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DOI: 10.1148/radiol.2372041323
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(Radiology 2005;237:701-708.)
© RSNA, 2005

Vascular and Interventional Radiology

CT Fluoroscopy–guided Biopsy of the Lung or Upper Abdomen with a Breath-hold Monitoring and Feedback System: A Prospective Randomized Controlled Clinical Trial1

Stephanie K. Carlson, MD, Joel P. Felmlee, PhD, Claire E. Bender, MD, Richard L. Ehman, MD, Kelly L. Classic, MS, Tanya L. Hoskin, MS, William S. Harmsen, MS and Houchun H. Hu, BS

1 From the Department of Radiology (S.K.C., J.P.F., C.E.B., R.L.E., H.H.H.), Section of Safety (K.L.C.), and Division of Biostatistics (T.L.H., W.S.H.), Mayo Clinic, 200 First St SW, Rochester, MN 55905. Received July 29, 2004; revision requested October 5; revision received November 29; accepted January 3, 2005. Supported in part by the General Electric–Association of University Radiologists' Radiology Research Academic Fellowship Program. Address correspondence to S.K.C. (e-mail: scarlson{at}mayo.edu).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
PURPOSE: To prospectively determine the clinical effectiveness of a breath-hold monitoring and feedback system in computed tomographic (CT) fluoroscopy–guided biopsies in which respiratory motion is a problem.

MATERIALS AND METHODS: Institutional review board approval and oral and written informed consent were obtained. This study was HIPAA compliant. A bellows-based system was used to monitor respiration and provide patient feedback. A randomized controlled clinical trial compared intermittent mode CT fluoroscopy–guided biopsies of the lung or upper abdomen performed with (n = 56) and without (n = 57) the bellows system. Inclusion criteria for 113 patients were lesions 6 cm or smaller in maximum dimension that were not affixed to the chest or abdominal wall. Primary outcome measurements were CT fluoroscopy exposure time and patient dose. Wilcoxon rank sum, {chi}2, and Fisher exact tests were used for statistical analysis.

RESULTS: Median CT fluoroscopy exposure time was 12.6 seconds (range, 2.4–44.4 seconds) for the bellows group and 18.0 seconds (range, 6.0–118.0 seconds) for the nonbellows group (P = .004). Patient dose was decreased in the bellows group (median dose, 29.5 mGy; range, 4.7–135.8 mGy) versus the nonbellows group (median, 41.3 mGy; range, 11.8–155.9 mGy) (P = .01). Lesions were accessed successfully with one needle puncture attempt in 43 of 56 patients (77%) in the bellows group and 30 of 57 patients (53%) in the nonbellows group (P = .007). Pneumothorax developed in 11 of 50 patients (22%) in the bellows group who underwent lung biopsy compared with 16 of 50 (32%) patients in the nonbellows group.

CONCLUSION: A breath-hold monitoring and feedback system allows depiction of mobile target lesions throughout CT fluoroscopy–guided biopsy of the lung and upper abdomen.

© RSNA, 2005


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
Respiratory motion poses a considerable problem in computed tomographic (CT)-guided biopsy of the lung or upper abdomen. Despite specific breath-hold instructions, the ability to reproduce consistent levels of suspended inspiration or expiration on command is a challenge for many patients. CT fluoroscopy originally was designed for real-time use to overcome the difficulties associated with respiratory motion. Because of substantial exposure times and radiation doses incurred with real-time CT fluoroscopy and the requirement of a standoff needle holder that is difficult to use when maneuvering the needle through resistant tissue planes, use of the intermittent (or quick-check) mode of image acquisition is advocated (1–5). The intermittent mode allows for a substantial reduction in CT fluoroscopy exposure time and radiation exposure to the patient and operator (1,3,4,6).

