Analysis of changes in dose distribution due to respiration during IMRT

PURPOSE: Intensity modulated radiation therapy (IMRT) is a high precision therapy technique that can achieve a conformal dose distribution on a given target. However, organ motion induced by respiration can result in significant dosimetric error. Therefore, this study explores the dosimetric error that result from various patterns of respiration. MATERIALS AND METHODS: Experiments were designed to deliver a treatment plan made for a real patient to an in-house developed motion phantom. The motion pattern; the amplitude and period as well as inhale-exhale period, could be controlled by in-house developed software. Dose distribution was measured using EDR2 film and analysis was performed by RIT113 software. Three respiratory patterns were generated for the purpose of this study; first the 'even inhale-exhale pattern', second the slightly long exhale pattern (0.35 seconds longer than inhale period) named 'general signal pattern', and third a 'long exhale pattern' (0.7 seconds longer than inhale period). One dimensional dose profile comparisons and gamma index analysis on 2 dimensions were performed RESULTS: In one-dimensional dose profile comparisons, 5% in the target and 30% dose difference at the boundary were observed in the long exhale pattern. The center of high dose region in the profile was shifted 1 mm to inhale (caudal) direction for the 'even inhale-exhale pattern', 2 mm and 5 mm shifts to exhale (cranial) direction were observed for 'slightly long exhale pattern' and 'long exhale pattern', respectively. The areas of gamma index >1 were 11.88%, 15.11%, and 24.33% for 'even inhale-exhale pattern', 'general pattern', and 'long exhale pattern', respectively. The long exhale pattern showed largest errors. CONCLUSION: To reduce the dosimetric error due to respiratory motions, controlling patient's breathing to be closer to even inhaleexhale period is helpful with minimizing the motion amplitude.

A case of petrous carotid artery pseudoaneurysm presenting with epistaxis after radiotherapy in a patient with nasopharyngeal cancer / 대한내과학회지

Rupture of an internal carotid artery pseudoaneurysm is a rare but lethal complication in patients with nasopharyngeal cancer. Here, we report a case of severe nasal bleeding from a left petrous internal carotid artery aneurysm after chemoradiotherapy in a patient with nasopharyngeal cancer. A 76-year-old man who was being treated with concurrent chemoradiotherapy and who had achieved a complete response for 14 months developed massive epistaxis . A postnasal space computed tomography scan showed an enhanced nodular lesion at the left petrous internal carotid artery, and angiography revealed a pseudoaneurysm measuring 11.5x9.1 mm in the left internal carotid artery. Bleeding was well controlled with endovascular occlusion using a coil. The patient showed no recurrence of bleeding during follow-up.

Acute Mesenteric Ischemia after Aortic Valve Replacement: A case report / 대한흉부외과학회지

Acute mesenteric ischemia after cardiac surgery is a serious complication associated with high mortality. Superior mesenteric artery is most commonly affected artery. Acute obstruction of mesenteric artery generally has an unfavorable prognosis because of late diagnosis. The keys to a successful outcome are early diagnosis and appropriate operative intervention. We successfully treated a patient with acute mesenteric ischemia after aortic valve replacement. Therefore, we report a case with a review of articles.

Arginine Vasopressin Therapy of Vasodilatory Shock after Cardiac Surgery / 대한흉부외과학회지

BACKGROUND: Vasodilatory shock has been implicated in life-threatening complications after open heart surgery, where the systemic inflammatory reaction is attributed to the cardiopulmonary bypass (CPB). The secretion of arginine vasopressin (AVP) has been found to be defective in a variety of vasodilatory shock states and administration of AVP markedly improves vasomotor tone and blood pressure. So we reviewed our experience of AVP therapy in patients with vasodilatory shock following heart surgery using CPB. MATERIAL AND METHOD: From January 2004 to July 2006, we reviewed the records of patients who received AVP therapy for vasodilatory shock following heart surgery using CPB. Vasodilatory shock was defined as a mean arterial pressure lower (MAP) than 70 mmHg, a cardiac index greater than 2.5 L/min/m2, peripheral vascular resistance lower than 800 dyn/s/cm5, and vasopressor requirements. The hemodynamic responses of patients who received AVP therapy for vasodilatory shock after cardiac surgery were analyzed retrospectively. RESULT: One hundred ninety nine open cardiac surgery patients were consecutively included in this study. Twenty two patients (11.1%) met criteria for vasodilatory shock. Despite the administration of high dose catecholamine vasopressor, all patients were hypotensive with a mean arterial pressure less than 70 mmHg. AVP therapy increased MAP from 53.3+/-7.4 to 82.0+/-12.0 mmHg at 1 hour (p <0.001) and decreased other vasopressor requirements from 25+/-7 to 18+/-6 at 1 hour (p <0.001) and individually maintained it for 12 hours. CONCLUSION: Our date suggest that AVP may be a safe and an effective vasopressor in patients with vasodilatory shock. In patients exhibiting vasodilatory shock after heart surgery, replacement of AVP increases blood pressure and reduces catecholamine vasopressor requirements.

