A disposable OSL dosimeter for in vivo measurement of rectum dose during brachytherapy.

PURPOSE: We aimed to develop a disposable rectum dosimeter and to demonstrate its ability to measure exposure dose to the rectum during brachytherapy for cervical cancer treatment using high-dose rate 192 Ir. Our rectum dosimeter measures the dose with an optically stimulated luminescence (OSL) sheet which was furled to a catheter. The catheter we used is 6 mm in diameter; therefore, it is much less invasive than other rectum dosimeters. The rectum dosimeter developed in this study has the characteristics of being inexpensive and disposable. It is also an easy-to-use detector that can be individually sterilized, making it suitable for clinical use. METHODS: To obtain a dose calibration curve, phantom experiments were performed. Irradiation was performed using a cubical acrylic phantom, and the response of the OSL dosimeter was calibrated with the calculation value predicted by the treatment planning system (TPS). Additionally, the dependence of catheter angle on the dosimeter position and repeatability were evaluated. We also measured the absorbed dose to the rectum of patients who were undergoing brachytherapy for cervical cancer (n = 64). The doses measured with our dosimeters were compared with the doses calculated by the TPS. In order to examine the causes of large differences between measured and planned doses, we classified the data into common and specific cases when performing this clinical study. For specific cases, the following three categories were considered: (a) patient movement, (b) gas in the vagina and/or rectum, and (c) artifacts in the X-ray image caused by applicators. RESULTS: A dose calibration curve was obtained in the range of 0.1 Gy-10.0 Gy. From the evaluation of the dependence of catheter angle on the dosimeter position and repeatability, we determined that our dosimeter can measure rectum dose with an accuracy of 3.1% (k = 1). In this clinical study, we succeeded in measuring actual doses using our rectum dosimeter. We found that the deviation of the measured dose from the planned dose was derived to be 12.7% (k = 1); this result shows that the clinical study included large elements of uncertainty. The discrepancies were found to be due to patient motion during treatment, applicator movement after planning images were taken, and artifacts in the planning images. CONCLUSIONS: We present the idea that a minimally invasive rectum dosimeter can be fabricated using an OSL sheet. Our clinical study demonstrates that a rectum dosimeter made from an OSL sheet has sufficient ability to evaluate rectum dose. Using this dosimeter, valuable information concerning organs at risk can be obtained during brachytherapy.

Use of 0.014-in. pushable bare platinum coils in super-selective embolization through the 1.6-Fr. microcatheter of the triaxial system.

BACKGROUND: A triple-coaxial (triaxial) system, which consists of a small microcatheter, a large microcatheter, and a 4-Fr. catheter, has been reported to allow super-selective catheterization. A 1.6-Fr. microcatheter has recently become available as the small microcatheter for the triaxial system, in addition to 0.014-in. pushable bare platinum coils that may be introduced into the 1.6-Fr. microcatheter. PURPOSE: The purpose of the present study was to evaluate the feasibility of 0.014-in. pushable bare platinum coils in embolization through the 1.6-Fr. microcatheter of the triaxial system. MATERIAL AND METHODS: Between November 2015 and October 2019, 19 embolizations were performed on 18 patients, 9 males and 9 females with a median age of 77 years (range, 41-88 years), using 0.014-in. pushable bare platinum coils through the 1.6-Fr. microcatheter of the triaxial system. The technical success rate, clinical success rate, and complications associated with the procedure were assessed. Technical success was defined as the successful delivery and placement of 0.014-in. pushable bare platinum coils, and clinical success as the immediate postembolic complete cessation of blood flow confirmed by digital subtraction angiography. RESULTS: Eighty-four 0.014-in. pushable bare platinum coils were delivered and 19 arteries were successfully embolized. The median number of 0.014-in. pushable bare platinum coils was 4 (range, 1-12). The technical success rate was 100% (84/84) and the clinical success rate was also 100% (19/19). There were no complications associated with the procedures. CONCLUSION: The use of 0.014-in. pushable bare platinum coils in super-selective embolization through the 1.6-Fr. microcatheter of the triaxial system appears to be feasible and safe.

Advanced monoenergetic reconstruction technique for dual-energy computed tomography to evaluate endoleaks after endovascular stent-graft placement.

