MR elastography of prostate cancer: quantitative comparison with histopathology and repeatability of methods

The purpose of this work was to assess trans‐perineal prostate magnetic resonance elastography (MRE) for (1) repeatability in phantoms/volunteers and (2) diagnostic power as correlated with histopathology in prostate cancer patients. The three‐dimensional (3D) displacement field was obtained using a fractionally encoded gradient echo sequence using a custom‐made transducer. The repeatability of the method was assessed based on three repeat studies and by changing the driving frequency by 3% in studies on a phantom and six healthy volunteers. Subsequently, 11 patients were examined with MRE prior to radical prostatectomy. The areas under the receiver operating characteristic curves were calculated using a windowed voxel‐to‐voxel approach by comparing the 2D registered slides, masked with the Gleason score. For the repeatability study, the average intraclass correlation coefficient for elasticity images was 99% for repeat phantom studies, 98% for ±6 Hz phantom studies, 95% for volunteer repeat studies with 2 min acquisition time, 82% for ±2 Hz volunteer studies with 2 min acquisition time and 73% for repeat volunteer studies with 8 min acquisition time. For the patient study, the average elasticity was 8.2 ± 1.7 kPa in the prostate capsule, 7.5 ± 1.9 kPa in the peripheral zone (PZ), 9.7 ± 3.0 kPa in the central gland (CG) and 9.0 ± 3.4 kPa in the transition zone. In the patient study, cancerous tissue with Gleason score at least 3 + 3 was significantly (p < 0.05) different from normal tissue in 10 out of 11 cases with tumors in the PZ, and 6 out of 9 cases with tumors in the CG. However, the overall case‐averaged area under the curve was 0.72 in the PZ and 0.67 in the CG. Cancerous tissue was not always stiffer than normal tissue. The inversion algorithm was sensitive to (i) vibration amplitude and displacement nodes and (ii) misalignment of the 3D wave field due to subject movement. Copyright © 2014 John Wiley & Sons, Ltd.     

A Coin-Like Peripheral Small Cell Lung Carcinoma Associated with Acute Paraneoplastic Axonal Guillain-Barre-Like Syndrome

A 65-year-old previously healthy male heavy smoker was hospitalized with a 2-week history of progressive muscle weakness in the lower and upper extremities. After 10 days of hospitalization, urinary sphincter incompetence and fecal incontinence were added and tetraparesis was established. The computer-tomography scan examination revealed a massive right hydrothorax and multifocal solid acinar structures with peripheral localization in the left lung, which suggested pulmonary cancer. Bone marrow metastases were also suspected. Based on the examination results, the final diagnosis was acute paraneoplastic axonal Guillain-Barre-like syndrome. The patient died 3 weeks after hospitalization. At autopsy, bronchopneumonia and a right hydrothorax were confirmed. Several 4 to 5-mm-sized round peripherally located white nodules were identified in the left lung, without any central tumor mass. Under microscope, a coin-shaped peripheral/subpleural small cell carcinoma was diagnosed, with generalized bone metastases. A huge thrombus in the abdominal aorta and acute pancreatitis was also seen at autopsy. This case highlights the difficulty of diagnosis of lung carcinomas and the necessity of a complex differential diagnosis of severe progressive ascending neuropathies. This is the 6th reported case of small cell lung cancer-associated acute Guillain-Barre-like syndrome and the first report about an association with a coin-like peripheral pattern.     

Prostate MR elastography with transperineal electromagnetic actuation and a fast fractionally encoded steady‐state gradient echo sequence

Our aim is to develop a clinically viable, fast‐acquisition, prostate MR elastography (MRE) system with transperineal excitation. We developed a new actively shielded electromagnetic transducer, designed to enable quick deployment and positioning within the scanner. The shielding of the transducer was optimized using simulations. We also employed a new rapid pulse sequence that encodes the three‐dimensional displacement field in the prostate gland using a fractionally encoded steady‐state gradient echo sequence, thereby shortening the acquisition time to a clinically acceptable 8–10 min. The methods were tested in two phantoms and seven human subjects (six volunteers and one patient with prostate cancer). The MRE acquisition time for 24 slices, with an isotropic resolution of 2 mm and eight phase offsets, was 8 min, and the total scan, including positioning and set‐up, was performed in 15–20 min. The phantom study demonstrated that the transducer does not interfere with the acquisition process and that it generates displacement amplitudes that exceed 100 µm even at frequencies as high as 300 Hz. In the in vivo human study, average wave amplitudes of 30 µm (46 µm at the apex) were routinely achieved within the prostate gland at 70 Hz. No pain or discomfort was reported. Results in a single patient suggest that MRE can identify cancer tumors, although this result is preliminary. The proposed methods allow the integration of prostate MRE with other multiparametric MRI methods. The results of this study clearly motivate the clinical evaluation of transperineal MRE in patients. Copyright © 2014 John Wiley & Sons, Ltd.     

