Hiraku Kawamura

Correlation between choline and MIB-1 index in human gliomas. A quantitative in proton MR spectroscopy study

BACKGROUND Choline (Cho) containing compounds are usually evaluated using magnetic resonance spectroscopy (MRS) by relative ratios such as Cho/N-acetylaspartate (NAA) and Cho/creatine (Cre) ratios. To clarify the significance of Cho level in gliomas, we evaluated the quantified Cho level using MRS and compared it with the proliferation activity as determined by MIB-1 immunoreactivity in the histological specimen. METHODS There were seven benign and seven malignant gliomas. MRS was obtained using a single-voxel proton regional imaging of metabolites (PRIME) sequence with three different TE for T2 compensation. Quantified Cho level was compared with the number of MIB-1 immunopositive positive cells and cell density in surgical specimens. RESULT A positive correlation was observed between Cho and MIB-1 in benign gliomas, whereas there was a trend to an inverse correlation in malignant gliomas. This inverse correlation became a positive correlation when the necrotic area of the tumor (on the T1-weighted gadolinium enhanced images) was excluded from the voxel of interest (VOI) for MRS, but this correlation did not reach statistical significance. CONCLUSIONS The quantification data clarified the behavior of Cho in malignant gliomas. The quantification method has the advantage of limiting the influence of other metabolites on Cho determination. In particular, the levels of other commonly measured metabolites, including Cre, may also be altered in glioma, making ratios between metabolites misleading. Heterogeneity in the MRS VOI should be considered when evaluating the proliferative activity of malignant glioma by MRS.

Non-invasive quantification of lactate by proton MR spectroscopy and its clinical applications

Lactate is an important metabolite in clinical cases indicating the status of metabolic impairment. We applied a clinically relevant simple method for lactate quantification using magnetic resonance spectroscopy (MRS). We used two long in-phase echo time (TE=272,544 ms) to calculate T2 relaxation time and the absolute concentration of lactate. This method was optimized using phantom study and applied to clinical cases. This technique does not require complicated processing and could be applied in daily clinical practice. Moreover, this technique enables lactate quantification in cases (e.g. tumor) where lipid peak is overlapped with the lactate peak at short echo times.

Proton magnetic resonance spectroscopy and 201Thallium-, 99m Technetium methoxyisobutylisonitrile single photon emission computed tomography findings of a patient with choroid plexus papilloma

Sir, Choroid plexus papilloma is a rare intraventricular tumor and there have been few reports of findings on proton magnetic resonance spectroscopy (H-MRS) and Thallium (Tl), Technetium methoxyisobutylisonitrile (MIBI) single photon emission computed tomography (SPECT). We would like to draw your reader’s attention to their potential in the diagnosis of this pathology. An 18-month-old girl was admitted to our hospital with normal physical and neurological examination. A CT scan showed mild ventriculomegaly and an isodense tumor in the left trigone which on MRI showed low intensity on T1-weighted images and high intensity on T2-weighted images (Fig. 1). The tumor was homogeneously enhanced after intravenous injection of gadolinium-diethyltriaminepentaacetic acid (Fig. 1). We performed SPECT 15 min and 3 h after intravenous injection of Tl Chloride 74 MBq or Tc MIBI 740 MBq and calculated Tl or MIBI indexes for tumor and normal tissue. Both Tl and MIBI SPECT showed a homogenous hot tumor uptake on both early and delayed images (Fig. 2). The delayed Tl index was 4.95 and it was lower than the early Tl index. The delayed MIBI index was 14.5 and it was higher than the early MIBI index. The retention index was calculated by the formula (radioactivity of ROI on the tumor in the delayed image−radioactivity of ROI on the tumor in the early image)/radioactivity of ROI on the tumor in the early image. The Tl retention index was −0.15 and the MIBI retention index was −0.64, these indexes showed moderate wash out of the tracer from the tumor. H-MRS was performed at 1.5 T with proton regional imaging of metabolites and point resolved spectroscopy sequences. These demonstrated an increase of Cho and a decrease of NAA and Cre (Fig. 1). The quantified tumor NAA was 2.51 mM/kg and this is remarkably decreased in comparison to the normal brain NAA (10.8 mM/kg) [4]. The quantified tumor Cre was 2.56 mM/kg which is slightly higher than in the normal brain Cre (2.1 mM/kg). High peaks at 3.4 and 3.6 ppm were found on the spectroscopy images, and these peaks were prominent in the image with a 64 ms echo time. These peaks were thought to represent taurine and inositol. The tumor was surgically resected and histological examination confirmed the imaging diagnosis of choroids plexus papilloma. The patient made an uneventful recovery. Post-operative MRI confirmed that there was no residual tumor and no recurrence has been observed on follow-up. There are a few reports of Technetium hexamethylpropyleneamine oxime SPECT of choroid plexus papilloma [1, 2]. No studies documenting the use of Tl and MIBI SPECT in a choroid plexus papilloma were found in a MEDLINE search in 2008. Tl and MIBI SPECT in this case showed high tumor uptake and good wash out. These findings are compatible with a high blood flow in a benign tumor. MIBI shows early accumulation into the normal choroid plexus and good wash out from it. In this case, the choroid plexus Neuroradiology (2008) 50:741–742 DOI 10.1007/s00234-008-0422-6

Feasibility study on using imaging plates to estimate thermal neutron fluence in neutron-gamma mixed fields.