PURPOSE: To evaluate the usefulness of the advanced monoenergetic imaging (AMI) reconstruction technique for dual-energy computed tomography to evaluate endoleaks after endovascular stent-graft placement. MATERIALS AND METHODS: Ninety-five dual-phase (early and delayed phases) enhanced CT examinations were performed for 60 patients who underwent endovascular stent-graft placement. AM images were reconstructed at 40 keV and compared with the standard 120-kVp images (SI). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the aorta and endoleak were measured. Two radiologists subjectively assessed endoleak delineation and contrast enhancement conditions using a 5-point Likert scale (1: poor-5: excellent). RESULTS: Mean SNRs of the aorta were higher by AMI (early; 34.7 ± 10.2 [SD], delay; 11.4 ± 3.2) than by SI (early; 23.1 ± 6.3, delay; 8.6 ± 2.2) (P < 0.001). SNRs of the endoleak were higher by AMI (early; 26.3 ± 7.5, delay; 10.5 ± 3.1) than by SI (early; 18.2 ± 4.7, delay; 8.3 ± 2.1) (P < 0.001). CNRs by AMI (early; 32.9 ± 9.8, delay; 8.9 ± 2.8) were higher than those by SI (early; 19.5 ± 6.0, delay; 4.7 ± 1.6) in both phases (P < 0.001). Endoleak delineation and contrast enhancement conditions by AMI (4.4 ± 1.0 and 4.5 ± 0.6) were higher than those by SI (3.4 ± 1.0 and 3.3 ± 0.8) in the delayed phase (P < 0.001). There was no difference in the early phase. CONCLUSION: AMI may be useful for evaluating endoleaks after endovascular stent-graft placement.

Feasibility and Safety of Sac Embolization Using N-Butyl Cyanoacrylate in Emergency Endovascular Aneurysm Repair for Ruptured Abdominal Aortic Aneurysms or Isolated Iliac Artery Aneurysms.

PURPOSE: To evaluate the feasibility and safety of sac embolization with N-butyl cyanoacrylate (NBCA) in emergency endovascular aneurysm repair (EVAR) for ruptured abdominal aortic aneurysm (AAA) and iliac artery aneurysm (IAA) in comparison to EVAR without sac embolization. MATERIALS AND METHODS: Between February 2012 and December 2019, among 44 consecutive patients with ruptured AAA or IAA, 29 underwent EVAR. Of these, 22 patients (median age 77.5 years; 18 men) had concomitant sac embolization using NBCA; the remaining 7 patients (median age 88 years; 6 men) underwent EVAR without sac embolization and form the control group. The technical success, clinical success (hemodynamic stabilization), procedure-related complications, and mortality were compared between the groups. RESULTS: All EVAR procedures and embolizations were successful. The clinical success rates in the NBCA and control groups were 95% (21/22) and 71% (5/7), respectively (p=0.14). There was no complication related to the procedure. Type II endoleak occurred in 4 of 21 patients (19%) in the NBCA group vs none of the control patients. One patient (5%) died in the NBCA group vs 3 (43%) in the controls (p=0.034). CONCLUSION: Sac embolization using NBCA in emergency EVAR appears to be feasible and safe for ruptured AAA and IAA.

Use of a steerable triaxial system for challenging catheterization.

Purpose: A steerable triaxial system consisting of a small microcatheter, a high-flow steerable microcatheter, and a 4-Fr. catheter is currently used in clinical settings. The purpose of the present study was to evaluate the efficacy and safety of the steerable triaxial system for challenging catheterization.Material and methods: Sixteen patients underwent an interventional procedure with the steerable triaxial system. Medical records and images of the procedures were reviewed, and the technical success rate, clinical success rate, and complications related to the procedures were evaluated. Technical success was defined as successful catheterization to the target artery using the steerable triaxial system, and clinical success as completion of the aimed procedure.Results: Catheterization to the target artery was successfully performed with the steerable triaxial system in 14 out of 16 patients, but was unsuccessful in two. Therefore, the technical success rate was 88% (14/16). The procedure was successfully accomplished in the 14 technical success patients. Thus, the clinical success rate was 88% (14/16). There were no complications related to the procedures.Conclusions: The steerable triaxial system has potential as a useful and safe technique for challenging catheterization.

Identification of the feeding arteries of hepatocellular carcinomas by performing dual arterial phase CT during pre-transarterial chemoembolization angiography.

