Biopsy of lung nodules with use of I-I device under intermittent CT fluoroscopic guidance: preliminary clinical study

Frequency and Risk Factors for Air Embolism in Computed Tomography Fluoroscopy-Guided Biopsy of Lung Tumor With the Use of Noncoaxial Automatic Needle

PURPOSE

The aim of the study is to analyze incidence and risk factors for air embolism during computed tomography (CT) fluoroscopy-guided lung biopsies using noncoaxial automatic needle.

MATERIALS AND METHODS

Between February 2014 and December 2019, 204 CT fluoroscopy-guided lung biopsies (127 men; mean age, 70.6 years) using noncoaxial automatic needle under inspiratory breath holding were performed. We retrospectively evaluated the incidence of air embolism as presence of air in the systemic circulation on whole-chest CT images obtained immediately after biopsy. Risk factors of the patient, tumor and procedural factors (size, location and type of nodule, distance from the pleura, the level of the lesion relative to the left atrium, emphysema, patient position, penetration of a pulmonary vein, etc) were analyzed.

RESULTS

The technical success rate was 97.1%. Air embolism was radiologically identified in 8 cases (3.92%, 7 males; size, 21.6 ± 18.2 mm; distance to pleura, 11.9 ± 14.5 mm). Two patients showed overt symptoms and the others were asymptomatic. Independent risk factors were needle penetration of the pulmonary vein ( P = 0.0478) and higher location relative to left atrium ( P = 0.0353). Size, location and type of nodule, distance from the pleura, emphysema, patient position, and other variables were not significant risk factors. As other complications, pneumothorax and alveolar hemorrhage were observed in 57.4% and 77.5%, respectively.

CONCLUSIONS

In CT fluoroscopy-guided lung biopsy using the noncoaxial automatic needles, radiological incidence of air embolism was 3.92%. Given the frequency of air embolism, it is necessary to incorporate this into postprocedure imaging and clinical evaluation.

Dual steristrip technique: a novel use of steristrips to reduce operator radiation dose during CT-guided intervention

OBJECTIVE

We describe a novel and safe needle-holding method that we have termed the 'dual steristrip technique'. This technique can be used to stabilize the bone biopsy needle without the need for the radiologist's hand to be in close proximity to the X-ray beam during CT-guided intervention.

MATERIALS AND METHODS

The dual steristrip technique uses steristrips to stabilize the bone biopsy needle and allows for accurate assessment of needle position and trajectory. This involves affixing one end of a steristrip to the skin 2 cm from the needle skin entry point, wrapping the mid-section of the steristrip around the biopsy needle and affixing the other end of the steristrip to the skin at the opposite side of the needle 2 cm from the needle skin entry point. A second steristrip is then applied in a similar fashion at 90° to the first steristrip.

RESULTS

In our institution, we have used the dual steristrip technique to stabilize the biopsy needle in certain cases where assessment of needle position/trajectory can be more challenging. This includes cases where there is a paucity of soft tissues overlying the bone or if the bone lesion is located in the superficial cortex. We have found it to be successful in 80% of cases.

CONCLUSIONS

The dual steristrip technique is a safe and effective needle stabilization method that should be considered by the interventional radiologist in challenging CT-guided bone biopsy cases.

Dose to the interventional radiologist in CTF-guided procedures

The aim of this work was to assess the occupational dose received by an interventional radiologist (IR) during computed tomography fluoroscopy (CTF)-guided procedures; to identify the most exposed areas of the body including the hands and fingers; to suggest recommendations for individual monitoring; and to improve radiation safety of the practice. A total of 53 CTF-guided procedures were studied. Twelve whole-body dosimeters were worn by the IR in each procedure for the assessment of the personal dose equivalent, H_p(10), on the chest, waist, and back, both over and under the lead apron, as well as the personal dose equivalent, H_p(0.07), on both arms, knees, and feet. Special gloves with casings to fit extremity dosimeters were prepared to assess H_p(0.07) to the fingers. The measured chest dose values were higher than those on the waist and back; the dominant hand or the left side was the most exposed. In general, the ring, middle, and index fingers of the dominant hand were the most exposed (maximum in the 36-39 mSv range), while wrist dose was negligible compared to finger doses. Based on the results obtained the following recommendations are suggested: protective devices (lead aprons, thyroid shield, and goggles) should be worn; H_p(10) should be assessed at the chest level both above and below the lead apron; finger doses can be measured on the basis of each middle finger; the arm closer to the beam should be monitored; and finally, a wrist dosimeter will not provide useful information.

