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ABSTRACT: The purpose of this study is to evaluate the crosstalk effect on spin-echo (SE) images at 1.5 and 3 T MRI. We examined the influence of crosstalk by comparing the full width at half-maximum (FWHM) and slice profile of images of a wedge-shaped phantom for various slice gaps. We also assessed crosstalk effect in the brain by comparing image contrast among healthy volunteers (n=8). Among the subjects, the shapes of the slice profiles at 1.5 T were similar to those at 3 T for long repetition times (TRs); however, at shorter TRs, differences in slice profiles were observed among the subjects and were more apparent at 3 than at 1.5 T. The relative contrast between white matter and gray matter on T(1)-weighted images was lower at 3 than at 1.5 T. The crosstalk effect was strongest when the TR of the excitation pulse was short. The influence of the adjacent excitation pulse is important in the process of T(1) relaxation because T(1) values are greater at 3 T. In conclusion, the influence of crosstalk on SE T(1)-weighted images is greater at 3 than at 1.5 T.
Nippon Hoshasen Gijutsu Gakkai zasshi 01/2011; 67(7):779-84.
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Yukio Miki,
Milliam L Kataoka,
Toshiya Shibata,
Tabassum L Haque,
Mitsunori Kanagaki,
Taro Shimono,
Tomohisa Okada, Akira Hiraga,
Sadahiko Nishizawa,
Hiroyuki Ueda,
Mahbubur Rahman,
Junji Konishi
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ABSTRACT: To longitudinally and prospectively investigate changes in the volume and signal intensity on T1-weighted magnetic resonance (MR) images of the pituitary gland up to 1 year after delivery and evaluate whether termination of lactation has an effect on these parameters.
All participants provided informed consent for participation in the study, which was approved by the institutional review board. Thirteen volunteers (mean age, 28 years; age range, 26-32 years) underwent MR imaging 2 and 4 weeks after delivery and then at intervals of 0.5-2.0 months until 1 year after delivery. Eight participants terminated lactation during the study period. Sagittal and coronal T1-weighted images were obtained. Signal intensities of the anterior and posterior lobes of the pituitary were calculated relative to that of the pons. The volume of the pituitary was also calculated. Two-tailed paired Student t tests and separate simple linear regression analyses were used to test for statistically significant differences.
The mean pituitary volume was 544 mm3 at 2 weeks, 523 mm3 at 4 months, 512 mm3 at 8 months, and 511 mm3 at 12 months after delivery, with significant differences between 2 weeks and 4 months (P = .002) and between 4 and 8 months (P = .003) after delivery. The mean ratio of the signal intensity of the anterior lobe of the pituitary to the signal intensity of the pons was 1.11 at 2 weeks, 1.07 at 4 months, 1.03 at 8 months, and 1.00 at 12 months after delivery, with significant differences between 2 weeks and 4 months (P = .004) and between 4 and 8 months (P = .0001) after delivery. Termination of lactation had no statistically significant effect on pituitary volume or the ratio of the signal intensity of the anterior or posterior lobe of the pituitary to the signal intensity of the pons.
The volume of the pituitary gland decreases up to 8 months after delivery, and the T1-weighted signal intensity of the anterior lobe of the pituitary decreases; termination of lactation has no statistically significant effect on these parameters.
Radiology 07/2005; 235(3):999-1004. · 5.73 Impact Factor
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ABSTRACT: We evaluated esophageal peristalsis in patients with esophageal tumors by cine MR using steady-state free precession (SSFP) sequence and correlated the alteration of the esophageal peristalsis with clinical symptoms and tumor stages. Thirteen patients with pathologically proven esophageal tumors, including 12 esophageal cancers and one submucosal leiomyoma, underwent cine MRI using true fast imaging with steady precession (trueFISP) sequence, which is one SSFP sequence, after contrast-enhanced MR scanning for clinical purposes. A total of 120 serial images were obtained within 60 s through the plane along the long axis of the esophagus while patients chewed gum. The serial trueFISP images were evaluated for the presence, frequency, speed of progression, and passage of peristalsis through the tumor. The data from cine MRI were compared with clinical symptoms and tumor stages. Peristalsis was clearly identified in all patients. Seven patients with complete interruption of peristalsis had dysphagia; one with partially impaired peristalsis could intake solid foods with discomfort; and two with partially impaired peristalsis and three with preserved peristalsis remained asymptomatic. Patients with complete or partial interruption of peristalsis had Stage T3 or T4 esophageal cancer. In conclusion, trueFISP cine MR imaging enables direct visualization of esophageal peristalsis in relation to esophageal tumors. Complete interruption of peristalsis causes dysphagia, whereas partial interruption of and preserved peristalsis usually do not cause digestive problems. Interruption of peristalsis may indicate impaired muscle function caused by invasion of advanced esophageal cancers.
Magnetic Resonance in Medical Sciences 02/2005; 4(3):109-14. · 0.97 Impact Factor
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ABSTRACT: To compare uterine peristalsis as seen on two different magnetic resonance (MR) imaging sequences and transvaginal ultrasound (TVUS), so as to better determine the best method for evaluating uterine peristalsis.