PURPOSE: This study evaluated the usefulness of performing dual arterial phase computed tomography (CT) during pre-transarterial chemoembolization (TACE) angiography for identifying the feeding arteries of hepatocellular carcinomas (HCC). MATERIALS AND METHODS: Dual arterial phase CT was performed during pre-TACE angiography in 73 patients with 139 HCC. Ten HCC underwent this procedure twice, so the total number of examined HCC was 149. Early and late arterial phase images were obtained 6 seconds after injection of an iodinated contrast material serially during a single breath-hold. The feeding artery was defined as the branch of the hepatic artery that was connected to the enhanced areas of the tumor. For HCC that could not be visualized on the early arterial phase images, fusion images superimposing the early and late arterial phase images were constructed. Furthermore, technical success defined as successful catheterization of the subsegmental or more distal feeding artery was evaluated. RESULTS: The feeding artery was correctly identified on dual arterial phase CT in 146 of the 149 tumors (98.0%). In two HCC, the feeding arteries could not be identified due to severe motion artifacts, and in one, due to the presence of anastomosis between the right and left hepatic arteries. Catheterization of the subsegmental feeding artery was successful in all TACE procedures (technical success rate: 100%). CONCLUSION: Performing dual arterial phase CT during angiography appears to be useful for identifying the feeding arteries of HCC.

Staged coil embolization after thoracic endovascular stent grafting for aneurysmal chronic type B aortic dissection: A case report.

We herein describe a 38-year-old woman with Marfan syndrome and chronic type A aortic dissection. Computed tomography showed that the sinus of Valsalva and thoracoabdominal aorta had a diameter of 62 and 55 mm, respectively. After 7 months of a Bentall operation and total arch replacement with the elephant trunk technique, we performed thoracic endovascular aortic repair for an aneurysm of the descending aorta, but we preserved the retrograde flow into the false lumen because it supplied vessels perfusing the spinal cord. Computed tomography angiography 14 months after thoracic endovascular aortic repair showed that the thoracic aortic diameter had increased to 68 mm. We then performed partial (proximal only) coil embolization of the false lumen. After 6 months, the thoracic aortic diameter had decreased to 60 mm and the spinal cord remained perfused via the distal false lumen. Staged coil embolization after thoracic endovascular aortic repair for aneurysmal chronic type B aortic dissection is feasible and can be beneficial.

Preoperative transcatheter arterial embolization using a gelatin sponge for head and neck tumors.

Purpose: To evaluate the usefulness of preoperative transcatheter arterial embolization using a gelatin sponge for hypervascular head and neck tumors to reduce intraoperative blood loss (IBL).　　　　 Material and methods: Nineteen patients underwent preoperative transcatheter arterial embolization for hypervascular head and neck tumors using a gelatin sponge. The technical success rate, devascularization rate, IBL, and complications were evaluated. Angiography images obtained before and after preoperative embolization were compared in all patients, and the devascularization rate was assessed from the relative reduction rate of contrast agent volumes. Results: The technical success rate was 100%. The median devascularization rate was 95% (range, 75-100%). The median period between embolization and surgical resection was one day (range, 1-12 days). The median IBL was 122 ml (range, 0-3780 ml). Blood transfusions were required in three cases, and their IBL and devascularization rates were 850, 1959, and 3780 ml, and 75%, 90%, and 80%, respectively. There was a complication of cerebral embolism in one out of 19 cases (5%). Conclusions: Preoperative transcatheter arterial embolization using a gelatin sponge was feasible and may contribute to decreasing IBL.

Time-resolved magnetic resonance angiography as a follow-up method for visceral artery aneurysm treated with coil-embolisation.

PURPOSE: The purpose of this study is to assess the feasibility and usefulness of time-resolved magnetic resonance angiography (TR-MRA) for follow-up of visceral artery aneurysms (VAAs) after embolotherapy. MATERIAL AND METHODS: Twenty-one VAAs (11 splenic, six renal, three internal iliac, and one superior pancreaticoduodenal artery aneurysms) in 18 patients (median age, 64 years; range, 36-88 years) previously treated by embolisation with platinum coils, were evaluated. The mean size of the aneurysm was 10.5 cm3 (range, 0.3-132 cm3). Among them, 19 lesions were treated by aneurysmal packing with or without distal-to-proximal embolisation. For the remaining two lesions, distal-to-proximal embolization alone was performed. The mean observation period after embolotherapy was 35 weeks (range, 4-216). All patients underwent TR-MRA following an intravenous bolus injection of gadolinium chelate. Recanalisation was diagnosed when any portion of the aneurysmal sac was enhanced in the arterial phase. RESULTS: On TR-MRA, two lesions were diagnosed as recanalised. They were confirmed by transcatheter arteriography and re-treated by embolotherapy. For the remaining 19 lesions, there were no findings of recanalisation on TR-MRA. CONCLUSIONS: TR-MRA appears to be a feasible method for follow-up examination of VAAs treated by embolotherapy.