The advantages of intermittent CT fluoroscopy far outweigh the disadvantages; however, respiratory motion can still be a problem in procedures that involve the lung or upper abdomen, in which structures can vary in position from 1 to 6 cm in the superior-to-inferior direction during normal breathing (7–10). To address this problem, a bellows-based breath-hold monitoring and feedback system was developed that was shown in phantom and volunteer studies to be sensitive and reliable for monitoring respiration and providing patient feedback (11). The bellows system monitors changes in chest or abdominal girth, which strongly correlate with diaphragm and internal target lesion position (11,12). Respiratory monitoring and feedback systems have proved valuable in other areas, such as magnetic resonance (MR) imaging and radiation therapy planning (13–16). Thus, the purpose of our study was to prospectively determine the clinical effectiveness of a breath-hold monitoring and feedback system in intermittent-mode CT fluoroscopy–guided biopsy of the lung or upper abdomen, in which respiratory motion is a problem.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 References
 
Patient Population and Study Design
Our institutional review board approved this study, which was compliant with the Health Insurance Portability and Accountability Act, and oral and written informed consent were obtained from all patients. A prospective, randomized controlled clinical trial was conducted comparing CT fluoroscopy–guided biopsies performed with and without the bellows system. Patients scheduled to undergo CT fluoroscopy–guided biopsy of a percutaneously accessible lesion in the lung or upper abdomen (at or above the level of the kidneys) with the interventional CT scanner at our hospital between January 2002 and August 2003 were considered eligible for our study. Our patient population consisted of inpatients and outpatients from local and surrounding communities and patients referred to our tertiary referral practice. Patients were included in this study if they had lesions measuring 6 cm or less in maximum dimension that were not affixed to the chest or abdominal wall. Exclusion criteria were as follows: (a) an inability to cooperate with breath-holding instructions (eg, patients with cognitive impairment), (b) bleeding diatheses (fewer than 50 x 109/L platelets), (c) international normalized ratio of more than 1.5 or an activated partial thromboplastin time of more than twice the normal value, and (d) lesions that abutted the pleura or abdominal wall for a distance of more than 3 cm (these lesions were assumed to be fixed in position and less likely to be affected by respiratory motion). Of 235 eligible patients, 120 were enrolled and randomized to either the bellows group (n = 60) or the nonbellows group (n = 60). Reasons for exclusion were refusal to participate (n = 4) or failure to meet the inclusion criteria (n = 111). After enrollment, seven patients withdrew consent and did not complete the study. This left 56 patients in the bellows group and 57 patients in the nonbellows group. All patients who were enrolled in the study, were randomized to a treatment group, and underwent scheduled CT fluoroscopy–guided biopsy were followed up until completion of the study follow-up period.

Random patient assignments were generated by a computer in the division of biostatistics and kept in sealed numbered envelopes. To minimize bias between the two groups, separate randomizations were generated for each radiologist, and patients were stratified within the randomization by lesion location (lung vs nonlung location). Before each procedure and after the radiologist had deemed the patient eligible for the study, a sealed envelope was opened by the research study coordinator, and the patient was assigned to the bellows or nonbellows group, as indicated on the enclosed randomization card. All patients remained in their originally assigned treatment group without crossover.

All biopsies were performed by eight staff radiologists (including S.K.C.) with experience in CT-guided interventional procedures (average experience, 13 years; range of experience, 7–24 years). All staff members participating in the study were required to attend an informational and training session on the use of the bellows system before enrolling patients in the study. A research study coordinator was present during all procedures to assist with setup of the bellows system and ensure that the study questionnaire was completed accurately.

All biopsies were performed with the same interventional CT scanner (HiSpeed CT/I with SmartView CT fluoroscopy; GE Medical Systems, Milwaukee, Wis) with the bellows system. The intermittent mode of CT fluoroscopy was used for all patients. A 19/20-gauge coaxial automated core needle biopsy system was used in 98 of the 100 lung biopsies. A 17/18-gauge coaxial automated core needle biopsy system was used in the other two lung biopsies and in all 13 upper abdominal biopsies. At our institution, a cytopathologist is not present during biopsy procedures; therefore, core biopsy specimens are obtained. Smears of the core tissue are then used for cytologic analysis after the procedure.

Bellows Breath-hold Monitoring and Feedback System
The bellows system was developed and modified by medical physicists and engineers, and it has been described in detail elsewhere (11). The basic components of the system are a Velcro belt with expandable bellows, a light-emitting diode (LED) monitor for patient feedback, and a system control unit located next to the CT operator console. Before a procedure is begun, the bellows belt is wrapped around the patient's upper abdomen or lower chest (generally at the level of the xiphoid); the placement of this belt depends on the area that expands the most during inspiration. Variation in the length of the bellows during breathing (corresponding to changes in chest or abdominal girth) causes pressure change within the tubing that is measured with a pressure-sensitive transducer. The transducer analog signal is digitized and displayed on the patient LED monitor attached to the CT table. When CT localization images are obtained through the area of interest and the patient has stabilized at a specific preselected reference breath-hold level, a solenoid switch on the control unit of the system is turned off and on. This action closes the airflow to and from the bellows, which allows the operator to correlate the center red LED on the display with the breath-hold level obtained during the acquisition of localization images. The images are then reviewed to determine if the lesion is optimally depicted and percutaneously accessible at this reference breath-hold level. If the level is deemed suitable, the patient is instructed to reproduce this same breath-hold level, as needed, throughout the procedure by inhaling or exhaling to light the center red diode on the LED display. The system can be used with the patient in any position on the CT table.

