Toward 3D-TRUS image-guided interstitial brachytherapy for cervical cancer

PURPOSETo qualitatively and quantitatively analyze needle visibility in combined intracavitary and interstitial cervical cancer brachytherapy on 3D transrectal ultrasound (TRUS) in comparison to gold standard MRI.METHODS AND MATERIALSImage acquisition was done with a customized TRUS stepper unit and software (Medcom, Germany; Elekta, Sweden; ACMIT, Austria) followed by an MRI on the same day with the applicator in place. Qualitative assessment was done with following scoring system: 0 = no visibility 1 (= poor), 2 (= fair), 3 (= excellent) discrimination, quantitative assessment was done by measuring the distance between each needle and the tandem two centimeters (cm) above the ring and comparing to the respective measurement on MRI.RESULTSTwenty-nine implants and a total of 188 needles (132 straight, 35 oblique, 21 free-hand) were available. Overall, 79% were visible (87% straight, 51% oblique, 76% free-hand). Mean visibility score was 1.4 ± 0.5 for all visible needles. Distance of the visible needles to tandem was mean ± standard deviation (SD) 21.3 millimeters (mm) ± 6.5 mm on MRI and 21.0 mm ± 6.4 mm on TRUS, respectively. Difference between MRI and TRUS was max 14 mm, mean ± SD -0.3 mm ± 2.6 mm. 11% differed more than 3 mm.CONCLUSIONSStraight needles were better detectable than oblique needles (87% vs. 51%). Detectability was impaired by insufficient rotation of the TRUS probe, poor image quality or anatomic variation. As needles show a rather indistinct signal on TRUS, online detection with a standardized imaging protocol in combination with tracking should be investigated, aiming at the development of real time image guidance and online treatment planning.     

Custom 3D-printed applicators for high dose-rate brachytherapy in skin cancer

PURPOSEThis paper describes the protocol for the development of 3D-printed custom applicators in treating skin carcinoma, the evaluation of the materials used, and the methods for segmentation and rendering of the applicators.MATERIAL AND METHODSThe segmentation and rendering process for the applicator had six phases: (i) determination of the volume of the lesion using a computed tomography (CT) scan; (ii) delineation of the patient surface, using the same CT images; (iii) creation of the applicator in the planner and segmentation of the mold; (iv) preliminary dosimetry and establishment of the route of the catheter from the brachytherapy unit; (v) creation of the 3D applicator using specialized software; and (vi) applicator printing. Following this process, the patient returned for a second CT to undergo the definitive dosimetry with the applicator in place. Radiation therapy was then administered.RESULTSWe made a total of 16 applicators. Only three applicators had to be remade, two due to an error in the infill and the other due to incorrect catheter geometry. In all cases, correct coverage of the planning target volume was achieved with the prescribed isodose.CONCLUSIONSThe creation of custom molds in plesiotherapy for skin cancer with 3D printing is feasible. Compared to manual methods, 3D printing increases precision in applicator geometry and optimization of the dosimetry.     

Individualized 3D-printed templates for high-dose-rate interstitial multicathether brachytherapy in patients with breast cancer

Purpose

High-dose-rate, multicatheter interstitial brachytherapy is technically complex and operator-dependent, requiring lengthy training and specialized skills. Furthermore, until the advent of contouring on computerized tomography (CT) images, difficulties existed in locating the target volume precisely. The present article reports the results of a study that aimed at producing and validating a 3D-printed template to aid in target volume localization for multicatheter interstitial brachytherapy in patients with breast cancer.

Evaluation and evolution of apparent diffusion coefficient (ADC) in image-guided adaptive brachytherapy (IGABT) for cervical cancer

