Kazuyoshi Nishino

The Usefulness of Three-Dimensional Angiography with a Flat Panel Detector of Direct Conversion Type in a Transcatheter Arterial Chemoembolization Procedure for Hepatocellular Carcinoma: Initial Experience

The purpose of this study was to assess the usefulness of a three-dimensional (3D) angiography system using a flat panel detector of direct conversion type in treatments with subsegmental transcatheter arterial chemoembolization (TACE) for hepatocellular carcinomas (HCCs). Thirty-six consecutive patients who underwent hepatic angiography were prospectively examined. First, two radiologists evaluated the degree of visualization of the peripheral branches of the hepatic arteries on 3D digital subtraction angiography (DSA). Then the radiologists evaluated the visualization of tumor staining and feeding arteries in 25 patients (30 HCCs) who underwent subsegmental TACE. The two radiologists who performed the TACE assessed whether the additional information provided by 3D DSA was useful for treatments. In 34 (94.4%) of 36 patients, the subsegmental branches of the hepatic arteries were sufficiently visualized. The feeding arteries of HCCs were sufficiently visualized in 28 (93%) of 30 HCCs, whereas tumor stains were sufficiently visualized in 18 (60%). Maximum intensity projection images were significantly superior to volume recording images for visualization of the tumor staining and feeding arteries of HCCs. In 27 (90%) of 30 HCCs, 3D DSA provided additional useful information for subsegmental TACE. The high-quality 3D DSA with flat panel detector angiography system provided a precise vascular road map, which was useful for performing subsegmental TACE .of HCCs.

A Cone-Beam Volume CT Using a 3D Angiography System with a Flat Panel Detector of Direct Conversion Type: Usefulness for Superselective Intra-arterial Chemotherapy for Head and Neck Tumors

BACKGROUND AND PURPOSE: The development of flat panel detectors (FPDs) has made cone-beam CT feasible for practical use in a clinical setting. Our purpose was to assess the usefulness of cone-beam CT using the FPD in conjunction with conventional digital subtraction angiography (DSA) for performing superselective intra-arterial chemotherapy for head and neck tumors. MATERIALS AND METHODS: Twenty-three consecutive patients (43 feeding arteries) were prospectively examined. All of the patients underwent intra-arterial rotational angiography using an FPD system, and the cone-beam CT was reconstructed from the volume dataset. Two radiologists evaluated the quality of the cone-beam CT and then evaluated whether the additional information provided by the cone-beam CT was useful for the interventional procedures. RESULTS: In 41 (95%) of 43 arteries, the extent of contrast material perfusion was sufficiently visualized on cone-beam CT. In 20 (47%) of 43 arteries, the DSA plus cone-beam CT was superior to the DSA alone regarding the precise understanding of vascular territory of each artery. This information was helpful for predicting the drug delivery for superselective intra-arterial chemotherapy, especially in deeply invasive tumors with multiple feeding arteries. CONCLUSION: In superselective intra-arterial chemotherapy for head and neck tumors, cone-beam CT with FPD provides useful additional information, which allows interventional radiologists to determine the feeders, as well as the dose of antitumor agent for each feeder.

Radiation dosimetry in digital breast tomosynthesis: Report of AAPM Tomosynthesis Subcommittee Task Group 223

The radiation dose involved in any medical imaging modality that uses ionizing radiation needs to be well understood by the medical physics and clinical community. This is especially true of screening modalities. Digital breast tomosynthesis (DBT) has recently been introduced into the clinic and is being used for screening for breast cancer in the general population. Therefore, it is important that the medical physics community have the required information to be able to understand, estimate, and communicate the radiation dose levels involved in breast tomosynthesis imaging. For this purpose, the American Association of Physicists in Medicine Task Group 223 on Dosimetry in Tomosynthesis Imaging has prepared this report that discusses dosimetry in breast imaging in general, and describes a methodology and provides the data necessary to estimate mean breast glandular dose from a tomosynthesis acquisition. In an effort to maximize familiarity with the procedures and data provided in this Report, the methodology to perform the dose estimation in DBT is based as much as possible on that used in mammography dose estimation.