Data Collection
The research study coordinator and staff radiologist who performed the biopsy completed a questionnaire during and after the procedure. Data included baseline demographic and clinical characteristics of the patients (ie, age, sex, body mass index, and history of chronic obstructive pulmonary disease) and important prognostic procedure-related variables (ie, lesion size, depth, and location). Other collected data included (a) the number of biopsy samples obtained, (b) the number of needle puncture attempts (ie, the number of times the radiologist attempted to directly puncture the target lesion, not including initial needle placement or redirection of the needle within the soft tissues), (c) successful puncture (ie, the ability to directly puncture the target lesion with the introducer needle), (d) number of pleural passes, (e) ability of the patient to reliably light the center red diode on the patient feedback display during consecutive breath-hold attempts, (f) bellows system setup, and (g) patient training time.

Radiologists were also asked to give their subjective rating of procedure difficulty on a five-point Likert scale (0 = easy, 5 = difficult) after the procedure to determine if the groups were similar with regard to procedure difficulty. Initially, radiologists were asked to complete this questionnaire after the procedure. For the last 18 patients in each group, however, we asked the radiologists to give their rating of anticipated difficulty before beginning the procedure and their rating of actual difficulty after the procedure; this allowed us to assess the effect of the bellows system on the rating of procedure difficulty.

The primary outcome variables were CT fluoroscopy exposure time (recorded in seconds on the technologist's monitor and in-room CT fluoroscopy screen) and patient-absorbed radiation dose. Important secondary outcome variables included pneumothorax rate, overall complication rate, needle placement and total procedure time (defined as the time from local anesthetic injection to successful puncture of the target lesion and final withdrawal of the biopsy needle, respectively), and diagnostic yield of the biopsy specimen. Biopsy findings were considered nondiagnostic when there was insufficient tissue for diagnosis or only atypical cells. All final diagnoses were confirmed at surgery, repeat percutaneous or bronchoscopic biopsy, or imaging or clinical follow-up (or both) for a minimum of 6 months (range, 6–21 months).

Radiation Monitoring
To obtain measurements of radiation dose to personnel per procedure, the radiologist wore a separate personal body dosimeter placed at the upper chest level and external to the required lead apron; a ring radiation dosimeter was worn under the sterile glove. These dosimeters were distributed just before and collected immediately after each procedure. All exposure results were monitored throughout the study by the radiation safety department at our institution.

The CT technologist and radiologist selected the appropriate tube voltage, tube current, and section collimation before each procedure. A standard tube voltage of 120 kVp was used in all patients. The tube current varied depending on the site of the procedure (range, 10–50 mA). The lowest tube current that still allowed adequate image quality in the region of interest was used. Section collimation was generally 5 mm, but it ranged from 3 to 7 mm.

Total radiation dose to the patient was calculated from measurements of tube potential, tube current, collimation, total CT fluoroscopy time, and CT dose index. The CT dose index was calculated from quality control measurements performed in a standard 32-cm Plexiglas cylindric phantom that was used to simulate a normal-sized patient. A conversion factor of 0.95 (conversion from air to soft tissue for 100-keV x-rays) was used to estimate maximum absorbed patient dose (17).

Statistical Analysis
Statistical analyses were performed with SAS software (version 8.2; SAS Institute, Cary, NC). Data were summarized separately for the bellows and nonbellows groups with mean values, standard deviations, medians, and ranges for quantitative variables and frequencies and proportions for categorical variables. Baseline and demographic characteristics were compared between the groups. Wilcoxon rank sum tests were used to compare continuous and ordinal variables, and {chi}2 and Fisher exact tests were used, when appropriate, to compare proportions between groups.

The same statistical tests were used to compare procedure and outcome variables between the bellows and nonbellows groups. The distributions of variables such as CT fluoroscopy time and patient radiation dose showed a strong right skew, which necessitated the use of the nonparametric Wilcoxon rank sum test. All tests were two-sided, with P values of .05 or less considered to indicate a statistically significant difference.