Modeling and simulation of flexible needles

Needle insertion is performed in many clinical and therapeutic procedures. Tissue displacement and needle bending which result from needle–tissue interaction make accurate targeting difficult. For performing physicians to gain essential needle targeting skills, needle insertion simulators can be used for training. An accurate needle bending model is essential for such simulators. These bending models are also needed for needle path planning.In this paper, three different models are presented to simulate the deformations of a needle. The first two models use the finite element method and take the geometric nonlinearity into account. The third model is a series of rigid bars connected by angular springs. The models were compared to recorded deformations during experiments of applying lateral tip forces on a brachytherapy needle. The model parameters were identified and the simulation results were compared to the experimental data. The results show that the angular spring model, which is computationally the most efficient model, is also the most accurate in modeling the bending of the brachytherapy needle.     

Semiautomatic segmentation for prostate brachytherapy: Dosimetric evaluation

PurposeTo demonstrate that manual prostate segmentation in transrectal ultrasound images can be replaced with semiautomatic segmentation.Methods and MaterialsSemiautomatic segmentation using a tapered ellipsoid model was applied to transrectal ultrasound images. Region-based volumetric evaluation was performed between original and physician-reviewed semiautomatic contours. For dosimetric assessment, treatment plans generated on semiautomatic contours were overlaid on physician-reviewed semiautomatic contours and dose parameters were computed. To establish a threshold for the acceptable amount of dosimetric degradation below which the adoption of semiautomatic planning is unacceptable, the range of variability in dosimetric quality attributed to manual variability was obtained and compared with that of semiautomatic contours.ResultsAn average volume error (1—Dice similarity coefficient) of less than 7% between semiautomatic and manual volumes (140 cases) was obtained. The difference between the mean V₁₀₀ of plans created for semiautomatic contours then overlaid on physician-reviewed semiautomatic contours and the original V₁₀₀ values, that is, before overlaying on the physician-reviewed contours (41 cases) was lower than 5%. An average total duration of 2–4 min, which includes algorithm initialization, 11.67 ± 3.57 s algorithm time, and contour modification is required per case. This algorithm is being used at the British Columbia Cancer Agency and to this date has been applied for the treatment of more than 600 patients.ConclusionsIn terms of volumetric and dosimetric accuracy, the proposed algorithm is a suitable replacement for manual segmentation in the context of our planning technique. The benefits are shorter segmentation times; greater consistency; less reliance on user experience; and smooth, symmetric contours.     

Bronchoscopy for bevacizumab-related hemoptysis

Bevacizumab is the first anti-angiogenic agent inhibiting vascular endothelial growth factor (VEGF) for treatment of patients suffering from cancer. Life-threatening hemoptysis is the most serious adverse effect of bevacizumab. The inhibition of VEGF is a possible mechanism involved in the destruction of normal lung tissue and subsequent hemoptysis. We report a case of bevacizumab-related hemoptysis and associated bronchoscopic findings that were successfully treated with rigid bronchoscopy and laser photocoagulation.     

Feasibility of Endobronchial Ultrasound-guided Transbronchial Needle Aspiration Cytology Specimens for Next Generation Sequencing in Non–small-cell Lung Cancer

Introduction

Next generation sequencing (NGS) testing of lung cancer is recommended by guidelines, and endobronchial ultrasound (EBUS)-guided transbronchial needle aspiration (TBNA) often provides the only material available for testing. Previous studies have demonstrated successful NGS testing on cell block samples obtained by EBUS; however, cytology smears provide a more reliable sample with better DNA quality for testing. In this study, we aimed to determine the success rate of OncoScreen (50 gene) and OncoPlus (1213 gene) panel NGS testing of cytology samples obtained by EBUS utilizing 22- and 25-gauge needles.