Instituting a Low-dose CT-guided Lung Biopsy Protocol

Rationale and Objectives

We aimed to evaluate whether implementation of a low-dose computed tomography (CT)-guided lung biopsy protocol, with the support of individual radiologists in the section, would lead to immediate and sustained decreases in radiation dose associated with CT-guided lung biopsies.

Materials and Methods

A low-dose CT-guided lung biopsy protocol was developed with modifications of kilovoltage peak, milliamperes, and scan coverage. Out of 413 CT-guided lung biopsies evaluated over a 3-year period beginning in 2009, 175 performed with a standard protocol before the development of a low-dose protocol, and 238 performed with a low-dose protocol. The dose-length product (DLP) was recorded for each lung biopsy and retrospectively compared between the two protocols. Individual radiologist level DLPs were also compared before and after the protocol change.

Results

The mean biopsy dose decreased by 64.4% with the low-dose protocol (113.8 milligray centimeters versus 319.7 milligray centimeters; P < 0.001). This decrease in radiation dose persisted throughout the entire 18 months evaluated following the protocol change. After the protocol change, each attending radiologist demonstrated a decrease in administered radiation dose. The diagnostic outcome rate and complication rate were unchanged over the interval.

Conclusions

Implementation of a low-dose CT-guided lung biopsy protocol resulted in an immediate reduction in patient radiation dose that was seen with all attending radiologists and persisted for at least 18 months. Such an intervention may be considered at other institutions wishing to reduce patient doses.

Introduction

The last decade has brought increased awareness of the cancer-inducing risks of radiation sustained from medical imaging, and with it, a movement to decrease doses from modalities such as computed tomography (CT) . CT-guided biopsies can result in high doses by virtue of the repetitive imaging required with some techniques ; however, biopsies are prime candidates for dose reduction because image quality is less of a concern when used solely for needle guidance.

Previous works have shown the success of low-dose protocols in a variety of procedural settings, including CT-guided spine procedures and CT-guided lung biopsies . However, the previous work with low-dose CT-guided lung biopsies was limited by small sample sizes, relatively short follow-up periods to evaluate dose reductions, and limited analysis of the effect of a standardized low-dose protocol on multiple operators. The present study examines the effect of a section-wide implementation of a low-dose CT-guided lung biopsy protocol in a high-volume referral center. This analysis includes an evaluation of the radiation doses over time and the radiation dose reductions achieved by individual attending radiologists.

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Materials and Methods

Low-dose CT-guided Lung Biopsy Protocol

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TABLE 1

Low-dose CT-guided Lung Biopsy Protocol \*

Phase Coverage Slice Thickness Voltage Tube Current Planning Prior CTs should first be reviewed to select the optimal target. If the selected nodule is visible on the biopsy scout image, then coverage approximately 0.5 cm above and below the lesion is acquired. If the lesion is not visible on the scout, a slightly larger range is acquired based on landmarks from prior CT. 2.5 mm 100 kVP for patient weight <140 lbs and arms up

120 kVp for patient weight >140 lbs and/or arms down 10 mA for scout

40 mA for patient weight <140 lbs and arms up

50 mA for patient weight >140 lbs and/or arms down

60 mA for patient weight >220 lbs and/or lesion at level of the liver Targeting Nine images per iteration, then seven images per iteration, then five images per iteration if possible 2.5 mm 100 kVP for patient weight <140 lbs and arms up

120 kVp for patient weight >140 lbs and/or arms down 20 mA for patient weight <140 and arms up

25 mA for patient weight >140 and/or arms down

30 mA for patient weight >220 and/or lesion at level of the liver Post Limited or whole chest 5 mm 100 kVP for patient weight <140 lbs and arms up

120 kVp for patient weight >140 lbs and/or arms down 20 mA for patient weight <220 lbs

30 mA for patient weight >220 lbs

CT, computed tomography; kVP, kilovoltage peak; mA, milliamperes.