Multiple variable regression models were used to assess the association between use of the bellows system and outcome variables while adjusting for baseline differences between the groups. A natural logarithm transformation was used for variables such as CT fluoroscopy time to satisfy the assumption of normality associated with regression modeling.

We assessed the association of procedure variables, such as CT fluoroscopy time and patient radiation dose, with the number of procedures the radiologist had performed in the particular study group. Spearman rank correlation coefficient was used to assess the association between the number of procedures performed and CT fluoroscopy time, procedure time, needle placement time, and patient radiation dose. This analysis was performed separately for the bellows and nonbellows groups, and the results are reported descriptively.

Associations between CT fluoroscopy time and other procedure variables, such as patient radiation dose, were also assessed with the Spearman rank correlation coefficient. Associations between CT fluoroscopy time and categorical procedure variables, such as complications, were assessed with the Wilcoxon rank sum test.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 References
 
Baseline Characteristics
Data for baseline characteristics of the patients are summarized in Table 1. The two groups of patients were similar demographically and with regard to baseline clinical characteristics, although there were slightly more patients with a history of chronic obstructive pulmonary disease (of any severity) in the bellows group (P = .224). The groups were also similar with regard to the stratification of lung versus nonlung biopsies and the prognostic procedure-related variables of lesion size, lesion depth, and procedure difficulty. There was no significant difference between the groups with regard to the CT variables used to calculate patient dose (ie, tube current, tube voltage, and section collimation).


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  		TABLE 1. Demographic and Baseline Comparisons between the Bellows and Nonbellows Groups

 
Lesions
Among the patients who underwent lung biopsy, there was a difference between the groups with regard to lesion location and the number of lesions that abutted the pleura. The nonbellows group had more patients with upper lobe lesions (24 of 50 patients) than did the bellows group (12 of 50 patients) (P = .019). The nonbellows group also had a higher number of patients with lung lesions that abutted the pleura (20 of 50 patients in the nonbellows group vs 17 of 50 patients in the bellows group) (P = .534).

A subset analysis was used to compare the bellows and nonbellows groups for the subset of patients with lung lesions that were 15 mm or less in diameter. The diameter of lesions was 15 mm or less in 32 of 50 lesions in the bellows group and 19 of 50 lesions in the nonbellows group (P = .009). The groups were similar with regard to baseline characteristics, with the exception of the lung lesion site. The nonbellows group had more upper lobe lesions (11 of 19 lesions) than did the bellows group (eight of 32 lesions) (P = .062). The bellows group had a higher number of potentially more difficult biopsies (smaller lesions and lesions in the middle and lower lung zones) than did the nonbellows group. The difference between the two groups in biopsy of lung lesions with a diameter of 15 mm or less with regard to CT fluoroscopy exposure time and number of needle puncture attempts remained significant (P = .038 and P = .001, respectively).

Outcome Variables
Differences in study outcome variables between the groups are summarized in Table 2. For all outcome variables except diagnostic yield, the results favored the bellows group. In the bellows group, 46 (82%) of the biopsies were diagnostic, whereas in the nonbellows group, 49 (86%) were diagnostic (P = .579). The bellows group had a higher proportion of benign diagnoses than did the nonbellows group (20 of 46 diagnostic biopsies vs nine of 49 diagnostic biopsies, respectively) (P = .015). One lesion in the nonbellows group (13-mm mesenteric nodule in the upper abdomen) was unsuccessfully punctured because of respiratory motion, and the procedure was eventually completed with ultrasonographic guidance.


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  		TABLE 2. Procedure and Outcome Variable Comparisons between the Bellows and Nonbellows Groups

 
Outcome results differed significantly in the bellows and nonbellows group for CT fluoroscopy exposure time (median, 12.6 seconds and 18.0 seconds, respectively; P = .004), patient absorbed radiation dose (median, 29.5 mGy and 41.3 mGy, respectively; P = .010), and needle puncture attempts; 13 (23%) patients in the bellows group and 27 (47%) patients in the nonbellows group required more than one puncture attempt (P = .007). Multivariable analysis with linear regression techniques to assess the association between use of the bellows system and these outcome variables after adjusting for patient age, procedure number, pleural abutment, and lung biopsy location showed no change in the univariate study conclusions.

