Dynamic arc radiosurgery and radiotherapy: commissioning and verification of dose distributions.

PURPOSE: Conformal stereotactic radiosurgery and radiotherapy using a linear accelerator and a micromultileaf collimator (mMLC) offer the possibility of irradiating irregularly shaped target volumes. Dynamic arc radiosurgery and radiotherapy, i.e., stereotactic radiation therapy combining a moving gantry with a dynamic mMLC, enable the radiation even of lesions with concave structures. METHODS AND MATERIALS: The dynamic arc method requires additional tools for quality assurance (QA) and three-dimensional verification at a high spatial resolution. A QA program was developed. Dose distributions of planning target volumes with concavities were investigated in polymer gel phantoms. The radiation-induced change of the relaxation rate R(2) was measured by magnetic resonance imaging. The distributions were compared with image processing tools. RESULTS: Using the therapy-planning software BrainSCAN 4.0 (and 4.1 beta) in combination with the mMLC m3, deviations between the planned and measured 90% isodoses of about 2 mm were registered in the isocenter plane. Three-dimensional verification was feasible in the range of accuracy achieved in planning and dose measurement. CONCLUSIONS: Dynamic arc radiosurgery and radiotherapy offer excellent conformation even for complicated planning target volumes with concavities. The dose distribution calculated with the treatment-planning software used can be accomplished with the available equipment. Patients can be treated by dynamic arc radiosurgery and radiotherapy.

Commissioning of a micro multi-leaf collimator and planning system for stereotactic radiosurgery.

PURPOSE: A computer controlled micro multi-leaf collimator, m3 mMLC, has been commissioned for conformal, fixed-field radiosurgery applications. Measurements were made to characterise the basic dosimetric properties of the m3, such as leaf transmission, leakage and beam penumbra. In addition, the geometric and dosimetric accuracy of the m3 was verified when used in conjunction with a BrainSCAN v3.5 stereotactic planning system. MATERIALS AND METHODS: The m3 was detachably mounted to a Varian Clinac 2100C accelerator delivering 6 MV X-rays. Leaf transmission, leakage, penumbra and multiple, conformal fixed field dose distributions were measured using calibrated film in solid water. Beam data were collected using a diamond detector in a scanning water tank and planned dose distributions were verified using LiF TLDs and film. A small, shaped phantom was also constructed to confirm field shaping accuracy using portal images. RESULTS: Mean transmission through the closed multi-leaves was 1.9 +/- 0.1% and leakage between leaves was 2.8 +/- 0.15%. Between opposing leaves abutting along the central beam-axis transmission was approximately 15 +/- 3%, but was reduced to a mean of 4.5 +/- 0.6% by moving the abutmen position 4.5 cm off-axis. Beam penumbrae were effectively constant as a function of increasing square field size and asymmetric fields and was seen to vary non-linearly when shaped to diagonal, straight edges. TMR, OAR and relative output beam data measurements of circular m3 fields were comparable to conventional, circular stereotactic collimators. Multiple, conformal field dose distributions were calculated with good spatial and dosimetric accuracy, with the planned 90% isodose curves agreeing with measurements to within 1-2 mm and to +/- 3% at isocentre. Portal films agreed with planned beams eye-view field shaping to within 1 mm. CONCLUSIONS: The m3 micro multi-leaf collimator is a stable, high precision field-shaping device suitable for small-field, radiosurgery applications. Dose distributions can be accurately calculated by a planning system using only a few beam data parameters.

Use of BANG polymer gel for dose measurements in a 68 MeV proton beam.

BANG polymer gel dosimetry using magnetic resonance imaging (MRI) was applied to an ophthalmologic 68 MeV proton beam. The object was to examine the use of BANG gel for the verification of proton fields in eye tumor therapy and to explore the applicability of polymer gel dosimetry in proton therapy under practical aspects. The gel phantoms were irradiated with monoenergetic and modulated proton beams. MRI analysis was carried out at clinical 1.5 and 3 T MR scanners. At constant LET, results show a linear relationship between spin-spin relaxation rates and dose. However, depth dose curves in BANG gel reveal a quenching of the Bragg maximum due to LET effects. The dose response of the gel for monoenergetic protons and spread-out depth dose distributions can be calculated based on ionization chamber measurements. Experiment and calculations show good agreement and indicate that BANG polymer gels might become a valuable tool in proton therapy quality assurance.

Successful treatment of a massive atenolol and nifedipine overdose with CVVHDF.

The aim of this paper was to describe a case of massive atenol and nifedipine poisoning, complicated by the co-existence of liver cirrhosis, where standard therapies (fluid replacement, vasopressors and inotropic agents, insulin, glucagon, calcium and bowel decontamination) were ineffective in restoring an adequate heart rate, blood pressure, renal and intestinal blood flow. This led to consequent anuric renal insufficiency and incipient multiple organ failure syndrome (MOFS). The patient recovered completely after Continuous Veno-Venous Hemo-Dia-Filtration (CVVHDF); this treatment removed atenolol from blood, with predicted clearance levels. The patient was a 45-year old female with a history of hypertension, liver cirrhosis, neurological and psychiatric disorders, with a massive atenolol (69.6 microg/mL) and nifedipine (63 ng/mL) overdose. CVVHDF at an ultrafiltration rate of 1 500 mL/h was started on day 1. From day 2 onwards, as the plasma atenolol concentration decreased, the blood pressure rose at a slow but constant rate. On day 5, there was restoration of an adequate blood pressure, which restored both renal and intestinal function, and also improved MOFS. The standard therapeutic approach was ineffective at eliminating both substances from the blood, and the clinical picture became worse due to incipient MOFS. CVVHDF was used in order to maintain the fluid and electrolyte balance and also to clear the beta blocker from the blood. The clearance kinetics of atenolol were consistent with the expected clearance values, on the basis of a CVVHDF ultrafiltration flow of 1 500 mL/h, which corresponds to a creatinine clearance of about 25 mL/min.

