/pdf/mapping-the-distribution-of-gamma-ray-emitting-isotopes-with-5fsfustltz.pdf

Mapping the distribution of gamma-ray-emitting isotopes with the scintillation camera

Washout of 10C and 11C implanted by radioactive beams in brain and thigh muscle of rabbits was studied. The biological washout effect in a living body is important in the range verification system or three-dimensional volume imaging in heavy ion therapy. Positron emitter beams were implanted in the rabbit and the annihilation gamma-rays were measured by an in situ positron camera which consisted of a pair of scintillation cameras set on either side of the target. The ROI (region of interest) was set as a two-dimensional position distribution and the time–activity curve of the ROI was measured. Experiments were done under two conditions: live and dead. By comparing the two sets of measurement data, it was deduced that there are at least three components in the washout process. Time–activity curves of both brain and thigh muscle were clearly explained by the three-component model analysis. The three components ratios (and washout half-lives) were 35% (2.0 s), 30% (140 s) and 35% (10 191 s) for brain and 30% (10 s), 19% (195 s) and 52% (3175 s) for thigh muscle. The washout effect must be taken into account for the verification of treatment plans by means of positron camera measurements.

https://iopscience.iop.org/article/10.1088/0031-9155/48/15/302/pdf

Washout measurement of radioisotope implanted by radioactive beams in the rabbit

Carbon ion radiotherapy (C-ion RT) offers superior dose conformity in the treatment of deep-seated tumors compared with conventional X-ray therapy. In addition, carbon ion beams have a higher relative biological effectiveness compared with protons or X-ray beams. C-ion RT for the first patient at Gunma University Heavy Ion Medical Center (GHMC) was initiated in March of 2010. The major specifications of the facility were determined based on the experience of clinical treatments at the National Institute of Radiological Sciences (NIRS), with the size and cost being reduced to one-third of those at NIRS. The currently indicated sites of cancer treatment at GHMC are lung, prostate, head and neck, liver, rectum, bone and soft tissue. Between March 2010 and July 2011, a total of 177 patients were treated at GHMC although a total of 100 patients was the design specification during the period in considering the optimal machine performance. In the present article, we introduce the facility set-up of GHMC, including the facility design, treatment planning systems, and clinical preparations.

Carbon Ion Radiotherapy at the Gunma University Heavy Ion Medical Center: New Facility Set-up

Heavy ion therapy has two definite advantages: good dose localization and higher biological effect. Range calculation of the heavy ions is an important factor in treatment planning. X-ray CT numbers are used to estimate the heavy ion range by looking up values in a conversion table which relates empirically photon attenuation in tissues to particle stopping power; this is one source of uncertainty in the treatment planning. Use of positron emitting radioactive beams along with a positron emission tomograph or a positron camera gives range information and may be used as a means of checking in heavy ion treatment planning. However, the metabolism of the implanted positron emitters in a living object is unpredictable because the chemical forms of these emitters are unknown and the metabolism is dependent on the organ species and may be influenced by many factors such as blood flow rate and fluid components present. In this paper, the washout rate of 11C activity implanted by injecting energetic 11C beams into thigh muscle of a rear leg of a rabbit is presented. The washout was found to consist of two components, the shorter one was about 4.2 ± 1.1 min and the longer one ranged from 91 to 124 min. About one third of the implanted β+ activity can be used for imaging and the rest was washed out of the target area.

https://iopscience.iop.org/article/10.1088/0031-9155/48/7/305/pdf

Washout studies of 11C in rabbit thigh muscle implanted by secondary beams of HIMAC

A treatment planning of heavy ion cancer therapy is performed with an aid of X-ray CT, which has uncertainties in an estimation of ion range. In order to obtain a dose distribution with high accuracy, irradiation and range measurement systems are developed at HIMAC using positron emitter beams. Exact stopping points of the ions can be measured by detecting annihilation γ-rays from positron emitters themselves. A new irradiation system has been installed, for creating an irradiation field with 3-dimensionally desired shape. A positron camera, which is similar to an Anger-type γ camera, is used to determine a range distribution of the heavy ions in a patient’s body. An existing PET system can be also used to measure an image of the 3dimensional irradiation-field.

/pdf/medical-application-of-the-positron-emitter-beam-at-himac-2bmhe1t51u.pdf

Medical application of the positron emitter beam at himac

A new beam course, a projectile fragment separator to provide radioactive beams, is under construction at HIMAC. A primary purpose of the new beam course is to study medical applications of radioactive beams. The specifications and status of the beam course and a preliminary result using carbon beams are summarized.

New secondary beam course for medical use in HIMAC

The positron camera system was designed and developed at the secondary beam course of HIMAC to measure heavy-ion ranges in bodies of patients. By using the pencil-like beam of positron emitters, such as 11 C, the range is checked directly and precisely by detecting pairs of annihilation gamma rays emitted from the stopping point of the beam. The positron camera consists of a pair of Anger-type scintillation cameras. In order to achieve high detection efficiency, each detector is equipped with a large NaI(Tl) crystal having a thickness of 30 mm and a diameter of 600 mm. The test results reveal that the range can be measured with accuracy of less than 1 mm under the limitation that the irradiation dose has to be less than a few percent of the therapeutic one.

/pdf/positron-camera-system-for-heavy-ion-radiotherapy-at-himac-p4bdwt6zig.pdf

Positron camera system for heavy-ion radiotherapy at himac

We have constructed the spot scanning irradiation system at the secondary beam course in HIMAC. This system has scanning magnet and range sifter. The response time of the range shifter is less than 300 milliseconds. Beam position is measured by a multi-strip parallel plate ionization chamber with strip pitch of 1mm. The calculation of beam center is completed within 1 milliseconds in the VME, which is placed independently for horizontal and vertical directions.

Spot scanning system with ri beam at himac

Since 1994 clinical trials have been performed successfully with carbon beam. To improve the clinical result further, new irradiation systems are under development such as a 3D-irradiation system and a verification system of range with positron emitter. There are also improvements on the accelerator performances. One is the wide range of ion species; the others are concerned with the machine devices and new beam monitors to get good machine operation. In this report we present current status of HIMAC.

/pdf/present-status-of-himac-at-nirs-2xyj8w1gxc.pdf

Present status of HIMAC at NIRS

Since 1994, the clinical trial with HIMAC at National Institute of Radiological Sciences (NIRS) has been successfully progressed, and more than 1,900 patients were already treated with carbon ions. In 2003, as a result, the carbon-ion cancer therapy was approved as a highly advanced medical technology by the Japanese government. Based on the development of the accelerator and irradiation technologies for ten-years, we propose a carbon-therapy facility. This paper reports the conceptual design of the facility.

/pdf/proposal-for-carbon-beam-facility-for-the-cancer-therapy-in-3il7m8r77f.pdf

T. Kanai

Papers

New secondary beam course for medical use in HIMAC

Positron camera system for heavy-ion radiotherapy at himac

Spot scanning system with ri beam at himac

Present status of HIMAC at NIRS

Proposal for carbon-beam facility for the cancer therapy in japan