Personnel Radiation Exposure
Resultant measurements of personnel radiation exposure showed all readings were between "m" (ie, <10 mrem) and 40 mrem for the body dosimeters. In the subset of 20 body dosimeters in which readings were between 10 and 40 mrem, eight readings occurred during bellows biopsies, and 12 occurred during nonbellows biopsies. Body dosimeter readings did not correlate with CT fluoroscopy exposure time or patient dose. These doses are well below regulatory annual occupational exposure limits. Ring dosimeter readings were below detectable levels.

Target Structure
In all but one of the bellows-assisted biopsies, patients were able to reliably light the center red diode on the patient feedback display during consecutive breath-hold attempts. This resulted in consistent return of the target structure to the reference breath-hold level throughout the procedure (Figs 1, 2). In one bellows biopsy, a 30-year-old man had problems consistently lighting the center diode, but he was able to keep his breath-hold level within one or two diodes above or below the center diode. Despite this difficulty, the radiologist was still able to visualize adequately and puncture successfully an 11-mm nodule in the patient's lower lung; in this patient, CT fluoroscopy exposure time was 17 seconds. Bellows system setup and patient training required 12 minutes for the first patient and 5 minutes or less for the remaining 55 patients.



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  		Figure 1a. Transverse CT images obtained with the patient in the prone position during bellows-assisted biopsy of a small nodule in the left lower lobe. (a) Intermittent mode CT fluoroscopic image obtained for verification of needle position (black arrow) shows the 1-cm nodule (white arrow) is accessible through a posterior rib interspace at this breath-hold level. (b–d) Sequential CT fluoroscopic images obtained at the same level show that the patient was able to reproduce the exact breath-hold level by using the bellows feedback display. This allowed successful puncture of the nodule with only 14.4 seconds of CT fluoroscopy exposure time. Biopsy results were consistent with metastatic melanoma.

 


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  		Figure 1b. Transverse CT images obtained with the patient in the prone position during bellows-assisted biopsy of a small nodule in the left lower lobe. (a) Intermittent mode CT fluoroscopic image obtained for verification of needle position (black arrow) shows the 1-cm nodule (white arrow) is accessible through a posterior rib interspace at this breath-hold level. (b–d) Sequential CT fluoroscopic images obtained at the same level show that the patient was able to reproduce the exact breath-hold level by using the bellows feedback display. This allowed successful puncture of the nodule with only 14.4 seconds of CT fluoroscopy exposure time. Biopsy results were consistent with metastatic melanoma.

 


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  		Figure 1c. Transverse CT images obtained with the patient in the prone position during bellows-assisted biopsy of a small nodule in the left lower lobe. (a) Intermittent mode CT fluoroscopic image obtained for verification of needle position (black arrow) shows the 1-cm nodule (white arrow) is accessible through a posterior rib interspace at this breath-hold level. (b–d) Sequential CT fluoroscopic images obtained at the same level show that the patient was able to reproduce the exact breath-hold level by using the bellows feedback display. This allowed successful puncture of the nodule with only 14.4 seconds of CT fluoroscopy exposure time. Biopsy results were consistent with metastatic melanoma.

 


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  		Figure 1d. Transverse CT images obtained with the patient in the prone position during bellows-assisted biopsy of a small nodule in the left lower lobe. (a) Intermittent mode CT fluoroscopic image obtained for verification of needle position (black arrow) shows the 1-cm nodule (white arrow) is accessible through a posterior rib interspace at this breath-hold level. (b–d) Sequential CT fluoroscopic images obtained at the same level show that the patient was able to reproduce the exact breath-hold level by using the bellows feedback display. This allowed successful puncture of the nodule with only 14.4 seconds of CT fluoroscopy exposure time. Biopsy results were consistent with metastatic melanoma.

 


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  		Figure 2a. Transverse CT images obtained with the patient in the prone position during bellows-assisted biopsy of a small peripheral nodule in the left upper lobe. (a) Initial spiral CT image obtained for localization purposes shows the lesion (arrow) located deep to the scapula but accessible through a posterior rib interspace at this breath-hold level. The nodule measured only 5 mm at soft-tissue window settings. (b, c) Intermittent mode CT fluoroscopic images obtained at consecutive breath-hold attempts show the patient is able to reproduce consistently the identical breath-hold level when instructed. Images demonstrate the local anesthetic needle (arrow in b) and 19-gauge introducer needle (arrow in c) in good position near the pleural surface before puncture of the nodule. (d) Final CT fluoroscopic image shows the introducer needle (arrow) adjacent to the medial edge of the nodule. The needle was angled slightly laterally before biopsy with a 20-gauge coaxial needle. Biopsy results were consistent with a benign dust macule.