Arginine Vasopressin Therapy of Vasodilatory Shock after Cardiopulmonary Bypass : Two cases / 대한흉부외과학회지

Vasodilatory shock has been implicated in life-threatening complications after cardiac surgery. This syndrome may result from the vasopressin deficiency following cardiopulmonary bypass (CPB), which do not respond to fluids or usual intravenous inotropes. We used arginine-vasopressin in adults with vasodilatory shock coming off cardiopulmonary bypass. Therefore, we report these cases with a review of articles.

Surgical Removal of Large Thrombus at the Suture Site of the Right Atriotomy after Atrial Septal Defect Closure Associated with Pulmonary Embolism: 1 case / 대한흉부외과학회지

Report of right atrial thrombus complicating pulmonary embolism after cardiac surgery is rare. A 54-year-old woman operated on the atrial septal defect 10 months ago was admitted for left pleuritic pain and dyspnea. Multiple segmental perfusion defects were detected in lung perfusion scan. Transesophageal echocardiography showed a large mobile right atrial mass attached to the free wall of the right atrium with a stalk. Despite the intravenous heparinization for 13 days, follow-up echocardiography revealed the right atrial mass had not diminished in size. The mass which was confirmed as an organizing thrombus was excised under cardiopulmonary bypass. The patient recovered uneventfully and was discharged on warfarin therapy.

Vasopressin in Young Patients with Congenital Heart Defects for Postoperative Vasodilatory Shock / 대한흉부외과학회지

BACKGROUND: Vasodilatory shock after cardiac surgery may result from the vasopressin deficiency following cardiopulmonary bypass and sepsis, which did not respond to usual intravenous inotropes. In contrast to the adult patients, the effectiveness of vasopressin for vasodilatory shock in children has not been known well and so we reviewed our experience of vasopressin therapy in the small babies with a cardiac disease. MATERIAL AND METHOD: Between February and August 2003, intravenous vasopressin was administrated in 6 patients for vasodilatory shock despite being supported on intravenous inotropes after cardiac surgery. Median age at operation was 25 days old (ranges; 2~41 days) and median body weight was 2,870 grams (ranges; 900~3,530 grams). Preoperative diagnoses were complete transposition of the great arteries in 2 patients, hypoplastic left heart syndrome in 1, Fallot type double-outlet right ventricle in 1, aortic coarctation with severe atrioventricular valve regurgitation in 1, and total anomalous pulmonary venous return in 1. Total repair and palliative repair were undertaken in each 3 patient. RESULT: Most patients showed vasodilatory shock not responding to the inotropes and required the vasopressin therapy within 24 hours after cardiac surgery and its readministration for septic shock. The dosing range for vasopressin was 0.0002~0.008 unit/kg/minute with a median total time of its administration of 59 hours (ranges; 26~140 hours). Systolic blood pressure before, 1 hour, and 6 hours after its administration were 42.7+/-7.4 mmHg, 53.7+/-11.4 mmHg, and 56.3+/-13.4 mmHg, respectively, which shows a significant increase in systolic blood pressure (systolic pressure 1hour and 6 hours after the administration compared to before the administration; p=0.042 in all). Inotropic indexes before, 6 hour, and 12 hours after its administration were 32.3+/-7.2, 21.0+/-8.4, and 21.2+/-8.9, respectively, which reveals a significant decrease in inotropic index (inotropic indexes 6 hour and 12 hours after the administration compared to before the administration; p=0.027 in all). Significant metabolic acidosis and decreased urine output related to systemic hypoperfusion were not found after vasopressin administration. CONCLUSION: In young children suffering from vasodilatory shock not responding to common inotropes despite normal ventricular contractility, intravenous vasopressin reveals to be an effective vasoconstrictor to increase systolic blood pressure and to mitigate the complications related to higher doses of inotropes.

Epicardial Microwave Ablation of Atrial Fibrillation / 대한흉부외과학회지

Even though the Cox-Maze III procedure is the gold standard in the therapy for atrial fibrillation (AF) and its outcome is excellent, the complexity of the operation, longer cardiopulmonary bypass time and the risk of bleeding have tended to dissuade cardiac surgeons from its application. The recent data of the pathogenesis of AF and the development of alternative energy sources have facilitated the development of the modified Cox-Maze procedure rapidly. We reported that atrial fibrillation was conversed to sinus rhythm by the epicardial microwave ablation without cardiopulmonary bypass and the normal sinus rhythm was observed during 33 months of follow-up period.