[Resuspension of erythrocyte concentrates: clinical examinations with human albumin and oxypolygelatine]. / Resuspension von Erythrozytenkonzentraten: Klinische Untersuchungen mit Humanalbumin und Oxypolygelatine.

The acid-base status of packed red cells and the influence of resuspension with human albumin, oxypolygelatine (Gelifundol), Human-serum and physiological saline were examined. It was found that the severe metabolic acidosis of packed red cells increased only slightly with storage time, while the resuspension exerted divergent effects: Human albumin and physiological saline increased the metabolic acidosis slightly, but significant. Humanserum and oxypolygelatine diminished it because of their bicarbonate content. The clinical significance especially in massive transfusion is discussed.

[Postoperative ventilation in non-intubated patients with iron lung versus conventional ventilation]. / Ventilazione postoperatoria con polmone d'acciaio in pazienti non intubati versus ventilazione convenzionale.

Postoperative ventilation using a steel lung is an alternative to conventional ventilation through an endotracheal cannula. Both methods were compared in two groups of patients undergoing major abdominal surgery. Group A was ventilated using a Servo Ventilator 900C, whereas group B was ventilated using a newly designed steel lung. The duration of ventilation using the steel lung and that of postoperative intubation were significantly shorter than those used in group A, in spite of a higher anesthesiological and surgical risk in patients in group B. pO2 was significantly increased during ventilation with the steel lung in comparison to conventional ventilation. An automatic classification of EEG activity was used to estimate depth of anesthesia. This showed a close correlation between clinical signs and anesthesiological levels. The spectroanalytical evaluation of ventilation curves allowed the early recognition of spontaneous breathing and determined tidal volumes using steel lung ventilation.

Visual disturbances representing occipital lobe epilepsy in patients with cerebral calcifications and coeliac disease: a case series.

Paroxysmal visual manifestations may represent epileptic seizures arising from the occipital lobe. In coeliac disease (CD) bilateral occipital calcifications and seizure semiology consistent with an occipital origin have been described, primarily in Mediterranean countries. By reporting three adult patients from an Australian outpatient clinic with visual disturbances, occipital cerebral calcifications, and CD, this study seeks to emphasise that CD should be considered even when patients of non-Mediterranean origin present with these symptoms. Seizure types included simple partial, complex-partial, and secondarily generalised seizures. The seizure semiology consisted of visual disturbances such as: blurred vision, loss of focus, seeing coloured dots, and brief stereotyped complex visual hallucinations like seeing unfamiliar faces or scenes. Symptoms of malabsorption were not always present. Neurological examination was unremarkable in two patients, impaired dexterity and mild hemiatrophy on the left was noted in one. Routine electroencephalography was unremarkable. In all cases, computed tomography demonstrated bilateral cortical calcification of the occipital-parietal regions. Magnetic resonance imaging showed no additional lesion. All patients had biopsy confirmed CD. Seizure control improved after treatment with gluten free diet and anticonvulsants. This report illustrates the association between seizures of occipital origin, cerebral calcifications, and CD even in patients not of Mediterranean origin.

[Idiopathic long QT-syndrome. Changes in the duration of the QTC during anesthesia with propofol]. / La sindrome idiopatica del QT lungo. Variazioni della durata del QTC durante anestesia con propofol.

A prolonged electrocardiographic QTc interval may be unsafe during general anesthesia; thus successful anesthetic management in patients affected by congenital long QT syndrome include avoidance of any event that increases sympathetic activity and drugs that prolong QT interval. Propofol seems to have less effect on the QTc interval than tiopentone in normal subjects. This report suggest that propofol administration and infusion in clinical doses in a patient with Jerwell Lange-Nielsen syndrome may be safe and without increase of duration of QTc interval. The most marked changes in HR and QTc followed tracheal intubation and awakening suggesting a specific effect of cathecolamines.

[Monitoring of cuff pressure in double-lumen endotracheal tubes during anesthesia for thoracic surgery]. / Il monitoraggio della pressione di cuffia in tubi endotracheali a doppio lume durante anestesia per chirurgia toracica.

It is well known that cuff overinflation in endotracheal tubes may cause serious damage to the tracheal mucosa. Cuff overinflation is also related to the diffusion of nitrous oxide across the cuff membrane, thus giving way to a progressive volume/pressure increase up to overcoming, critical capillaric perfusion pressure. The kinetics of hi-lo cuff-pressure in single-lumen endotracheal tubes during general anesthesia using nitrous oxide has been well documented. The authors have investigated the cuff-pressure modifications in 40 left double-lumen tubes (DLTs), monitoring the inflation pressure for both the endotracheal and endobronchial cuffs at the sealing of the airways and at different phases of the anesthetic procedures performed using nitrous oxide, in 40 male patients undergoing thoracic surgery. In ten of these case, special equipment was used in order to keep the cuff-pressures steady and at the lowest sealing level. The pressure shows the same trend in both cuffs but, depending on the medium calibre of the main left bronchus and the volume/pressure relations of the endobronchial cuffs, the pressure in the latter increases faster. The investigation was performed using an original equipment developed by the authors; such equipment is able not only to monitor the cuff-pressures, but also to maintain them at steady controlled levels (below 20 cm water seal), by means of counterregulating all the volume variations due either to anesthetic requirements, or to the diffusion of nitrous oxide.(ABSTRACT TRUNCATED AT 250 WORDS)