The use of needle holders in CTF guided biopsies as a dose reduction tool

PURPOSE

The purpose of this study was to evaluate the efficacy of needle holders in reducing staff hand exposure during biopsies guided by computed tomography fluoroscopy (CTF), through the analysis of data acquired during a detailed monitoring study, undertaken in parallel with an ongoing optimization process to reduce hand irradiation.

METHODS

Hand monitoring was performed with 11 extremity detectors, two per finger (base and tip) and one on the back of the wrist, for the left (dominant) hand, during two series of biopsies with comparable characteristics. The first series (47 biopsies) were performed with only quick-check method (QC) and occasional side-handle (SH) manipulation of the needle. The second series (63 biopsies) were performed after introducing needle holders (NH) in the course of an optimization process.

RESULTS

Choice of technique (QC, QC + NH, QC + SH) by the interventional radiologist (IR) was related to biopsy difficulty. Measured hand exposure was low (< 1 mSv) for all QC-only procedures, and for most of the QC + NH procedures. Occasional side-handle manipulation still occurred during challenging biopsies, so that 8% of biopsies in the second series accounted for ~70% of total fingertip dose (~90 mSv). The methodology used allowed a detailed insight into the dose reduction achievable with needle holders during real procedures, without the limitations of phantom measurements.

CONCLUSIONS

Needle holders proved effective in reducing mean hand exposure during clinical procedures where real-time manipulation was necessary. Occasional side-handle manipulation was found to contribute disproportionately to hand exposure. This highlights the importance of individual hand monitoring during CTF guided procedures.

A Review of Radiation Protection Requirements and Dose Estimation for Staff and Patients in CT Fluoroscopy

The combination of fluoroscopically guided interventional procedures with computed tomography (CTF) has become widespread around the world. The benefits of CTF include the ability to obtain a real-time visualization of the entire body, increased target accuracy and improved visualization of biopsy needles. Modern CTF units work with variable frame rates for image selection, and therefore the dose distributions for patients and staff can considerably vary, creating growing concern in terms of the occupational exposure of interventionists and the drawback of a higher exposure of the patient. A literature review of the latest CTF publications is summarized in this article. A wide range of CTF studies reveal different treatment methods used in clinical practice, and therefore the differences in the exposures between them; as well as in the radiation protection tools and dose monitoring. Further optimization of radiation protection methods, harmonization of exposure patterns as well as training and education of CTF staff on the basis of the information in the survey, are strongly recommended.

Gafchromic XR-QA2 film as a complementary dosimeter for hand-monitoring in CTF-guided biopsies

Computed tomography fluoroscopy (CTF) is a useful imaging technique to guide biopsies, particularly lung biopsies, but it also has the potential for very high hand exposures, despite use of quick-check method and needle holders whenever feasible. Therefore, reliable monitoring is crucial to ensure the safe use of CTF. This is a challenge, because ring dosimeters monitor exposure only at the base of one finger, while the fingertips may be exposed to the highly collimated CT beam. In this work we have explored the possibility of using Gafchromic XR-QA2 self-developing film as a complementary dosimeter to quantify hand exposure during CTF-guided biopsies. A glove used in a previous study and designed to contain 11 TLDs was adapted to include Gafchromic strips 7 mm wide, covering the fingers. A total of 22 biopsies were successfully performed wearing this GafTLD glove under sterile gloves, and the IR reported no difficulty or reduction of dexterity while wearing it. Comparison of dose distributions obtained from digitization of the Gafchromic film strips and absolute Hp(0.07) readings from TLDs showed good agreement, despite some positional uncertainty due to relative movement. Per procedure, doses at the base of the ring finger can be as low as 3%-8% of hand dose maximum. Accumulated dose at the base of the ring finger was four times lower than the dose maximum.

