Koichi Yoshimura

Development of a tissue-equivalent MRI phantom using carrageenan gel.

A new tissue‐equivalent MRI phantom based on carrageenan gel was developed. Carrageenan gel is an ideal solidifying agent for making large, strong phantoms in a wide variety of shapes. GdCl3 was added as a T1 modifier and agarose as a T2 modifier. The relaxation times of a very large number of samples were estimated using 1.5‐T clinical MRI equipment. The developed phantom was found to have a T1 value of 202–1904 ms and a T2 value of 38–423 ms when the GdCl3 concentration was varied from 0–140 μmol/kg and the agarose concentration was varied from 0–1.6% in a carrageenan concentration that was fixed at 3%. The range of measured relaxation times covered those of all types of human tissue. Empirical formulas linking the relaxation time with the concentration of the modifier were established to enable the accurate and easy calculation of the modifier concentration needed to achieve the required relaxation times. This enables the creation of a phantom having an arbitrary combination of T1 and T2 values and which is capable of retaining its shape. Magn Reson Med 50:1011–1017, 2003.

Composition of MRI phantom equivalent to human tissues.

We previously developed two new MRI phantoms (called the CAG phantom and the CAGN phantom), with T1 and T2 relaxation times equivalent to those of any human tissue at 1.5 T. The conductivity of the CAGN phantom is equivalent to that of most types of human tissue in the frequency range of 1 to 130 MHz. In this paper, the relaxation times of human tissues are summarized, and the composition of the corresponding phantoms are provided in table form. The ingredients of these phantoms are carrageenan as the gelling agent, GdCl3 as a T1 modifier, agarose as a T2 modifier, NaCl (CAGN phantom only) as a conductivity modifier, NaN3 as an antiseptic, and distilled water. The phantoms have T1 values of 202-1904 ms and T2 values of 38-423 ms when the concentrations of GdCl3 and agarose are varied from 0-140 micromol/kg, and 0%-1.6%, respectively, and the CAGN phantom has a conductivity of 0.27-1.26 S/m when the NaCl concentration is varied from 0%-0.7%. These phantoms have sufficient strength to replicate a torso without the use of reinforcing agents, and can be cut by a knife into any shape. We anticipate the CAGN phantom to be highly useful and practical for MRI and hyperthermia-related research.

Development of a phantom compatible for MRI and hyperthermia using carrageenan gel—relationship between T1 and T2 values and NaCl concentration

The authors developed a phantom, designated as the CAGN phantom, compatible for MRI and hyperthermia that is useful in the fundamental studies of non-invasive MR thermometry. The ingredients of this phantom are carrageenan, GdCl3 as a T1 modifier, agarose as a T2 modifier, NaCl as a conductivity modifier, NaN3 as an antiseptic and distilled water. Another phantom that was developed, the CAG phantom, has relaxation times that are adjustable to those of any human tissue. To use this phantom for electromagnetic heating, NaCl was added to change the conductivity of the phantom and clarified the relationship between the conductivity and NaCl concentration. This study examined the relationship between relaxation times and NaCl concentration of the CAGN phantom. The results showed that both T1 and T2 values were affected by NaCl and the experimental results led to the empirical formulae expressing the relationship between the relaxation rates (1/T1, 1/T2) and the concentrations of GdCl3, agarose and NaCl. The appropriate concentrations of T1 and T2 modifiers were calculated from these empirical formulae when making a specified phantom that has the required relaxation times and NaCl concentration.

Transcatheter embolization of an aortobronchial fistula with N-butyl cyanoacrylate.

Aortobronchial fistula is a fatal complication after thoracic aortic surgery. So far, treatment options for aortobronchial fistula have included surgical and endovascular stent-graft methods. Herein, a case of an aortobronchial fistula with life-threatening hemoptysis managed with transcatheter embolization of the fistula with N-butyl cyanoacrylate is reported. For the patient with an aortobronchial fistula who cannot be treated by surgical or endovascular stent-graft methods, transcatheter embolization of the fistula may be the only available life-saving method.

Development of a phantom compatible for MRI and hyperthermia using carrageenan gel--relationship between dielectric properties and NaCl concentration.

A phantom has previously been developed containing carrageenan, agarose and gadolinium chloride (called CAG phantom) for MRI with 1.5u2009T. T1 and T2 relaxation times of this phantom are independently changeable by varying concentrations of relaxation-time modifiers to simulate relaxation times of the various types of human tissues. The CAG phantom has a T1 value of 202–1904u2009ms and a T2 value of 38–423u2009ms, when the GdCl3 concentration is varied from 0–140u2009µmol/kg and the agarose concentration is varied from 0–1.6%. A new phantom has now been developed (called CAGN phantom), made by adding an electric conductive agent, NaCl, to the CAG phantom for use in the areas of MRI and hyperthermia research. Dielectric properties of the CAGN phantom were measured and the results of experiments were expressed by the Cole–Cole equation in the frequency range of 5–130u2009MHz. The relationship between the conductivity of the CAGN phantom and the concentration of NaCl was expressed by a linear function in the frequency range of 1–130u2009MHz. The linear function involves a parameter of frequency and, when the frequency is 10u2009MHz, the conductivity of the CAGN phantom can be changed from 0.27–1.26u2009Sm−1 by increasing the NaCl concentration from 0–0.7%. The CAGN phantom developed can be employed in basic experiments for non-invasive temperature measurement using MRI and as a loading phantom for MRI with up to 3u2009T.

Transcatheter Embolization of Pulmonary Artery False Aneurysm Associated with Primary Pulmonary Hypertension

AbstractA 29-year-old woman with primary pulmonarynhypertension presented with recurrent hemoptysis. Contrast-enhanced CTnof the chest demonstrated the enhanced mass surrounded by consolidationnrelated to parenchymal hemorrhage. Pulmonary angiography suggested thatnthe mass was a pulmonary artery false aneurysm. After a microcatheternwas superselectively inserted into the parent artery of the falsenaneurysm, the false aneurysm was successfully treated by transcatheternembolization with coils. Her hemoptysis has never recurred.

Letter to the Editor Re: Transcatheter Embolization of the Left Inferior Phrenic Artery for Hemorrhage from Failure of Esophagojejunostomy

No Abstract