Clinical evaluation of 3D high-resolution isotropic knee MRI using Multi-Interleaved X-prepared TSE with inTUitive RElaxometry (MIXTURE) for simultaneous morphology and T2 mapping.

PURPOSE: Quantitative MRI techniques such as T2 mapping are useful in comprehensive evaluation of various pathologies of the knee joint yet require separate scans to conventional morphological measurements and long acquisition times. The recently introduced 3D MIXTURE (Multi-Interleaved X-prepared Turbo-Spin Echo with Intuitive Relaxometry) technique can obtain simultaneous morphologic and quantitative information of the knee joint. To compare MIXTURE with conventional methods and to identify differences in morphological and quantitative information. METHODS: Phantom studies were conducted, and in vivo human scans were performed (20 patients) presented with knee arthralgia. MIXTURE is based on 3D TSE without and with T2 preparation modules in an interleaved manner for both morphology with PDW and fat suppressed T2W imaging as well as quantitative T2 mapping within one single scan. Image quality and lesion depiction were visually assessed and compared between MIXTURE and conventional 2D TSE by two experienced radiologists. Contrast-to-noise ratio was used to assess the adjacent tissue contrast in a quantitative way for both obtained PDW and fat suppressed T2W images. Quantitative T2 values were measured in phantom and from in vivo knee cartilage. RESULTS: The overall diagnostic confidence and contrast-to-noise ratio were deemed comparable between MIXTURE and 2D TSE. While the chosen T2 preparation modules for MIXTURE rendered consistent T2 values comparing to the current standard, measured cartilage T2 values ranged from 26.1 to 50.7 ms, with significant difference between the lesion and normal areas (p < 0.05). CONCLUSIONS: MIXTURE can help to provide high-resolution information for both anatomical and pathological assessment.

Relationship between assistant's lens exposure and dose information during computed tomography examinations.

According to International Commission of Radiological Protection, the equivalent dose limit for the eye lens for occupational exposure is recommended to be 20 mSv yr-1, averaged over 5 years, with no single year above 50 mSv. Some studies reported the measurement of assistant's lens exposure in diagnostic computed tomography (CT) examinations, but further investigation is still required in the association between the lens dose for assistants and various dose parameters. Therefore, we measured the assistant's lens exposure using small optically stimulated luminescence dosimeters. The type of occupation, type of assistance, total scan time, total mAs, total scan length, and dose-length product (DLP) were recorded and analyzed in association with air kerma at the lens position. The assistance was classified into four types: 'assisted ventilation,' 'head holding,' 'body holding,' and 'raising patient's arm.' The air kerma of lens position was not significantly different for each assistance type (p< 0.05, Kruskal-Wallis test). Further, the lens doses for assistants correlated with DLP, but with various strengths of correlation with the assistance type and were influenced by the distance from the CT gantry. In conclusion, lens dose during assistance and DLP demonstrated the strongest correlation. 'Raising patient's arm' and 'head holding' exhibited stronger correlations, which required less table movement during the CT scan than 'assisted ventilation' and 'body holding'.

Evaluation of x-ray effective focal spot size dependency on x-ray exposure settings using edge response analysis.

The effective focal spot size of x-ray tubes is one of the major factors that substantially affect the resultant x-ray images, and it is known to be dependent on the x-ray exposure setting used. This study aims to evaluate the relationship between the effective focal spot size and the tube current and voltage and assess its reproducibility among several x-ray tubes. The evaluation was performed using edge response analysis, in which a 1-mm thick tungsten edge was projected onto a flat panel detector with a magnification factor of 2. The edge image was then differentiated to obtain the line spread function, followed by a detector blur-removing process through Fourier analysis to obtain the true focus profile. The resultant focal spot size increased as the tube current increased, whereas it decreased as the tube voltage increased, as expected. The rate of change was similar along the width and the length directions, while the small focus changed more significantly than the large focus. The reproducibility among four x-ray tubes of the same model was excellent as the maximum variation < 20%. In conclusion, the edge response method can provide useful information on the x-ray focal spot relationship with the x-ray exposure settings used, as well as its reproducibility among several x-ray tubes.

Usefulness of a lead-acrylic shield for reducing lens dose of assistant in x-ray CT examination.

