Minoru Hosoba

Development of an integrated radiotherapy network system

PURPOSE To introduce the process of developing an integrated radiotherapy network. METHODS AND MATERIALS We developed a new radiotherapy treatment-planning system in 1987 that we named the Computer Tomography (CT) simulator. CT images were immediately transported to multiimage monitors and to a planning computer, and treatment planning could be performed with the patient lying on the CT couch. The results of planning were used to guide a laser projector, and radiation fields were projected onto the skin of the patient. Since 1991, an integrated radiotherapy network system has been developed, which consists of a picture archiving and communicating system (PACS), a radiotherapy information database, a CT simulator, and a linear accelerator with a multileaf collimator. RESULTS Clinical experience has been accumulated in more than 1,000 patients. Based on our 7 years of experience, we have modified several components of our original CT simulator and have developed a second generation CT simulator. A standard protocol has been developed for communication between the CT scanner, treatment planning computer, and radiotherapy apparatus using the Ethernet network. As a result, treatment planning data can be transported to the linear accelerator within 1 min after completion of treatment planning. CONCLUSION This system enables us to make optimal use of CT information and to devise accurate three-dimensional (3D) treatment-planning programs. Our network also allows for the performance of fully computer-controlled dynamic arc conformal therapy.

Two dimensional polar display of cardiac blood pool SPECT

A new method of ECG gated cardiac blood pool SPECT to illustrate the left ventricular (LV) wall motion in a single static image, two dimensional polar display (2DPD), was described. Circumferential profiles of the difference between end diastolic and end systolic short axis images of the LV were displayed in a similar way to the bulls eye plot of 201Tl myocardial SPECT. The diagnoses by 2DPDs agreed with those by cinematic displays of ECG gated blood pool SPECT in 74 out of 84 segments (85.5%) of abnormal motion, and 155 our of 168 segments (80.3%) of normal motion. It is concluded that 2DPD can evaluate regional wall motion by a single static image in a significant number of patients, and is also useful in comparing with the bulls eye image of 201Tl myocardial SPECT.

PACS workstation for computer-assisted image diagnosis

Major two functions that a PACS workstation is considered to be equipped with are 1) efficient retrieval of image data and 2) supporting or consultation of writing reports, as radiologists have to diagnose increasing number of digital images in routine clinical studies. The authors developed a prototype PACS workstation with high speed image retrieving architecture and computer aided diagnosis and reporting function by using an artificial intelligence technology (AIPACS workstation). When physician selects the patient and his studies, the system performs feature extraction and generates diagnostic report by the inference engine with backward reasoning using the knowledge installed as production rules. Clinical application to the system for thyroid diagnosis showed good correlation with the diagnosis done by the physician.

Off-line image exchange between two PACS modules using the "ISAC" magneto-optical disk

In order to exchange digital imaging data between two independent PACS modules, the ISAC (Image Save And Carry: JPACS/MEDIS-DC) formatted 130-mm magneto-optical disk (MOD) was used as an interchangeable off-line data transferring and recording medium. This system can provide the means for connecting distributed image databases and is useful for clinical studies.

Clinical validation of fully-automated contour detection for gated radionuclide ventriculography with a slant-hole collimator

A new fully-automated method for processing gated blood-pool images is presented and its clinical validity and performance for images with various noise levels are investigated using data obtained from a slant-hole collimator. The optimal preprocessing conditions are evaluated for the images with various noise levels to obtain the accurate ejection fraction, end-diastolic and end-systolic counts. This new method has successfully detected left ventricular contour in 92% of the 61 patients. The left ventricular ejection fraction obtained by the method related closely to that of contrast ventriculography (correlation coefficient r=0.90). The end-diastolic volume also had a good correlation with contrast ventriculography (r=0.90).

Factor analysis of multigated cardiac blood pool scintigram for the measurement of left ventricular ejection fraction

Left ventricular ejection fraction (EF) was measured by factor analysis (FA) of multigated cardiac blood pool scintigram in 38 consecutive patients, and compared with that measured by the variable ROI method (EFVROI) with automated left ventricular contour detection. FA was automatically performed without operator intervention with a success rate of 100%. The correlation of EF with EFVROI was significant in the group of 22 patients with normal wall motion (r=0.65, p<0.001), and the entire group of patients (r=0.70, p<0.001), but not significant (p=0.19) in the group of 16 patients with abnormal wall motion. In conclusion, left ventricular ejection fraction can be estimated by factor analysis of MUGA in patients with normal wall motion.

New secure communication-layer standard for medical image management (ISCL)

This paper introduces a summary of the standard draft of ISCL 1.00 which will be published by MEDIS-DC officially. ISCL is abbreviation of Integrated Secure Communication Layer Protocols for Secure Medical Image Management Systems. ISCL is a security layer which manages security function between presentation layer and TCP/IP layer. ISCL mechanism depends on basic function of a smart IC card and symmetric secret key mechanism. A symmetry key for each session is made by internal authentication function of a smart IC card with a random number. ISCL has three functions which assure authentication, confidently and integrity. Entity authentication process is done through 3 path 4 way method using functions of internal authentication and external authentication of a smart iC card. Confidentially algorithm and MAC algorithm for integrity are able to be selected. ISCL protocols are communicating through Message Block which consists of Message Header and Message Data. ISCL protocols are evaluating by applying to regional collaboration system for image diagnosis, and On-line Secure Electronic Storage system for medical images. These projects are supported by Medical Information System Development Center. These project shows ISCL is useful to keep security.

The unfolded map using 201Tl myocardial SPECT

The unfolded map is a new method to show the 201Tl distribution of left ventricle using SPECT. In 52 cases these maps were obtained at the stress study and 4 h later. The maximal count profiles of the perimeters for each short axis image were unfolded and were arranged from the apex to base of the left ventricle into a two dimensional map. All patients had chest pain and were suspected of coronary artery disease. The unfolded map had significant correlations between coronary arteriogram and exercise ECG findings. In conclusion, this method reflects the ischemic area of left ventricular myocardium, closer to the real left ventricular myocardium than Bulls eye display and is useful in the diagnosis of coronary heart disease.