Monte Carlo simulation study to explore optimum conditions for Astatine-211 SPECT.

211At is a promising nuclide for targeted radioisotope therapy. Direct imaging of this nuclide is important for in vivo evaluation of its distribution. We investigated suitable conditions for single-photon emission computed tomography (SPECT) imaging of 211At and assessed their feasibility using a homemade Monte Carlo simulation code, MCEP-SPECT. Radioactivity concentrations of 5, 10, or 20 kBq/mL were distributed in six spheres in a National Electrical Manufactures Association (NEMA) body phantom with a background of 1 kBq/mL. The energy window, projection number, and acquisition time were 71-88 keV, 60, and 60 s, respectively, per projection. A medium-energy collimator and three low-energy collimators were tested. SPECT images were reconstructed using the ordered subset expectation maximization (OSEM) method with attenuation correction (Chang method) and scatter correction (triple-energy-windows method). Image quality was evaluated using the contrast-to-noise ratio (CNR) for detectability and the contrast recovery coefficient (CRC) for quantitavity. The low-energy, high-sensitivity collimator exhibited the best detectability among the four types of collimators, with a maximum CNR value of 43. In contrast, the low-energy, high-resolution collimator exhibited excellent quantitavity, with a maximum CRC value of 102%. Scatter correction improved the image quality. In particular, the CRC value almost doubled after scatter correction. The detection of spheres smaller than 20 mm in diameter was difficult. In summary, low-energy collimators were suitable for the SPECT imaging of 211At. In addition, scatter correction was extremely effective in improving the image quality. The feasibility of 211At SPECT was demonstrated for lesions larger than 20 mm.

13N-ammonia positron emission tomography-derived endocardial strain for the assessment of ischemia using feature-tracking in high-resolution cine imaging.

BACKGROUND: Assessing endocardial strain using a single 13N-ammonia positron emission tomography (PET) scan would be clinically useful, given the association between ischemia and myocardial deformation. However, no software has been developed for strain analysis using PET. We evaluated the clinical potential of feature tracking-derived strain values measured using PET, based on associations with the myocardial flow reserve (MFR). METHODS AND RESULTS: This retrospective study included 95 coronary artery disease patients who underwent myocardial 13N-ammonia PET. Semi-automatic measurements were made using a feature-tracking technique during myocardial cine imaging, and values were calculated using a 16-segment model. Adenosine-stressed global circumferential strain (CS) and global longitudinal strain (LS) values were compared with global MFR values. Stressed and resting global strain values were also compared. Global strain values were significantly lower in 39 patients with abnormal MFRs [< 2.0] than in 56 patients with normal MFRs [≥ 2.0]. The global CS values in the stressed state were significantly decreased than the resting state values in patients with abnormal MFRs. CONCLUSIONS: This study applied endocardial feature-tracking to 13N-ammonia PET, and the results suggested that blood flow and myocardial motility could be clinically assessed in ischemic patients using a single PET scan.

Estimation of the lower limits for feasible Ra-223 SPECT imaging: a Monte Carlo simulation study.

