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Effect of X-ray tube parameters, iodine concentration, and patient size on image quality in pulmonary computed tomography angiography: a chest-phantom-study.
Invest Radiol. 2008 Jun; 43(6):374-81.IR

Abstract

OBJECTIVES

The aim of this phantom study was to evaluate the contrast-to-noise ratio (CNR) in pulmonary computed tomography (CT)-angiography for 300 and 400 mg iodine/mL contrast media using variable x-ray tube parameters and patient sizes. We also analyzed the possible strategies of dose reduction in patients with different sizes.

MATERIALS AND METHODS

The segmental pulmonary arteries were simulated by plastic tubes filled with 1:30 diluted solutions of 300 and 400 mg iodine/mL contrast media in a chest phantom mimicking thick, intermediate, and thin patients. Volume scanning was done with a CT scanner at 80, 100, 120, and 140 kVp. Tube current-time products (mAs) varied between 50 and 120% of the optimal value given by the built-in automatic dose optimization protocol. Attenuation values and CNR for both contrast media were evaluated and compared with the volume CT dose index (CTDI(vol)). Figure of merit, calculated as CNR/CTDIvol, was used to quantify image quality improvement per exposure risk to the patient.

RESULTS

Attenuation of iodinated contrast media increased both with decreasing tube voltage and patient size. A CTDIvol reduction by 44% was achieved in the thin phantom with the use of 80 instead of 140 kVp without deterioration of CNR. Figure of merit correlated with kVp in the thin phantom (r = -0.897 to -0.999; P < 0.05) but not in the intermediate and thick phantoms (P = 0.09-0.71), reflecting a decreasing benefit of tube voltage reduction on image quality as the thickness of the phantom increased. Compared with the 300 mg iodine/mL concentration, the same CNR for 400 mg iodine/mL contrast medium was achieved at a lower CTDIvol by 18 to 40%, depending on phantom size and applied tube voltage.

CONCLUSIONS

Low kVp protocols for pulmonary embolism are potentially advantageous especially in thin and, to a lesser extent, in intermediate patients. Thin patients profit from low voltage protocols preserving a good CNR at a lower exposure. The use of 80 kVp in obese patients may be problematic because of the limitation of the tube current available, reduced CNR, and high skin dose. The high CNR of the 400 mg iodine/mL contrast medium together with lower tube energy and/or current can be used for exposure reduction.

Authors+Show Affiliations

Department of Interventional and Diagnostic Radiology, University Hospital of Berne, Berne, Switzerland. zsolt.szuecs@insel.chNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

18496042

Citation

Szucs-Farkas, Zsolt, et al. "Effect of X-ray Tube Parameters, Iodine Concentration, and Patient Size On Image Quality in Pulmonary Computed Tomography Angiography: a Chest-phantom-study." Investigative Radiology, vol. 43, no. 6, 2008, pp. 374-81.
Szucs-Farkas Z, Verdun FR, von Allmen G, et al. Effect of X-ray tube parameters, iodine concentration, and patient size on image quality in pulmonary computed tomography angiography: a chest-phantom-study. Invest Radiol. 2008;43(6):374-81.
Szucs-Farkas, Z., Verdun, F. R., von Allmen, G., Mini, R. L., & Vock, P. (2008). Effect of X-ray tube parameters, iodine concentration, and patient size on image quality in pulmonary computed tomography angiography: a chest-phantom-study. Investigative Radiology, 43(6), 374-81. https://doi.org/10.1097/RLI.0b013e3181690042
Szucs-Farkas Z, et al. Effect of X-ray Tube Parameters, Iodine Concentration, and Patient Size On Image Quality in Pulmonary Computed Tomography Angiography: a Chest-phantom-study. Invest Radiol. 2008;43(6):374-81. PubMed PMID: 18496042.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effect of X-ray tube parameters, iodine concentration, and patient size on image quality in pulmonary computed tomography angiography: a chest-phantom-study. AU - Szucs-Farkas,Zsolt, AU - Verdun,Francis R, AU - von Allmen,Gabriel, AU - Mini,Roberto L, AU - Vock,Peter, PY - 2008/5/23/pubmed PY - 2008/10/1/medline PY - 2008/5/23/entrez SP - 374 EP - 81 JF - Investigative radiology JO - Invest Radiol VL - 43 IS - 6 N2 - OBJECTIVES: The aim of this phantom study was to evaluate the contrast-to-noise ratio (CNR) in pulmonary computed tomography (CT)-angiography for 300 and 400 mg iodine/mL contrast media using variable x-ray tube parameters and patient sizes. We also analyzed the possible strategies of dose reduction in patients with different sizes. MATERIALS AND METHODS: The segmental pulmonary arteries were simulated by plastic tubes filled with 1:30 diluted solutions of 300 and 400 mg iodine/mL contrast media in a chest phantom mimicking thick, intermediate, and thin patients. Volume scanning was done with a CT scanner at 80, 100, 120, and 140 kVp. Tube current-time products (mAs) varied between 50 and 120% of the optimal value given by the built-in automatic dose optimization protocol. Attenuation values and CNR for both contrast media were evaluated and compared with the volume CT dose index (CTDI(vol)). Figure of merit, calculated as CNR/CTDIvol, was used to quantify image quality improvement per exposure risk to the patient. RESULTS: Attenuation of iodinated contrast media increased both with decreasing tube voltage and patient size. A CTDIvol reduction by 44% was achieved in the thin phantom with the use of 80 instead of 140 kVp without deterioration of CNR. Figure of merit correlated with kVp in the thin phantom (r = -0.897 to -0.999; P < 0.05) but not in the intermediate and thick phantoms (P = 0.09-0.71), reflecting a decreasing benefit of tube voltage reduction on image quality as the thickness of the phantom increased. Compared with the 300 mg iodine/mL concentration, the same CNR for 400 mg iodine/mL contrast medium was achieved at a lower CTDIvol by 18 to 40%, depending on phantom size and applied tube voltage. CONCLUSIONS: Low kVp protocols for pulmonary embolism are potentially advantageous especially in thin and, to a lesser extent, in intermediate patients. Thin patients profit from low voltage protocols preserving a good CNR at a lower exposure. The use of 80 kVp in obese patients may be problematic because of the limitation of the tube current available, reduced CNR, and high skin dose. The high CNR of the 400 mg iodine/mL contrast medium together with lower tube energy and/or current can be used for exposure reduction. SN - 0020-9996 UR - https://www.unboundmedicine.com/medline/citation/18496042/Effect_of_X_ray_tube_parameters_iodine_concentration_and_patient_size_on_image_quality_in_pulmonary_computed_tomography_angiography:_a_chest_phantom_study_ L2 - https://doi.org/10.1097/RLI.0b013e3181690042 DB - PRIME DP - Unbound Medicine ER -