Diagnostic performance of percutaneous lung biopsy using automated biopsy needles under CT-fluoroscopic guidance for ground-glass opacity lesions

OBJECTIVE

The goal of our study was to evaluate the diagnostic performance of percutaneous lung biopsy under CT-fluoroscopic guidance for ground-glass opacity (GGO) lesions.

METHODS

85 percutaneous needle lung biopsies were performed in 73 patients. Specimens were obtained by core biopsy utilising an automated cutting needle and were evaluated histologically. Final diagnosis was confirmed by independent surgical pathology, independent culture results or clinical follow-up.

RESULTS

Rates of adequate specimens obtained and of precise diagnosis by needle biopsy were 92.9% (79/85) and 90.6% (77/85) of evaluated lung lesions, respectively. Precise diagnosis was achieved in 87.1% (27/31) of lesions ≤10 mm in diameter, 90.0% (36/40) of lesions >10 mm to ≤20 mm and 100.0% (14/14) of lesions >20 mm. Precision in diagnosing GGO lesions according to the GGO component was 73.9% (17/23) for pure GGO lesions and 96.8% (60/62) for part-solid GGO lesions. Obtaining a precise diagnosis did not differ significantly according to the lesion size (p=0.3840), but differences were significant according to the GGO component (p=0.0047). Malignancy was accurately diagnosed in 35 of 36 malignant lesions for which surgery was later performed. The specific cell type determined from specimens obtained by needle biopsy was exactly the same as the final histological diagnosis obtained after surgery in 20 lesions.

CONCLUSION

Tissue-core lung biopsy under CT-fluoroscopic guidance for a GGO lesion provides a high degree of diagnostic accuracy but is less reliable for determining the specific cell type.

ADVANCES IN KNOWLEDGE

Percutaneous lung biopsy under CT-fluoroscopic guidance for GGO is useful in differentiating malignancy.

Comparison of fully automated and semi-automated biopsy needles for lung biopsy under CT fluoroscopic guidance

OBJECTIVE

The aim of this study was to compare two different automated biopsy needles, a fully automated biopsy needle (Monopty; Bard, Covington, GA) and a semi-automated biopsy needle (Temno; Bauer Medical, Clearwater, FL), for lung biopsy.

METHODS

50 consecutive percutaneous lung biopsies using the Monopty needle between June 2006 and January 2007 and 66 consecutive lung biopsies for 1 nodule in each session using the Temno needle between February 2007 and August 2008 were performed under CT fluoroscopic guidance followed by histopathological evaluation.

RESULTS

In 42/50 lung biopsies performed with the Monopty needle and 54/66 lung biopsies performed with the Temno needle, the final diagnosis was confirmed by independent surgical pathological findings or clinical follow-up. Sufficient samples for histopathological evaluation were obtained in all 50 (100%) biopsies using the Monopty needle and in 55 (83.3%) of the 66 biopsies using the Temno needle (p<0.01). Accurate diagnosis was achieved in 41 (97.6%) of 42 biopsies using the Monopty needle and in 45 (83.3%) of 54 biopsies using the Temno needle (p=0.04). Biopsy-induced complications were pneumothorax, haemoptysis and haemothorax in 44.0%, 10.0% and 6.0% of biopsies, respectively, using the Monopty needle and in 48.3%, 8.3% and 3.3%, respectively, using the Temno needle.

CONCLUSION

There is a possibility that a fully automated biopsy needle such as the Monopty is more useful for CT scan-guided lung biopsy than semi-automated biopsy needles.