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Retrospective Data Collection

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Statistical Analysis

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Results

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TABLE 2

(A) Radiation Dose before and after the CT-guided Lung Biopsy Protocol Change. (B) Radiation Dose over 6-month Periods Surrounding Protocol Change, Median [IQR]

(A) Standard-dose Protocol ( n = 175)

Median [IQR] Low-dose Protocol ( n = 238)

Median [IQR] Percentage Change (%)P Value (Mann-Whitney U ) Age (years) 67[58–76] 66[60–75] NA 0.803 Male (%) 114/175(65.1%) 163/238(68.5%) NA 0.475 Total DLP (mGy-cm) 319.7[156.1–872.9] 113.8[66.1–187.8] −64.4 <0.001 Total coverage (cm) 492.5[367.5–647.5] 467.5[345–587.5] −5.1 0.149 Total series # 9[7–12] 12[9–15] +33.3 <0.001 Planning DLP (mGy-cm) 142.4[51.7–317.9] 32.2[15.5–72.9] −77.4 <0.001 Coverage (cm) 156.3[112.5–225] 122.5[90.5–175] −21.6 <0.001 Series # 1[1–2] 2[1–2] +100.0 0.001 Targeting DLP (mGy-cm) 82.4[34.0–282.2] 39.3[23.5–60.6] −52.3 <0.001 Coverage (cm) 142.5[75–225] 140[90–221.5] −1.8 0.643 Series # 6[4–9] 9[6–12] +50.0 <0.001 Post DLP (mGy-cm) 62.1[23.4–208] 21.2[12.4–42.7] −65.9 <0.001 Coverage (cm) 165.6[82.5–260] 190[100–260] +14.7 0.495 Series # 1[1–1] 1[1–1] 0.0 0.007 \*

(B) 12–18 Months before ( n = 46) 6–12 Months before ( n = 56) 6 Months before ( n = 73) 6 Months after ( n = 89) 6–12 Months after ( n = 78) 12–18 Months

after ( n = 71)P Value (Kruskal-Wallis) Total DLP (mGy-cm) 284.5 400.0 309.2 102.3 120.8 117.8 <0.001 [165.7–859.2] [193.3–1080.1] [110.0–782.1] [70.0–148.4] [64.9–214.2] [59.9–202.5] Planning DLP (mGy-cm) 118.6 178.4 144.8 31.7 34.2 31.6 <0.001 [57.8–354.8] [65.8–342.9] [38.4–277.9] [19.2–63.7] [13.5–74.7] [16.0–79.2] Coverage (cm) 162.5 165.3 150 122.5 132.5 115 <0.001 [132.5–240] [110–223.4] [100–202.5] [90–170] [92.5–192.5] [90–162.5] Series # 1 2 1 2 2 2 0.002 [1–2] [1–2] [1–2] [1–2] [1–2] [1–2] Targeting DLP (mGy-cm) 93.2 67.0 83.6 34.7 40.5 42.3 <0.001 [38.6–339.4] [37.3–504.3] [30.4–220.6] [22.3–59.8] [22.2–60.2] [24.3–73.5] Coverage (cm) 125 143.8 150 150 143.8 115 0.436 [75–245] [72.5–232.5] [90–210] [90–225] [100–221.5] [70–200] Series # 6 6 7 9 9 9 <0.001 [4–10] [4–9.5] [5–9] [6–10] [6–12] [6–13] Post DLP (mGy-cm) 67.3 104.5 37.3 20.8 29.0 19.7 <0.001 [28.8–204.3] [36.9–264.2] [20.3–180.5] [11.6–35.3] [13.7–61.0] [11.8–40.6] Coverage (cm) 147.5 169 166.3 197.5 205 157.5 0.317 [50–245] [95–270] [90–277.5] [98.1–260] [115–272.8] [80–262.5] Series # 1 1 1 1 1 1 0.109 [1–1] [1–1] [1–1] [1–1] [1–1] [1–1]

cm, centimeter; DLP, dose-length product; IQR, interquartile range; mGy, milligray.

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Discussion

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Conclusions

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References

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Instituting a Low-dose CT-guided Lung Biopsy Protocol

Rationale and Objectives

Materials and Methods

Results

Conclusions

Introduction

Materials and Methods

Low-dose CT-guided Lung Biopsy Protocol

Retrospective Data Collection

Statistical Analysis

Results

Discussion

Conclusions

References

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