Dosimetric impact of switching from AAA to Acuros dose-to-water and dose-to-medium for RapidArc plans of nasopharyngeal carcinomas.

PURPOSE: This work aims to evaluate the dosimetric consequences of replacing the Anisotropic Analytical Algorithm (AAA) by Acuros XB (AXB), dose-to-water (Dw) or dose-to-medium (Dm), for RapidArc plans of nasopharyngeal carcinomas (NPC). MATERIALS AND METHODS: Seventeen NPC plans created with AAA (v15.6) were recalculated with AXB (v15.6) Dw and Dm. The dose-volume parameters to the planning target volumes (PTV) and relevant organs at risk (OAR) were compared. The high dose PTV was divided into bone, air and tissue components and the comparison was performed for each of them. RESULTS: AXB Dw revealed no significant differences in the PTVs compared to AAA. Lower values were observed to spinal cord, brainstem, oral cavity and parotids (0.5% to 2.3%), and higher values to cochleas (up to 5.4%) and mandible (up to 6.7%). AXB Dm predicted lower values than AAA for all PTVs and OARs (2.0% to 6.1%). For the bone PTV subvolume, AXB Dw and Dm predicted respectively higher (2.4%) and lower (2.2% to 3.4%) values. No significant differences were noted in air. AXB predicted lower values than AAA in soft tissues (0.4% to 1.6%). The largest difference was found to the mandible V60Gy parameter, with median differences of 6.7% for AXB Dw and -6.0% for AXB Dm. CONCLUSION: Significant dose differences are expected when switching from AAA to AXB in NPC cases. The dose prescriptions and the tolerance limits for some OARs, especially those of high density, may need to be adjusted depending on the selected dose calculation algorithm and reporting mode.

Collision prediction for intracranial stereotactic radiosurgery planning: An easy-to-implement analytical solution.

PURPOSE: Gantry collision is a concern in linac-based stereotactic radiosurgery (SRS). Without collision screening, the planner may compromise optimal planning, unnecessary re-planning delays can occur, and incomplete treatments may be delivered. To address these concerns, we developed a software for collision prediction based on simple machine measurements. MATERIALS AND METHODS: Three types of collision were identified; gantry-couch mount, gantry-couch and gantry-patient. Trigonometric formulas to calculate the distance from each potential point of collision to the gantry rotation axis were generated. For each point, collision occurs when that distance is greater than the gantry head to gantry rotational axis distance. The colliding arc for each point is calculated. A computer code incorporating these formulas was generated. The inputs required are the couch coordinates relative to the isocenter, the patient dimensions, and the presence or absence of a circular SRS collimator. The software outputs the collision-free gantry angles, and for each point, the shortest distance to the gantry or the colliding sector when collision is identified. The software was tested for accuracy on a TrueBEAM® machine equipped with BrainLab® accessories for 80 virtual isocenter-couch angle configurations with and without a circular collimator and a parallelepiped phantom. RESULTS: The software predicted the absence of collision for 19 configurations. The mean absolute error between the measured and predicted gantry angle of collision for the remaining 61 cases was 0.86 (0.01-2.49). CONCLUSION: This tool accurately predicted collisions for linac-based intracranial SRS and is easy to implement in any radiotherapy facility.

[Early breast cancer without axillary lymph node involvement]. / Cancer du sein sans atteinte ganglionnaire axillaire.

Breast cancer is the most common cancer in women. In France, breast cancer incidence was 88.9 per 100,000 women in 2000. Early detection of breast tumours by screening mammography allows a breast conserving treatment, i.e., breast irradiation preceded by a lumpectomy and a sentinel node biopsy. The standard irradiation of early breast cancers consists in delivering 50 Gy to the whole breast in 2 Gy fractions over a five-week period followed by an additional dose targeting the tumour bed of 16 Gy in eight fractions. The 3D-conformal treatment planning optimizes dose distribution to the whole breast and to the tumour bed and lessens the normal tissue irradiation (heart and ipsilateral lung). The aim of this article is to describe epidemiologic, radio anatomic and prognostic features of early stage breast cancer and to propose guidelines for 3D-conformal treatment planning in early breast cancers. This review is illustrated by a case report.

