Voxel-based statistical analysis and quantification of amyloid PET in the Japanese Alzheimer's disease neuroimaging initiative (J-ADNI) multi-center study.

Background: Amyloid PET plays a vital role in detecting the accumulation of in vivo amyloid-β (Aβ). The quantification of Aβ accumulation has been widely performed using the region of interest (ROI)-based mean cortical standardized uptake value ratio (mcSUVR). However, voxel-based statistical analysis has not been well studied.

Effects of different fat-suppression methods on T1 values in dynamic contrast-enhanced magnetic resonance imaging: a phantom study.

Dynamic contrast-enhanced MRI may yield variable longitudinal-relaxation time (T1) values depending on the precision of the fat-suppression (FS) technique. This study aimed to investigate the influences of FS methods on T1 value measurements on phantoms containing test tubes filled with mixtures of five volumes of fat, six amounts of contrast agent, and water. Volumetric interpolated images were obtained using several FS methods and flip angles.

Temporal subtraction of computed tomography images improves detectability of bone metastases by radiology residents.

Objective: Temporal subtraction of CT (TS) images improves detection of newly developed bone metastases (BM). We sought to determine whether TS improves detection of BM by radiology residents as well.

Methods: We performed an observer study using a previously reported dataset, consisting of 60 oncology patients, each with previous and current CT images.

CT temporal subtraction improves early detection of bone metastases compared to SPECT.

Objectives: To compare observer performance of detecting bone metastases between bone scintigraphy, including planar scan and single-photon emission computed tomography, and computed tomography (CT) temporal subtraction (TS).

Methods: Data on 60 patients with cancer who had undergone CT (previous and current) and bone scintigraphy were collected. Previous CT images were registered to the current ones by large deformation diffeomorphic metric mapping; the registered previous images were subtracted from the current ones to produce TS.

[Development of Novel Immobilization Adapter for Head and Neck Radiotherapy with Low-attenuation Material].

Purpose: The dosimetric error due to immobilization devices has been highlighted by the AAPM Task Group 176. We developed a novel low-radiation-absorbent immobilization adaptor (HMA), which can be used with a Styrofoam headrest for head and neck region in radiotherapy. The purpose of this study was to investigate the impact of the HMA on the dose distribution and compare with a commercially released plastic adapter.

Optimal beam quality for chest flat panel detector system: realistic phantom study.

Objective: To investigate optimal beam quality for chest flat panel detector (FPD) system by semi-quantitatively assessment using a realistic lung phantom.

Materials And Methods: Chest FPD radiographs were obtained on a realistic lung phantom with simulated lung opacities using various X-ray tube voltage levels (90-140 kV) with/without copper filter. Entrance skin dose was set to maintain identical for all images (0.

[Usefulness of the Principle of Selective Excitation Technique Non-electrocardiogramgated 3D-TOF Method in Lower-extremity MRA Using a Whole-body Coil].

Purpose: Generally, non-contrast, lower-extremity, magnetic resonance angiography (MRA) uses electrocardiography; thus, examination is difficult in patients who exhibit arrhythmia. However, the use of electrocardiography can be avoided by using the selective excitation technique in non-electrocardiogram-gated three-dimensional time-of-flight (TOF) (pNon-Gate) MRA. Therefore, patients who exhibit arrhythmia can be examined with pNon-Gate MRA.

Automatic inference model construction for computer-aided diagnosis of lung nodule: Explanation adequacy, inference accuracy, and experts' knowledge.

We aimed to describe the development of an inference model for computer-aided diagnosis of lung nodules that could provide valid reasoning for any inferences, thereby improving the interpretability and performance of the system. An automatic construction method was used that considered explanation adequacy and inference accuracy. In addition, we evaluated the usefulness of prior experts' (radiologists') knowledge while constructing the models.

Sub-solid nodule detectability in seven observers of seventy-nine clinical cases: comparison between ultra-low-dose chest digital tomosynthesis with iterative reconstruction and chest radiography by receiver-operating characteristics analysis.