 


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  		Figure 2b. Transverse CT images obtained with the patient in the prone position during bellows-assisted biopsy of a small peripheral nodule in the left upper lobe. (a) Initial spiral CT image obtained for localization purposes shows the lesion (arrow) located deep to the scapula but accessible through a posterior rib interspace at this breath-hold level. The nodule measured only 5 mm at soft-tissue window settings. (b, c) Intermittent mode CT fluoroscopic images obtained at consecutive breath-hold attempts show the patient is able to reproduce consistently the identical breath-hold level when instructed. Images demonstrate the local anesthetic needle (arrow in b) and 19-gauge introducer needle (arrow in c) in good position near the pleural surface before puncture of the nodule. (d) Final CT fluoroscopic image shows the introducer needle (arrow) adjacent to the medial edge of the nodule. The needle was angled slightly laterally before biopsy with a 20-gauge coaxial needle. Biopsy results were consistent with a benign dust macule.

 


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  		Figure 2c. Transverse CT images obtained with the patient in the prone position during bellows-assisted biopsy of a small peripheral nodule in the left upper lobe. (a) Initial spiral CT image obtained for localization purposes shows the lesion (arrow) located deep to the scapula but accessible through a posterior rib interspace at this breath-hold level. The nodule measured only 5 mm at soft-tissue window settings. (b, c) Intermittent mode CT fluoroscopic images obtained at consecutive breath-hold attempts show the patient is able to reproduce consistently the identical breath-hold level when instructed. Images demonstrate the local anesthetic needle (arrow in b) and 19-gauge introducer needle (arrow in c) in good position near the pleural surface before puncture of the nodule. (d) Final CT fluoroscopic image shows the introducer needle (arrow) adjacent to the medial edge of the nodule. The needle was angled slightly laterally before biopsy with a 20-gauge coaxial needle. Biopsy results were consistent with a benign dust macule.

 


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  		Figure 2d. Transverse CT images obtained with the patient in the prone position during bellows-assisted biopsy of a small peripheral nodule in the left upper lobe. (a) Initial spiral CT image obtained for localization purposes shows the lesion (arrow) located deep to the scapula but accessible through a posterior rib interspace at this breath-hold level. The nodule measured only 5 mm at soft-tissue window settings. (b, c) Intermittent mode CT fluoroscopic images obtained at consecutive breath-hold attempts show the patient is able to reproduce consistently the identical breath-hold level when instructed. Images demonstrate the local anesthetic needle (arrow in b) and 19-gauge introducer needle (arrow in c) in good position near the pleural surface before puncture of the nodule. (d) Final CT fluoroscopic image shows the introducer needle (arrow) adjacent to the medial edge of the nodule. The needle was angled slightly laterally before biopsy with a 20-gauge coaxial needle. Biopsy results were consistent with a benign dust macule.

 
Correlations
Spearman rank correlation coefficients were calculated to determine the association between CT fluoroscopy time and other procedure-related outcome variables. CT fluoroscopy time was correlated moderately with patient dose (r = 0.69), needle placement time (r = 0.60), and total procedure time (r = 0.67) (P < .001). The correlations between CT fluoroscopy time and needle puncture attempts, target size, and target depth were somewhat weaker but were still significant. There was also a trend toward a decrease in complications and an increase in diagnostic yield, with a decrease in CT fluoroscopy time.

Spearman rank correlation coefficients were also calculated to determine if there was a learning curve associated with use of the bellows system. Results showed an inverse relationship between individual radiologist procedure number and the procedure-related variables of CT fluoroscopy exposure time, patient absorbed dose, needle placement time, and procedure time in the bellows group. These correlation coefficients were relatively weak (r = –0.16, –0.08, –0.20, and –0.27, respectively) and were significant only for procedure time (P = .04).


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
References
 
Patient cooperation with breath holding is critical to the success and safety of many CT-guided procedures (18–21). Interventional procedures in the lung and upper abdomen, particularly small lung nodule biopsies, are some of the most technically challenging procedures because minimal changes in patient respiration can result in inaccurate needle placement, increased complication rates, and decreased diagnostic yield (18,21–28).