In computed tomography (CT) examinations, the usefulness of protective glasses for reducing lens exposure to assistants has been reported. The present study aimed to compare the dose reduction effect for assistants with lead-acrylic shields and protective glasses (0.07 mm Pb, 0.5 mm Pb) during CT examination. The air dose distribution in a CT examination room with and without a lead-acrylic shield was compared. It was found that the amount of scattered radiation was significantly reduced by installing a lead-acrylic shield at the CT gantry aperture. Moreover, the reduction rate of air kerma at the assistant's lens was higher using the lead acrylic shield than with the protective glasses-95.7% during head holding and 76.1% during assisted ventilation.

The Quantity and Quality of Lumbar Muscles and Lumbopelvic Parameters in Patients With Degenerative Spondylolisthesis.

Introduction Lumbar degenerative spondylolisthesis (DS) is one of the most common causes of low back pain. The lumbar muscles, such as the psoas major (PM), erector spinae (ES), and multifidus (MF) muscles, play an important role in the stability and functional movement of the lumbar spine. The quantities and qualities of these muscles may be related to the occurrence of DS and lumbopelvic parameters, such as lumbar lordosis (LL) and sacral slope (SS). However,the influence of lumbar muscles on DS and lumbopelvic alignment is not well understood. Methods Patients with L4 DS (DS group, n=25) and without DS (non-DS group, n=25) were included. Using sagittal reconstructed CT images of patients who visited our hospital for reasons other than low back disorders, LL, upper lumbar lordosis ([ULL] L1-L4), lower lumbar lordosis ([LLL] L4-S1), and SS were examined. To evaluate the quantity and quality of lumbar muscles, the gross cross-sectional area (GCSA), functional cross-sectional area (FCSA), and fat infiltration (FI) of the PM, ES, and MF muscles were measured by CT images. The lumbopelvic parameters, FCSA, GCSA, and FI of lumbar muscles were compared between the two groups. Then, each lumbar muscle parameter was analyzed for correlation with DS and lumbopelvic parameters. Results DS patients displayed significantly greater ULL and lower FI of the PM and ES muscles than non-DS patients (p=0.0078, 0.031, and 0.010, respectively). The FI of the ES muscle was significantly correlated with the presence of DS (p=0.010). The FCSA of the ES and MF muscles and the GCSA of the MF muscle showed a significant correlation with LL and SS in the non-DS group (p<0.05), but not in the DS group.. Conclusion ULL was greater in L4 DS patients, possibly related to the better quality of the ES muscle. All DS patients showed mild (grade I) spondylolisthesis, suggesting the possibility that lumbar muscle quality is better in patients with mild DS than in those without DS. The ES and MF muscles may play an important role in maintaining the lumbar lordotic angle in non-DS patients but not in DS patients.

Computed Tomographic Assessment of Age- and Gender-Specific Sagittal Lumbopelvic Alignment in a Japanese Population.

INTRODUCTION: Previous studies have reported differences in lumbopelvic alignment between standing and supine positions. Computed tomography (CT) images taken in the supine position are often used for clinical studies in addition to standing radiographs, although not frequently. Our study aims to clarify normative values of CT-evaluated lumbopelvic parameters and the characteristics of age- and gender-related lumbopelvic alignment in the supine position. METHODS: Patients undergoing CT scans of abdominal or lumbar regions for reasons other than low back disorders were included (n=581). Sagittal multiplanar reconstruction CT images were obtained, and lumbar lordosis (LL), L5-S1 angle, and sacral slope (SS) were measured. Mean values of the parameters in patients aged 59 years and under, 60-69, 70-79, and 80 and over, and in males and females, were calculated. Age- and gender-related differences in these parameters were statistically analyzed. RESULTS: Among the four age groups, patients 80 years and over showed significantly lower LL and SS than patients aged 70-79. Females 80 years and over showed significantly lower LL and SS than all other age groups, but those in males did not. The comparison between males and females showed no significant differences in LL and SS; however, the L5-S1 angle was significantly higher in males than in females. In patients 80 years and over, females showed significantly lower LL and SS than in males. CONCLUSIONS: This study provides normative CT-evaluated lumbopelvic parameters, such as LL, L5-S1 angle, and SS, which will be utilized for comparisons in future studies. The present study first revealed that pelvic retroversion and lumbar kyphosis occur in elderly females in the supine position, which raised a possibility that age-related decrease of LL and SS in females occurs at an older age in the supine position than in the standing position.

[Imaging Parameter Optimization of 3D Radial Stack-of-stars MRA with FID Sampling after Treatment of Cerebral Aneurysms with Metallic Devices].