Metal artifact reduction in tomosynthesis by metal extraction and ordered subset-expectation maximization (OS-EM) reconstruction

Tomosynthesis is a useful imaging tool for breast, lung, and orthopedic diagnostics. Compared with computed tomography (CT), fewer artifacts are caused by metal components (metal artifacts). This advantage makes tomosynthesis particularly useful for orthopedics. Implementing filtered back projection (FBP) with a modified kernel leads to an increase in the low-frequency components of reconstructed images and reduces metal artifacts in tomosynthesis. However, even using this reconstruction method, metal artifacts are present in the region very close to any piece of metal. Due to the modified kernel, the observation of fine structures is difficult. We developed a new reconstruction algorithm to provide fewer metal artifacts in tomosynthesis images than in conventional images without filtering. Our new algorithm consists of four steps: 1) automatically extracting metal components from projection images using a novel method that we developed; 2) dividing projection images into metal-free projection images and metal-only projection images; 3) reconstructing these two projection images using the ordered subset-expectation maximization (OS-EM) method to create metal-free tomosynthesis images and metal-only tomosynthesis images; and 4) combining the tomosynthesis images and thereby obtaining metal artifact-reduced tomosynthesis images. Our new metal extraction method in step 1 is based on the graph cuts algorithm. We compared four image reconstruction algorithms: (a) FBP, (b) FBP with a modified kernel, (c) simple OS-EM and (d) the proposed method. The results demonstrate that the proposed method significantly reduces metal artifacts when compared with the other methods.

First physical measurements and clinical evaluation for long-view tomosynthesis

Recently, Tomosynthesis (TS) has been evaluated as a useful diagnostic imaging examination for the breast, the lung and orthopedics. However the size of the reconstructed region is limited by the mechanical acquisition motion of the X-ray tube and image detector so it is not possible to generate long view images for the spinal columns or the lower limbs examinations. Long-View Tomosynthesis (LVTS) method uses a different acquisition motion and post processing algorithm but results in a similar high resolution image slice free of anatomy above and below slice of interest. This method consists of three steps. First, acquire multi images while X-ray tube and Flat Panel Detector (FPD) are moving continuously in same linear direction. Then each image is divided into strips and strips from different images having similar X-ray beam trajectory are stitched together. Then multi slice coronal images are reconstructed from the long stitched images using filtered backprojection technique (FBP) which is similar to reconstruction algorithms used with Computed Tomography (CT) and TS. As a result, LVTS has 1.6 cycle/mm spatial resolution and 432[mm] × 800[mm] image size at a maximum. We conclude that LVTS improves depiction of long view tomograms, which can not be acquired by TS. Like TS, LVTS can produce images for weight bearing or partial weight bearing anatomy that is not possible with CT since LVTS has been integrated onto a tilting table.

An approach of long-view tomosynthesis in peripheral arterial angiographic examinations

Tomosynthesis (TS) has been evaluated as a useful diagnostic imaging tool for the orthopedic market and lung cancer screening. Previously, we proposed Long-View Tomosynthesis (LVTS) to apply further clinical application by expanding the reconstructed region of TS. LVTS method consists of three steps. First, it acquires multiple images while X-ray tube and Flat Panel Detector (FPD) are moving in the same linear direction simultaneously at a constant speed. Second, each image is divided into fixed length strips, and then the strips from different images having similar X-ray beam trajectory angles are stitched together. Last, multi slice coronal images are reconstructed by utilizing the Filtered Back Projection (FBP) technique from the long stitched images. The present LVTS method requires the acquisition by the constant speed motion to stitch each strip precisely. It is necessary to improve the LVTS method to apply peripheral angiographic examinations that are usually acquired at arbitrary variable speeds to chase the contrast media in the blood vessel. We propose adding the method of detecting the moved distance of frames along with anatomical structure and the method of selecting pixel values with contrast media to stitching algorithm. As a result, LVTS can extract new clinical information like 3-D structure of superficial femoral arteries and the entire blood vessel from images already acquired by routine bolus chasing techniques.

An application of the Peter–Weyl theorem to non‐Abelian lattice gauge theory

This article presents an application of the Peter–Weyl theorem to obtain a new formula for the physical states of the Kogut–Susskind Hamiltonian model. In this formula a physical state is identified with a matrix element of a suitable representation of the infinite product of the gauge group. The Clebsch–Gordan coefficients for the physical states are obtained. A handy formula is deduced for the plaquette term in the Hamiltonian, so that the matrix elements of the Hamiltonian in the physical space for the (2+1)‐dimensional SU(2) model can be calculated without using the Wigner–Eckart theorem for tensor operators.