Transthoracic needle biopsy using a C-arm cone-beam CT system: diagnostic accuracy and safety

OBJECTIVE

The purpose of this study was to evaluate the diagnostic accuracy and safety of performing transthoracic needle biopsy (TNB) under combined fluoroscopy and CT guidance using a C-arm cone-beam CT (CBCT) system.

METHODS

We evaluated the diagnostic accuracy and safety of performing TNB using a C-arm CBCT system. We retrospectively evaluated 99 TNB cases performed in 98 patients using a C-arm CBCT system with an 18-gauge automated cutting needle. We reviewed the diagnostic accuracy according to the size and depth of the lesion, incidence of complications, additional treatment for complications, procedure time, number of needle passes per biopsy and radiation dose.

RESULTS

The final diagnoses revealed 72 malignant and 27 benign lesions. The overall malignancy sensitivity, malignancy specificity and diagnostic accuracy were 95.8%, 100% and 97.0%, respectively, and those for small pulmonary nodules <20 mm in size were 94.1%, 100% and 96.6%, respectively. There was no significant difference in the correct diagnosis of malignancy according to lesion size (p = 0.634) or depth (p = 0.542). For benign lesions, a specific diagnosis was obtained in 14 cases (51.9%). TNB induced complications in 19 out of 99 procedures (19.2%), including pneumothorax (16.2%), immediate haemoptysis (2.0%) and subcutaneous emphysema (1.0%). Among these, four patients with pneumothorax required chest tube insertion (2.0%) or pig-tail catheter drainage (2.0%). The mean procedure time, number of needle passes and radiation doses were 11.9 ± 4.0 min, 1.2 ± 0.5 times and 170.0 ± 67.2 mGy, respectively.

CONCLUSION

TNB using a C-arm CBCT system provides high diagnostic accuracy with a low complication rate and a short procedure time, particularly for small pulmonary nodules.

Clinical value of CT-guided needle biopsy for retroperitoneal lesions

OBJECTIVE

The purpose of this study was to investigate retrospectively the clinical procedural performance of CT-guided needle biopsy for retroperitoneal lesions.

MATERIALS AND METHODS

CT-guided needle biopsy was performed in 74 consecutive patients (M:F = 44:30; mean age, 59.7 years) with retroperitoneal lesions between April 1998 and June 2009. The target lesion ranged from 1.5 to 12.5 cm in size. The biopsy access path ranged from 3.5 to 11.5 cm in depth. A biopsy specimen was obtained using an 18-gauge core needle under a CT or CT-fluoroscopy guidance and with the patient under local anesthesia. The histopathological diagnoses from the biopsies were obtained. The diagnostic confirmation of the subtype of lymphoma was evaluated.

RESULTS

Satisfactory biopsy samples were obtained in 73 (99%) of 74 patients and a pathological diagnosis was made in 70 (95%) of 74 patients. Sixty three lesions were malignant (45 lymphomas, nine primary tumors, nine lymph node metastases) and seven were benign. The subtype of lymphoma was specified in 43 (96%) of 45 patients who were diagnosed with lymphoma. Analysis of the value of CT-guided biopsy in this series indicated 63 true positives, zero false positive, six true negatives and five false negatives. This test had a sensitivity of 93%, a specificity of 100% and an accuracy of 93%. No major complications were seen and minor complications were noted in seven patients (five with local hematomas, two with transient pain at the puncture site).

CONCLUSION

CT-guided needle biopsy for retroperitoneal lesions is highly practical and useful, and particularly for determining the subtypes in patients with lymphoma.

Combined fluoroscopy- and CT-guided transthoracic needle biopsy using a C-arm cone-beam CT system: comparison with fluoroscopy-guided biopsy

OBJECTIVE

The aim of this study was to evaluate the usefulness of combined fluoroscopy- and CT-guided transthoracic needle biopsy (FC-TNB) using a cone beam CT system in comparison to fluoroscopy-guided TNB (F-TNB).