Magnetic resonance angiography (MRA) using ultra-short TE (uTE) is known to be used for the evaluation of cerebral aneurysm after treatment such as clipping and coiling. However, conventional uTE sequences are not appropriate as an additional imaging sequence for 3D time-of-flight (TOF)-MRA because it is not possible to shorten scan time and acquire selective-volume imaging. To solve the problem, we focused on the combination of uTE sampling and 3D radial scan sequences. In this study, we examined the optimal imaging parameters of the proposed uTE-MRA. A simulated blood flow phantom with stents (Enterprise) and titanium clips (YASARGIL) was used for optimizing the TR, flip angle (FA), and radial percentage. The signal intensity in the simulated vessel was measured in each imaging condition, and the ratio of the presence or absence of a stent was evaluated as a relative in-stent signal (RIS). In addition, the diameter of the signal loss of the simulated artery was measured for each imaging condition, and signal loss length (SLL) of a clip was calculated from the average value. The RIS improved with increasing the FA and shortening the TR, but it did not change by changing the radial percentage. The SLL became smaller at the coil as the FA increased, but there was no significant difference between the intersection and the blade. There was also no significant difference between TR and radial percentage. The effective imaging conditions for uTE-MRA to improve the vascular description of the evaluation after treatment of cerebral aneurysms with metallic devices were those with large FA and short TR.

Age-Specific Characteristics of Lumbopelvic Alignment in Patients with Spondylolysis: How Bilateral L5 Spondylolysis Influences Lumbopelvic Alignment During the Aging Process.

BACKGROUND: To elucidate the influence of spondylolysis on age-related lumbar degenerative changes, age-specific lumbopelvic alignment in patients with or without spondylolysis was examined. METHODS: Sagittal reconstructed computed tomography images of the lumbar spine in consecutive patients (n = 581) undergoing computed tomography scans of abdominal or lumbar regions for reasons other than low back disorders were obtained. Lumbar lordosis (LL), L5-S1 angle, and sacral slope (SS) were measured. Lumbopelvic parameters in patients with or without spondylolysis were evaluated in 3 age groups (<50, 50-69, and ≥70). The influence of bilateral L5 spondylolysis (L5-lysis) and L5 vertebral slip on each lumbopelvic parameter, as well as correlation between cross-sectional area (CSA) of paraspinal muscles and the degree of vertebral slip, were examined by multiple regression analysis. RESULTS: Patients with bilateral spondylolysis showed greater LL and SS than patients without spondylolysis. When analyzing the influence of L5-lysis, only elderly patients (≥70) with L5-lysis showed significantly greater LL and SS than nonspondylolysis (nonlysis) patients. L5-lysis patients more frequently showed L5 vertebral slip than nonlysis patients, and a smaller L5-S1 angle was observed when L5 vertebral slip accompanied L5-lysis. The degree of vertebral slip was significantly correlated with CSA of psoas muscles, but not with CSA of paraspinal extensor muscles. CONCLUSIONS: When patients have L5-lysis, lumbar lordosis and pelvic anteversion occurred age dependently. In elderly patients with L5-lysis, L5 vertebral slip with decrease of the L5-S1 angle occurs frequently. The progression of vertebral slip was correlated with atrophy of psoas muscles, but not that of paraspinal extensor muscles.

[Usefulness of a Contrast Dose Administration System Using the Radiology Information System].

We report on the construction of a system for managing prior information and injection condition used for contrast enhance CT examination using radiology information system (RIS). Contrast dose administration system using the RIS was possible to retrospectively investigate optimal injection conditions from the database. As the prior information, we designed the patient's profile information of the hospital information system (HIS) to reflect the patient's height, weight, and kidney function (eGFR, Cre), which is necessary information for contrast enhance CT examination, in the RIS. By adding E-Box (DICOM Gateway) to the injector, it became possible to reflect the amount of contrast agent used in patients and injection conditions at contrast enhance CT examination. The contrast agent use information is transmitted to RIS by using modality performed procedure step (MPPS). Database of injection condition at contrast enhance CT examination using the RIS, to determine the optimal injection conditions retrospectively. By utilizing the massive amount of clinical information stored in the RIS, the amount of contrast agent and injection condition at contrast enhance CT examination could be optimized. Reproducibility of the contrast effect can be secured. In the CE, evidence system linked with RIS, when considering the reproducibility at follow-up observation and comparative diagnosis in clinical practice, the contrast effect could be made constant. Contrast dose administration system using the RIS was useful.

Functional Assessment of Lumbar Nerve Roots Using Coronal-plane Single-shot Turbo Spin-echo Diffusion Tensor Imaging.