Correction to: Usefulness of Hydrogel-Coated Coils in Embolization of Pulmonary Arteriovenous Malformations.

The article "Usefulness of Hydrogel-Coated Coils in Embolization of Pulmonary Arteriovenous Malformations," written by Masashi Shimohira, Tatsuya Kawai, Takuya Hashizume, Masahiro Muto, Masanori Kitase and Yuta Shibamoto, was originally published electronically on the publisher's Internet portal (currently SpringerLink) on January 17, 2018, without open access.

Usefulness of Hydrogel-Coated Coils in Embolization of Pulmonary Arteriovenous Malformations.

PURPOSE: To evaluate the usefulness of hydrogel-coated coils for preventing recanalization after coil embolization of pulmonary arteriovenous malformations (PAVMs). MATERIALS AND METHODS: Thirty-seven consecutive patients with 57 untreated PAVMs underwent coil embolization with hydrogel-coated coils between January 2013 and Jun 2017. The mean age was 49 years (range 9-83 years), and there were seven male patients and 30 female patients. The median size of the feeding artery was 3.7 mm (range 1.5-6.1 mm), and the median size of the venous sac was 9.3 mm (range 2.6-36.6 mm). For all PAVM, embolization was attempted using 0.018-in. hydrogel-coated coils with or without other coils (0.0135-0.018-in. bare platinum coils and fibered platinum coils). Technical success rate, recanalization rate, and complications were evaluated. Technical success was defined as completion of embolization using hydrogel-coated coils. Recanalization was evaluated with time-resolved magnetic resonance angiography and/or pulmonary angiography. RESULTS: In 56 of 57 PAVMs, embolization was successfully performed with hydrogel-coated coils. Therefore, the technical success rate was 98% (56/57). The number of PAVMs at risk was 56, 42, 18, and 12 at 0, 12, 24, and 36 months, respectively. There was no recanalization with a mean follow-up period of 19 months (range 2-47 months) in 56 PAVMs embolized with hydrogel-coated coils. There were no major complications. As a minor complication, local pain was observed in 8 of 43 sessions (19%) after embolization. CONCLUSIONS: Hydrogel-coated coils may be useful for preventing recanalization after the embolization of PAVMs.

Unilateral pulmonary artery pre-operative occlusion test: technical feasibility and safety prior to pneumonectomy or pleuropneumonectomy for malignancy.

OBJECTIVE: The aim of the present study was to assess the technical feasibility and safety of the unilateral pulmonary artery occlusion (UPAO) test in pre-operative evaluation of pneumonectomy or pleuropneumonectomy for lung or pleural tumours. METHODS: The UPAO test was performed on 91 patients who were scheduled to undergo or were being considered for pneumonectomy or pleuropneumonectomy between June 2003 and July 2016. There were 74 males and 17 females, with a median age of 65 years (range, 23-80). The technical success rate, procedure time and complication rate were evaluated. Technical success was defined as completion of the UPAO test. RESULTS: The diagnoses of the 91 patients were as follows: lung cancer in 63, malignant pleural mesothelioma in 21, thymoma in 5, lung metastasis in 1 and lung carcinoid in 1. The UPAO test was performed successfully on 88 out of 91 patients (technical success rate: 97%). The median procedure time was 57 min (range, 34-120). Cardiac arrest due to migration of the balloon catheter to the pulmonary trunk occurred in 1 patient (complication rate: 1.1%). CONCLUSION: The UPAO test in pre-operative evaluation of pneumonectomy or pleuropneumonectomy for lung or pleural tumours appears to be technically feasible. However, it needs to be performed with care in order to avoid severe complications. Advances in knowledge: The UPAO test can be safely performed and is helpful in evaluating patients for pneumonectomy or pleuropneumonectomy.

Transcatheter Arterial Embolization for Renal Angiomyolipoma Using a Micro-balloon Catheter and a Mixture of Ethanol and Lipiodol.