MATERIALS AND METHODS

We retrospectively evaluated 74 FC-TNB cases (group A) and 97 F-TNB cases (group B) to compare their respective diagnostic accuracies according to the size and depth of the lesion, as well as complications, procedure time, and radiation dose.

RESULTS

The sensitivity for malignancy and diagnostic accuracy for small (< 30 mm in size) and deep (≥ 50 mm in depth) lesions were higher in group A (91% and 94%, 92% and 94%) than in group B (73% and 81%, 84% and 88%), however not statistically significant (p > 0.05). Concerning lesions ≥ 30 mm in size and < 50 mm in depth, both groups displayed similar results (group A, 91% and 92%, 80% and 87%; group B, 90% and 92%, 86% and 90%). Pneumothorax occurred 26% of the time in group A and 14% for group B. The mean procedure time and patient skin dose were significantly higher in group A (13.6 ± 4.0 minutes, 157.1 ± 76.5 mGy) than in group B (9.0 ± 3.5 minutes, 21.9 ± 15.2 mGy) (p < 0.05).

CONCLUSION

Combined fluoroscopy- and CT-guided TNB allows the biopsy of small (< 30 mm) and deep lesions (≥ 50 mm) with high diagnostic accuracy and short procedure times, whereas F-TNB is still a useful method for large and superficial lesions with a low radiation dose.

Newly developed application system for CT-guided puncture based on multidetector row CT without CT fluoroscopy

PURPOSE

The aim of this article is to describe a preliminary clinical experience with a new multidetector CT (MDCT) system (GuideShot system) for CT-guided intervention.

MATERIALS AND METHODS

This system enabled simultaneous acquisition and quick display of three axial CT images. Only a single-shot mode was used, with no continuous CT fluoroscopic (CTF) mode. The exposure and the table movement could be controlled by the interventional radiologist using foot pedal switches that are on the floor beside the table. We used this system for biopsy (n = 48), drainage tube placement (n = 7), and hook wire placement prior to video-assisted thoracic surgery (n = 69).

RESULTS

Technical success was achieved in all 124 cases. In 123 of 124 cases, each intervention was done within a single breath-hold (99%). The table controller was used in 22 cases (17.7%), and the central portion of the target or the needle tip was easily shifted into the CT collimation after a single table movement.

CONCLUSION

This new system improved Z-axis orientation for the interventional radiologist and enabled rapid interventional procedures without the CTF system. MDCT with this system could be one of the options when single-slice CT with CTF is replaced by MDCT.

Chest Wall Dissemination of Nocardiosis after Percutaneous Transthoracic Needle Biopsy

We described a case of chest wall dissemination after percutaneous transthoracic needle biopsy. A 65-year-old man had a lung nodule which was suspected to be lung carcinoma. He underwent percutaneous transthoracic needle biopsy using an 18G semiautomated biopsy needle and pathologic diagnosis showed organizing pneumonia. Two months after the biopsy, chest wall dissemination occurred. Implantation of carcinoma along the biopsy route was suspected, but the mass was actually due to pulmonary nocardiosis.

Small (≤2-cm) Subpleural Pulmonary Lesions: Short- versus Long-Needle-Path CT-guided Biopsy—Comparison of Diagnostic Yields and Complications

PURPOSE

To retrospectively compare the diagnostic yield and complications associated with the use of short versus long needle paths for computed tomography (CT)-guided biopsy of small subpleural lung lesions.

MATERIALS AND METHODS

The study was approved by the institutional review board, and the requirement for informed patient consent was waived. The medical and imaging records of patients who underwent CT-guided biopsy of subpleural pulmonary nodules measuring up to 2 cm in diameter were reviewed. The study included 176 patients (79 men, 97 women; age range, 18-84 years) who were divided into two groups: In group A, a direct approach in which the needle traversed a short lung segment was used. In group B, an indirect approach involving the use of a longer needle path was used. Diagnostic yield, accuracy, and pneumothorax and chest tube placement rates were compared between the two groups. Two-tailed t tests and Pearson chi(2) tests were used to analyze continuous and categorized variables, respectively.

