RESUMEN
MR-guided high-dose-rate (HDR) brachytherapy has gained increasing interest as a treatment for patients with localized prostate cancer because of the superior value of MRI for tumor and surrounding tissues localization. To enable needle insertion into the prostate with the patient in the MR bore, a single needle MR-compatible robotic system involving needle-by-needle dose delivery has been developed at our institution. Throughout the intervention, dose delivery may be impaired by: (1) sub-optimal needle positioning caused by e.g. needle bending, (2) intra-operative internal organ motion such as prostate rotations or swelling, or intra-procedural rectum or bladder filling. This may result in failure to reach clinical constraints. To assess the first aforementioned challenge, a recent study from our research group demonstrated that the deposited dose may be greatly improved by real-time adaptive planning with feedback on the actual needle positioning. However, the needle insertion sequence is left to the doctor and therefore, this may result in sub-optimal dose delivery. In this manuscript, a new method is proposed to determine and update automatically the needle insertion sequence. This strategy is based on the determination of the most sensitive needle track. The sensitivity of a needle track is defined as its impact on the dose distribution in case of sub-optimal positioning. A stochastic criterion is thus presented to determine each needle track sensitivity based on needle insertion simulations. To assess the proposed sequencing strategy, HDR prostate brachytherapy was simulated on 11 patients with varying number of needle insertions. Sub-optimal needle positioning was simulated at each insertion (modeled by typical random angulation errors). In 91% of the scenarios, the dose distribution improved when the needle was inserted into the most compared to the least sensitive needle track. The computation time for sequencing was less than 6 s per needle track. The proposed needle insertion sequencing can therefore assist in delivering an optimal dose in HDR prostate brachytherapy.
Asunto(s)
Braquiterapia/instrumentación , Imagen por Resonancia Magnética , Agujas , Neoplasias de la Próstata/radioterapia , Dosis de Radiación , Radioterapia Guiada por Imagen/instrumentación , Procedimientos Quirúrgicos Robotizados/instrumentación , Humanos , Masculino , Posicionamiento del Paciente , Neoplasias de la Próstata/diagnóstico por imagen , Dosificación Radioterapéutica , Factores de TiempoRESUMEN
PURPOSE: To describe the principles and report on the performance of a novel real-time electromagnetic (EM) seed drop detection technology for permanent implants brachytherapy procedures. METHODS: A novel EM hollow needle prototype was recently developed by Philips. It possesses standard 3D tracking capability as well as a seed drop detection mechanism, both performed from a single custom built EM sensor. The detection mechanism is based on the magnetic permeability changes in the sensor as the seeds pass through. Drop position estimates are generated by the tracking information at the dropping instants. Three validation experiments were carried out in this study. First, the robustness of the detection mechanism was tested in free air with four different seed types. Detection waveforms were measured and commented. The accuracy of the seed drop position estimates was then evaluated using both 2D and 3D experiments. The procedures consisted of dropping seeds in phantoms, recording the drop position estimates, and finally registering the resulting spatial distributions on reference ones obtained by accurate modalities. Seeds were dropped on a specially designed plastic support adapted to brachytherapy template dimensions for 2D experiments, and true seed positions (reference distribution) were obtained by optical detection. In 3D experiments, seeds were dropped in edible gelatin and reference distributions were obtained by localizing the implants from CT scans of the phantoms. RESULTS: All four seed types were correctly detected by the needle prototype. In total, 250 seeds were dropped on the plastic support, and 96 were dropped in gelatin phantoms. The detection rate was 100% in both cases. The minimum, maximum, and average drop position errors were, respectively, 0.1(+1.6/ - 0.1), 2.9(+1.4/ - 1.5), and 0.9(+1.4/ - 0.7) mm for 2D, and 0.1(+1.0/ - 0.1), 2.1(+1.1/ - 0.8), and 0.6(+1.2/ - 0.5) mm for 3D experiments. CONCLUSIONS: The hollow needle prototype combines both EM tracking and automatic seed drop detection in a compact and convenient form. The EM detection mechanism is robust, and the seed drop position estimates appear sufficiently accurate for potential integration of the technology to current brachytherapy treatment planning systems. In that context, it would serve as a valuable tool for rapid dosimetry validation in real-time treatment delivery.
Asunto(s)
Braquiterapia/métodos , Fenómenos Electromagnéticos , Prótesis e Implantes , Humanos , Imagenología Tridimensional , Permeabilidad , Fantasmas de Imagen , Factores de TiempoRESUMEN
The development of magnetic resonance (MR) guided high dose rate (HDR) brachytherapy for prostate cancer has gained increasing interest for delivering a high tumor dose safely in a single fraction. To support needle placement in the limited workspace inside the closed-bore MRI, a single-needle MR-compatible robot is currently under development at the University Medical Center Utrecht (UMCU). This robotic device taps the needle in a divergent way from a single rotation point into the prostate. With this setup, it is warranted to deliver the irradiation dose by successive insertions of the needle. Although robot-assisted needle placement is expected to be more accurate than manual template-guided insertion, needle positioning errors may occur and are likely to modify the pre-planned dose distribution.In this paper, we propose a dose plan adaptation strategy for HDR prostate brachytherapy with feedback on the needle position: a dose plan is made at the beginning of the interventional procedure and updated after each needle insertion in order to compensate for possible needle positioning errors. The introduced procedure can be used with the single needle MR-compatible robot developed at the UMCU. The proposed feedback strategy was tested by simulating complete HDR procedures with and without feedback on eight patients with different numbers of needle insertions (varying from 4 to 12). In of the cases tested, the number of clinically acceptable plans obtained at the end of the procedure was larger with feedback compared to the situation without feedback. Furthermore, the computation time of the feedback between each insertion was below 100 s which makes it eligible for intra-operative use.