We investigated the usefulness of diffusion tensor imaging using single-shot turbo spin-echo sequence (TSE-DTI) in detecting the responsible nerve root by multipoint measurements of fractional anisotropy (FA) values. Five patients with bilateral lumbar spinal stenosis showing unilateral neurological symptoms were examined using TSE-DTI. In the spinal canal, FA values in the symptomatic side were lower than those in the asymptomatic side. TSE-DTI using multipoint measurements of FA values can differentiate the responsible lumbar nerve root.

Evaluation of scattered radiation from fluoroscopy using small OSL dosimeters.

Recently, there has been a significant amount of interest in studying the importance of radiation doses to the eye lens during endoscopic retrograde cholangiopancreatography (ERCP). A study that focused on measuring the scattered radiation using an ionization chamber survey meter reported that a lead curtain was useful in reducing the scattered radiation. The over-couch X-ray tube system tends to deliver higher doses to the head and neck of the staff involved in the procedure than the under-couch X-ray tube position. In this study, a small optically stimulated luminescence (OSL) dosimeter called the nanoDot was used to evaluate and measure the amount of radiation; this dosimeter was developed by Landauer Ltd. and was specifically designed for point measurements. There are numerous studies that have reported the usefulness of personal OSL dosimeters other than the nanoDot to measure scattered radiation. Here, we evaluated the amount of scattered radiation, along with the degree of reduction achieved with the use of a protective curtain, while employing a personal OSL dosimeter and nanoDot. When the scattered radiation dose was measured using the nanoDot, the maximum recorded value without a protective curtain was 0.363 mGy and that with a protective curtain was 0.026 mGy, both at the height of 100 cm. The maximum reduction rate of scattered radiation while using a protective curtain was approximately 93% and 97% at 100 cm and 150 cm, respectively. The measured values recorded using both personal OSL dosimeters and nanoDot machine were strongly correlated.

[Examination of Lower-extremity MRA Using Single-shot Balanced SSFP with Saturation Recovery].

Currently, non-contrast angiography using the balanced steady-state free precession (b-SSFP) method, which uses a short scan time imaging method, has been reported as an alternative to lower-extremity MRA's conventional method. We investigated a new imaging method using balanced SSFP. This method uses a sequence of spectral attenuated inversion recovery (SPAIR) pulse for fat suppression, selective saturation pre-pulse for imaging range of background signal suppression, and rest slab on the downstream side of the imaging range for vein signal suppression. In the examination, we changed dummy pulse (0, 5, 10), saturation delay time (150 ms, 225 ms, 300 ms), and acquisition time (200 ms, 250 ms, 300 ms). For physical evaluation, we used the ROI method and for visual evaluation, we used the Scheffe's method. CR was the best and the visual evaluation was also good 10 for dummy pulse, a saturation delay time of 150 ms, and an acquisition time of 200 ms. Balanced SSFP with saturation recovery has the potential to shorten scanning times. Balanced SSFP with saturation recovery is useful for lower-extremity MRA.

Coronal reformatted CT images contribute to the precise evaluation of the radiofrequency ablative margin for hepatocellular carcinoma.

OBJECTIVE: The purpose of the present study was to evaluate the usefulness of coronal reformatted images obtained from 64-slice multi-detector computed tomography to assess the ablative margin (AM) in hepatocellular carcinoma (HCC) treated with radio frequency ablation (RFA). METHODS: Ninety-five HCC nodules were analyzed in 66 HCC patients treated with RFA. Two radiologists and one hepatologist independently reviewed axial CT images with or without coronal reformatted images in HCC treated with RFA. Nodules were determined as AM-sufficient (≥5 mm) or AM-insufficient (<5 mm). The level of interobserver agreement was measured using the weighted kappa test. The sensitivity, specificity, and positive and negative predictive values (NPVs) of an insufficient AM (<5 mm) to predict local recurrence were evaluated. RESULTS: The numbers of AM-sufficient nodules judged by readers 1-3 based on axial images and both axial and coronal images were 56, 49, and 58, and 47, 33, and 48, respectively. Excellent agreement and good to excellent agreement were obtained among the three readers on axial image readings and both axial and coronal image readings, respectively. The mean sensitivity, specificity, and positive and NPVs of an insufficient AM on axial images and both axial and coronal images to predict local recurrence were 64%, 60%, 17%, and 93%, and 95%, 50%, 20%, and 97%, respectively. CONCLUSIONS: Coronal reformatted CT images should be utilized to evaluate the AM in HCC treated with RFA in order to decrease the risk of local recurrence following treatment.

