Overview of commercial treatment planning systems for targeted radionuclide therapy

IntroductionTargeted Radionuclide Therapy (TRT) is a branch of cancer medicine dealing with the therapeutic use of radioisotopes associated with biological vectors accumulating in the tumors/targets, indicated as Molecular Radiotherapy (MRT), or directly injected into the arteries that supply blood to liver tumour vasculature, indicated as Selective RT (SRT). The aim of this work is to offer a panoramic view on the increasing number of commercially-available TRT treatment planning systems (TPSs).Materials and methodsA questionnaire was sent to manufacturers' representatives. Academic software were not considered. Questions were grouped as follows: general information, clinical workflow, calibration procedure, image processing/reconstruction, image registration and segmentation tools, time-activity curve (TAC) fitting and absorbed dose calculation.ResultsAll software reported have CE-marking. TPSs were divided between SRT-dedicated software [4] and MRT [5] dosimetry software. In SRT, since no kinetic process is involved, absorbed dose calculation does not require TAC fitting, and image registration is not fully developed in all TPS. All software requires a radionuclide-specific calibration. In SRT, a relative image calibration can be obtained by scaling the counts to a known activity. Automated VOI contouring and rigid/deformable propagation between different acquisitions time-points is implemented in most TPSs, although DICOM export is rare. Different TAC fits are available depending on the number of time-points. Voxel S-value and Local deposition methods are the most frequent dosimetric approaches; dose-voxel kernel convolution and semi-Monte Carlo method are also available.ConclusionsAvailable TPSs allows performing personalized dosimetry in clinical practice. Individual variations in methodology/algorithms must be considered in the standardisation/harmonization processes.     

A role for magnetic susceptibility in synthetic computed tomography

PurposeRadiotherapy treatment planning based on magnetic resonance imaging (MRI) benefits from increased soft-tissue contrast and functional imaging. MRI-only planning is attractive but limited by the lack of electron density information required for dose calculation, and the difficulty to differentiate air and bone. MRI can map magnetic susceptibility to separate bone from air. A method is introduced to produce synthetic CT (sCT) through automatic voxel-wise assignment of CT numbers from an MRI dataset processed that includes magnetic susceptibility mapping.MethodsVolumetric multi-echo gradient echo datasets were acquired in the heads of five healthy volunteers and fourteen patients with cancer using a 3 T MRI system. An algorithm for CT synthesis was designed using the volunteer data, based on fuzzy c-means clustering and adaptive thresholding of the MR data (magnitude, fat, water, and magnetic susceptibility). Susceptibility mapping was performed using a modified version of the iterative phase replacement algorithm. On patient data, the algorithm was assessed by direct comparison to X-ray computed tomography (CT) scans.ResultsThe skull, spine, teeth, and major sinuses were clearly distinguished in all sCT, from healthy volunteers and patients. The mean absolute CT number error between X-ray CT and sCT in patients ranged from 78 and 134 HU.ConclusionSusceptibility mapping using MRI can differentiate air and bone for CT synthesis. The proposed method is automated, fast, and based on a commercially available MRI pulse sequence. The method avoids registration errors and does not rely on a priori information, making it suitable for nonstandard anatomy.     

VMAT-like plans for magnetic resonance guided radiotherapy: Addressing unmet needs

PurposeVMAT delivery technique is currently not applicable to Magnetic Resonance-guided radiotherapy (MRgRT) hybrid systems. Aim of this study is to evaluate an innovative VMAT-like (VML) delivery technique.Material and methodsFirst, planning and dosimetric evaluation of the MRgRT VML treatment have been performed on 10 different disease sites and the results have been compared with the corresponding IMRT plans. Then, in the second phase, 10 of the most dosimetrically challenging locally advanced pancreas treatment plans have been retrospectively re-planned using the VML approach to explore the potentiality of this new delivery technique. Finally, VML robustness was evaluated and compared with the IMRT plans, considering a lateral positioning error of ± 5 mm.ResultsIn phase one, all VML plans were within constraint for all OARs. When PTV coverage is considered, in the 50% of the cases VML PTV coverage is equal or higher than in IMRT plan. In the remaining 50%, the highest target under coverage difference in comparison with IMRT plan is −1.71%. The mean and maximum treatment time differences (VML-IMRT) is 0.2 min and 3.1 min respectively. In phase two, the treatment time variation (VML-IMRT), shows a mean, maximum and minimum variations of 1.3, 4.6 and −0.6 min respectively. All VML plans have a better target coverage if compared with IMRT plans, keeping in any case the OARs constraints within tolerance. VML doesn’t increase plan robustness.ConclusionVMAT-like treatment approach appeared to be an efficient planning solution and it was decided to clinically implement it in daily practice, especially in the frame of hypo fractionated treatments.     