OBJECTIVES: Ra-223 is a promising radionuclide for the treatment of skeletal metastases in castration-resistant prostate cancer patients. This study aims to estimate the lower limits for feasible Ra-223 single-photon emission computerized tomography (SPECT) imaging using a Monte Carlo simulation study. METHODS: The SPECT images were produced on a homemade code: the Monte Carlo simulation of electrons and photons for SPECT (MCEP-SPECT). The National Electrical Manufacturers Association (NEMA) phantom with six hot spheres of diameters of 37, 28, 22, 17, 13, and 10 mm installed inside, was used. The background activity concentration was 0.6 kBq/mL, and the ratios of hot concentrations to the background (R HB) were 25, 20, 15, 10, and 5. When R HB was 15, the background concentrations of 1.5, 0.9, 0.3, and 0.15 kBq/mL were also tested. The energy window was 84 keV±10%. The number of projections was 60/360°, and the acquisition time was 60 s per projection. Two kinds of collimators: middle-energy general-purpose (MEGP) and high-energy general-purpose (HEGP), were examined. The SPECT images were evaluated based on two quantitative indexes: contrast-to-noise ratio (CNR) for detectability and contrast recovery coefficient (CRC) for quantitative accuracy. RESULTS: The CRC for the HEGP collimator was 35-40%, while the CRC for the MEGP collimator was 25-30%. The CNRs for the MEGP collimator were larger than those for the HEGP collimator. The CNRs of the hot spheres with diameters less than 22 mm were lower than 5.0 for both collimators, when R HB and the background concentration were 15 and 0.6 kBq/mL, respectively. Based on the obtained results, it was estimated that the lower limit of R HB for the detection of the hot sphere with a diameter of 37 mm would be approximately 20 if the background concentration is 0.05 kBq/mL. CONCLUSIONS: The MEGP collimator is superior in terms of detectability, while the HEGP collimator is superior in terms of quantitative accuracy. When the lesion size is small, the MEGP collimator may be favorable. Based on these results, the estimated lower limit of the activity concentration would be approximately 1 kBq/mL if the background concentration is 0.05 kBq/mL for a large lesion.

Monte Carlo simulation of the acquisition conditions for 177Lu molecular imaging of hepatic tumors.

OBJECTIVE: To examine the impact of acquisition time on Lutetium-177 (177Lu) single-photon emission computed tomography (SPECT) images using Monte Carlo simulation. METHODS: A gamma camera simulation based on the Monte Carlo method was performed to produce SPECT images. The phantom was modeled on a NEMA IEC BODY phantom including six spheres as tumors. After the administration of 7.4 GBq of 177Lu, radioactivity concentrations of the tumor/liver at 6, 24, and 72 h after administration were set to 1.85/0.201, 2.12/0.156, and 1.95/0.117 MBq/mL, respectively. In addition, the radioactivity concentrations of the tumor at 72 h after administration varied by 1/2, 1/4, and 1/8 when comparison was made. Acquisition times examined were 1.2, 1.5, 2, 3, 6, and 12 min. To assess the impact of collimators, SPECT data acquired at 72 h after the administration using six collimators of low-energy high-resolution (LEHR), extended low-energy general-purpose (ELEGP), medium-energy, and general-purpose (MEGP-1, MEGP-2, and MEGP-3) and high-energy general-purpose (HEGP) were examined. After prefiltering using a Butterworth filter, projection images were reconstructed using ordered subset expectation maximization. The detected photons were classified into direct rays, scattered rays, penetrating rays, and characteristic X-rays from lead. The image quality was evaluated through visual assessment, and physical assessment of contrast recovery coefficient (CRC) and contrast-to-noise ratio (CNR). In this study, the CNR threshold for detectability was assumed to be 5.0. RESULTS: To compare collimators, the highest sensitivity was observed with ELEGP, followed by LEHR and MEGP-1. The highest ratio of direct ray was also observed in ELEGP followed by MEGP-1. In comparison of the radioactivity concentration ratios of tumor/liver, CRC and CNR were significantly decreased with smaller radioactivity concentration ratios. This effect was greater with larger spheres. According to the visual assessment, the acquisition time of 6, 6, and 3 min or longer was required using ELEGP collimator at 6, 24, and 72 h after administration, respectively. Physical assessment based on CNR and CRC also suggested that 6, 6, and 3 min or longer acquisition time was necessary at 6, 24, and 72 h after administration. CONCLUSION: 177Lu-SPECT images generated via the Monte Carlo simulation suggested that the recommended acquisition time was 6 min or longer at 6 and 24 h and 3 min or longer at 72 h after administration.

Evaluation of a Monte Carlo-based algorithm for the influence of totally implantable venous access ports in external radiation therapy.

