Table 8.

Summary of (a) multivariate logistic regression model with GEE method results for failure type, number of channels, and use type and (b) univariate logistic regression model with GEE method results for modality.

Factor	Level	Estimated failure rate (#failures/1000 scan days)	95% lower confidence level	95% upper confidence level	p-value
(a) Multivariate logistic regression model
Use type	Interventional	0.98	0.39	2.42	0.64
	Hybrid	1.65	0.96	2.84
	Routine	1.71	1.06	2.74
Failure type	Water, standard deviation	5.11	3.29	7.93	0.02
	Water, mean CT no.	0.85	0.49	1.47
	Water, uniformity	0.41	0.23	0.74
	Linearity, air	0.55	0.22	1.40
	Linearity, water	0.65	0.29	1.43
	Linearity, acrylic	1.23	0.55	2.79
	Water phantom artifact	2.85	1.76	4.60
	Large phantom artifact	6.63	2.62	16.74
No. of channel	4	0.74	0.31	1.79	0.07
	6	0.28	0.07	1.06
	8	2.69	0.93	7.80
	16	1.33	0.83	2.14
	24	2.92	1.54	5.52
	64	3.54	2.47	5.08
(b) Univariate logistic regression model
Modality	SPECT/CT	1.20	0.41	3.55	0.24
	PET/CT	2.85	1.31	6.21
	CT	3.00	2.28	3.94