Asunto(s)
Braquiterapia/métodos , Neoplasias de la Próstata/radioterapia , Errores de Configuración en Radioterapia/prevención & control , Radioterapia Guiada por Imagen/métodos , Braquiterapia/efectos adversos , Humanos , Imagen por Resonancia Magnética , Masculino , Agujas/efectos adversos , Posicionamiento del Paciente , Dosificación Radioterapéutica , Radioterapia Guiada por Imagen/efectos adversosRESUMEN
Focal high-dose-rate (HDR) for prostate cancer has gained increasing interest as an alternative to whole gland therapy as it may contribute to the reduction of treatment related toxicity. For focal treatment, optimal needle guidance and placement is warranted. This can be achieved under MR guidance. However, MR-guided needle placement is currently not possible due to space restrictions in the closed MR bore. To overcome this problem, a MR-compatible, single-divergent needle-implant robotic device is under development at the University Medical Centre, Utrecht: placed between the legs of the patient inside the MR bore, this robot will tap the needle in a divergent pattern from a single rotation point into the tissue. This rotation point is just beneath the perineal skin to have access to the focal prostate tumor lesion. Currently, there is no treatment planning system commercially available which allows optimization of the dose distribution with such needle arrangement. The aim of this work is to develop an automatic inverse dose planning optimization tool for focal HDR prostate brachytherapy with needle insertions in a divergent configuration. A complete optimizer workflow is proposed which includes the determination of (1) the position of the center of rotation, (2) the needle angulations and (3) the dwell times. Unlike most currently used optimizers, no prior selection or adjustment of input parameters such as minimum or maximum dose or weight coefficients for treatment region and organs at risk is required. To test this optimizer, a planning study was performed on ten patients (treatment volumes ranged from 8.5 cm(3)to 23.3 cm(3)) by using 2-14 needle insertions. The total computation time of the optimizer workflow was below 20 min and a clinically acceptable plan was reached on average using only four needle insertions.
Asunto(s)
Braquiterapia/instrumentación , Braquiterapia/normas , Agujas/normas , Neoplasias de la Próstata/radioterapia , Radioterapia Guiada por Imagen/métodos , Automatización , Fraccionamiento de la Dosis de Radiación , Humanos , Imagen por Resonancia Magnética , MasculinoRESUMEN
Conventional quantitative assessments of myocardial perfusion analyze the temporal relation between the arterial input function and the myocardial signal intensity curves, thereby neglecting the important spatial relation between the myocardial signal intensity curves. The new method presented in this article enables characterization of sub-endocardial to sub-epicardial gradients in myocardial perfusion based on a two dimensional, "gradientogram" representation, which displays the evolution of the transmural gradient in myocardial contrast uptake over time in all circumferential positions of the acquired images. Moreover, based on segmentation in these gradientograms, several new measurements that characterize transmural myocardial perfusion distribution over time are defined. In application to clinical image data, the new two-dimensional representations, as well as the newly defined measurements revealed a clear distinction between normal perfusion and inducible ischaemia. Thus, the new measurements may serve as diagnostic markers for the detection and characterization of epicardial coronary and microvascular disease.
Asunto(s)
Circulación Coronaria/fisiología , Imagen por Resonancia Magnética/métodos , Medios de Contraste/metabolismo , Humanos , Perfusión , Pericardio/fisiologíaRESUMEN
BACKGROUND: Fructooligosaccharides have been claimed to lower fasting glycemia and serum total cholesterol concentrations, possibly via effects of short-chain fatty acids produced during fermentation. OBJECTIVE: We studied the effects of fructooligosaccharides on blood glucose, serum lipids, and serum acetate in 20 patients with type 2 diabetes. DESIGN: In a randomized, single-blind, crossover design, patients consumed either glucose as a placebo (4 g/d) or fructooligosaccharides (15 g/d) for 20 d each. Average daily intakes of energy, macronutrients, and dietary fiber were similar with both treatments. RESULTS: Compliance, expressed as the proportion of supplements not returned, was near 100% during both treatments. Fructooligosaccharides did not significantly affect fasting concentrations (mmol/L) of serum total cholesterol (95% CI: -0.07, 0.48), HDL cholesterol (-0.04, 0.04), LDL cholesterol (-0.06, 0.34), serum triacylglycerols (-0.21, 0.44), serum free fatty acids (-0.08, 0.04), serum acetate (-0.01, 0.01), or blood glucose (-0.37, 0.40). CONCLUSIONS: We conclude that 20 d of dietary supplementation with fructooligosaccharides had no major effect on blood glucose, serum lipids, or serum acetate in patients with type 2 diabetes. This lack of effect was not due to changes in dietary intake, insufficient statistical power, or noncompliance of the patients.