PURPOSE: This study aimed to assess whether a Monte Carlo (MC)-based algorithm reflects the influence of totally implantable venous access ports (TIVAPs) in external radiation therapy. MATERIALS AND METHODS: The present study comprised two steps: experimental measurements of depth doses and surface doses with and without TIVAPs and calculation with an MC-based algorithm. RESULTS: The TIVAP-associated maximum dose reduction compared with the dose at the same depths without TIVAPs was 7.8% at 4 MV, 6.9% at 6 MV, and 5.7% at 10 MV in measurement, and 7.4% at 4 MV, 6.6% at 6 MV, and 5.5% at 10 MV in calculation. Relative surface doses were higher with TIVAPs made of titanium, due to a higher fluence of backscattered electrons from the TIVAPs, than with plastic TIVAPs. There were no significant differences in the relative differences between the measured and calculated doses of the titanium TIVAP group and the plastic TIVAP group at 4 MV (p = 0.99), 6 MV (p = 0.67), and 10 MV (p = 0.54). CONCLUSION: TIVAPs caused target dose reductions and dose increase near the TIVAP, especially when made of titanium. The influences are reflected in the MC-based algorithm.

Assessment of collimators in radium-223 imaging with channelized Hotelling observer: a simulation study.

OBJECTIVE: Radium-223 (223Ra) is used in unsealed radionuclide therapy for metastatic bone tumors. The aim of this study is to apply a computational model observer to 223Ra planar images, and to assess the performance of collimators in 223Ra imaging. METHODS: The 223Ra planar images were created via an in-house Monte Carlo simulation code using HEXAGON and NAI modules. The phantom was a National Electrical Manufacturers Association body phantom with a hot sphere. The concentration of the background was 55 Bq/mL, and the sphere was approximately 1.5-20 times that of the background concentration. The acquisition time was 10 min. The photopeaks (and the energy window) were 84 (full width of energy window: 20%), 154 (15%), and 270 keV (10%). Each 40 images, with and without hot concentration, were applied to a three-channel difference-of-Gaussian channelized Hotelling observer (CHO), and the signal-to-noise ratio (SNR) of the hot region was calculated. The images were examined using five different collimators: two low-energy general-purpose (LEGP), two medium-energy general-purpose (MEGP), and one high-energy general-purpose (HEGP) collimators. RESULTS: The SNR value was linearly proportional to the contrast of the hot region for all collimators and energy windows. The images of the 84-keV energy window with the MEGP collimator that have thicker septa and larger holes produced the highest SNR value. The SNR values of two LEGP collimators were approximately half of the MEGP collimators. The HEGP collimator was halfway between the MEGP and LEGP. Similar characteristics were observed for other energy windows (154, 270 keV). The SNR value of images captured via the 270-keV energy window was larger than 154-keV, although the sensitivity of the 270-keV energy window is lower than 154-keV. The results suggested a positive correlation between the SNR value and the fraction of unscattered photons. CONCLUSIONS: The SNR value of CHO reflected the performance of collimators and was available to assess and quantitatively evaluate the collimator performance in 223Ra imaging. The SNR value depends on the magnitudes of unscattered photon count and the fraction of unscattered photon count. Consequently, in this study, MEGP collimators performed better than LEGP and HEGP collimators for 223Ra imaging.

Comparison of TOF-PET and Bremsstrahlung SPECT Images of Yttrium-90: A Monte Carlo Simulation Study.

