[Incidental Cardiac Uptake in Bone Scintigraphy Establishing a Diagnosis of Transthyretin Amyloid Cardiomyopathy: A Case Report].

This is a case of a male patient in his 70s undergoing endocrine therapy for castration-resistant prostate cancer. On follow-up, he underwent whole-body bone scintigraphy for bone metastasis surveillance, and incidental cardiac uptake was identified. The findings were reported by the radiologist to the urologist, which was followed by a cardiac consultation. Late gadolinium enhancement magnetic resonance imaging did not detect typical patterns suggestive of cardiac amyloidosis. However, pyrophosphate scintigraphy identified cardiac uptake. These findings were indicative of transthyretin amyloid cardiomyopathy, and we confirmed the diagnosis by endomyocardial biopsy. In about 0.4-2.0 percentage of elderly patients, incidental cardiac uptake in bone scintigraphy has been reported. Bone scintigraphy is the most commonly utilized techniques among all scintigraphies. Thus, it is crucial that radiologists recognize and report the findings to establish a diagnosis of transthyretin amyloid cardiomyopathy.

[Impact of Misregistration between the Myocardial Perfusion Images and CT Attenuation Correction Map on the %up Take with 17 Segments Polar Map].

PURPOSE: Computed tomography (CT) attenuation correction of myocardial perfusion in single-photon emission computed tomography (SPECT) /CT systems is possibility of misregistration between emission and transmission scans. This study aimed to evaluate the influence of misregistration using a polar map of 17 segments model. METHODS: Using the fusion software, we assessed the magnitude and direction of misregistration in 200 consecutive myocardial perfusion SPECT images with 99mTechnetium (99mTc) tetrofosmin. After registration, CT data was shifted by ±1, ±2, and ±3 pixels along the cephalad/caudal, dorsal/ventral, and left/right axes, respectively. The registered image was compared with the shifted image. RESULTS: Misregistration between the SPECT and CT images occurred by 1-2 pixels in 127 cases (63.5%) and by 2 or more pixels in four cases (2%); the maximum misregistration was 1.2±0.4 pixels on average. The polar map scoring was most significantly affected by 3 pixel ventral shift. A ventral shift of 1 pixel affected the scores for the anterolateral and inferolateral segments, whereas a caudal shift of 1 pixel affected the scores for the anterior segment. CONCLUSION: Since the 17 segments model can evaluate the position more precisely than the five segments model, it is possible to evaluate up to 1 pixel misregistration.

An in vitro verification of strength estimation for moving an 125I source during implantation in brachytherapy.

This study aims to demonstrate the feasibility of a method for estimating the strength of a moving brachytherapy source during implantation in a patient. Experiments were performed under the same conditions as in the actual treatment, except for one point that the source was not implanted into a patient. The brachytherapy source selected for this study was 125I with an air kerma strength of 0.332 U (µGym2h-1), and the detector used was a plastic scintillator with dimensions of 10 cm × 5 cm × 5 cm. A calibration factor to convert the counting rate of the detector to the source strength was measured and then the accuracy of the proposed method was investigated for a manually driven source. The accuracy was found to be under 10% when the shielding effect of additional needles for implantation at other positions was corrected, and about 30% when the shielding was not corrected. Even without shielding correction, the proposed method can detect dead/dropped source, implantation of a source with the wrong strength, and a mistake in the number of the sources implanted. Furthermore, when the correction was applied, the achieved accuracy came close to within 7% required to find the Oncoseed 6711 (125I seed with unintended strength among the commercially supplied values of 0.392, 0.462 and 0.533 U).

Evaluation of Size Correction Factor for Size-specific Dose Estimates (SSDE) Calculation.

American Association of Physicists in Medicine (AAPM) Report No.204 recommends the size-specific dose estimates (SSDE), wherein SSDE=computed tomography dose index-volume (CTDIvol )×size correction factor (SCF), as an index of the CT dose to consider patient thickness. However, the study on SSDE has not been made yet for area detector CT (ADCT) device such as a 320-row CT scanner. The purpose of this study was to evaluate the SCF values for ADCT by means of a simulation technique to look into the differences in SCF values due to beam width. In the simulation, to construct the geometry of the Aquilion ONE X-ray CT system (120 kV), the dose ratio and the effective energies were measured in the cone angle and fan angle directions, and these were incorporated into the simulation code, Electron Gamma Shower Ver.5 (EGS5). By changing the thickness of a PMMA phantom from 8 cm to 40 cm, CTDIvol and SCF were determined. The SCF values for the beam widths in conventional and volume scans were calculated. The differences among the SCF values of conventional, volume scans, and AAPM were up to 23.0%. However, when SCF values were normalized in a phantom of 16 cm diameter, the error tended to decrease for the cases of thin body thickness, such as those of children. It was concluded that even if beam width and device are different, the SCF values recommended by AAPM are useful in clinical situations.