PURPOSE: To evaluate the efficacy and safety of transcatheter arterial embolization (TAE) for renal angiomyolipoma (AML) using a micro-balloon catheter and a mixture of ethanol and lipiodol. MATERIALS AND METHODS: Twelve consecutive patients with 15 AMLs, 9 females and 3 males, with a median age of 44 years (range, 11-81), underwent this procedure between 2011 and 2016. In all procedures, a micro-balloon catheter was advanced to the feeding artery of the AML and TAE was performed with a mixture of ethanol and lipiodol under balloon inflation. We reviewed medical records and images, and evaluated the technical success rate, clinical success rate, and complications. Technical success was defined as completion of TAE using the micro-balloon catheter and the mixture of ethanol and lipiodol. Clinical success was defined as reduction of tumor size on CT, which was performed before and after TAE. RESULTS: In 14 of 15 AMLs, the micro-balloon catheter could be advanced to the feeding artery, and TAE was performed successfully. Thus, the technical success rate was 93%. Among these 14 AMLs of 11 patients, 13 AMLs of 10 patients could be followed and tumor shrinkage was confirmed in all. Thus, the clinical success rate was 100%. Four patients had mild symptoms after TAE; the minor complication rate was 33% (4/12), and the major complication rate was 0%. CONCLUSION: TAE for renal AML using the micro-balloon catheter and mixture of ethanol and lipiodol appears to be effective and safe.

Entrance surface dose measurements using a small OSL dosimeter with a computed tomography scanner having 320 rows of detectors.

Entrance surface dose (ESD) measurements are important in X-ray computed tomography (CT) for examination, but in clinical settings it is difficult to measure ESDs because of a lack of suitable dosimeters. We focus on the capability of a small optically stimulated luminescence (OSL) dosimeter. The aim of this study is to propose a practical method for using an OSL dosimeter to measure the ESD when performing a CT examination. The small OSL dosimeter has an outer width of 10 mm; it is assumed that a partial dose may be measured because the slice thickness and helical pitch can be set to various values. To verify our method, we used a CT scanner having 320 rows of detectors and checked the consistencies of the ESDs measured using OSL dosimeters by comparing them with those measured using Gafchromic™ films. The films were calibrated using an ionization chamber on the basis of half-value layer estimation. On the other hand, the OSL dosimeter was appropriately calibrated using a practical calibration curve previously proposed by our group. The ESDs measured using the OSL dosimeters were in good agreement with the reference ESDs from the Gafchromic™ films. Using these data, we also estimated the uncertainty of ESDs measured with small OSL dosimeters. We concluded that a small OSL dosimeter can be considered suitable for measuring the ESD with an uncertainty of 30 % during CT examinations in which pitch factors below 1.000 are applied.

Transcatheter Arterial Embolization for Hepatic Arterial Injury Related to Percutaneous Transhepatic Portal Intervention.

PURPOSE: To assess the usefulness of transcatheter arterial embolization (TAE) for the hepatic arterial injury related to percutaneous transhepatic portal intervention (PTPI). MATERIALS AND METHODS: Fifty-four patients, 32 males and 22 females with a median age of 68 years (range 43-82 years), underwent PTPI. The procedures consisted of 33 percutaneous transhepatic portal vein embolizations, 19 percutaneous transhepatic variceal embolizations, and 2 percutaneous transhepatic portal venous stent placements. Two patients with gastric varices underwent percutaneous transhepatic variceal embolization twice because of recurrence. Therefore, the total number of procedures was 56. Among them, hepatic arterial injury occurred in 6 PTPIs in 5 patients, and TAE was performed. We assessed technical success, complications related to TAE, and clinical outcome. Technical success was defined as the disappearance of findings due to hepatic arterial injury on digital subtraction angiography. RESULTS: As hepatic arterial injuries, 4 extravasations and 2 arterioportal shunts developed. All TAEs were performed successfully. The technical success rate was 100 %. Complication of TAE occurred in 5 of 6 TAEs; 3 were focal liver infarction, not requiring further treatment, and 2 were biloma that required percutaneous drainage. Five TAEs in 4 patients were performed immediately after the PTPI, and these 4 patients were alive. However, one TAE was performed 10 h later, and the patient died due to multiple organ failure 2 months later although TAE was successful. CONCLUSION: TAE is a useful treatment for hepatic arterial injury related to PTPI. However, it should be performed at an early stage.

Visualization of the Spinal Artery by CT During Embolization for Pulmonary Artery Pseudoaneurysm.

BACKGROUND: Spinal artery ischemia is a rare but serious complication of embolization for treatment of hemoptysis. When the spinal artery is visualized at angiography, embolization should not be performed. However, it has been reported that spinal artery feeders are not visible on angiography in patients with developing spinal infarction. CASE REPORT: A 70-year-old man with a history of pulmonary aspergillosis had hemoptysis and underwent contrast-enhanced CT, revealing a pulmonary artery pseudoaneurysm (PAP) in the left upper lobe. Systemic angiography from the fifth left intercostal artery showed the PAP at the distal site, but the access route to the PAP was very tortuous and long. Although the spinal branch could not be observed with that angiography, CT during angiography was performed, and it visualized the posterior spinal artery obviously. Thus, the artery distal and proximal to the PAP was then successfully coil-embolized from the pulmonary artery. CONCLUSIONS: CT during angiography may be useful to confirm the presence of the spinal artery for treatment of hemoptysis by embolization.