Purpose: To compare sub-solid nodules detectability (SSND) between ultra-low-dose chest digital tomosynthesis (ULD-CDT) with/without iterative reconstruction (IR) and chest radiography (CR) by using low-dose computed tomography (LDCT) as the standard of reference (SOR).

Materials And Methods: Institutional Review Board approved this study and written informed consent was obtained. In a single visit, 79 subjects underwent ULD-CDT at 120 kV and 10 mA, CR and LDCT (effective dose: 0.

Detection of suspected brain infarctions on CT can be significantly improved with temporal subtraction images.

Objective: To assess whether temporal subtraction (TS) images of brain CT improve the detection of suspected brain infarctions.

Methods: Study protocols were approved by our institutional review board, and informed consent was waived because of the retrospective nature of this study. Forty-two sets of brain CT images of 41 patients, each consisting of a pair of brain CT images scanned at two time points (previous and current) between January 2011 and November 2016, were collected for an observer performance study.

Temporal Subtraction of Serial CT Images with Large Deformation Diffeomorphic Metric Mapping in the Identification of Bone Metastases.

Purpose To determine the improvement of radiologist efficiency and performance in the detection of bone metastases at serial follow-up computed tomography (CT) by using a temporal subtraction (TS) technique based on an advanced nonrigid image registration algorithm. Materials and Methods This retrospective study was approved by the institutional review board, and informed consent was waived. CT image pairs (previous and current scans of the torso) in 60 patients with cancer (primary lesion location: prostate, n = 14; breast, n = 16; lung, n = 20; liver, n = 10) were included.

Automated prediction of emphysema visual score using homology-based quantification of low-attenuation lung region.

Objective: The purpose of this study was to investigate the relationship between visual score of emphysema and homology-based emphysema quantification (HEQ) and evaluate whether visual score was accurately predicted by machine learning and HEQ.

Materials And Methods: A total of 115 anonymized computed tomography images from 39 patients were obtained from a public database. Emphysema quantification of these images was performed by measuring the percentage of low-attenuation lung area (LAA%).

A study of computer-aided diagnosis for pulmonary nodule: comparison between classification accuracies using calculated image features and imaging findings annotated by radiologists.

Purpose: In our previous study, we developed a computer-aided diagnosis (CADx) system using imaging findings annotated by radiologists. The system, however, requires radiologists to input many imaging findings. In order to reduce such an interaction of radiologists, we further developed a CADx system using derived imaging findings based on calculated image features, in which the system only requires few user operations.

Development of a four-dimensional Monte Carlo dose calculation system for real-time tumor-tracking irradiation with a gimbaled X-ray head.

Purpose: To develop a four-dimensional (4D) dose calculation system for real-time tumor tracking (RTTT) irradiation by the Vero4DRT.

Methods: First, a 6-MV photon beam delivered by the Vero4DRT was simulated using EGSnrc. A moving phantom position was directly measured by a laser displacement gauge.

A phantom study for ground-glass nodule detectability using chest digital tomosynthesis with iterative reconstruction algorithm by ten observers: association with radiation dose and nodular characteristics.

Objective: To compare detectability of simulated ground-glass nodules (GGNs) on chest digital tomosynthesis (CDT) among 12 images obtained at 6 radiation doses using 2 reconstruction algorithms and to analyze its association with nodular size and density.

Methods: 74 simulated GGNs [5, 8 and 10 mm in diameter/-630 and -800 Hounsfield units (HU) in density] were placed in a chest phantom in 14 nodular distribution patterns. 12 sets of coronal images were obtained using CDT at 6 radiation doses: 120 kV-10 mA/20 mA/80 mA/160 mA, 100 kV-80 mA and 80 kV-320 mA with and without iterative reconstruction (IR).

Report of a nationwide survey on actual administered radioactivities of radiopharmaceuticals for diagnostic reference levels in Japan.

Objective: The optimization of medical exposure is one of the major issues regarding radiation protection in the world, and The International Committee of Radiological Protection and the International Atomic Energy Agency recommend establishing diagnostic reference levels (DRLs) as tools for dose optimization. Therefore, the development of DRLs based on the latest survey has been required for nuclear medicine-related societies and organizations. This prompted us to conduct a nationwide survey on the actual administered radioactivity to adults for the purpose of developing DRLs in nuclear medicine.