OBJECTIVES: Yttrium-90 (90Y) is a beta particle nuclide used in targeted radionuclide therapy which is available to both single-photon emission computed tomography (SPECT) and time-of-flight (TOF) positron emission tomography (PET) imaging. The purpose of this study was to assess the image quality of PET and Bremsstrahlung SPECT by simulating PET and SPECT images of 90Y using Monte Carlo simulation codes under the same conditions and to compare them. METHODS: In-house Monte Carlo codes, MCEP-PET and MCEP-SPECT, were employed to simulate images. The phantom was a torso-shaped phantom containing six hot spheres of various sizes. The background concentrations of 90Y were set to 50, 100, 150, and 200 kBq/mL, and the concentrations of the hot spheres were 10, 20, and 40 times of those of the background concentrations. The acquisition time was set to 30 min, and the simulated sinogram data were reconstructed using the ordered subset expectation maximization method. The contrast recovery coefficient (CRC) and contrast-to-noise ratio (CNR) were employed to evaluate the image qualities. RESULTS: The CRC values of SPECT images were less than 40%, while those of PET images were more than 40% when the hot sphere was larger than 20 mm in diameter. The CNR values of PET images of hot spheres of diameter smaller than 20 mm were larger than those of SPECT images. The CNR values mostly exceeded 4, which is a criterion to evaluate the discernibility of hot areas. In the case of SPECT, hot spheres of diameter smaller than 20 mm were not discernable. On the contrary, the CNR values of PET images decreased to the level of SPECT, in the case of low concentration. CONCLUSION: In almost all the cases examined in this investigation, the quantitative indexes of TOF-PET 90Y images were better than those of Bremsstrahlung SPECT images. However, the superiority of PET image became critical in the case of low activity concentrations.

Analysis of the influence of 111In on 90Y-bremsstrahlung SPECT based on Monte Carlo simulation.

OBJECTIVE: 90Y-ibritumomab tiuxetan (Zevalin) which is used for the treatment of malignant lymphomas can be used for SPECT imaging based on bremsstrahlung from 90Y beta particles. However, gamma rays emitted by 111In, which is administered to evaluate the indication for the treatment, contaminate the 90Y bremsstrahlung images. Our objective is to investigate the influence of 111In on the 90Y SPECT images using Monte Carlo simulation. METHODS: We used an in-house developed simulation code for the Monte Carlo simulation of electrons and photons (MCEP). Two hot spheres with diameters of 40 mm were put in an elliptical phantom. Both spheres ("sphere 1" and "sphere 2") were filled with 90Y and 111In mixed solutions. The activities of 90Y in sphere 1 and sphere 2 were 241 and 394 kBq/mL, respectively, and the ones of 111In were 8.14 and 13.3 kBq/mL, respectively. The background activity of 90Y was 38.6 kBq/mL, whereas that of 111In was 1.30 kBq/mL; moreover, the acquisition time was 30 min. Two energy windows were used: one is 90-190 keV included the 111In photopeak; the other is 90-160 keV. To evaluate the quality of the SPECT images, the contrast recovery coefficient (CRC) and the constant noise ratio (CNR) of the SPECT images were derived. RESULTS: For the energy window between 90 and 160 keV, the 111In count was 74 % of the total. In that case, the CRC values were 30.1 and 30.7 % for "sphere 1" and "sphere 2", respectively, whereas the CNR values were 6.8 and 12.1, respectively. For the energy window between 90 and 190 keV, the 111In count reached 85 % of the total count. The CRC and CNR values were 38.6 and 40.0 % and 10.6 and 19.4, respectively. CONCLUSIONS: Our simulation study revealed that the cross talk between 111In and 90Y in SPECT imaging is rather serious. Even for the energy window excluding the 111In photopeak, the count ratio of 90Y was less than 30 % of the total. However, the influence of 111In on 90Y-SPECT imaging cannot be ignored, and the count ratio because of 111In is important to estimate the density of 90Y.

A Monte Carlo study on (223)Ra imaging for unsealed radionuclide therapy.

