[The protocol of dose reduction in liver perfusion computed tomography].

Cerebral perfusion computed tomography (CT) has been widespread, but abdominal perfusion CT has not been very popular because there has been a problem with regard to the limit of irradiation range and respiratory effects. Recently, it became easy to perform perfusion of abdominal organs because the use of multi detector row CT (MDCT) has been extensive. Along with it, the number of hospitals that perform liver perfusion CT has increased. However, patient dose of the liver perfusion CT is very high, making it very important to reduce patient dose. We created the virtual data that reduced the number of irradiation by partly reducing the data obtained on the liver perfusion CT. We compared the analysis results of all data with that of the partly reduced. It is possible to reduce the patient dose by reducing the number of irradiation because there was no significant difference in the analysis results.

Leukemia inhibitory factor functions as a growth factor in pancreas carcinoma cells: Involvement of regulation of LIF and its receptor expression.

Leukemia inhibitory factor (LIF) is a pleiotrophic cytokine, which plays an important role in inducing cancer cachexia. We have previously reported that LIF promotes cell proliferation in some human carcinoma cells through c-fos, jun-B and cyclin-E expression. In the present study, we analyzed the regulation of LIF and its receptor (LIFR) expression in pancreatic carcinoma cells. Seven pancreatic carcinoma cells expressed constitutively LIF and its heterodimer receptor (LIFR and gp130) mRNA in RPMI-1640 medium without FBS. The amount of LIF immunoreactive protein was 132.5+/-52 pg/10(6) cells in culture supernatants without FBS. Pro-inflammatory cytokines, such as TNF-alpha, IL-1beta, IL-6, IL-8, or LIF, enhanced the expression of LIF mRNA in Hs-700T and Hs-766T cells. Addition of LIF significantly induced cell proliferation of Hs700T in 13 days LIF dose-dependently. However, anti-LIF IgG failed to suppress cell proliferation in Hs-700T cells. LIF acted as a paracrine growth factor in Hs-700T cells, which expressed low amount of LIF without stimuli. Cellular signal transductions by LIF was down-regulated by inhibitors of protein kinase C (PKC), protein tyrosine kinase (PTK), and Ca/Calmodulin. LIF induced phosphorylation of STAT3. Moreover, exogenous LIF upregulated the expression of LIFR mRNA. Antisense LIFR oligonucleotide significantly suppressed cell growth in the presence of LIF in Hs-700T cells. These results suggest that cytokine network might alter the expression and responsiveness to LIF in tumor microenvironment.

[Evaluation of low contrast resolution in cone beam CT using FPD].

We examined the low contrast resolution of cone beam CT (CBCT) equipped with an indirect-type flat panel detector and compared it with a commercial CT unit (Robusto) . In CBCT, the X-ray tube voltage of 110 kV was used, and in the Robusto, the usual 120 kV was used for examinations. The computed tomography dose index (CTDI) of the two systems was measured, and images scanned at about the same exposure to radiation were compared. The modulation transfer factors of the two systems were measured, and the convolution kernel that was the nearest to the characteristic of CBCT was chosen among kernels of the Robusto. A water phantom with a diameter of 200 mm was scanned, Wiener spectra were calculated, and signal-to-noise ratios were compared. The low contrast resolution phantom was scanned, and detectability and contrast-to-noise ratio (CNR) were measured. In addition, we placed diluted contrast medium into a phantom, scanned the phantom, and measured the detectability and CNR. When the X-ray irradiation condition of CBCT was 75 mAs at 110 kV, the equal dose of radioactivity in the Robusto was 50 mAs at 120 kV. In the low contrast resolution phantom, detectability was 8.7%mm in CBCT, and 9.4%mm in the Robusto. In the low contrast resolution evaluation phantom, CNR was 1.39 in CBCT, and 2.69 in the Robusto. With diluted contrast medium, CNR was 1.28 in CBCT, and 0.60 in the Robusto. CBCT was inferior to the Robusto in a low contrast resolution phantom, but CBCT was superior to the Robusto using diluted contrast medium. We found that CBCT was useful in examinations using contrast media.

[A design of the measuring chart for magnifying-power compensation in brain angiography].

PURPOSE: When brain angiography was performed, we devised the calculation theory for rectifying magnifying power, and produced the auxiliary tool. METHOD: We produced the frame with a size of 300 x 300 x 15 mm from the thin board made from carbon. The frame is around arranged for every 1 cm in Pb-ball of the diameter of 1 mm. We named this the measuring-chart. The measuring-chart has been arranged so that head may be surrounded. A photograph of a measuring-chart and head was taken simultaneously. The projected mark used for computing the magnifying power of a brain aneurysm. Magnifying power was used in order to measure the size of an aneurysm. RESULTS: In the basic experiment using the stainless-steel ball whose size is known, the standard error was -2.29% +/- 5.61%. A measurement value and true value showed high correlation (R(2) = 0.9986). CONCLUSION: The measuring-chart did not need a proofreading factor peculiar to equipment. This method had high accuracy. This method has high flexibility. It suggested that this method was useful on clinical use.

