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Helical CT for Nephrolithiasis and Ureterolithiasis: Comparison of Conventional and Reduced Radiation-Dose Techniques¹

¹ From the Department of Radiology, Duke University Medical Center, Durham, NC. From the 2002 RSNA scientific assembly. Received October 8, 2002; revision requested December 17; revision received January 27, 2003; accepted March 10. Address correspondence to J.P.H., Department of Radiology, Waterford Regional Hospital, Waterford, Ireland (e-mail: heneghanj@sehb.ie).

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
PURPOSE: To determine the accuracy of unenhanced helical computed tomography (CT) performed at reduced milliampere-second, and therefore at a reduced patient radiation dose, by using conventional unenhanced helical CT as the standard.

MATERIALS AND METHODS: Fifty patients with acute flank pain who weighed less than 200 lb (90 kg) were prospectively recruited for this study. Conventional helical CT scans were obtained with patients in the prone position by using 5-mm-thick sections, 140 kVp, 135–208 mAs (mean, 160 mAs), and a pitch of 1.5 (single–detector row CT) or 0.75 (multi–detector row CT, 4 x 5-mm detector configuration). Conventional CT was immediately followed by low-dose scanning, whereby the tube current was reduced to 100 mA (mean, 76 mAs). All other technical parameters and anatomic coverage remained constant. Three independent readers who were blinded to patient identity interpreted the scans in random order. The observers noted the location, size, and number of calculi; secondary signs of obstruction; and other clinically relevant findings. High- and low-dose scans were compared by using paired t tests and the signed rank test.

RESULTS: Calculi were found in 33 (66%) patients; 25 (50%) had renal calculi and 19 (38%) had an obstructing ureteral calculus. The accuracy rates (averaged over the three readers) for determining the various findings on the low-dose scan compared with the high-dose scan were as follows: nephrolithiasis, 91%; ureterolithiasis, 94%; obstruction, 91%; and normal findings, 92%. When interpretations between readers were compared, agreement rates were 90%–95% for standard-dose scans and 90%–92% for reduced-dose scans (P > .5). Uncomplicated mild diverticulitis was found in three patients. No other clinically important abnormality was identified. A reduction in the tube current to 100 mA resulted in a dose reduction of 25% for multi–detector row CT and 42% for single–detector row CT.

CONCLUSION: In patients who weighed less than 200 lb, unenhanced helical CT performed at a reduced tube current of 100 mA, and therefore at a reduced patient dose, resulted in scans of high accuracy.

© RSNA, 2003

Index terms: Computed tomography (CT), helical, 81.12115, 82.12115 • Kidney, calculi, 81.81 • Phantoms • Radiations, exposure to patients and personnel • Ureter, calculi, 82.81

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Unenhanced helical computed tomography (CT) for renal and ureteral calculi has gained widespread acceptance among radiologists, urologists, and emergency medicine physicians since it was first described in 1995 by Smith et al (1). It is now the standard technique for evaluation of patients with flank pain or of those suspected of having renal stone disease. Unenhanced helical CT has been shown to have a high degree of accuracy (2–4), can be rapidly performed and interpreted, and does not require the administration of intravenous contrast material. It does, however, involve a relatively high radiation dose, particularly to the gonads. Thermoluminescent dosimeter measurements obtained with our standard CT protocol (140 kVp; mean, 200 mAs) revealed doses to the uterus and ovariesof 18 mGy with our single–detector row scanner (CT/i; GE Medical Systems, Milwaukee, Wis) and of 23 mGy with our multi–detector row scanner (QX/i Lightspeed; GE Medical Systems). Because many patients with stone disease are young and have a tendency to experience repeat stone formation, they may undergo helical CT of the abdomen and pelvis many times during the course of their lives. As a result, the use of radiation in these patients should be judicious.

In a previous study (5), human renal stones were implanted in porcine kidneys and scanned in a phantom at varying milliampere settings while other technical parameters remained constant. The results of that study demonstrated that renal size and conspicuity remained constant as the tube current was decreased from 220 to 60 mA. The purpose of our study was to determine the accuracy of helical CT performed at reduced milliampere-second, and therefore at a reduced patient radiation dose, by using standard unenhanced helical CT as the reference.