PURPOSE: Radium-223 ((223)Ra), an α-emitting radionuclide, is used in unsealed radionuclide therapy for metastatic bone tumors. The demand for qualitative (223)Ra imaging is growing to optimize dosimetry. The authors simulated (223)Ra imaging using an in-house Monte Carlo simulation code and investigated the feasibility and utility of (223)Ra imaging. METHODS: The Monte Carlo code comprises two modules, hexagon and nai. The hexagon code simulates the photon and electron interactions in the tissues and collimator, and the nai code simulates the response of the NaI detector system. A 3D numeric phantom created using computed tomography images of a chest phantom was installed in the hexagon code. (223)Ra accumulated in a part of the spine, and three x-rays and 19 γ rays between 80 and 450 keV were selected as the emitted photons. To evaluate the quality of the (223)Ra imaging, the authors also simulated technetium-99m ((99m)Tc) imaging under the same conditions and compared the results. RESULTS: The sensitivities of the three photopeaks were 147 counts per unit of source activity (cps MBq(-1); photopeak: 84 keV, full width of energy window: 20%), 166 cps MBq(-1) (154 keV, 15%), and 158 cps MBq(-1) (270 keV, 10%) for a low-energy general-purpose (LEGP) collimator, and those for the medium-energy general-purpose (MEGP) collimator were 33, 13, and 8.0 cps MBq(-1), respectively. In the case of (99m)Tc, the sensitivity was 55 cps MBq(-1) (141 keV, 20%) for LEGP and 52 cps MBq(-1) for MEGP. The fractions of unscattered photons of the total photons reflecting the image quality were 0.09 (84 keV), 0.03 (154 keV), and 0.02 (270 keV) for the LEGP collimator and 0.41, 0.25, and 0.50 for the MEGP collimator, respectively. Conversely, this fraction was approximately 0.65 for the simulated (99m)Tc imaging. The sensitivity with the LEGP collimator appeared very high. However, almost all of the counts were because of photons that penetrated or were scattered in the collimator; therefore, the proportions of unscattered photons were small. CONCLUSIONS: Their simulation study revealed that the most promising scheme for (223)Ra imaging is an 84-keV window using an MEGP collimator. The sensitivity of the photopeaks above 100 keV is too low for (223)Ra imaging. A comparison of the fractions of unscattered photons reveals that the sensitivity and image quality are approximately two-thirds of those for (99m)Tc imaging.

Monte Carlo simulation of PET and SPECT imaging of 90Y.

PURPOSE: Yittrium-90 ((90)Y) is traditionally thought of as a pure beta emitter, and is used in targeted radionuclide therapy, with imaging performed using bremsstrahlung single-photon emission computed tomography (SPECT). However, because (90)Y also emits positrons through internal pair production with a very small branching ratio, positron emission tomography (PET) imaging is also available. Because of the insufficient image quality of (90)Y bremsstrahlung SPECT, PET imaging has been suggested as an alternative. In this paper, the authors present the Monte Carlo-based simulation-reconstruction framework for (90)Y to comprehensively analyze the PET and SPECT imaging techniques and to quantitatively consider the disadvantages associated with them. METHODS: Our PET and SPECT simulation modules were developed using Monte Carlo simulation of Electrons and Photons (MCEP), developed by Dr. S. Uehara. PET code (MCEP-PET) generates a sinogram, and reconstructs the tomography image using a time-of-flight ordered subset expectation maximization (TOF-OSEM) algorithm with attenuation compensation. To evaluate MCEP-PET, simulated results of (18)F PET imaging were compared with the experimental results. The results confirmed that MCEP-PET can simulate the experimental results very well. The SPECT code (MCEP-SPECT) models the collimator and NaI detector system, and generates the projection images and projection data. To save the computational time, the authors adopt the prerecorded (90)Y bremsstrahlung photon data calculated by MCEP. The projection data are also reconstructed using the OSEM algorithm. The authors simulated PET and SPECT images of a water phantom containing six hot spheres filled with different concentrations of (90)Y without background activity. The amount of activity was 163 MBq, with an acquisition time of 40 min. RESULTS: The simulated (90)Y-PET image accurately simulated the experimental results. PET image is visually superior to SPECT image because of the low background noise. The simulation reveals that the detected photon number in SPECT is comparable to that of PET, but the large fraction (approximately 75%) of scattered and penetration photons contaminates SPECT image. The lower limit of (90)Y detection in SPECT image was approximately 200 kBq/ml, while that in PET image was approximately 100 kBq/ml. CONCLUSIONS: By comparing the background noise level and the image concentration profile of both the techniques, PET image quality was determined to be superior to that of bremsstrahlung SPECT. The developed simulation codes will be very useful in the future investigations of PET and bremsstrahlung SPECT imaging of (90)Y.