CT-guided biopsy procedures have been improved with the development of CT fluoroscopy, which results in markedly decreased procedure times compared with conventional CT guidance (1,22,29,30). Further improvements are required to monitor accurately and allow optimal depiction of target lesions throughout CT fluoroscopy–guided biopsies in which respiratory motion is a challenge.

Breath-hold monitoring and feedback systems have been evaluated for use in CT examinations to improve image quality for detection of small lesions and multiplanar reconstructions, monitoring of contrast medium distribution, and measurement of target volumes and attenuation values (10,31,32). Tomiyama et al (33) reported the use of a commercially available respiratory-gating device in conventional CT-guided biopsy of small pulmonary nodules. With this device, the diagnostic accuracy was 96% for nodules with a diameter of 15 mm or less. This was significantly greater than the diagnostic accuracy of 69% without use of the device (P < .05), although this comparison used historical controls. A disadvantage of this respiratory-gating system is that it requires a mouthpiece to monitor patient respiration. Mouth-mounted spirometry systems can interfere with normal breathing, and they were less tolerated in a study comparing breath-hold monitoring devices for MR imaging (14). Our breath-hold monitoring and feedback system has a user-friendly bellows-based Velcro belt with an LED display that is well tolerated by patients, easily adapted to any commercial CT scanner, and extremely sensitive and reliable for monitoring breath-hold level and internal target location (11).

Katada et al (18) developed CT fluoroscopy in 1993 to allow real-time image guidance during interventional CT procedures. The intermittent mode is preferred at many institutions, however, because of the lowered CT fluoroscopy exposure times, reduced radiation dose to patients, minimal exposure to personnel, and lack of the needle holder requirement (1–5). For needle puncture attempts, complications, and diagnostic yield, we report rates similar to those in studies in which the real-time mode was used (18,19,29,30,34,35) but with significantly decreased CT fluoroscopy exposure times (median time, 12.6 seconds; maximum time, 44.4 seconds in the bellows group) and similar or decreased overall procedure times. We also report negligible radiation doses to the radiologists performing the procedures.

We found a considerable reduction in the pneumothorax rate between the bellows and nonbellows groups (22% vs 32%, respectively). Although this reduction did not reach statistical significance, this trend toward a difference in proportions is clinically important, and the lack of statistical significance may be due to the low power for assessment of this outcome. Although the percentage of pneumothoraces that required chest tube drainage was equal (8%), the time and costs involved with in- or outpatient monitoring and follow-up of patients with even small pneumothoraces (many of whom are elderly and have comorbidities) can be substantial.

There was an overall decrease in median needle placement time in the bellows group. Several authors have reported a correlation between needle placement time (23,36) and an increased pneumothorax rate. The longer the biopsy needle remains in the chest, the greater the chance of tearing the pleura and normal lung tissue as the patient breathes or coughs during the procedure. Other authors reported a correlation between the number of pleural punctures and pneumothorax rate (20,25,26,37). Our study showed a significant decrease in needle puncture attempts (P = .007) in the bellows group, which may have contributed to the decreased pneumothorax rate in this group as well.

Our diagnostic yields are similar to those reported in the literature (34,38). The percentage of nondiagnostic biopsies was slightly higher in the bellows group than in the nonbellows group (18% vs 14%), although this difference was not significant. This difference may be due to a higher proportion of benign diagnoses in the bellows group. Benign lung lesions are more difficult to diagnose than malignant lung lesions (28,38,39), likely because the pathologist requires more tissue. The addition of an on-site cytopathologist during biopsy procedures may decrease our nondiagnostic biopsy rate. In addition, the bellows group had a higher number of lung lesions with a diameter of 15 mm or less, a higher number of lesions in the middle and lower lung zones, and a lower number of lesions abutting the pleura, possibly contributing to the decreased diagnostic yield in this group. These lesions may be the more difficult cases because of the higher rate of respiratory excursion (20,33,40).

Because our randomization stratified patients only on the basis of lung or nonlung biopsy, it did not ensure balance between the two groups with regard to lesion size and location. Although it is not optimal that these baseline differences occurred by random chance between the bellows and nonbellows groups, in every case, the trend was for the bellows group to have the more difficult procedures. We may have observed even more favorable results for the bellows system if the two groups had been more similar with respect to procedure difficulty. In addition, multivariable models were used to adjust for these baseline differences, and multivariable analysis resulted in the same conclusions with regard to the bellows system.