RESULTS

Group A comprised 48 patients; and group B, 128 patients. The mean needle path length was 0.4 cm in group A and 5.6 cm in group B. The short-path approach necessitated more needle punctures (mean, 2.9 vs 1.8 with long-path approach, P < .001) through the pleura. The diagnostic yield in group A was significantly lower than that in group B (71% vs 94%, P < .001), particularly in patients with small (0-1-cm) nodules (40% in group A vs 94% in group B, P < .001). The frequency of postbiopsy pneumothorax was identical (69%) in the two groups. However, more group B than group A patients required chest tube placement for treatment of pneumothorax (38% vs 17%, P = .006).

CONCLUSION

Use of long-needle-path biopsy of subpleural lesions resulted in a higher diagnostic yield, especially for small nodules. However, compared with the short-needle-path technique, this approach was associated with a higher frequency of chest tube placement for pneumothorax.

Evaluation of patient and staff doses during various CT fluoroscopy guided interventions

As CT scanners are more routinely used as a guidance tool for various types of interventional radiological procedures, concern has grown for high patient and staff doses. CT fluoroscopy provides the physician immediate feedback and can be a valuable tool to dynamically assist various types of percutaneous interventions. However, the fixed position of the scanning plane in combination with high exposure factors may lead to high cumulative patient skin doses that can reach deterministic threshold limits. The staff is also exposed to a considerable amount of scatter radiation while standing next to the patient during the procedures. Although some studies have been published dealing with this subject, data of patient skin doses determined by direct in vivo dosimetry remains scarce. The purpose of this study is to quantify and to evaluate both patient and staff doses by direct thermoluminescent dosimetry during various clinical CT fluoroscopy guided procedures. Patient doses were quantified by determining the entrance skin dose with direct thermoluminescent dosimetry and by estimating the effective dose (E). Staff doses were quantified by determining the entrance skin dose at the level of the eyes, thyroid, and both the hands with direct thermoluminescent dosimetry. For a group of 82 consecutive patients, the following median values were determined (data per procedure): patient E (19.7 mSv), patient entrance skin dose (374 mSv), staff entrance skin dose at eye level (0.21 mSv), thyroid (0.24 mSv), at the left hand (0.18 mSv), and at the right hand (0.76 mSv). The maximum recorded patient entrance skin dose stayed well below the deterministic threshold level of 2 Gy. Poor correlation between both patient/staff doses and integrated procedure mAs emphasizes the need for in vivo measurements. CT fluoroscopy doses are markedly higher than classic CT-scan doses and are comparable to doses from other interventional radiological procedures. They consequently require adequate radiation protection management. An important potential for dose reduction exists by limiting the fluoroscopic screening time and by reducing the tube current (mA) to a level sufficient to provide adequate image quality.

CT-guided percutaneous fine-needle aspiration biopsy of small (< or =1-cm) pulmonary lesions

PURPOSE

To determine the accuracy of percutaneous computed tomography (CT)-guided fine-needle aspiration biopsy (FNAB) of small (< or =1.0-cm in diameter) pulmonary lesions.

MATERIALS AND METHODS

Sixty-one patients (34 men and 27 women) 21-89 years old (mean age, 61.3 years) with lung nodules 1.0 cm or smaller underwent CT-guided transthoracic FNAB. Fifty-seven of the 61 patients had an underlying primary malignancy. Maximum nodule diameters were 0.5-0.7 cm in 10 patients and 0.8-1.0 cm in 51 patients. Cytopathologic evaluation of FNAB samples was immediate in all patients. Sensitivity and accuracy were calculated, and each case was reviewed for complications, including pneumothorax and thoracostomy tube insertion. Four patients were not included in our statistical analysis because of a lack of follow-up information.

