Real-time intra-fraction-motion tracking using the treatment couch: a feasibility study

Significant differences between planned and delivered treatments may occur due to respiration-induced tumour motion, leading to underdosing of parts of the tumour and overdosing of parts of the surrounding critical structures. Existing methods proposed to counter tumour motion include breath-holds, gating and MLC-based tracking. Breath-holds and gating techniques increase treatment time considerably, whereas MLC-based tracking is limited to two dimensions. We present an alternative solution in which a robotic couch moves in real time in response to organ motion. To demonstrate proof-of-principle, we constructed a miniature adaptive couch model consisting of two movable platforms that simulate tumour motion and couch motion, respectively. These platforms were connected via an electronic feedback loop so that the bottom platform responded to the motion of the top platform. We tested our model with a seven-field step-and-shoot delivery case in which we performed three film-based experiments: (1) static geometry, (2) phantom-only motion and (3) phantom motion with simulated couch motion. Our measurements demonstrate that the miniature couch was able to compensate for phantom motion to the extent that the dose distributions were practically indistinguishable from those in static geometry. Motivated by this initial success, we investigated a real-time couch compensation system consisting of a stereoscopic infra-red camera system interfaced to a robotic couch known as the Hexapod, which responds in real time to any change in position detected by the cameras. Optical reflectors placed on a solid water phantom were used as surrogates for motion. We tested the effectiveness of couch-based motion compensation for fixed fields and a dynamic arc delivery cases. Due to hardware limitations, we performed film-based experiments (1), (2) and (3), with the robotic couch at a phantom motion period and dose rate of 16 s and 100 MU min(-1), respectively. Analysis of film measurements showed near-equivalent dose distributions (相似文献   

Long-term follow-up in children with functional hemispherectomy for Rasmussen’s encephalitis

Introduction Cerebral hemispherectomy has been performed for over 60 years. Multiple variations of functional hemispherectomy have been performed since its inception by Rasmussen. Long-term follow-up for these variations is lacking in the medical literature.Methods We review the long-term follow-up for five children with Rasmussens encephalitis who underwent a modification of functional hemispherectomy.Results The length of follow-up for this cohort ranged from 13 to 23 years (mean 15.6 years). All patients experienced immediate and complete elimination of seizures. Only one patient underwent ventriculoperitoneal shunt placement. All patients are capable of ambulating on their own. Many years following their procedures, this cohort of patients remains seizure free.     

Low failure rate of fixed administered activity of 400 MBq 131I with pre-treatment with carbimazole for thyrotoxicosis: the Gateshead Protocol

BACKGROUND: Thyrotoxicosis is associated with significant morbidity, therefore adequate control of the disease is paramount. The outcome of treatment of thyrotoxicosis using radioiodine shows variable failure rates depending, amongst other things, on the administered activity of radioiodine and the use of anti-thyroid drugs. Thus, management should follow an evidence based protocol, which has a low failure rate. METHOD: We prospectively analysed the outcome of treatment using our Gateshead protocol of a fixed administered activity of radioiodine therapy (400 MBq) given to 201 patients (including 140 with Graves' disease, 48 with toxic multinodular goitre (TMNG) and 13 with toxic nodule) followed up for a median period of 12 months (range, 6-77 months). Carbimazole was discontinued in patients rendered euthyroid 16 days prior to radioiodine. No routine anti-thyroid drugs or thyroxine were given following radioiodine unless hypothyroidism or thyrotoxicosis occurred. RESULTS: Following the Gateshead protocol led to a failure rate of 6.5% (eight females with Graves' disease, four females with TMNG and one female with toxic nodule), 29% euthyroidism and 64% hypothyroidism. The rates of hypothyroidism for women and for men were: in Graves' disease 77% and 79%, in TMNG 29% and 75%, in toxic nodule 42% and 0%, respectively. CONCLUSIONS: Our observations show that withholding an antithyroid drug in excess of just over 2 weeks prior to administering a fixed administered activity of radioiodine in patients with thyrotoxicosis leads to the lowest reported failure rate, irrespective of the underlying cause. One possible mechanism for this could be the avoidance of drug induced radio-resistance.     

Port catheter placement by nephrologists in an interventional nephrology training program

We retrospectively reviewed all subcutaneous single- and double-lumen port catheters (PCs) inserted by interventional nephrologists at our institution to determine the success rate, immediate and late complications, and functional life. From January 2000 to August 2002, 187 PCs were placed in 187 patients (42% males, 51% Caucasians, mean age 50 +/- 14 years). There were no immediate complications related to the procedure such as hemorrhage, pulmonary embolism, or pneumothorax. There were a total of 35,078 catheter-days of follow-up. Sixteen catheters were removed during the observation period: three because of infection, seven after completion of chemotherapy, and six for other reasons. The remaining PCs are either functioning or the patients have died. The initial success rate was 100%. Kaplan-Meier analysis showed a 30-day survival of 97% and a 1-year survival of 92%. Interventional nephrologists, who have adequate training in central venous tunneled cuffed catheter placements, can successfully place PCs, with excellent success and minimal complications.     

A closer look at food allergy and intolerance

Food allergy is a condition prevalent in over 2 percent of the world's population. The topic has been subject to research from ancient Greek times and continues to attract modern scientific and medical communities. In susceptible individuals certain foods produce a wide spectrum of unwanted effects like eczema, asthma, and urticaria. The management of food allergy and intolerance chiefly involves elimination diets, accurate diagnosis and detecting the causative mechanism providing us with ample food for thought. In this article, we have attempted to summarize and simplify the research on the various aspects of food allergy and intolerance, and discuss the natural history, manifestations, mechanisms, diagnosis, and management of this condition affecting countless worldwide.     

Cardiac arrhythmia as presentation of snakebite

Snakebite cases may have myriad presentations. we are describing a previously healthy young man presenting within half an hour of snakebite who experienced abrupt fatal cardiac rhythm changes ranging from bradycardia to ventricular tachycardia/fibrillation over a short span of time.     

Acute dissection of the thoracic aorta

Aortic dissection is an acute medical emergency with a high mortality. Crucial to improving survival is early recognition and appropriate treatment. This review describes the presenting clinical features and imaging techniques used in the diagnosis of aortic dissection and outlines the treatment modalities.