Biomedical subjects
Publications and source records attributed to P J Lin.
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The technique of applying an air gap between the patient and the x-ray detector reduces scattered radiation from the patient's neck sufficiently to allow performance of DSA of the extracranial carotid arteries with the antiscatter grid removed. When compared with the conventional grid technique, air gap allows 25 to 88% reduction of mA without increasing the kVp or exposure time and without loss of spatial resolution or diagnostic image quality. These considerable patient radiation-exposure savings can be implemented on DSA systems that use ordinary under-table x-ray tube fluoroscopic equipment without the purchase of additional hardware.
Mobile chest radiographs obtained with manual technique and with an automatic exposure control device were compared in 50 patients requiring three radiographs within a 48 hr period. Parameters evaluated were overall quality, internal consistency, film latitude, lung field (consistency and quality), cardiac contour, hilar anatomy, pulmonary vascularity, mediastinum, tracheobronchial tree, and tubes and appliances. Radiographs obtained with the automatic exposure control system demonstrated better overall quality, consistency, film latitude, and lung field consistency and quality than manual technique. There was no definite advantage of the automatic exposure control device in the visualization of the hila, pulmonary vascularity, heart, or mediastinum. Tubes and appliances were seen equally well with both techniques. The automatic exposure control device has the potential to increase the quality and consistency of mobile radiographs, particularly in those critically ill patients who are radiographed at least on a daily basis.
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Antibodies to Epstein-Barr virus capsid antigen (anti-VCA) and early antigen (anti-EA) were measured in 263 patients with nasopharyngeal carcinoma (NPC), 624 age- and sex-matched neighborhood controls, 570 family members of NPC patients and 830 family members of neighborhood controls in Taiwan. The distribution of antibody titers was significantly different between NPC patients and the other three groups. More than 55% and 45% of NPC patients had titers of greater than or equal to 1:640 and greater than or equal to 1:80 for anti-VCA and anti-EA, respectively, while less than 6.7% and 2.5% of the other three groups had such high titers. The geometric means of anti-VCA and anti-EA titers were 1:352 and 1:45, respectively, in NPC patients compared to less than 1:77 and 1:12, respectively, in the comparison groups. Anti-VCA and anti-EA titers were significantly correlated. The association of EBV with NPC is discussed.
A simplified method for standardization of roentgenographic image quality is described. The method employs the concept of penetration quality (PQ) originally established for calibration of x-ray tube potential (kVp). In order to verify that the PQ measurement is useful for standardization of roentgenographic image quality in a clinical situation, a cadaver was selected for patient simulation. It has been shown that PQ may be utilized for roentgenographic technique specification in place of kVp. The validity of this standardization was evaluated subjectively by radiologists.
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Thoracic esophagus was usually removed through the transhiatal approach or via an open thoracotomy. The long incision and spreading of the ribs usually resulted in much pain and interference with chest wall mechanics. Today, with the development of a video-assisted endoscopic procedure, many intrathoracic lesions can be removed through small incision. Since March 1992 we have attempted 20 esophagectomies and reconstruction using a right thoracoscopic approach in 16 males and 4 females whose average age was 56 years. Indications for its use were esophageal cancer in 17 patients (squamous cell carcinoma in 12 patients, adenocarcinoma in 5) and caustic stenosis in 3. It is our impression that video-assisted endoscopic esophagectomy and reconstruction potentially causes less trauma, less postoperative discomfort, and a rapid functional recuperation. Our initial experiences showed that it is a feasible, effective procedure.
Interchange or transfer of radiographic techniques through measurement of penetration quality is discussed. The usefulness of this achievement is verified using an aluminum step wedge. Also, the procedure described provides a method for performance evaluation of kVp compensation on diagnostic x-ray installations.
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Fluoroscopic procedures, in general, result in much higher exposures to patients than do most types of radiographic procedures [National Council on Radiation Protection, Report 100, p. 31 (1989)]. In spite of this, fluoroscopic exposure rates can vary widely between systems, and often for no apparent reason. The charge of AAPM Task Group No. 11 was to evaluate fluoroscopic exposure rates at the entrant surface of the x-ray image intensifier, and to disseminate this information so that medical physicists could compare their own exposure rate measurements with typical values. The measurement protocol was defined for various system configurations. Sheets of copper were used to attenuate the x-ray beam, and the input exposure rate at the image intensifier (at the input mode closest to 23-cm diameter) in the absence of a scattering medium was determined. With 2 mm of copper as x-ray beam filtration, the median fluoroscopic exposure rate at the image intensifier was found to be 16.5 nC/kg/s (64.0 microR/s), with an average kV of 77 and mA of 2.0 (n = 62).
Acceptance testing and quality control of video and laser cameras is relatively simple, especially with the use of the SMPTE test pattern. Photographic quality control is essential if one wishes to be able to maintain the quality of video and laser cameras. In addition, photographic quality control must be carried out with the film used clinically in the video and laser cameras, and with a sensitometer producing a light spectrum similar to that of the video or laser camera. Before the end of the warranty period a second acceptance test should be carried out. At this time the camera should produce the same results as noted during the initial acceptance test. With the appropriate acceptance and quality control the video and laser cameras should produce quality images throughout the life of the equipment.
The heparinized-coated tube is widely used for arterial bypass, mainly in patients with aneurysms or trauma of the thoracic aorta. Its application in venous bypass was less frequent. We report a 26-year-old woman who sustained blunt abdominal injury which resulted in complete severance of the suprahepatic hepatic vein and multiple partial lacerations of the inferior vena cava. For hemostasis, total hepatectomy with interruption of the inferior vena cava was performed. During the anhepatic phase, end-to-end portocaval anastomosis and a bypass shunt using 9 mm Gott tube from the right femoral vein to the right atrium were set up for veno-venous bypass. Orthotopic liver transplantation was performed later. Gott tube was placed for 18 hours with good venous return. We concluded that heparinized-coated tube is good for veno-venous bypass with the following advantages: 1) simple operative procedure, 2) enough flexibility to be kept out of the operative field, 3) no anticoagulant is necessary, consequently less bleeding resulted.