	MATERIALS AND METHODS

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Phantom-Dose Study
We initially calculated the dose reduction that would be achieved if our standard clinical protocol were altered and the dose were reduced to 100 mAs for both single– and multi–detector row scanners. To measure individual organ doses, we imaged an anthropomorphic phantom (Rando; Rando Phantom Laboratory, Salem, NY), in which two thermoluminescent dosimeters (Harshaw LiF TLD-100; Saint-Gobain Industrial Ceramics, Solon, Ohio) had been placed. Individual organ doses were determined by using the average dose of the two dosimeter chips; the background was subtracted by using unexposed control chips. The effective dose equivalent was estimated by using weighting factors recommended by the International Commission on Radiological Protection (6). The standard CT protocol used in our institution for renal stones was used with both single– and multi–detector CT scanners. The parameters used for the single–detector row scanner were as follows: 140 kVP, 240 mA, pitch of 1.5, and 0.8-second gantry rotation time. The parameters for the multi–detector row scanner were as follows: 140 kVp, 170 mA, pitch of 0.75 (4 x 5-mm detector configuration), and 0.8- or 0.5-second gantry rotation time.

For the lower-dose scans, the tube current was reduced to 100 mA. All other technical parameters remained constant. The radiation output, and thus the dose, was directly proportional to the tube current. Thus, the organ doses for the scanning protocols with reduced tube current were estimated from results obtained with scanning protocols with standard tube current by using proportionality between the dose and the tube current (7).

Patient Study
For the clinical component of the study, 50 patients were prospectively recruited from September 1, 2001, to December 15, 2001. All patients had acute flank pain or were suspected of having renal stone disease or ureteral obstruction owing to a stone and were referred to undergo renal stone CT on clinical grounds. The patients were not consecutive, as we did not attempt to recruit patients between the hours of 10 PM and 7 AM because the on-call residents at our institution are overburdened with duties during these hours. There were 28 men and 22 women (age range, 18–83 years; mean age, 46 years; median age, 42 years). All patients gave informed consent, and this study was approved by our institutional review board. Patients who weighed more than 200 lb (90 kg) were excluded from this study. All premenopausal women underwent a laboratory test to exclude the possibility of pregnancy before they were included in this study.

All patients underwent standard helical CT with either a single–detector row unit (n = 32) or a multi–detector row unit (n = 18). Patients were imaged in the prone position by using 5-mm-thick sections. The kilovolt peak was maintained at 140 for all patients. The milliampere-second level was varied according to the patient’s body habitus and ranged from 135 to 208 mAs (mean, 160 mAs). Imaging was performed at a pitch of 1.5 (single–detector row scanner) or 0.75 (multi–detector row scanner, 4 x 5-mm detector configuration). The standard scanning technique was immediately followed by the low-dose technique, for which the tube current was reduced to 100 mA (mean, 76 mAs). All other technical parameters and coverage remained constant. The standard scans and the reduced milliampere-second scans were obtained at identical window widths and levels.

Three fellowship-trained abdominal radiologists (J.P.H., R.C.N., R.A.L.) with 6–12 years experience in abdominal CT interpreted the image sets. The readers were unaware of patient identifiers and clinical history and interpreted the image sets independently. Because of obvious differences in image noise, the reviewers were not blinded to the milliampere setting used to obtain the scan. The CT scans were read in random order on hard-copy images. The images, however, were hung such that the standard-dose and reduced-dose scans of any patient were not interpreted within 20 cases of each other. Each reader documented the location, size, and number of all calculi present, as well as the presence of secondary signs of obstruction. Specifically, these signs included perinephric stranding, collecting system dilatation, ureteral dilatation, and periureteric stranding. When any of the secondary findings was present, current or recent obstruction was considered to be present. Any other clinically relevant findings were also documented.

Statistical Analysis
Clopper-Pearson 95% CIs were computed for proportion estimates (8). To compute individual error rates, each reader’s high-dose scan was considered to be his or her standard relative to the low-dose scan. Results of the statistical tests were considered significant when the corresponding P values were less than .05. Differences in agreement among readers at the high- and low-dose settings were evaluated by averaging the number of disagreements over the three pairs of readings for each patient at each setting and then comparing the pair-wise averages between high- and low-dose settings by means of the signed rank test. Because each patient served as his or her own control, the standard-dose scan was considered the standard, and the readings of the reduced-dose scan were compared by using the Student t test. Individual reader assessments were determined by using the binomial test, and reader-averaged assessments were determined with the signed rank test.

	RESULTS

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Renal or ureteral stone disease was found in 33 (66%) of 50 patients; 25 (50%) patients had renal calculi and 19 (38%) had an obstructing ureteral calculus (Figs 1–4). Eleven (22%) patients had both renal calculi and an obstructing ureteral calculus, and eight (16%) had an isolated obstructing ureteral calculus without other evidence of stone disease.