Eleven women in the periovulatory phase of the menstrual cycle underwent TVUS and cine MR imaging within a time period of three hours. Findings on cine MR images obtained with a serial 60 half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence and a 300 true fast imaging with steady-state precession (FISP) sequence were compared with TVUS.
The image quality of the HASTE technique was the best among the three methods, followed by TVUS, and then true FISP technique (P < 0.001). Uterine peristalsis was detected in 100% of subjects using HASTE, 82% with True FISP, and 100% with TVUS. With HASTE technique, true FISP, and TVUS, respectively, endometrial stripping movement was identified in 100%, 82%, and 100%; direction was identified in 100%, 45% (P = 0.014), and 73%; and wave conduction toward the outer myometrium was identified in 55%, 9% (P = 0.025), and 0% (P = 0.014).
Cine MR imaging by HASTE technique with a time resolution of two seconds best delineated uterine peristalsis compared to that by true FISP technique or with TVUS.
Journal of Magnetic Resonance Imaging 09/2004; 20(3):463-9. · 2.70 Impact Factor
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Academic Radiology 09/2002; 9 Suppl 2:S452-4. · 1.69 Impact Factor
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Hisataka Kobayashi,
Satomi Kawamoto,
Sang-Kyung Jo,
Noriko Sato,
Tsuneo Saga, Akira Hiraga,
Junji Konishi,
Susan Hu,
Kaori Togashi,
Martin W Brechbiel,
Robert A Star
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ABSTRACT: A noninvasive technique to evaluate the structure and function of the kidney would be useful to investigate renal diseases, especially acute renal failure. We have developed a novel technique to visualize functional micro-magnetic resonance (MR) images of the mouse kidney with a dendrimer-based macromolecular renal MR contrast agent.
Mice were injected with cisplatin or vehicle, then examined three days later by contrast-enhanced, dynamic high-resolution micro-MRI with 160 microm spatial resolution using a 1.5 T clinical MRI unit, a surface coil, and the renal contrast agent G4D-(1B4M-Gd)64.
The cortex and outer stripe of the outer medulla of the mouse kidney were clearly visualized in the normal mice. In animals treated with cisplatin, the gradation of tubular damage as assessed by contrast enhanced dynamic MRI correlated with renal function.
Contrast-enhanced, dynamic high-resolution micro-MRI with a novel dendrimer-based macromolecular renal MR contrast agent can be a powerful tool for in vivo observation of renal structural and functional damage.
Kidney International 07/2002; 61(6):1980-5. · 6.61 Impact Factor
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Hisataka Kobayashi,
Kazuo Shirakawa,
Satomi Kawamoto,
Tsuneo Saga,
Noriko Sato, Akira Hiraga,
Ichiro Watanabe,
Yuji Heike,
Kaori Togashi,
Junji Konishi,
Martin W Brechbiel,
Hiro Wakasugi
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ABSTRACT: The rapid blood flow and perfusion of macromolecules in the inflammatory breast cancer xenograft (WIBC-9), which exhibits a "vasculogenic mimicry" type of angiogenesis without the participation of endothelial cells and expresses high levels of the HER-2/neu antigen, was evaluated in mice using 3D-micro-MR angiography using a novel macromolecular MR contrast agent [G6-(1B4M-Gd)(256)]. Herceptin, which recognizes the HER-2/neu antigen and has similar size (10 nm) to G6-(1B4M-Gd)(256), accumulated and internalized in the WIBC-9 tumors more quickly than in the control MC-5 tumors that progress with normal angiogenesis. Three dimensional micro-MRI with the G6-(1B4M-Gd)(256) macromolecular MRI contrast agent distinguishes between the different types of angiogenesis and is predictive of the rapid accumulation and internalization of Herceptin in the WIBC-9 inflammatory breast cancer xenograft.
Cancer Research 03/2002; 62(3):860-6. · 7.86 Impact Factor
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ABSTRACT: Four macromolecular contrast agents are synthesized to visualize small vessels by MRI using generation-3 (G3D), -4 (G4D), -5 (G5D), and -6 (G6D) polyamidoamine dendrimers conjugated to chelated gadolinium (Gd). The pharmacokinetics, enhancement patterns, and the ability of these constructs to visualize fine vessels is evaluated by dynamic MRI in relationship to their size. Gd-G6D and -G5D exhibit a prolonged high vascular (ventricular) signal intensity (SI) with high ventricle-to-organ SI ratios. The initial high vascular SI with Gd-G4D decreases to a value as low as that obtained with Gd-G3D and Gd-dimeglumine-diethylenetriaminepentaacetic acid (Gd-DTPA). Gd-G5D, -G4D, and -G3D show high renal SIs, and Gd-DTPA prominently enhances the skin. Gd-G6D and -G5D present fine vasculature significantly more clearly than Gd-G3D and -DTPA (P < 0.005). As the molecular size increases, the excretion of the 153Gd-conjugates is retarded. In conclusion, Gd-G6D and -G5D are retained in the blood and present fine vessels with high quality and detail, and should be adequate for visualizing small tumor vasculature. Magn Reson Med 46:1169–1173, 2001. © 2001 Wiley-Liss, Inc.