Image quality and variability for routine diagnostic FDG-PET scans in a Japanese community hospital: current status and possibility of improvement.

Purpose: In Japan, commercially delivered FDG is manufactured in three batches per day at fixed constant activity and distributed in vials. Consequently, the amount of activity administered to the patient varies depending on the timing of injection. We evaluated a method for adjusting the scan time according to the body mass index (BMI) to obtain equivalent image quality for every patient.

The essence of the Japan Radiological Society/Japanese College of Radiology Imaging Guideline.

Diagnostic imaging is undoubtedly important in modern medicine, and final clinical decisions are often made based on it. Fortunately, Japan has the highest numbers of diagnostic imaging instruments, such as CT and MRI devices, and boasts easy access to them as well as a high level of diagnostic accuracy. In consequence, a very large number of imaging examinations are performed, but diagnostic instruments are installed in so many medical facilities that expert management of these examinations tends to be insufficient.

Safety management of nuclear medicine personnel with visualisation of air dose rate.

Many people are anxious about radiation exposure for the reason that radiation cannot be seen. With the aim of devising a way for medical personnel to perform their medical duties without worry about radiation exposure, we attempted safety management using a system that displays the air dose of radiation in real time. Measurements were made in a lung ventilation scintigraphy examination room with the use of Xe-133.

The reproducibility of time-of-flight PET and conventional PET for the quantification of myocardial blood flow and coronary flow reserve with (13)N-ammonia.

Background: This study aimed to validate the reproducibility of quantitative analysis using time-of-flight (TOF) and conventional PET with (13)N-ammonia ((13)N-NH3).

Methods And Results: Phantom images were reconstructed with and without TOF, and recovery coefficients (RCs) and the percent contrast of each sphere over the percent background variability were assessed. In the clinical study, 21 subjects underwent dynamic (13)N-NH3 PET scanning under stress and rest conditions.

[Optimal beam quality for chest digital radiography].

To investigate the optimal beam quality for chest computed radiography (CR), we measured the radiographic contrast and evaluated the image quality of chest CR using various X-ray tube voltages. The contrast between lung and rib or heart increased on CR images obtained by lowering the tube voltage from 140 to 60 kV, but the degree of increase was less. Scattered radiation was reduced on CR images with a lower tube voltage.

Development of an expanded-field irradiation technique using a gimbaled x-ray head.

Purpose: The Vero4DRT has a maximum field size of 150.0 × 150.0 mm.

Evaluation of dynamic tumour tracking radiotherapy with real-time monitoring for lung tumours using a gimbal mounted linac.

Purpose: To evaluate feasibility and acute toxicities after dynamic tumour tracking (DTT) irradiation with real-time monitoring for lung tumours using a gimbal mounted linac.

Materials And Methods: Spherical gold markers were placed around the tumour using a bronchoscope prior to treatment planning. Prescription dose at the isocentre was 56 Gy in 4 fractions for T2a lung cancer and metastatic tumour, and 48 Gy in 4 fractions for the others.

Performance Evaluation of a New Dedicated Breast PET Scanner Using NEMA NU4-2008 Standards.

Unlabelled: The aim of this work was to evaluate the performance characteristics of a newly developed dedicated breast PET scanner, according to National Electrical Manufacturers Association (NEMA) NU 4-2008 standards.

Methods: The dedicated breast PET scanner consists of 4 layers of a 32 × 32 lutetium oxyorthosilicate-based crystal array, a light guide, and a 64-channel position-sensitive photomultiplier tube. The size of a crystal element is 1.

Intrafractional tracking accuracy in infrared marker-based hybrid dynamic tumour-tracking irradiation with a gimballed linac.

Purpose: To verify the intrafractional tracking accuracy in infrared (IR) marker-based hybrid dynamic tumour tracking irradiation ("IR Tracking") with the Vero4DRT.

Materials And Methods: The gimballed X-ray head tracks a moving target by predicting its future position from displacements of IR markers in real-time. Ten lung cancer patients who underwent IR Tracking were enrolled.