PURPOSEImage-guided adaptive brachytherapy (IGABT) recently has shown excellent clinical outcomes with superior local control and less toxicity. For IGABT, T2W (T2-weighted) MRI is the gold standard. However, studies have shown that target delineation with the same results in uncertainties, poor interobserver variabilities, and low conformity indices for high-risk clinical target volume contours. In this study, we investigate the role of diffusion-weighted imaging–derived apparent diffusion coefficient (ADC) maps to aid in IGABT. We also evaluated ADC from the baseline to brachytherapy.Methods and MaterialsThirty selected patients were enrolled for this study, and two MRIs were taken at diagnosis and before brachytherapy. Patients were divided into two groups, Group 1 being patients with parametrial involvement before external beam radiotherapy and no parametrial involvement before brachytherapy. Group 2 included patients with parametrial involvement before external beam radiotherapy and persistent parametrial involvement before brachytherapy. ADC was measured at the center, edge, and 1 cm from the edge.ResultsThe measured ADC increased from diagnosis to brachytherapy, and this increase was more for the patients in Group 1 than in Group 2. The mean TDadc (diagnosis ADC, center), TEadc (tumor edge ADC diagnosis), and T1cmDadc (1 cm from edge at diagnosis) were 0.884, 1.45, and 1.9 × 10^?3 mm²/s, respectively. The TBadc (ADC at brachytherapy, center), TEBadc (tumor edge ADC at brachytherapy), and TE1cmBadc (1 cm from edge brachytherapy) were 1.2, 1.8, and 2.3 × 10^?3 mm²/s, respectively, p-value <0.00001. No abnormal ADC was present outside the high-risk clinical target volume contours.ConclusionMRI-based IGABT using T2W imaging essentially covers all functionally abnormal zones at brachytherapy. Diffusion-weighted imaging, along with ADC maps, should only be used as a supplement for target delineation.     

Gastric phantom for training beginners in gastric segment (Stomap) recognition

It is usually difficult for a beginner to understand precisely and quickly the three-dimensional (3D) construction of gastric lesions in a gastric X-ray examination with barium meal. In this study, a training-use stomach phantom was developed using the stomach segment to provide beginners with an understanding of 3D stomach construction. The hook-shaped phantom (the shape of the stomach when a patient is in the supine position) was formed by using styrene, wire, and clay. It was then coated with dental stiffening agent, and wires were attached along the stomach segment. After drying, the stomach phantom was cut off and the oil clay was removed. The phantom then was immersed in water and the oil clay was dried. After that, the phantom again was glued together with a dental stiffening agent. The usefulness of the phantom was determined by an evaluation experiment. Ten students, as observers, were selected randomly for evaluation from 40 students of the Department of Radiological Technology, College of Medical Technology, Hokkaido University. Eight films were shown to the observers, 4 films with segment and 4 films without segment. The observers checked 5 markers in different positions of the phantom and recorded the results on an answer sheet with segment picture. The significance of position recognition was identified by Wilcoxon's sign rank sum test (p=0.021) between the segment film and non-segment film.     

A novel end-to-end test for combined dosimetric and geometric treatment verification using a 3D-printed phantom

The dosimetric and geometric accuracy are important components to ensure safe patient treatment in radiation therapy. Therefore, these components must be checked during quality control. This work presents a possible solution for the determination of the geometric isocenter deviation in the entire treatment chain. Additionally, the dose measurement of the established end-to-end test workflow measured in the same procedure as the geometric deviation is described. An in-house designed end-to-end test phantom went through the entire procedure of a standard patient treatment and the dosimetric and geometric accuracy were determined. At 3 linear accelerators (linac), the phantom was positioned either with cone beam computed tomography or with surface guidance. In this position, a Winston-Lutz test was performed and the deviations of the gantry, collimator and couch isocenter measurements to the phantom position were determined. Additionally, a dose measurement in the phantom was performed and compared to the dose predicted in the treatment planning system. To validate the results obtained with the in-house designed phantom, comparative measurements with commercial phantoms were performed. According to the performed end-to-end test, 2 out of the 3 linacs showed isocenter variations larger than 1 mm for collimator and gantry rotations and larger than 2 mm for couch rotations. With an isocenter variation of less than 1 mm for collimator and gantry rotations, 1 linac fulfilled the tolerance for stereotactic treatments without couch rotation. With couch rotation, an isocenter variation of less than 2 mm was detected at this linac, which fulfilled the tolerance for IMRT treatments. The mean dose deviation between measurement and treatment planning system was 1.82% ± 1.03%. The results acquired with the UMM phantom did not show statistically significant deviations to those acquired with relevant other commercial phantoms. The novel end-to-end test procedure allows for a combined dosimetric and geometric treatment evaluation. Besides the commonly performed dose end-to-end test the geometric isocenter deviation within a patient treatment workflow was evaluated and categorized for IMRT or SBRT.     