[Breast cancer with axillary lymph node involvement]. / Cancer du sein avec atteinte ganglionnaire axillaire.

Breast cancer is the most frequent cancer of women in western countries. There are one million new cases per year in the world which represents 22% of all female cancers, and more than 370,000 deaths due to breast cancer per year (14% of cancer mortality). More than half of breast cancers are associated with axillary nodal involvement. Post-operative radiation therapy (XRT) is a crucial part of locoregional treatment in axillary nodal involvement breast cancer owing to a 15-years risk reduction of locoregional recurrence of 70% and to a 5.4% risk reduction of specific mortality. In 3D-conformal irradiation in such breast cancers, target volumes are chest wall when mastectomy was performed or breast and boost of tumor bed in case of breast conservative surgery, and supra-clavicular and/or axillary and/or internal mammary node areas. The main organs at risk are ipsilateral lung, heart and brachial plexus. The aim of this article is to describe epidemiologic, radio anatomic and prognostic features of axillary nodal involvement breast cancer and to propose guidelines for 3D-conformal treatment planning in locally advanced breast cancers. This review is illustrated by a case report.

[Role of radiotherapy in heterotopic ossification]. / Rôle de la radiothérapie dans l'ossification hétérotopique.

PURPOSE: To evaluate the use of radiation therapy for the prevention of heterotopic ossification. PATIENTS AND METHODS: Twenty-two patients, 20 to 76 years old were irradiated for the prevention of heterotopic ossification. All patients received a postoperative irradiation consisting of 700 cGy delivered by 18 MV photons using a linear accelerator. The delay between surgery and irradiation was 24 hours for 20 patients, 48 hours for three patients, 72 hours for two patients and 96 hours for one patient. The follow-up of all patients was based on radiologic findings (Brooker score) as well as the clinical status of the articulation before and after surgery. Of the 14 cases for which follow-up data was available, seven received primary prophylaxis and seven received secondary prophylaxis. RESULTS: Heterotopic ossification prophylaxis using radiation therapy was radiologically successful in 71.5% of patients: 85.7% success for patients receiving primary prophylaxis and 57.1% success for patients receiving secondary prophylaxis. No functional failure was reported. No patient developed radiation related side effects. CONCLUSION: Radiation therapy is proven to be effective in preventing heterotopic ossification. A larger study group is needed in order to compare our results with those seen in the literature.

Off-pump reoperative coronary artery bypass grafting by thoracotomy: patient selection and operative technique.

BACKGROUND: Reoperative coronary artery bypass grafting (CABG) in patients with contraindications to sternotomy or cardiopulmonary bypass (CPB) presents a technical challenge. In this study we reviewed patient selection, operative technique, and early results in patients having redo-CABG to the circumflex artery system by a thoracotomy without CPB. METHODS: From January 1996 through December 1999, 21 patients with contraindications to conventional redo-CABG had target vessel revascularization off-pump by thoracotomy. A posterolateral thoracotomy approach was used. RESULTS: No patient required sternotomy or CPB. There was no hospital mortality. Postoperative cardiac morbidity included non-Q wave myocardial infarction (5%), need for intraaortic balloon pump support postoperatively (5%), and atrial fibrillation (5%). Two grafts were studied early and two were studied late (more than 6 months later). One venous graft was found to be occluded early. Survival at 2 years was 95%. Ninety percent of surviving patients were in New York Heart Association functional class I or II. CONCLUSIONS: This approach was associated with no mortality, low morbidity, and favorable early symptomatic improvement. This is the approach of choice in cases of reoperative CABG to the circumflex system when resternotomy or CPB are undesirable, and the culprit coronary vessels are accessible through a thoracotomy.

Interposition vein graft for giant coronary aneurysm repair.

Coronary aneurysms in adults are rare. Surgical treatment is often concomitant to treating obstructing coronary lesions. However, the ideal treatment strategy is poorly defined. We present a case of successful treatment of a large coronary artery aneurysm with a reverse saphenous interposition vein graft. This modality offers important benefits over other current surgical and percutaneous techniques and should be considered as an option for patients requiring treatment for coronary aneurysms.