[Development of a Lead-covered Case for a Wireless X-ray Output Analyzer to Perform CT Half-value Layer Measurements].

Measurement of the half-value layer (HVL) is a difficult task in computed tomography (CT) , because a nonrotating X-ray tube must be used. The purpose of this study is to develop a lead-covered case, which enables HVL measurements with a rotating CT X-ray tube. The lead-covered case was manufactured from acrylic and lead plates, which are 3 mm thick and have a slit. The slit-detector distance can be selected between 14 mm and 122 mm. HVL measurements were performed using a wireless X-ray output analyzer "Piranha." We used the following exposure conditions: tube voltages of 80, 100, and 120 kV; a tube current of 550 mA; and an exposure time of 1.0 s. The HVLs were measured by using the following two methods: (a) Nonrotating method-a conventional method that uses the nonrotating exposure mode. (b) Rotating method-a new method that uses the lead-covered case and the rotating exposure mode. As a result, when the slit-detector distance was 58 mm, the HVL values obtained by the nonrotating and rotating methods were 4.38 and 4.24 mmAl at 80 kV, 5.51 and 5.37 mmAl at 100 kV, 6.61 and 6.48 mmAl at 120 kV, respectively. A lead-covered case, which enables the measurement of the HVL in a rotating X-ray tube, was developed. The case is useful in measuring the HVLs at facilities that cannot fix the X-ray tube.

A comparison of the dose distributions between the brachytherapy 125I source models, STM1251 and Oncoseed 6711, in a geometry lacking radiation equilibrium scatter conditions.

The purpose of this study was to estimate the uncertainty in the dose distribution for the (125)I source STM1251, as measured with a radiophotoluminescent glass rod dosimeter and calculated using the Monte Carlo code EGS5 in geometry that included the source structure reported by Kirov et al. This was performed at a range of positions in and on a water phantom 18 cm in diameter and 16 cm in length. Some dosimetry positions were so close to the surface that the backscatter margin was insufficient for photons. Consequently, the combined standard uncertainty (CSU) at the coverage factor k of 1 was 11.0-11.2% for the measurement and 1.8-3.6% for the calculation. The calculation successfully reproduced the measured dose distribution within 13%, with CSU at k ≤ 1.6 (P > 0.3). Dose distributions were then compared with those for the (125)I source Oncoseed 6711. Our results supported the American Association of Physicists in Medicine Task Group No. 43 Updated Protocol (TG43U1) formalism, in which STM1251 dose distributions were more penetrating than those of Oncoseed 6711. This trend was also observed in the region near the phantom surface lacking the equilibrium radiation scatter conditions. In this region, the difference between the TG43U1 formalism and the measurement and calculation performed in the present study was not significant (P > 0.3) for either of the source models. Selection of the source model based on the treatment plans according to the TG43U1 formalism will be practical.

Strength estimation of a moving 125Iodine source during implantation in brachytherapy: application to linked sources.

This study sought to demonstrate the feasibility of estimating the source strength during implantation in brachytherapy. The requirement for measuring the strengths of the linked sources was investigated. The utilized sources were (125)I with air kerma strengths of 8.38-8.63 U (µGy m(2) h(-1)). Measurements were performed with a plastic scintillator (80 mm × 50 mm × 20 mm in thickness). For a source-to-source distance of 10.5 mm and at source speeds of up to 200 mm s(-1), a counting time of 10 ms and a detector-to-needle distance of 5 mm were found to be the appropriate measurement conditions. The combined standard uncertainty (CSU) with the coverage factor of 1 (k = 1) was ∼15% when using a grid to decrease the interference by the neighboring sources. Without the grid, the CSU (k = 1) was ∼5%, and an 8% overestimation due to the neighboring sources was found to potentially cause additional uncertainty. In order to improve the accuracy in estimating source strength, it is recommended that the measurment conditions should be optimized by considering the tradeoff between the overestimation due to the neighboring sources and the intensity of the measured value, which influences the random error.

A dosimetry method for low dose rate brachytherapy by EGS5 combined with regression to reflect source strength shortage.

The post-implantation dosimetry for brachytherapy using Monte Carlo calculation by EGS5 code combined with the source strength regression was investigated with respect to its validity. In this method, the source strength for the EGS5 calculation was adjusted with the regression, so that the calculation would reproduce the dose monitored with the glass rod dosimeters (GRDs) on a water phantom. The experiments were performed, simulating the case where one of two (125)I sources of Oncoseed 6711 was lacking strength by 4-48%. As a result, the calculation without regression was in agreement with the GRD measurement within 26-62%. In this case, the shortage in strength of a source was neglected. By the regression, in order to reflect the strength shortage, the agreement was improved up to 17-24%. This agreement was also comparable with accuracy of the dose calculation for single source geometry reported previously. These results suggest the validity of the dosimetry method proposed in this study.

