CT dose and image quality in the last three scanner generations

Table 1 Reduction of noise and dose using iterative reconstruction and the stellar detector

		Soft tissue				Air				Bone
		Lowest dose		Highest dose		Lowest dose		Highest dose		Lowest dose		Highest dose
	Δ HUsd	Range			Δ HUsd	Range			Δ HUsd	Range
Noise reduction from FBP to IR	10 (31%)	15 (30%)	to	7 (31%)	31 (44%)	53 (49%)	to	22 (41%)	64 (30%)	128 (37%)	to	28 (21%)
Noise reduction from IR to IR with Sd	7 (32%)	16 (42%)	to	4 (24%)	12 (31%)	19 (34%)	to	9 (28%)	24 (15%)	51 (22%)	to	9 (7%)
	Δ DLP	Range			Δ DLP	Range			Δ DLP	Range
Dose reduction from FBP to IR for the same noise level	53 (52%)	116 (55%)	to	25 (50%)	133 (80%)	165 (78%)	to	106 (81%)	48 (30%)	24 (12%)	to	40 (55%)
Dose reduction from IR to IR with Sd for the same noise level	69 (54%)	96 (39%)	to	46 (65%)	106 (70%)	166 (67%)	to	65 (72%)	35 (27%)	33 (21%)	to	25 (43%)

HUsd: Noise (sd of Hounsfield Units); FBP: Filtered back projection; IR: Iterative reconstruction; Sd: Stellar detector; DLP: Dose length product.

Table 2 Dose, signal to noise ratio and improved subjective image quality using iterative reconstruction and the stellar detector

	Soft tissue					lung
	△HUsd	Range				△Points	Range
		Lowest dose		Highest dose			Lowest dose		Highest dose
Signal to noise reduction from FBP to IR	0.7 (36%)	0.2 (31%)	to	1 (39%)	Improving subjective image quality from FBP to IR	0.2 (7%)	0.4 (13%)	to	0.1 (3%)
Signal to noise reduction from IR to IR with Sd	0.6 (38%)	0.5 (41%)	to	0.8 (32%)	Improving subjective image quality from IR to IR with Sd	0.5 (13%)	0.2 (8%)	to	0.9 (17%)
	△DLP	Range				△DLP	Range
		Lowest SNR		Highest SNR			lowest SNR		highest SNR
Dose reduction from FBP to IR for the same SNR	59 (45%)	20 (40%)	to	107 (47%)	Dose reduction from FBP to IR for same subjective quality	19 (25%)	22 (42%)	to	5 (2%)
Dose reduction from IR to IR with Sd for the same SNR	52 (41%)	23 (49%)	to	72 (36%)	Dose reduction from IR to IR with Sd for same subjective quality	57 (44%)	10 (33%)	to	130 (54%)

HUsd: Noise (sd of Hounsfield Units); FBP: Filtered back projection; IR: Iterative reconstruction; Sd: Stellar detector; DLP: Dose length product; SNR: Signal to noise ratio.