Estimation of identification limit for a small-type OSL dosimeter on the medical images by measurement of X-ray spectra.

Our aim in this study is to derive an identification limit on a dosimeter for not disturbing a medical image when patients wear a small-type optically stimulated luminescence (OSL) dosimeter on their bodies during X-ray diagnostic imaging. For evaluation of the detection limit based on an analysis of X-ray spectra, we propose a new quantitative identification method. We performed experiments for which we used diagnostic X-ray equipment, a soft-tissue-equivalent phantom (1-20 cm), and a CdTe X-ray spectrometer assuming one pixel of the X-ray imaging detector. Then, with the following two experimental settings, corresponding X-ray spectra were measured with 40-120 kVp and 0.5-1000 mAs at a source-to-detector distance of 100 cm: (1) X-rays penetrating a soft-tissue-equivalent phantom with the OSL dosimeter attached directly on the phantom, and (2) X-rays penetrating only the soft-tissue-equivalent phantom. Next, the energy fluence and errors in the fluence were calculated from the spectra. When the energy fluence with errors concerning these two experimental conditions was estimated to be indistinctive, we defined the condition as the OSL dosimeter not being identified on the X-ray image. Based on our analysis, we determined the identification limit of the dosimeter. We then compared our results with those for the general irradiation conditions used in clinics. We found that the OSL dosimeter could not be identified under the irradiation conditions of abdominal and chest radiography, namely, one can apply the OSL dosimeter to measurement of the exposure dose in the irradiation field of X-rays without disturbing medical images.

Percutaneous fiducial marker placement prior to stereotactic body radiotherapy for malignant liver tumors: an initial experience.

The aim of this study was to describe our initial experience with a gold flexible linear fiducial marker and to evaluate the safety and technical and clinical efficacy of stereotactic body radiotherapy using this marker for malignant liver tumors. Between July 2012 and February 2015, 18 patients underwent percutaneous fiducial marker placement before stereotactic body radiotherapy for malignant liver tumors. We evaluated the technical and clinical success rates of the procedure and the associated complications. Technical success was defined as successful placement of the fiducial marker at the target site, and clinical success was defined as the completion of stereotactic body radiotherapy without the marker dropping out of position. All 18 fiducial markers were placed successfully, so the technical success rate was 100% (18/18). All 18 patients were able to undergo stereotactic body radiotherapy without marker migration. Thus, the clinical success rate was 100% (18/18). Slight pneumothorax occurred as a minor complication in one case. No major complications such as coil migration or bleeding were observed. The examined percutaneous fiducial marker was safely placed in the liver and appeared to be useful for stereotactic body radiotherapy for malignant liver tumors.

Energy dependence measurement of small-type optically stimulated luminescence (OSL) dosimeter by means of characteristic X-rays induced with general diagnostic X-ray equipment.

For X-ray inspections by way of general X-ray equipment, it is important to measure an entrance-skin dose. Recently, a small optically stimulated luminescence (OSL) dosimeter was made commercially available by Landauer, Inc. The dosimeter does not interfere with the medical images; therefore, it is expected to be a convenient detector for measuring personal exposure doses. In an actual clinical situation, it is assumed that X-rays of different energies will be detected by a dosimeter. For evaluation of the exposure dose measured by a dosimeter, it is necessary to know the energy dependence of the dosimeter. Our aim in this study was to measure the energy dependence of the OSL dosimeter experimentally in the diagnostic X-ray region. Metal samples weighing several grams were irradiated and, in this way, characteristic X-rays having energies ranging from 8 to 85 keV were generated. Using these mono-energetic X-rays, the dosimeter was irradiated. Simultaneously, the fluence of the X-rays was determined with a CdTe detector. The energy-dependent efficiency of the dosimeter was derived from the measured value of the dosimeter and the fluence. Moreover, the energy-dependent efficiency was calculated by Monte-Carlo simulation. The efficiency obtained in the experiment was in good agreement with that of the simulation. In conclusion, our proposed method, in which characteristic X-rays are used, is valuable for measurement of the energy dependence of a small OSL dosimeter in the diagnostic X-ray region.