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 1a. (a) Transverse unenhanced helical single-detector row CT scan obtained with 170 mA (136 mAs) and pitch of 1.5 demonstrates left pelvicaliectasis (arrow). (b) Repeat scan obtained at 100 mA (80 mAs) clearly demonstrates left pelvicaliectasis (arrow).

View larger version (126K): [in this window] [in a new window] [Download PPT slide]   Figure 1b. (a) Transverse unenhanced helical single-detector row CT scan obtained with 170 mA (136 mAs) and pitch of 1.5 demonstrates left pelvicaliectasis (arrow). (b) Repeat scan obtained at 100 mA (80 mAs) clearly demonstrates left pelvicaliectasis (arrow).

View larger version (109K): [in this window] [in a new window] [Download PPT slide]   Figure 2a. (a) Transverse unenhanced multi-detector row CT scan obtained at 220 mA (176 mAs) and pitch of 0.75 (4 x 5-mm detector configuration) demonstrates a 5-mm-diameter proximal left ureteral calculus (arrow). (b) Repeat scan obtained at 100 mA (80 mAS) also demonstrates the left ureteral calculus (arrow).

View larger version (111K): [in this window] [in a new window] [Download PPT slide]   Figure 2b. (a) Transverse unenhanced multi-detector row CT scan obtained at 220 mA (176 mAs) and pitch of 0.75 (4 x 5-mm detector configuration) demonstrates a 5-mm-diameter proximal left ureteral calculus (arrow). (b) Repeat scan obtained at 100 mA (80 mAS) also demonstrates the left ureteral calculus (arrow).

View larger version (136K): [in this window] [in a new window] [Download PPT slide]   Figure 3a. (a) Transverse unenhanced multi-detector row CT scan obtained at 220 mA (176 mAs) and pitch of 0.75 (4 x 5-mm detector configuration) demonstrates right pelvicaliectasis (arrow) and perinephric fluid (arrowhead). (b) Repeat multi-detector row CT scan obtained at 100 mA (80 mAS) demonstrates right pelvicaliectasis (arrow), although the perinephric fluid (arrowhead) is not readily discerned.

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 3b. (a) Transverse unenhanced multi-detector row CT scan obtained at 220 mA (176 mAs) and pitch of 0.75 (4 x 5-mm detector configuration) demonstrates right pelvicaliectasis (arrow) and perinephric fluid (arrowhead). (b) Repeat multi-detector row CT scan obtained at 100 mA (80 mAS) demonstrates right pelvicaliectasis (arrow), although the perinephric fluid (arrowhead) is not readily discerned.

View larger version (118K): [in this window] [in a new window] [Download PPT slide]   Figure 4a. (a) Transverse unenhanced multi-detector row CT scan obtained at 210 mA (168 mAs) and pitch of 0.75 (4 x 5-mm detector configuration) demonstrates right ureteral dilatation (arrow). (b) Repeat scan obtained with 100 mA (80 mAs) demonstrates right ureteral dilatation (arrow).

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 4b. (a) Transverse unenhanced multi-detector row CT scan obtained at 210 mA (168 mAs) and pitch of 0.75 (4 x 5-mm detector configuration) demonstrates right ureteral dilatation (arrow). (b) Repeat scan obtained with 100 mA (80 mAs) demonstrates right ureteral dilatation (arrow).

View larger version (55K): [in this window] [in a new window] [Download PPT slide]   Figure 5. Chart depicts the mean agreement (in percentages, shown as numbers at tops of bars) averaged over three independent readers for findings of renal calculi (ren calc), ureteral calculi (ur calc), obstruction (obst), or other abnormalities (other abn). Agreement is depicted for standard- versus reduced-dose scans (black bars), standard-dose scans alone (gray bars), and low-dose scans alone (white bars).

View larger version (118K): [in this window] [in a new window] [Download PPT slide]   Figure 6a. Images in a 55-year-old man with left-sided pain. (a) Transverse unenhanced single-detector row CT scan obtained with 170 mA (136 mAs) and pitch of 1.5 demonstrates fat stranding around sigmoid diverticula (arrow), a finding that is consistent with diverticulitis. (b) Repeat CT scan obtained with 100 mA (80 mAs) demonstrates inflammatory changes in the left lower quadrant (arrow).

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 6b. Images in a 55-year-old man with left-sided pain. (a) Transverse unenhanced single-detector row CT scan obtained with 170 mA (136 mAs) and pitch of 1.5 demonstrates fat stranding around sigmoid diverticula (arrow), a finding that is consistent with diverticulitis. (b) Repeat CT scan obtained with 100 mA (80 mAs) demonstrates inflammatory changes in the left lower quadrant (arrow).