Three-dimensional radiochromic film dosimetry for volumetric modulated arc therapy using a spiral water phantom.

We validated 3D radiochromic film dosimetry for volumetric modulated arc therapy (VMAT) using a newly developed spiral water phantom. The phantom consists of a main body and an insert box, each of which has an acrylic wall thickness of 3 mm and is filled with water. The insert box includes a spiral film box used for dose-distribution measurement, and a film holder for positioning a radiochromic film. The film holder has two parallel walls whose facing inner surfaces are equipped with spiral grooves in a mirrored configuration. The film is inserted into the spiral grooves by its side edges and runs along them to be positioned on a spiral plane. Dose calculation was performed by applying clinical VMAT plans to the spiral water phantom using a commercial Monte Carlo-based treatment-planning system, Monaco, whereas dose was measured by delivering the VMAT beams to the phantom. The calculated dose distributions were resampled on the spiral plane, and the dose distributions recorded on the film were scanned. Comparisons between the calculated and measured dose distributions yielded an average gamma-index pass rate of 87.0% (range, 91.2-84.6%) in nine prostate VMAT plans under 3 mm/3% criteria with a dose-calculation grid size of 2 mm. The pass rates were increased beyond 90% (average, 91.1%; range, 90.1-92.0%) when the dose-calculation grid size was decreased to 1 mm. We have confirmed that 3D radiochromic film dosimetry using the spiral water phantom is a simple and cost-effective approach to VMAT dose verification.

[Evaluation of magnetic resonance signal intensity in bone marrow after administration of super paramagnetic iron oxide (SPIO)].

Super paramagnetic iron oxide (SPIO) is taken up in the bone marrow and lymph nodes, as well as by the liver. Focusing on the intervertebral disks, which are unaffected by contrast effects, we examined the relationship between magnetic resonance image (MRI) signal intensity after SPIO uptake in the vertebral body and intervertebral disks and investigated MRI signal intensity in bone marrow metastases and osteomyelitic (inflammatory) lesions after SPIO uptake by bone marrow. The lumbar spine was imaged in 5 healthy volunteers (age range, 26-48 years). A specified amount of SPIO was administered intravenously, and signal intensities before and after administration were measured. The signal intensity ratio with respect to the value before administration was calculated, and quantitative signal analysis was conducted. A similar investigation was performed in patients with bone metastasis and osteomyelitis. As a result of the metastasis, the signal intensity ratio showed a low value in comparison with normal marrow, and the osteomyelitis showed a high value in comparison with normal marrow. We report the usefulness of evaluations of changes in marrow signal intensity using SPIO in MRI.

[Impact of planning CT slice thickness on the accuracy of automatic target registration using the on-board cone-beam CT].

We have evaluated relationship between planning CT slice thickness and the accuracy of automatic target registration using cone-beam CT (CBCT). Planning CT images were acquired with reconstructed slice thickness of 1, 2, 3, 5, and 10mm for three different phantoms: Penta-Guide phantom, acrylic ball phantom, and pelvic phantom. After correctly placing the phantom at the isocenter using an in-room laser, we purposely displaced it by moving the treatment couch and then obtained CBCT images. Registration between the planning CT and the CBCT was performed using automatic target registration software, and the registration errors were recorded for each planning CT data set with different slice thickness. The respective average and standard deviation of errors for 10 mm slice thickness CT in the lateral, longitudinal, and vertical directions (n=15 data sets) were: 0.7 +/- 0.2mm, 0.8 +/- 0.2mm, and 0.2 +/- 0.2mm for the Penta-Guide phantom; 0.5 +/- 0.4 mm, 0.6 +/- 0.3 mm, and 0.4 +/- 0.3 mm for the acrylic ball phantom; and 0.6 +/- 0.2 mm, 0.9 +/- 0.2 mm, and 0.2 +/- 0.2 mm for the pelvic phantom. We found that the mean registration errors were always less than 1 mm regardless of the slice thickness tested. The results suggest that there is no obvious correlation between the planning CT slice thickness and the registration errors.

Analysis of respiration-related movement of upper abdominal arteries: preliminary measurement for the development of a respiratory motion compensation technique of roadmap navigation.