Presurgical Functional Magnetic Resonance Imaging (fMRI)

Abstract Preoperative functional magnetic resonance imaging (fMRI) permits noninvasive measurement, localization and lateralization of important functions of the human brain in patients with brain tumors, facilitating selection of the least harmful treatment and surgery which preserves function. Preoperative fMRI of motor and language function can be performed when reliably proven clinical imaging protocols are used. Standardization of the respective imaging procedures is essential to the diagnostic use of fMRI. However, fMRI cannot be considered a fully established method of diagnostic neuroimaging due to a lack of recommendations or guidelines from the relevant medical associations, and also the lack of medical licensing of important hardware and software components. This article reviews current research in the field and provides the reader with the practical information necessary to perform presurgical fMRI.      

Study of susceptibility-weighted imaging (SWI) using a simple MR phantom

We evaluated the visibility of hypointensity regions on susceptibility-weighted (SW) magnetic resonance imaging (MRI). A commercial simple phantom filled uniformly with a gel material was demonstrated to include small regions affected by different magnetic susceptibilities compared to their surroundings. For detection of these regions in the phantom, the three-dimensional SW imaging (SWI) technique is superior to a conventional two-dimensional gradient-recalled-echo (GRE) MRI technique. The mean contrast between the hypointensity regions and their surroundings on GRE images (T2* weighted images) of 4 mm slice thickness is approximately 88% less than that on SWI of 4 mm effective slice thickness. When the effective slice thickness of SWI is increased more than 4 mm, the contrast on SW images is decreased. While the mean contrast on SWI of 7 mm effective slice thickness is approximately 75-65% compared to that of 4 mm effective slice thickness, its contrast of 7 mm is determined to be higher than that on GRE images of 4 mm slice thickness; this suggests that the SWI technique could be applied to whole brain examination by reducing the acquisition time. The quantitative results in this article are considered to be useful for evaluating the visibility of hypointensity regions on SWI, when comparing them with GRE images and varying the effective slice thickness of SWI.     

The British Association of Magnetic Resonance Radiographers (BAMRR)

The British Association of Magnetic Resonance Radiographers (BAMRR) has been in existence for about 15 years and was formed to promote the professional development of radiographers and other professionals within the speciality of MRI, through encouraging and developing educational forums and conferences and facilitating the exchange of information for its members.This article describes the structure of the association together with its mission statement, aims and achievements and ongoing educational activities.     

原发性扩张型心肌病的MRI诊断(初步报告)

本文分析4例原发性扩张型心肌病(DCM)MRI所见,并讨论有关诊断和鉴别诊断问题。心脏尤其左心室普遍扩张,容积显著增加,肌壁不厚为其主要征象。因左室横径增加大于长径,心腔多呈球形。室壁运动普遍减弱或消失,射血分数及短轴缩短率明显下降。上述MRI所见可反映DCM的主要病理及病理生理改变,对本病的诊断具有重要意义。     

3D TOF turbo MR angiography for intracranial arteries: phantom and clinical studies

This work investigated whether turbo magnetic resonance angiography (MRA) can replace conventional MRA in screening examination of intracranial arteries. A phantom was used to evaluate the effect of the zero-filling interpolation (ZFI) technique on spatial resolution and partial volume effect. Thirty-one consecutive patients underwent both turbo MRA with a slice thickness of 0.7 mm (data were measured as 1.33 mm sections) and conventional MRA with 1.0 mm sections. In the phantom studies, ZFI did not improve the spatial resolution, but the partial volume effect was somewhat reduced. In the clinical evaluation, turbo MRA showed better signal-to-noise and contrast-to-noise ratios of the intracranial major vessels than conventional MRA. The lesions included cerebral aneurysms less than 3 mm in diameter, occlusive vascular disease, arteriovenous malformations, and arteriovenous fistulas. These were all depicted on both turbo MRA and conventional MRA. Turbo MRA is a useful screening procedure because of its capability of delineating lesions in approximately half the usual imaging time. J. Magn. Reson. Imaging 1999;10:939-944.     

Magnetic resonance (MR) imaging of the normal mediastinum

Magnetic Resonance (MR) cross sectional images of the normal mediastinum are presented and discussed. In normal subjects most mediastinal structures visible on Computed Tomography (CT) are also visible using MR. The primary advantages of MR over CT in the evaluation of mediastinum are the greater soft tissues contrast resolution, the multiplanar (axial, coronal and sagittal) display of the mediastinal anatomy and its ability to distinguish vascular from nonvascular structures without injection of contrast media.