Measurement of the strength of iodine-125 seed moving at unknown speed during implantation in brachytherapy.

The aim of this study is to demonstrate the feasibility of estimating the strength of the moving radiation source during patient implantation. The requirement for the counting time was investigated by comparing the results of the measurements for the static source with those for the source moving at 2, 5, 10 and 20 cm s(-1). The utilized source was (125)I with an air-kerma strength of 0.432 U (µGym(2)h(-1)). The detector utilized was a plastic scintillation detector (8 cm × 5 cm × 2 cm in thickness) set at 8 cm away from the needle to guide the source. Experiments were conducted in order to determine the most desirable counting time. Analysis using the maximum of the measured values while the source passed through the needle indicated that the results for the moving source increased more than those for the static source as the counting time decreased. The combined standard uncertainty, with the coverage factor of 1, was within 4% at the counting time of 100 ms. This investigation supported the feasibility of the method proposed for estimating the source strength during the implantation procedure, regardless of the source speed. The method proposed is a potential option for reducing the risk of accidental replacements of sources with those of incorrect strengths.

[Study of radiation dose to the eye lens by multi-detector row computed tomography of the temporal bone].

The exposure of the eye lens caused by multi-detector row computed tomography (MDCT) of the temporal bone is a serious problem. Our aim was to evaluate the radiation dose to the eye lens by different scan baselines (orbitomeatal line; OML, acanthiomeatal line; AML) and examine the difference of the depiction of the temporal bone structures. Measurement of the exposure to the eye lens was performed by means of MDCT of the temporal bone with a radio-photoluminescence glass dosimeter using a rand phantom. Moreover, we studied only one volunteer (58-year-old male) who had no symptom and was not suspected of having any ear abnormalities with a two scan baseline. Visualization of the major anatomical structures of the temporal bone (the tympanic portion of the facial nerve canal, the body of the incus, stapes superstructures, vestibule etc.) was performed on the volunteer. The average absorbed dose was 6.42 mGy by the OML and 1.59 mGy by the AML, respectively. With regard to visualization of the temporal bone structures, all structures were of equal quality with the two scan baseline. With the AML line, the radiation dose to the eye lens was reduced to 75%. Therefore, the authors recommended an AML for use for MDCT of the temporal bone. In clinical practice, the optimization of scanning factor (kVp, mAs etc.) and the use of the radio-protection should be implemented for radiation dose reduction of the eye lens by MDCT of the temporal bone.

A dosimetry study of the Oncoseed 6711 using glass rod dosimeters and EGS5 Monte Carlo code in a geometry lacking radiation equilibrium scatter conditions.

PURPOSE: The aim of this study was to develop a dose calculation method which is applicable to the interseed attenuation and the geometry lacking the equilibrium radiation scatter conditions in brachytherapy. METHODS: The dose obtained from measurement with a radiophotoluminescent glass rod dosimeter (GRD) was compared to the dose calculated with the Monte Carlo (MC) code "EGS5," using the 125I source structure detailed in by Kennedy et al. The GRDs were irradiated with 125I Oncoseed 6711 in a human head phantom. The phantom was a cylinder made of 2 mm thick PMMA with a diameter of 18 cm and length of 16 cm. Some of the GRD positions were so close to the phantom surface that the backscatter margin was less than 5 cm, insufficient for photons. RESULTS: The EGS5 simulations were found to reproduce the relative dose distributions as measured with the GRDs to within 25% uncertainty in the geometry lacking the equilibrium radiation scatter conditions. The absolute value of the GRD measurement agreed with the American Association of Physicist in Medicine Task Group No 43 Updated Protocol (AAPM-TG43U1) formalism to within 3% of the reference point (r = 1 cm, theta = 90 degrees), where the TG43U1 is especially reliable because of the abundant data accumulation in composing the formalism. The factor to normalize the measured or calculated dose to the TG43U1 estimate at the reference point was evaluated to be 0.97 for the GRD measurement and 1.8 for the MC calculation, which uses the integration of the apparent activity with the time as the amount of disintegration during the irradiation. Also, F(r,theta) and g(r) estimated by this calculation method were consistent with those proposed in the TG43U1. CONCLUSIONS: The results of this investigation support the validity of both the MC calculation method and GRD measurement in this study as well as the TG-43U1 formalism. Also, this calculation is applicable to interseed attenuation and the geometry lacking the equilibrium radiation scatter.