In this study, we analyzed the respiratory motion of the upper abdominal arteries preliminary to developing a method of respiratory motion correction for the roadmap technique used in vascular interventions. We retrospectively obtained six digital angiography sequences taken during respiration. The levels of the right and left hemidiaphragms and the positions of artery bifurcation points were measured manually through each sequence. Artery bifurcation points were classified as the hepatic artery group (HAG), splenic artery group (SAG), and celiac group (CG). Correlations between the motions of each hemidiaphragm and of the artery bifurcation points in each group were determined. We found that the vertical motion of the HAG and CG matched that of the right hemidiaphragm (r = 0.924 and r = 0.888, respectively). The vertical motion of the SAG matched that of the left hemidiaphragm (r = 0.949). The mean horizontal movements for all groups were up to 1.90 mm. The vertical motion for each group matched that of the right or the left hemidiaphragm. These findings will facilitate the development of a method of respiratory motion correction for the roadmap technique.

Clinical evaluation of a newly developed method for avoiding artifacts caused by dental fillings on X-ray CT.

To evaluate the clinical usefulness of gantry tilt scanning as an image reconstruction technique for avoiding artifacts caused by metallic dental fillings. Gantry tilt scanning was used with multidetector-row computed tomography for imaging in patients with dental fillings. Using a novel PC-based program, the oblique images obtained were reconstructed to transverse images using nearest neighbor and bilinear interpolation methodologies in order to avoid metallic streak artifacts. Coronal images were reformatted with the reconstructed transverse images, and the continuity of the reconstructed images was evaluated. Gantry tilt scanning was performed in 12 patients with metal artifacts, and the original and reconstructed images were classified into four grades and assessed by two radiologists. Results of the clinical evaluation indicated that the original images with artifacts, only 4% had good image quality in the region around the medial pterygoid muscle, only 8% depicted areas around the internal carotid artery and internal jugular vein, and only 12% could depict the areas around the parotid gland in the clinical evaluation. These values were improved to 60, 96, and 100%, respectively, in the reconstructed transverse images. Gantry tilt scanning as an image reconstruction technique improves image quality and removes most, if not all, artifacts caused by metallic dental fillings. The resulting images can be used in the evaluation of oropharyngeal lesions in patients with dental fillings.

Role of Na+/L-carnitine transporter (OCTN2) in renal handling of pivaloylcarnitine and valproylcarnitine formed during pivalic acid-containing prodrugs and valproic acid treatment.

Pivalic acid and valproic acid decreases L-carnitine concentration in the body via urinary excretion of their acylcarnitines, pivaloylcarnitine (PC) and valproylcarnitine (VC). To obtain an information about the mechanism of the physiological response, we investigated the renal handling of these acylcarnitines by Na+/L-carnitine cotransporter, OCTN2 using the isolated perfused rat kidney, rat OCTN2 (rOCTN2) and human OCTN2 (hOCTN2) expressing cells. In the perfused rat kidney, PC and VC were strongly reabsorbed with an efficiency comparable to L-carnitine, and these reabsorption were inhibited by 1 mM L-carnitine, suggesting that the interaction of L-carnitine with PC and VC reabsorption would be responsible for renal handling of these acylcarnitines in rats. The rOCTN2-mediated uptake of PC was lower than that of L-carnitine, whereas rOCTN2-mediated uptake of VC was as high as that of L-carnitine, indicating that contribution of rOCTN2 in renal handling of PC and VC would be different. Furthermore, hOCTN2-mediated uptake of these acylcarnitines was markedly lower than that of L-carnitine. On the other hand, both PC and VC inhibited L-carnitine reabsorption in the perfused rat kidney and their concentration-dependent inhibition was also observed for rOCTN2 and hOCTN2. These results suggest that low renal reabsorption and interaction of hOCTN2 for these acylcarnitines might possibly affect the decrease of L-carnitine concentration in humans.

Cone-beam CT with flat-panel-detector digital angiography system: early experience in abdominal interventional procedures.

We developed a cone-beam computed tomography (CBCT) system equipped with a large flat-panel detector. Data obtained by 200 degree rotation imaging are reconstructed by means of CBCT to generate three-dimensional images. We report the use of CBCT angiography using CBCT in 10 patients with 8 liver malignancies and 2 hypersplenisms during abdominal interventional procedures. CBCT was very useful for interventional radiologists to confirm a perfusion area of the artery catheter wedged on CT by injection of contrast media through the catheter tip, although the image quality was slightly degraded, scoring as 2.60 on average by streak artifacts. CBCT is space-saving because it does not require a CT system with a gantry, and it is also time-saving because it does not require the transfer of patients.