Magnetic Resonance in Medicine 11/2001; 46(6):1169 - 1173. · 2.96 Impact Factor
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ABSTRACT: Macromolecules conjugated with polyethylene glycol (PEG) acquire more hydrophilicity, resulting in a longer half-life in circulation and lower immunogenicity. Two novel conjugates for MRI contrast agents were synthesized from a generation-4 polyamidoamine dendrimer (G4D), 2-(p-isothiocyanatobenzyl)-6-methyl-diethylenetriaminepentaacetic acid (1B4M), and one or two PEG molecules with a molecular weight of 20000 Da (PEG2-G4D-(1B4M-Gd)62 (MW: 96 kD), PEG1-G4D-(1B4M-Gd)63 (MW: 77 kD)). Their pharmacokinetics, excretion, and properties as vascular MRI contrast agents were evaluated and compared with those of G4D-(1B4M-Gd)64 (MW: 57 kD). PEG2-G4D-(1B4M-Gd)62 remained in the blood significantly longer and accumulated significantly less in the liver and kidney than the other two preparations (P < 0.01). Although the blood clearance was slower, PEG2-G4D-(1B4M-Gd)62 was excreted more readily without renal retention than the other two preparations. In conclusion, the positive effects of PEG conjugation on a macromolecular MRI contrast agent were found to be prolonged retention in the circulation, increased excretion, and decreased accumulation in the organs. Magn Reson Med 46:781–788, 2001. © 2001 Wiley-Liss, Inc.
Magnetic Resonance in Medicine 09/2001; 46(4):781 - 788. · 2.96 Impact Factor
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Hisataka Kobayashi,
Satomi Kawamoto,
Tsuneo Saga,
Noriko Sato, Akira Hiraga,
Takayoshi Ishimori,
Yukio Akita,
Marcelo H. Mamede,
Junji Konishi,
Kaori Togashi,
Martin W. Brechbiel
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ABSTRACT: As MRI contrast agents, more hydrophobic molecules reportedly accumulate in the liver and thus are potentially useful as liver MRI contrast agents. In this study, a generation-4 polypropylenimine diaminobutane dendrimer (DAB-Am64), which is expected to be more hydrophobic than the generation-4 polyamidoamine dendrimer (PAMAM-G4D), was used to synthesize a conjugate with 2-(p-isothiocyanatobenzyl)-6-methyl-diethylenetriaminepentaacetic acid (1B4M) [DAB-Am64-(1B4M-Gd)64] for complexing Gd(III) ions. This DAB conjugate quickly accumulated in the liver and its characteristics were studied and compared with those of a PAMAM conjugate [PAMAM-G4D-(1B4M-Gd)64], which is known to be a useful vascular MRI contrast agent, in regard to its availability as a liver MRI contrast agent. DAB-Am64-(1B4M-Gd)64 accumulated significantly more in the liver and less in blood than PAMAM-G4D-(1B4M-Gd)64 (P < 0.001). Contrast-enhanced MRI with DAB-Am64-(1B4M-Gd)64 was able to homogeneously enhance liver parenchyma and visualize both portal and hepatic veins of 0.5 mm diameter in mice. In conclusion, DAB-Am64-(1B4M-Gd)64 is a good candidate for a liver MRI contrast agent. Magn Reson Med 46:795–802, 2001. © 2001 Wiley-Liss, Inc.
Magnetic Resonance in Medicine 09/2001; 46(4):795 - 802. · 2.96 Impact Factor
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ABSTRACT: Noninvasive methods to visualize blood flow in the intratumoral vasculature have not previously been studied. In the present study, the use of a novel intravascular MR contrast agent with a generation-6 polyamidoamine dendrimer core (G6-(1B4M-Gd)192; MW: 175kD) was investigated, and the vasculature in experimental tumors was visualized using 3D MR angiography (MRA). Xenografted tumors in nude mice of two different histologies—KT005 (human osteogenic sarcoma) and LS180 (human colon carcinoma)—were used to obtain 3D MRA using G6-(1B4M-Gd)192 and Gd-DTPA. The contrast MR sectional images were correlated with the corresponding histological sections. The intratumoral vasculature in the KT005 tumor was clearly visualized by 3D MRA, which became more evident with the growth of the tumor xenograft. In contrast, the intratumoral vasculature in the LS180 tumor was sparser and much less developed than that in KT005 tumors. Blood vessels with a diameter as small as 100 μm based on histology were visualized using 0.033 mmol Gd/kg of G6-(1B4M-Gd)192. In conclusion, intratumoral vasculature with a 100-μm diameter was visualized better using 3D MRA with G6-(1B4M-Gd)192 than with Gd-DTPA. Magn Reson Med 46:579–585, 2001. © 2001 Wiley-Liss, Inc.
Magnetic Resonance in Medicine 08/2001; 46(3):579 - 585. · 2.96 Impact Factor