RESULTS

FNAB samples were adequate for diagnosis in 47 (77%) of 61 patients. Diagnoses were malignancy (n = 29) or suspected malignancy (n = 3) in 52% (n = 32) and benign or atypical findings in 25% (n = 15). Findings were nondiagnostic in 23% (n = 14). Of the 29 patients without evidence of malignancy, 25 had follow-up findings available. Follow-up included chest CT in 16 patients and surgical resection in nine. Four patients were not included in statistical analysis because of a lack of follow-up information. Overall sensitivity was 82% (32 of 39); specificity, 100% (18 of 18); and diagnostic accuracy, 88% (50 of 57) on the basis of 57 patients being evaluable. Results for 47 0.8-1.0-cm lesions were considerably better (sensitivity, 88%; accuracy, 92%) than those for 10 0.5-0.7-cm lesions (sensitivity, 50%; accuracy, 70%). Sensitivity (75% vs 87%) and accuracy (87% vs 89%) also improved when comparing subpleural (< or =1.0 cm from pleural surface, n = 30) with deeper (>1 cm from pleural surface, n = 27) pulmonary lesions, but the improvement did not indicate statistical significance. Core biopsy did not reveal malignancy in any of the nine patients in whom preliminary cytologic results were inconclusive and did not improve diagnostic yield. Thirty-eight (62%) patients had pneumothorax, with 19 (31%) requiring thoracostomy tube placement.

CONCLUSION

CT-guided FNAB of pulmonary lesions 1.0 cm or smaller can yield high diagnostic accuracy rates approaching those of larger lesions; FNAB of 0.8-1.0-cm lesions that are not subpleural offers the best opportunity for success.

CT fluoroscopy-guided intervention: marked reduction of scattered radiation dose to the physician's hand by use of a lead plate and an improved I-I device

PURPOSE

To estimate the effects of a lead plate, three types of needle holders, tube current, and slice thickness on decreasing the radiation dose to the physician's hand during interventional procedures with computed tomographic (CT) fluoroscopic guidance. The needle holders (I-I devices), which were developed by the authors, maintained the distance between the physician's hand and the CT plane at 7 cm, 10 cm, and 15 cm, respectively.

MATERIALS AND METHODS

The dose rate (mSv/tube current/CT fluoroscopy time) was measured in 55 cases, which were divided into six groups. In group A (n = 14), the current was 135 kV, there was a 5-mm slice thickness, and a 7-cm I-I device was used without the lead plate. Group B (n = 11) entailed a 120-kV current, a 5-mm slice thickness, and a 7-cm I-I device without the lead plate. Group C (n = 8) entailed a 120-kV current, 5-mm slice thickness, and 7-cm I-I device with the lead plate. Group D (n = 9) entailed a 120-kV current, 5-mm slice thickness, and 10-cm I-I device with the lead plate. Group E (n = 7) entailed a 120-kV current, 5-mm slice thickness, and 15-cm I-I device with the lead plate. Group F (n = 6) entailed a 120-kV current, 1-mm slice thickness and 10-cm I-I device with the lead plate. To compare the effects of tube voltage, lead plate use, slice collimation, and I-I devices, differences were compared between groups A and B, B and C, D and F, and among groups C, D, and E.

RESULTS

The dose rates of groups A, B, C, D, E, and F were 126.3, 75.2, 17.8, 13.9, 2.8, and 4.1 mSv/mA/sec x 100,000, respectively. There were significant differences in dose rates between groups A and B (t-test, P =.037), B and C (Student t-test, P =.002), D and F (Mann-Whitney test, P =.011), and among groups C, D, and E (Kruskal-Wallis test, P =.016).

CONCLUSION

The lead plate, the improved I-I devices, use of a 120 kV (vs 135 kV) current, and 1-mm (vs 5 mm) collimation were all useful in decreasing the dose rate.