Assessment of the efficacy of early phase parameters by (123)I-MIBG dynamic imaging for distinguishing Lewy body-related diseases from Parkinson's syndrome.

OBJECTIVE: The aim of this study was to assess the efficacy of early phase washout rate (early WR) and area under the time-activity curve (AUTAC) by (123)I-metaiodobenzylguanidine (MIBG) dynamic chest imaging for distinguishing Lewy body-related diseases (LBRD) from Parkinson's syndrome (PS) and reducing examination time. METHODS: Sixty-two patients with suspected LBRD who underwent (123)I-MIBG dynamic imaging in early phase were retrospectively selected. The early WR and AUTAC were calculated from (123)I-MIBG dynamic data of the heart. We evaluated the relationships between proposed and conventional parameters by using Spearman's rank correlation coefficient. Differences in parameters between LBRD and PS groups were tested for statistical significance using the Mann-Whitney U test. The diagnostic performance of all parameters for distinguishing LBRD from PS was assessed in terms of receiver operating characteristic (ROC) analysis. Additionally, combination diagnostic performance and concordance rate between early phase parameters and late H/M ratio by kappa statistics were also assessed. RESULTS: The early WR and AUTAC showed a positive and negative correlation with conventional parameters. Both the early WR and AUTAC of LBRD group were significantly distinguishable from those of the PS group (p < 0.001). Area under the ROC curve of the early WR (0.98) was greater than that of AUTAC (0.91). The diagnostic performance of combination of the early phase parameters was 93 % sensitivity and 100 % specificity. Moreover, the early phase parameters showed excellent agreement with late H/M ratio (k = 0.93). CONCLUSIONS: The early WR and AUTAC showed high performance for distinguishing LBRD from PS, and the combination diagnosis with early H/M ratio and early WR contribute to improve the diagnostic performance. Thus, these parameters would be useful for reducing the examination time of myocardial (123)I-MIBG scintigraphy to diagnose LBRD.

Optimal radiation shielding for beta and bremsstrahlung radiation emitted by (89)Sr and (90)Y: validation by empirical approach and Monte Carlo simulations.

OBJECTIVE: High-energy beta emitters such as Strontium-89 ((89)Sr) and Yttrium-90 ((90)Y) are becoming increasingly popular nuclear therapy sources in Japan for treating cancer. Various characteristics of materials must be considered when designing radiation protection device for high-energy beta emitters. We empirically measured and simulated dose equivalents of beta and bremsstrahlung radiation arising from (89)Sr and (90)Y radiation shielded with various materials and determined optimal shielding materials against these sources. METHODS: The dose equivalents of (89)Sr and (90)Y determined experimentally using an ionization chamber survey meter were compared with those of Monte Carlo simulations. The relative dose equivalents of beta and bremsstrahlung radiation separately transmitted by changing the thickness of acrylic, aluminum, iron, lead and tungsten shielding materials were simulated. RESULTS: Dose equivalents were consistent between the empirical measurements and the simulation to within ±5%. Shielding ability was more effective in the order of tungsten, lead, iron, aluminum and acrylic against both (89)Sr and (90)Y. The amount of beta and bremsstrahlung radiation transmitted through tungsten and lead was relatively small. Although such high-density material generates much bremsstrahlung radiation, it absorbs the bremsstrahlung radiations. CONCLUSIONS: Tungsten was the optimal material for efficient shielding against (89)Sr and (90)Y radiation and preferable among operators. The present findings provide useful information about how to define an appropriate shielding strategy for high-energy beta emitters.

Decreased resting energy expenditure in patients with Duchenne muscular dystrophy.