Although it is reported that end expiration is a highly reproducible breath-hold level because it is close to residual volume or functional residual capacity (33), we did not find this to be true. In several patients in the bellows group, we used end expiration as our reference breath-hold level; these patients were unable to reproduce the reference level without watching the LED display. Patients were sometimes off target by more than six diodes on the LED display, which is equal to a variation of approximately 2–3 cm. This can be a substantial problem in biopsy of lesions with a diameter smaller than 1 cm.

CT-guided biopsy of subpleural lesions is difficult because of overlying ribs (41,42). An oblique or angulated puncture can be used; however, shallow pleural puncture angles have been associated with an increased risk of pneumothorax (20,43). The bellows system can be used to adjust the patient's breath-hold level until the subpleural lesion can be depicted optimally and accessed directly with a perpendicular needle entry into the skin and pleura through an intercostal space. This also decreases the amount of healthy lung tissue that is traversed to access the lesion, which is also associated with a decreased risk of pneumothorax (23,44).

An additional benefit of the bellows system is that it allows biopsy of lesions that are difficult to see without intravenous contrast medium administration or because of decreased tube current and resolution. If the patient is able to light the center diode and reproduce the reference breath hold, the radiologist can use anatomic landmarks to guide the needle into the lesion, even if it is not visible. It also decreases both the variability of the patient's breathing pattern associated with sedation, anxiety, or pain and the number and duration of breath holds. Although data on the use of sedation were not collected prospectively, we did note that in several patients who received intravenous conscious sedation with fentanyl and midazolam during the procedure, the sedation did not adversely affect their ability to cooperate and use the bellows system.

There were several limitations to our study. We started the trial before many of the participating radiologists had an adequate chance to gain clinical experience with the bellows system. This resulted in a learning curve that produced a trend toward a decrease in CT fluoroscopy exposure time, patient dose, needle placement time, and procedure time as the number of procedures performed increased. Another limitation was the variability in the level of physician expertise, biopsy technique, and biopsy tools. Although this variability may slightly decrease the internal validity of our results, it increases the external generalizability of the results because operator variability is common in virtually all radiology practices.

The inclusion of lesions measuring 6 cm in maximum size may have been too generous; therefore, this may be a limitation. The size of 6 cm was chosen because published studies dealing with respiratory motion report that lesions in the lung and upper abdomen can move up to 6 cm in the superior-inferior direction. We based our pleural abutment criteria of 3 cm or less on previous personal experience with pleural-based lesions that exhibited considerable motion during breathing. The overall number of large lesions (larger than 3 cm in diameter) in both groups was low (seven in the bellows group and six in the nonbellows group). The percentage of lesions that abutted the pleura for any distance was higher in the nonbellows group (40% vs 34%, respectively); therefore, the bellows group had potentially more difficult cases.

Finally, use of the bellows system did require system setup and patient training time. Given the benefits of the system, we believe the minimal time expenditure is justified.

We believe that use of the bellows system allows us to perform biopsies that may have been considered impossible previously because of small lesion size or lesion location. Before a new technology can be implemented clinically, however, the efficacy with respect to patient outcomes needs to be addressed. We believe we have demonstrated a positive effect of the bellows system on patient outcomes with a reduction in patient radiation exposure and procedure-related complications.

In conclusion, the bellows breath-hold monitoring and feedback system improves intermittent mode CT fluoroscopy–guided biopsies of the lung or upper abdomen by allowing consistent depiction of the target lesion throughout the procedure. The benefits of this improvement include a decrease in CT fluoroscopy exposure time; reduced radiation exposure to patients and personnel; a decrease in needle puncture attempts, needle placement time, and total procedure time; and fewer procedure-related complications.


   ACKNOWLEDGMENTS
 
We thank all participating CT interventional staff radiologists at our institution. We also thank Lori M. Johnson, who served as our study coordinator.


   FOOTNOTES
 

Abbreviations: LED = light-emitting diode

Authors stated no financial relationship to disclose.

Author contributions: Guarantor of integrity of entire study, S.K.C.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, S.K.C., J.P.F., C.E.B., K.L.C.; clinical studies, S.K.C., C.E.B., K.L.C., T.L.H., W.S.H.; experimental studies, all authors; statistical analysis, S.K.C., T.L.H., W.S.H.; and manuscript editing, all authors


   References
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 

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