Diffusion-weighted magnetic resonance imaging of symptomatic nerve root of patients with lumbar disk herniation.

INTRODUCTION: Diffusion-weighted imaging (DWI) can provide valuable structural information that may be useful for evaluating pathological changes of the lumbar nerve root. Diffusion-weighted magnetic resonance (MR) neurography has recently been introduced as an alternative way to visualize nerves, but to date, quantitative DWI and MR neurography have not been applied to evaluate the pathology of lumbar nerve roots. METHODS: Our purpose was to visualize lumbar nerve roots and to analyze their morphology by MR neurography, and to measure the apparent diffusion coefficient (ADC) of lumbar nerve roots compressed by herniated disks using 1.5-T MR imaging. Ten consecutive patients (median age, 48.0 and range, 20-72 years) with monoradicular symptoms caused by a lumbar herniated disk and 14 healthy volunteers were studied. Regions of interests were placed on the lumbar roots at dorsal root ganglia (DRG) and distal spinal nerves on DWI to quantify mean ADC values. The spinal nerve roots were also visualized by MR neurography. RESULTS: In the patients, mean ADC values were significantly greater in the compressed DRG and distal spinal nerves than in intact nerves. MR neurography also showed abnormalities such as nerve swelling at and below the compression in the symptomatic nerve root. Increased ADC values were considered to be because of edema and Wallerian degeneration of compressed nerve roots. CONCLUSION: DWI is a potential tool for analysis of the pathophysiology of lumbar nerve roots compressed by herniated disks.

Diffusion magnetic resonance imaging to differentiate degenerative from infectious endplate abnormalities in the lumbar spine.

STUDY DESIGN: A retrospective observational study of healthy volunteers and patients with degenerative and infectious endplate abnormalities in the lumbar spine. OBJECTIVES: Our purpose was to evaluate the usefulness of diffusion-weighted imaging (DWI) for the differentiation of degenerative and infectious endplate abnormalities using 1.5-T magnetic resonance imaging (MRI). SUMMARY OF BACKGROUND DATA: DWI can provide valuable structural information about tissues that may be useful for clinical applications in differentiation between degenerative and infectious endplate abnormalities. METHODS: Sixteen consecutive patients with endplate abnormalities that was detected by MRI of the lumbar spine, and 15 healthy volunteers were studied. DWI was performed using whole-body imaging with background body signal suppression with a b value of 1000 s/mm2. Apparent diffusion coefficient values of normal and abnormal vertebral bone marrow were calculated. RESULTS: Twenty-nine vertebral abnormalities were found in 16 patients. Nine vertebral abnormalities in 5 patients were because of infections and 20 vertebral abnormalities in 11 patients were because of degenerative changes; 7 levels were classified as Modic type 1, 7 levels as type 2, and 6 levels as type 3. DWI showed hyperintensity in all patients with infection, similar to that used in positron emission tomography, but not in the intervertebral spaces of any patients with degenerative disease. Apparent diffusion coefficient values of infectious bone marrow were significantly higher than normal and degenerative bone marrow. CONCLUSION: DWI is useful for differentiation of degenerative and infectious endplate abnormalities. Moreover, MRI is widely used clinically because of the lack of ionizing radiation, low cost, and fast imaging time as compared with positron emission tomography. Therefore, DWI has the potential to be used as a screening tool.

Clinical applications of diffusion magnetic resonance imaging of the lumbar foraminal nerve root entrapment.

Diffusion-weighted imaging (DWI) can provide valuable structural information about tissues that may be useful for clinical applications in evaluating lumbar foraminal nerve root entrapment. Our purpose was to visualize the lumbar nerve root and to analyze its morphology, and to measure its apparent diffusion coefficient (ADC) in healthy volunteers and patients with lumbar foraminal stenosis using 1.5-T magnetic resonance imaging. Fourteen patients with lumbar foraminal stenosis and 14 healthy volunteers were studied. Regions of interest were placed at the fourth and fifth lumbar root at dorsal root ganglia and distal spinal nerves (at L4 and L5) and the first sacral root and distal spinal nerve (S1) on DWI to quantify mean ADC values. The anatomic parameters of the spinal nerve roots can also be determined by neurography. In patients, mean ADC values were significantly higher in entrapped roots and distal spinal nerve than in intact ones. Neurography also showed abnormalities such as nerve indentation, swelling and running transversely in their course through the foramen. In all patients, leg pain was ameliorated after selective decompression (n = 9) or nerve block (n = 5). We demonstrated the first use of DWI and neurography of human lumbar nerves to visualize and quantitatively evaluate lumbar nerve entrapment with foraminal stenosis. We believe that DWI is a potential tool for diagnosis of lumbar nerve entrapment.