View larger version (32K): [in this window] [in a new window] [Download PPT slide]   Figure 7. Graph shows comparison of effective dose equivalent from standard- and reduced-dose scans obtained with both single-detector row (CT/i) and multi-detector row (QX/i) CT. Numbers at tops of bars are values from the x axis. low = reduced dose, std = standard dose.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

In determination of the presence or absence of obstruction, the accuracy of low-dose CT was 90% compared with that of standard CT. The agreement between the three readers in the interpretation of obstruction on standard scans was also 90%; agreement was 91% for the reduced-dose scans. Again, this did not reflect the fact that 10% of the cases of obstruction were missed on the low-dose scans or even by some of the readers on the standard-dose scans when the individual readings were compared. Our study design necessitated that each reader document the presence or absence of each of the secondary signs of obstruction. If any of these signs were present, then that patient was considered to have obstruction. In a small number of cases, isolated perinephric stranding was identified on one scan but not on the other, and no other secondary signs of obstruction were present. These cases were classified as demonstrating obstruction, and we believe that this likely accounts for the reduced accuracy of the low-dose technique and the discrepancy between readers in the interpretation of standard scans (and reduced-dose scans) when compared with each other.

Several authors have previously addressed the relatively high radiation dose delivered with renal stone CT. Diel et al (13) demonstrated that increasing the pitch from 1.5 to 3.0 reduced the average entrance dose from 913 to 461 mR, but at a cost of reduced image quality. Liu et al (14) described a low-dose CT protocol and compared it with intravenous pyelography. They used a single–detector row CT scanner with 120 kVp and 280 mAs—higher parameters than those used in our study. Denton et al (15) also compared doses from CT and intravenous pyelography and determined that the average dose for CT was 4.7 mSv while that for a limited three-image intravenous pyelogram was 1.5 mSv. They cautioned the need to balance the greater accuracy of CT against the associated higher radiation dose incurred.

Our study has several limitations. The patient population was small (n = 50); however, the percentage of patients with stone disease was relatively high (66%). The patients were not consecutive; however, this limitation was one of logistics, as previously mentioned. We had very few patients with other causes of abdominal pain, which reflects the practice in our emergency department to use fairly strict criteria for the triaging of patients with stone disease versus other causes of abdominal pain. The latter group is typically scheduled to undergo contrast material–enhanced CT. The patients who were identified as having evidence of diverticulitis, however, demonstrated relatively subtle stranding in the pericolonic fat on the standard scan. This was detected on the low-dose scan by two of the readers. The third reader did not comment on the finding on either the standard- or reduced-dose scan. The fact that perinephric and periureteric stranding were readily apparent on the low-dose scans is encouraging; nonetheless, we have insufficient data to assess the accuracy of reduced-dose CT in the detection of inflammatory processes.

In areas other than renal stone protocols, other authors have demonstrated that a diagnostic-quality scan can be obtained with a significantly lower milliampere- second. Rusinek et al (16) evaluated pulmonary nodules and Kamel et al (17) evaluated the pediatric pelvis. In both of these studies, patients were scanned at a low milliampere-second, and image quality was compared with that in a different group of patients scanned with conventional parameters. This method did not permit comparison of the same abnormality in the same patient with both standard and reduced-dose scans. In a more recent study, however, Ravenel et al (18) obtained chest CT scans of diagnostic quality after the milliampere-second was reduced from 280 to 120. They evaluated images obtained in a chest biopsy series with a range of tube currents (from 40 to 280 mA in the same patient); thus, they had the advantage of performing a section-by-section comparison with different techniques. To our knowledge, no other investigators have compared standard diagnostic scans with reduced-dose scans in the same population cohort.

In summary, in patients who weighed less than 200 lb (90 kg), unenhanced helical CT performed at a reduced tube current of 100 mA demonstrated a high accuracy when compared with the accuracy of the standard technique. Of note, the variation between interpretations of standard- and reduced-dose scans does not differ significantly from the variation in interpretation of standard scans by differing experienced readers. This CT technique results in a concomitant decrease in radiation dose of 25% for multi–detector row CT and 42% for single–detector row CT. This technique has been incorporated into our routine protocol for detection of stones and, in our opinion, promises to be of particular benefit to young patients who experience repeat stone formation.

	FOOTNOTES

 
R.C.N. is a consultant for GE Medical Systems.

