Perfusion computed tomography in renal cell carcinoma

Table 1 Protocol for dynamic perfusion computed tomography acquisition

No. of scans	Cycle time (s)	Accumulated time since start of scan (s)
3	3	9
9	1.5	22.5
5	3	37.5
5	6	68.0
22 (in total)		Examination time: 68

Table 2 Computed tomography perfusion parameters[2-4]

Perfusion parameters	Definition	Unit	Biomarker
Regional blood flow	Blood flow per unit volume or mass of tissue	mL/100 mL per minute	Tumour vascularization
Regional tumour blood volume	Ratio of blood volume to tumour volume	mL/100 mL	Tumour vascularization
Permeability/blood flow extraction (PMB/PS/k-trans)	Rate of transfer of contrast agent from the intravascular to the extravascular compartment	mL/100 gm per minute	Vascular immaturity
Mean transit time	Average time taken to travel from artery to vein	s	Perfusion pressure
Time to peak	Time from arrival of the contrast in major arterial vessels to thepeak enhancement	s	Perfusion pressure
Maximum peak intensity	Maximum increase in tissue density after contrast injection	HU	Tissue blood volume

Table 3 Perfusion computed tomography parameter values for kidney (renal cell carcinoma vs normal renal cortex)[7]

	Normal renal cortex (mean ± SD)	Renal cell carcinoma (mean ± SD)	t value	P value
Blood flow (mL/min per 100 g)	454.32 ± 110.90	261.96 ± 175.86	-7.620	0.000
Blood volume (mL/100 g)	23.53 ± 5.71	17.17 ± 8.34	-5.193	0.000
Mean transit time (s)	3.62 ± 1.38	7.08 ± 3.42	7.670	0.000
Permeability (mL/min per 100 g)	63.95 ± 18.85	25.07 ± 13.20	-14.193	0.000

Table 4 Response evaluation using changes in computed tomography perfusion parameters in two representative cases

	Date of study		MIP (HU)	TTP (s)	BF (mL/100 mL per minute)	BV (mL/100 mL)	MTT (s)	PMB (mL/100 mL per minute)
Case 1	2013-4-2	Normal cortex	120	11.1	202.9	31.6	8.7	47.1
		Renal tumour	134	13.5	184.9	30.8	10.4	45.95
	2013-9-11	Normal cortex	121	13.2	209	30.2	9.2	50.2
		Renal tumour	79	11.5	174	13.2	5	18.1
	2013-11-20	Normal cortex	130	10.8	229	32	9.6	45.3
		Renal tumour	42	12.3	5.7	1.2	12.4	8.2
Case 2	2013-10-23	Normal cortex	157	11.9	236	27.8	8.9	43.7
		Renal tumour	88	12.3	64.4	9.3	8.9	18.7
	2013-12-26	Normal cortex	140	15.2	170.9	29.5	10.5	42.1
		Renal tumour	82.7	14.8	60.9	7.9	8.4	13.8
	2013-8-3	Normal cortex	216	12.5	315	38	72	55.2
		Renal tumour	84.6	12.3	72.3	8	7.4	10.8

BF: Blood flow; BV: Blood volume; MTT: Mean transit time; PMB: Permeability; MIP: Maximum peak intensity; TTP: Time to peak.

Table 5 Comparison of the acquisition parameters and dose in dynamic acquisition of perfusion computed tomography and normal contrast enhanced computed tomography chest and abdomen in our institute

	Dynamic acquisition	Chest and abdomenscan (routine)
Exposure time (s)	33	14.24
Scan length (mm)	155	655
Collimation (mm)	1.2	0.6
KVp	100	100
Ma	523	211
CTDI vol (mGy)	180.1	7.2
DLP (mGycm)	2789.69	458.68

CTDI vol: Computed tomography dose index volumetric; DLP: Dose length product.