Posterior cingulate gyrus metabolic changes in chronic schizophrenia with generalized cognitive deficits.

N-Methyl-d-aspartate (NMDA) receptor antagonists are known to induce schizophrenia-like psychotic symptoms and cognitive deficits in humans, and have been shown to cause neuronal damage in the posterior cingulate gyrus (PCG) of rodents. Patients with chronic schizophrenia exhibit generalized cognitive deficits, but it remains unclear whether or not the PCG is related to their cognitive dysfunction. To determine what biochemical changes may occur in the PCG of patients with chronic schizophrenia, and to ascertain whether or not such abnormalities may be related to the incidence of cognitive deficits, we obtained cognitive scores and proton magnetic resonance spectra (MRS) from the PCG and the left and right medial temporal lobes (MTL) of 19 patients with schizophrenia and 18 age- and sex-matched normal healthy controls. Compared to the normal controls, the patients with chronic schizophrenia showed significantly worse cognitive performance on verbal and visual memory tests, verbal fluency tests, and the Trail Making Test. The ratio of N-acetylaspartate to creatine and phosphocreatine (NAA/Cr) in the PCG of the patients was significantly lower than that of the controls. Moreover, the NAA/Cr in the PCG of the healthy controls exhibited age-related decline, whereas in the patients with schizophrenia, the corresponding values were consistently low, regardless of age. These findings are thus in accord with current speculation about neuronal dysfunction in the PCG based on the NMDA hypofunction hypothesis regarding the pathophysiology of chronic schizophrenia.

Influence of heart rate on the detectability and reproducibility of multislice computed tomography for measuring coronary calcium score using a pulsating calcified mock-vessel in comparison with electron beam tomography.

BACKGROUND: The influence of heart rate on detectability and reproducibility of multislice computed tomography (MSCT) for measuring coronary calcium score was evaluated using pulsating calcified mock-vessels and compared with electron beam tomography (EBT). MATERIALS AND METHODS: Four calcified mock-vessels with 200-350 HU were made to pulsate at a rate of 40-80 beat/min. Retrospective ECG-gating MSCT (Light Speed Ultra 16) scanning with 0.625 mm slice-thickness was performed twice at each pulsation rate. For comparison, EBT (Imatron C150 XP) was performed with 3 and 1.5 mm beam collimation with prospective ECG-gating and calcium scores were measured. RESULTS: The comparison revealed that MSCT did not have better reproducibility than EBT, but the calcium scores with MSCT were less influenced by pulsation rates than those with EBT. Especially in mild calcification, the calcium scores decreased with EBT with 3 mm beam collimation with increasing pulsation rate, but the scores were stable in any rate with MSCT. CONCLUSION: MSCT effectively detects coronary calcification, especially mild calcification, without being influenced by heart rate. This is accomplished by reducing the partial volume effect in the through plane using sub millimeter slice thickness, and using appropriate reconstruction methods, which improve temporal resolution.

[Gonad protective effect of radiation protective apron in chest radiography].

Depending on the facility, a radiation protective apron (protector) is used to protect the gonad from radiation exposure in chest radiography. To determine the necessity of using a protector during chest radiography, we measured the effect of the protector on the gonad in this study. First, using a human body phantom, we measured the absorbed dose of the female gonad with and without the protector, using a thermoluminescence dosimeter (TLD), and confirmed its protective effect. Using the protector, the absorbed dose was reduced to 28+/-2% and 39+/-4% for field sizes of 14 x 17 inch and 14 x 14 inch, respectively. Next, we used Monte Carlo simulation and confirmed, not only the validity of the actual measurement values, but also the fact that the influence of radiation on the absorbed dose of the gonad was mostly from scattered radiation from inside the body for the 14 x 17 inch field size, and also from the X-ray tube for the 14 x 14 inch field size. Although a certain protective effect is achieved by using the protector, the radiation dose to the gonad is only a few microGy even without a protector. Thus, the risk of a genetic effect would be as small as 10(-8). Given that acceptable risk is below 10(-6), we conclude the use of a radiation protective apron is not necessary for diagnostic chest radiography.