BACKGROUND: Skeletal muscle metabolism is a major determinant of resting energy expenditure (REE). Although the severe muscle loss that characterizes Duchenne muscular dystrophy (DMD) may alter REE, this has not been extensively investigated. METHODS: We studied REE in 77 patients with DMD ranging in age from 10 to 37 years using a portable indirect calorimeter, together with several clinical parameters (age, height, body weight (BW), body mass index (BMI), vital capacity (VC), creatine kinase, creatinine, albumin, cholinesterase, prealbumin), and assessed their influence on REE. In addition, in 12 patients maintaining a stable body weight, the ratio of energy intake to REE was calculated and defined as an alternative index for the physical activity level (aPAL). RESULTS: REE (kcal/day, mean±SD) in DMD patients was 1123 (10-11 years), 1186±188 (12-14 years), 1146±214 (15-17 years), 1006±136 (18-29 years) and 1023±97 (≥30 years), each of these values being significantly lower than the corresponding control (p<0.0001). VC (p<0.001) was the parameter most strongly associated with REE, followed by BMI (p<0.01) and BW (p<0.05). The calculated aPAL values were 1.61 (10-11 years), 1.19 (12-14 years), 1.16 (15-17 years), and 1.57 (18-29 years). CONCLUSION: The REE in DMD patients was significantly lower than the normal value in every age group, and strongly associated with VC. Both the low REE and PAL values during the early teens, resulting in a low energy requirement, might be related to the obesity that frequently occurs in this age group. In contrast, the high PAL value in the late stage of the disease, possibly due to the presence of respiratory failure, may lead to a high energy requirement, and thus become one of the risk factors for development of malnutrition.

Brachial and lumbar plexuses in chronic inflammatory demyelinating polyradiculoneuropathy: MRI assessment including apparent diffusion coefficient.

INTRODUCTION: Our purpose was to clarify the magnetic resonance (MR) imaging characteristics of the brachial and lumbar plexuses in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) using various kinds of sequences, including diffusion-weighted images (DWI). METHODS: We evaluated the MR imaging findings for lumbar and/or brachial nerve plexuses in 13 CIDP patients and 11 normal volunteers. The nerve swelling was evaluated in comparison with normal controls by coronal short tau inversion recovery (STIR), and signal abnormalities were evaluated by coronal STIR, T1-weighted images, and DWIs. The degrees of contrast enhancement and apparent diffusion coefficient (ADC) values of the plexus were also assessed. RESULTS: In the patient group, diffuse enlargement and abnormally high signals were detected in 16 out of 24 plexuses (66.7%) on STIR, a slightly high signal was detected in 12 of 24 plexuses (50%) on T1-weighted images, and a high-intensity signal was detected in 10 of 18 plexuses (55.6%) on DWIs with high ADC values. Contrast enhancement of the plexuses was revealed in 6 of 19 plexuses (31.6%) and was mild in all cases. There were statistically significant differences between the ADC values of patients with either swelling or abnormal signals and those of both normal volunteers and patients without neither swelling nor abnormal signals. There were no relationships between MR imaging and any clinical findings. CONCLUSION: STIR is sufficient to assist clinicians in diagnosing CIDP. T1-weighted images and DWIs seemed useful for speculating about the pathological changes in swollen plexuses in CIDP patients.

[The parents' assessment and needs for home mechanical ventilation in patients with pediatric neurological disorders].

Parents' of patients with pediatric neurological disorders were sent a questionnaire, on their assessment and needs for home mechanical ventilation (HMV). Nine of 12 enrolled families responded. Respirator troubles were handled by a contracted HMV company. Decreased SpO2 levels and endotracheal bleeding were cared by family members under telephone instructions of doctors, though they felt anxious about dealing the problems. The mothers felt happy to live with their children by virtue of HMV, however, they had strong stress about the management of emergency care and medical care technique. They also felt very tired physically, but refreshed by being free from daily HMV care for a short time and enjoying their own time. The parents were not satisfied with the present house facilities and education system. They evaluated the induction of HMV positively but were most anxious for a better home care nursing system, doctors responding to a house call, more information on HMV, reduction of their anxieties and fatigue, and improvement of economical and educational environments.