Author contributions: Guarantor of integrity of entire study, J.P.H.; study concepts and design, J.P.H., R.C.N.; literature research, J.P.H.; clinical studies, J.P.H., K.A.M., R.A.L., R.C.N.; experimental studies, J.P.H., T.Y.; data acquisition, J.P.H., K.A.M.; data analysis/ interpretation, J.P.H., D.M.D.; statistical analysis, D.M.D.; manuscript preparation, J.P.H.; manuscript definition of intellectual content, J.P.H., R.C.N.; manuscript editing, J.P.H.; manuscript revision/review, J.P.H., R.A.L., R.C.N., T.Y., D.M.D.; manuscript final version approval, all authors

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 

1. Smith RC, Rosenfield AT, Choe KA, et al. Acute flank pain: comparison of noncontrast-enhanced CT and intravenous urography. Radiology 1995; 194:789-794.[Abstract/Free Full Text]
2. Smith RC, Verga M, McCarthy S, Rosenfield AT. Diagnosis of acute flank pain: value of unenhanced helical CT. AJR Am J Roentgenol 1996; 166:97-101.[Abstract/Free Full Text]
3. Chen MY, Zagoria RJ. Can noncontrast helical computed tomography replace intravenous urography for evaluation of patients with acute urinary tract colic? J Emerg Med 1999; 17:299-303.[CrossRef][Medline]
4. Preminger GM, Vieweg J, Leder RA, Nelson RC. Urolithiasis: detection and management of unenhanced spiral CT—urologic prospective. Radiology 1998; 207:308-309.[Free Full Text]
5. Spielmann AL, Heneghan JP, Lee LJ, Yoshizumi T, Nelson RC. Decreasing the radiation dose for renal stone CT: a feasibility study of single and multi-detector CT. AJR Am J Roentgenol 2002; 178:1058-1062.[Free Full Text]
6. Radiation protection. ICRP Publication no 26 Elmsford, NY: Pergamon, 1977.
7. Wagner LK, Lester RG, Saldana LR. In: Exposure of the pregnant patient to diagnostic radiation Madison, Wis: Medical Physics Publishing, 1997; 227-229.
8. Clopper CJ, Pearson ES. The use of confidence or fiducial limits illustrated in the case of the binomial. Biometrika 1934; 26:404-413.[Free Full Text]
9. Slovis TL. CT and computed radiography: the pictures are great, but is the radiation dose greater than required? (opinion). AJR Am J Roentgenol 2002; 179:39-41.[Free Full Text]
10. Rogers LF. Radiation exposure in CT: why so high? (editorial). AJR Am J Roentgenol 2001; 177:277.[Free Full Text]
11. Donnelly LF, Emery KH, Brody AS, et al. Minimizing radiation dose for pediatric body applications of single detector helical CT: strategies at a large children’s hospital. AJR Am J Roentgenol 2001; 176:303-306.[Free Full Text]
12. Sternberg S. CT scans in children linked to cancer. USA Today 2001; June 19.
13. Diel J, Perlmutter S, Venkataramanan N, Mueller R, Lane MJ, Katz DS. Unenhanced helical CT using increased pitch for suspected renal colic: an effective technique for radiation dose reduction? J Comput Assist Tomogr 2000; 24:795-801.[CrossRef][Medline]
14. Liu W, Esler SJ, Kenny BJ, Goh RH, Rainbow AJ, Stevenson GW. Low-dose nonenhanced helical CT of renal colic: assessment of ureteric stone detection and measurement of effective dose equivalent. Radiology 2000; 215:51-54.[Abstract/Free Full Text]
15. Denton ER, Mackenzie A, Greenwell T, Popert R, Rankin SC. Unenhanced helical CT for renal colic: is the radiation dose justifiable? Clin Radiol 1999; 54:444-447.[CrossRef][Medline]
16. Rusinek H, Naidich D, McGuinness G, et al. Pulmonary nodule detection: low dose versus conventional CT. Radiology 1998; 209:243-249.[Abstract/Free Full Text]
17. Kamel IR, Hernandez RJ, Martin JE, Schlesinger AE, Niklason LT, Guire KE. Radiation dose reduction in CT of the pediatric pelvis. Radiology 1994; 190:683-687.[Abstract/Free Full Text]
18. Ravenel JG, Scalzetti EM, Huda W, Garrisi W. Radiation exposure and image quality in chest CT examinations. AJR Am J Roentgenol 2001; 177:279-284.[Abstract/Free Full Text]

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This Article Abstract Figures Only Full Text (PDF) All Versions of this Article: 2292021261v1 229/2/575    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Heneghan, J. P. Articles by Nelson, R. C. Search for Related Content PubMed PubMed Citation Articles by Heneghan, J. P. Articles by Nelson, R. C.