Dose calculation accuracy in proximity of a pacemaker: A multicenter study with threecommercial treatment planning systems

This study compares Treatment Planning System (TPS) out of field dose calculation on a pacemaker (PMK) during external beam radiotherapy treatment. We consider four TPSs (Elekta-Monaco, Oncentra- Masterplan and two Philips-Pinnacle3) commissioned for two linacs (Elekta Sinergy and Varian Clinac) delivering two test beams (a highly modulated one and a square field) and two clinical breast plans. To calculate and measure dose to a PMK we built a Real Water3 phantom with a PMK embedded in it. Measures are performed with thermo-luminescent dosimeters and Mosfet dosimeters. We evaluate differences between TPS calculated values for the dose to the PMK (both point dose and dose-volume histogram parameters) when the PMK is positioned in the first 10 cm outside the radiation fields. TPS calculation accuracy is evaluated comparing such values with measures. Differences in TPS calculations are on average 3.5 cGy Gy^-1 for the modulated beam, and always lower than 2 cGy Gy^-1 for the square beam. TPS dose calculation depends mostly on the TPS algorithm and model rather than the linac commissioned. TPSs considered show different degrees of calculation accuracy. In the first 4 cm to the field edge three out of four TPSs are in good agreement with measurements in the square beam, but only one keeps the agreement in the modulated beam: the others show over and underestimations up to +20% −40%. The same accuracy is found considering a homogeneous phantom. Our results confirm what reported in previous studies and highlight the impact of TPS commissioning.     

An international survey of imaging practices in radiotherapy

Improvements in delivery of radiation dose to target tissues in radiotherapy have increased the need for better image quality and led to a higher frequency of imaging patients. Imaging for treatment planning extends to function and motion assessment and devices are incorporated into medical linear accelerators (linacs) so that regions of tissue can be imaged at time of treatment delivery to ensure dose distributions are delivered as accurately as possible. A survey of imaging in 97 radiotherapy centres in nine countries on six continents has been undertaken with an on-line questionnaire administered through the International Commission on Radiological Protection mentorship programme to provide a snapshot of imaging practices. Responses show that all centres use CT for planning treatments and many utilise additional information from magnetic resonance imaging and positron emission tomography scans. Most centres have kV cone beam CT attached to at least some linacs and use this for the majority of treatment fractions. The imaging options available declined with the human development index (HDI) of the country, and the frequency of imaging during treatment depended more on country than treatment site with countries having lower HDIs imaging less frequently. The country with the lowest HDI had few kV imaging facilities and relied on MV planar imaging intermittently during treatment. Imaging protocols supplied by vendors are used in most centres and under half adapt exposure conditions to individual patients. Recording of patient doses, a knowledge of which is important in optimisation of imaging protocols, was limited primarily to European countries.     

A cost-effective technique for cardiac sparing with deep inspiration-breath hold (DIBH)

Deep inspiration breath hold (DIBH) is an effective technique to reduce cardiac and pulmonary dose during breast radiotherapy (RT). However, as a result of expense and the technical challenges of program implementation, DIBH has not been widely adopted in clinical practice.This report describes a program for DIBH this is relatively inexpensive to implement and has little impact on patient throughput. Multiple redundant mechanisms are incorporated to assure accurate and safe delivery of RT during DIBH. Laser alignment verifies that chest wall excursion is reliably reproduced and maintained during treatment. Chest wall excursion is also monitored independently using an infrared camera trained on a reflective marker on the chest wall. This system automatically triggers “beam off” in the event of movement of the target beyond pre-determined thresholds. Finally, physician review of cine imaging obtained during treatment provides an off-line verification of accurate RT delivery. The approach described herein lowers the investment necessary for implementation of DIBH and may facilitate broader adoption of this valuable technique.     

