quality parameters, including image homogeneity (noise), uniformity, geometrical distortion, pixel intensity value, contrast resolution, spatial resolution [line pair (LP) chart, point spread function (PSF) and modulation transfer function (MTF)] and metal artefacts, were evaluated using a QA phantom proposed by SEDENTEXCT. Exposure parameters, slice thickness and field of view position changed variously, and the number of total protocols was 22. RESULTS: Many protocols showed a uniform gray value distribution except in the minimum slice thickness image acquired using 3D Accuitomo 80 (Morita, Kyoto, Japan) and Veraviewepocs 3Df (Morita). Noise levels differed among the protocols. There was no geometric distortion, and the pixel intensity values were correlated with the CT value. Low contrast resolution differed among the protocols, but high contrast resolution performed well in all. Many protocols showed that the maximum line pair was larger than 1 LP mm(-1) but smaller than 3 LP mm(-1). PSF and MTF did not correlate well with the pixel size. The measured metal artefact areas varied for each device. CONCLUSIONS: We studied the image quality of three CBCT machines using the SEDENTEXCT phantom. Image quality varied with exposure protocols and machines.

Present status of Maconellicoccus hirsutus (Hemiptera: Pseudococcidae) in the Mariana Islands and its control by two fortuitously introduced natural enemies.

The mealybug Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae), attacks ornamental and fruit crops in the Mariana Islands. Insecticides cannot penetrate the heavy layers of wax that protect the insect's body. We surveyed the mealybug's locally recruited natural enemies and their effects on its population on Guam, Rota, Saipan, and Tinian to assess the need for introduction of exotic natural enemies. We monitored population densities of M. hirsutus, those of its natural enemies, and parasitism rates for 3 yr, 2005-2007. Our surveys revealed the presence of two parasitoids, Anagyrus kamali Moursi (Hymenoptera: Encyrtidae) and Allotropa sp. near mecrida (Walker) (Hymenoptera: Platygastridae), fortuitously introduced to the Mariana Islands with M. hirsutus. The predator Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) also was often found feeding on M. hirsutus. Population density of M. hirsutus was below the economic threshold at all locations. Rainfall seemed to affect mean numbers of M. hirsutus and mean numbers of eggs at some locations. On all four islands, the two parasitoids, complemented by the predator, were effectively controlling the M. hirsutus population. No evidence of hyperparasitism was recorded. Currently, economic damage by M. hirsutus is not a concern in the Mariana Islands, and additional parasitoids need not be introduced to control M. hirsutus.

[Case of multiple posterior mediastinal and retroperitoneal neurinomas].

We report a case of multiple neurinomas arising in the posterior mediastinum and the retroperitoneum. A 49-year-old man was admitted to our department for operation after an abnormal shadow appeared on routine chest X-ray film. A left adrenal tumor was found incidentally with ultrasonography at the time of a previous thoracic surgery. First, the posterior mediastinal tumor was surgically removed. Histologic diagnosis was neurinoma. After resection, endocrinologic findings were within normal limits. A left adrenal tumor was diagnosed, and surgery was performed. The tumor was separated from the adrenal gland; the histologic diagnosis was neurinoma. Neurinomas are usually solitary; multiple neurinomas are extremely rare.

[A case of rectal cancer metastatic to the tonsil].

Metastatic tumors of the tonsils are rarer than primary tumors. Few cases of metastatic tonsillar tumor have been reported. A 51-year-old man expectorated a portion of a tumor from the left side of the pharynx after an operation for cancer metastatic to the lung. Biopsy revealed that the pharyngeal tumor was rectal cancer (adenocarcinoma) metastatic to the tonsil. To our knowledge, this is the first case of primary rectal cancer metastatic to the tonsil to be reported in Japan. The clinical features of metastatic tonsillar tumor are discussed.

[Three cases of pulmonary embolism incorrectly diagnosed as lung cancer].

Pulmonary embolism is commonly misdiagnosed as lung cancer, since sputum cytological tests often show atypical or malignant cells. We report three operated cases of pulmonary embolism incorrectly diagnosed as lung cancer. The first patient is a 39-year-old male with chest pain an bloody sputum. Chest x-ray revealed abnormal shadows and subsequent sputum cytological tests identified malignant cells. The second patient is a 63-year-old male with the same diagnostic pattern as the first case. The third patient is a 72-year-old male whose routine chest x-ray showed an abnormal shadow; malignant cells were identified by cytological tests on transbronchial fiberscope brushings. These three patients were histopathologically diagnosed as suffering pulmonary embolism by wedge resection under thoracotomy. When a patient has chest pain or bloody sputum with showing temporarily malignant cells on cytology, the possibility of pulmonary embolism should be taken into consideration.

[A case of asymptomatic posterior mediastinal pheochromocytoma diagnosed during the procedure of video-assisted thoracic surgery (VATS)].

The patient was a 20-year-old male. On routine check-ups, a posterior mediastinal tumor was found radiologically and referred to our hospital for the operation. During the Video-Assisted Thoracic Surgery (VATS), sudden elevation of the blood pressure up to 270 mmHg was observed by the tumor palpation. At once we diagnosed as pheochromocytoma. Changing the VATS to usual thoracotomy the tumor was completely removed and histologically confirmed. After the operation the patient was uneventful and the value of norèpinephrine reduced to normal range from 2912 pg/ml. The posterior mediastinal pheochromocytoma is rare and this report is the 6 th case in Japan. Clinical characteristics were discussed in addition to the review of the literature.

[A case of intrathoracic multiple schwannoma].

A case of intrathoracic multiple schwannoma originating in the left sympathetic nerve was reported. A 38-year-old male was admitted to our department for re-evaluation of his nephrotic syndrome, the chest X-ray revealed an abnormal shadow. A chest tomogram and a chest computed tomogram revealed multiple masses along the left 10th thoracic vertebra. The operation was done on September 4, 1989 under the diagnosis of posterior mediastinal tumor. At thoracotomy, four tumors were seen along the 10th thoracic vertebra and the sympathetic nerve was ascertained to be connected. Histologically, the tumors were composed of spindle cells arranged in scattered palisading fashion, and diagnosed as schwannoma. Multiple schwannomas are very rare. There have been only 12 cases of intrathoracic multiple schwannoma in Japan. Available Japanese literature on the subject was reviewed and discussed.