In current radiotherapy, neutrons are produced in a photonuclear reaction when incident photon energy is higher than the threshold. In the present study, a method of discriminating the neutron component was investigated using an imaging plate (IP) in the neutron-gamma-ray mixed field. Two types of IP were used: a conventional IP for beta- and gamma rays, and an IP doped with Gd for detecting neutrons. IPs were irradiated in the mixed field, and the photo-stimulated luminescence (PSL) intensity of the thermal neutron component was discriminated using an expression proposed herein. The PSL intensity of the thermal neutron component was proportional to thermal neutron fluence. When additional irradiation of photons was added to constant neutron irradiation, the PSL intensity of the thermal neutron component was not affected. The uncertainty of PSL intensities was approximately 11.4 %. This method provides a simple and effective means of discriminating the neutron component in a mixed field.

Note: Utilization of polymer gel as a bolus compensator and a dosimeter in the near-surface buildup region for breast-conserving therapy

Tangential beam radiotherapy is routinely used for radiation therapy after breast conserving surgery. A tissue-equivalent bolus placed on the irradiated area shifts the depth of the dose distribution; this bolus provides uniform dose distribution to the breast. The gel bolus made by the BANG-Pro(®) polymer gel and in an oxygen non-transmission pack was applicable as a dosimeter to measure dose distribution in near-surface buildup region. We validated the use of the gel bolus to improve in the whole-breast/chest wall, including the near-surface buildup region.

Investigation of Temperature Dependence of Polymer Gels for Use with Scanning Magnetic Resonance Imaging

Polymer gels are three-dimensional dosimetric tools. The purpose of the present study was to investigate the temperature dependence of polymer gels during scanning Magnetic Resonance Imaging. Prepared gels were irradiated with a 6MV X-ray beam at intensities ranging from 0 to 20 Gy in order to investigate their dose-R2 and dose-R1 responses. Irradiated gels were evaluated from 1.5-T magnetic resonance R2 and R1 images for each 5°C change in temperature from 5°C to 41°C, and then the four-field box technique irradiation plan was used to deliver a total dose of 4 Gy using the same beam weight in each direction to the prepared gels. The profile of the dose map generated from the four-field irradiated gel data at 20°C was then compared with the planned data. The dose-R2 response curve was linear up to 20 Gy at 20°C, with a slope of 1.17 Gy-1ds-1. The slopes of the fitted curves of the dose-R2 decreased as gel temperature increased. The slopes of the dose-R1 curves were more parallel than the slopes of the dose-R2 curves between 5 and 41°C. The difference in the full width of half maximum of the gel profile data obtained using the four-field box technique at 20°C and the planned data were below 5% on average. The dose map from the irradiated gels obtained using the dose-R2 curve was the same as that from the planned data under the same temperature conditions. Measurement of difference between various temperatures is significant with dose accuracy. It is suitable to evaluate the gel dosimeter under the thermal equilibrium condition, MRI room temperature from the point of view of the stability of the irradiated gels.

Evaluation of three-dimensional polymer gel dosimetry using X-ray CT and R2 MRI.

It is difficult to obtain images of thin slices from measurement of spin-spin relaxation (R2) with magnetic resonance imaging (MRI) using the traditional dose reading method of polymer gel dosimetry. In this study, the dose reading method was performed using X-ray computed tomography (CT) for proton beam measurements in order to enable collection of thin slices. In addition, three-dimensional (3D) images of polymer gels were constructed using volume rendering. As a result of acquisition of thin slices, more detailed 3D data consisting of smaller voxel sizes compared to R2 were acquired. However, it was found that with thin slice thicknesses and small voxels, the signal-to-noise ratio around the voxels deteriorated. In addition, the coefficient of variation of non-irradiated gels with CT was smaller than that with R2 MRI.

Convenient Method of Thermal Neutron Measurement Using Imaging Plates in Proton Therapy

In proton therapy, measurement of secondary neutron emission is important, because such radiation can influence the occurrence of secondary cancers and the radioactivity of the treatment room. In this study, we investigated the possibility of neutron detection using a neutron imaging plate (IP) and a general IP.