Apport du 68Ga-PSMA-TEP dans la prise en charge initiale par radiothérapie des cancers de la prostate

Radiotherapy is one of major modality for prostate cancer treatment. Technical improvements allow to deliver higher doses to the tumor, and improve protection of healthy tissues. Those improvements are enlarging indications and change treatment modalities for prostate cancer patients, on primary staging or at time of relapse (local or metastatic). Accounting to recent publications, 68Ga-PSMA PET should have an impact on radiotherapy treatment planning for those patients, especially in case of intermediate to high risk tumor. In case of metastatic disease, early detection of metastasis allows selection of patients with oligo-metastatic cancer for whom local treatments are in development. For localized prostate cancer, diagnosis of nodal extension permit volumes and doses modifications for radiotherapy. An accurate detection of the dominant intra-prostatic lesion gives the possibility of a focalized dose escalation to this significant cancer (“index lesions”). This new treatment strategies coming from technical progress are currently evaluated to assess their clinical benefit.     

脑转移瘤局部推量的临床观察

目的:观察脑转移瘤放射治疗局部推量的疗效。方法:回顾性分析63例进行放射治疗脑转移瘤病人,采用6MeV-X线,两侧平行相对野作全脑照射,临床靶体积(CTV)包括肿瘤靶体积(GTV)及周围水肿区,处方剂量为30~40Gy,分割次数为10~20次。其中27例缩野后局部推量20Gy。分析常规处方剂量后进行局部推量与未进行局部推量的两个组别局部区域复发率(LRR)、总生存率(OS)和KPS评分改变的差别。结果:中位随访6个月。局部推量组和未局部推量组的LRR分别为18.5%(5/27)和27.8%(10/36);局部推量组和未局部推量组的OS分别为85.2%(23/27)和77.8%(28/36);局部推量组和未局部推量组的KPS>=70分别为18和19。结论:脑转移瘤常规处方剂量放疗后进行局部推量对脑转移瘤的局部控制率及KPS评分有益。     

免疫学技术在棘球蚴病临床免疫诊断中的应用

免疫学方法是人体包虫病重要的辅助诊断方法,是手术前确诊和临床治疗后随访的重要指标。近些年来,随着免疫学、分子生物学等生物技术的发展,为包虫感染的试验诊断提供更多的方法和信息。本文主要通过对皮内实验、抗原的检查、抗体的检查、免疫复合物的检查以及DNA的检查的逐个分析,探讨目前临床上对棘球蚴病的免疫学诊断方法研究进展。     

The effect of lymphadenectomy and radiotherapy on recurrence and survival in endometrial carcinoma. Experience in a population reference centre

Aim

To evaluate the effect of lymphadenectomy and/or radiotherapy on recurrence and survival patterns in endometrial carcinoma (EC) in a radiotherapy reference centre population.

Material and Methods

A retrospective population-based review was conducted on 261 patients with stages I–III EC. Univariate and multivariate analyses were carried out. Both recurrence and survival were analysed according to patient age, FIGO stage, tumour size, myometrial invasion, tumour grade, lymphadenectomy, external beam irradiation (EBI), and brachytherapy (BT).

Results

Median age: 64.8 years. Median follow-up: 151 months. The following treatments were administered: surgery, 97.32%; lymph-node dissection, 54.4%; radiotherapy, 162 patients (62%) (EBI and BT: 64.1%, BT alone: 30.2%, EBI alone: 5.6%).Twenty-six patients (9.96%) suffered loco-regional recurrence, whilst 27 (10.34%) suffered distant failure. The 5-year overall survival (OS) for all stages was 80.1%. The 5-year disease free survival (DFS) was 92.1% for all patients. The 10-year DFS was 89.9%.The independent significant prognostic factors for a good outcome identified through the multivariate analysis were: age <75 years (p = 0.001); tumour size ≤2 cm (p = 0.003); myometrial invasion ≤50% (p = 0.011); lymphadenectomy (p = 0.02); EBI (p = 0.001); and BT (p = 0.031).Toxicity occurred in 114 of the 162 patients who received radiotherapy (70.5%). The toxicity was mainly acute, and late in only 28.3% (n = 45) of cases. The majority experienced G1-2 toxicity, and only 3% of patients experienced G3 late toxicity (5/162).

Conclusions

Our results suggest that age <75 years, tumour size ≤2 cm, myometrial invasion ≤50%, lymphadenectomy, EBI, and BT, are predictors of a good outcome in EC.