Metered Cryospray™: a novel uniform, controlled, and consistent in vivo application of liquid nitrogen cryogenic spray

Figures & data

Figure 1 Cooling-induced cellular changes.

Figure 2 Gels and test fixture process.

Abbreviation: MCS, Metered Cryospray^™.

Table 1 Thermal property data for porcine tracheal mucosa (Analytical Answers, Inc., Woburn, MA, USA)

Property	Value	Units	Tolerance
Melt/solidification temperature	3.5	°C	±1.5
Latent heat of fusion	207	J/g	±4
Crystallization temperature	−14	°C	±1
Latent heat of crystallization	−96	J/g	±10
Specific heat capacity at 20°C	3.85	J/g-K	±0.2
Specific heat capacity at −20°C	1.92	J/g-K	±0.06
Thermal conductivity at 20°C	0.453	W/m-K	±0.05
Thermal conductivity at −170°C	1.619	W/m-K	±0.85
Density	1050	kg/m^3	±10

Table 2 Thermal property data for high-temperature nontoxic (HTNT) gel (Analytical Answers, Inc., Woburn, MA, USA)

Property	Value	Units	Tolerance
Melt/solidification temperature	−1.82	°C	±0.1
Latent heat of fusion	142	J/g	±9
Crystallization temperature	−18.5	°C	±0.3
Latent heat of crystallization	141	J/g	±4
Specific heat capacity at 20°C	6.76	J/g-K	±0.03
Specific heat capacity at −20°C	4.05	J/g-K	±0.01
Thermal conductivity at 25°C	0.624	W/m-K	±0.06
Thermal conductivity at −170°C	1.083	W/m-K	±0.03

Figure 3 Hole patterns tested for spray capabilities.

Figure 4 Freeze zone determinations in ballistic gel for LN₂ spray testing.

Figure 5 Test structure with multiple thermocouples (black arrow) embedded in gel.

Figure 6 Temperatures as a function of spray time for 18 mm lumen diameter (T Ch refers to each embedded thermocouple).

Figure 7 Mesh and stress simulation for test radial pattern.

Figure 8 Phase Doppler particle analyzer measurement of catheter spray output.

Table 3 Phase Doppler particle analyzer results of drop size for various catheter types

Catheter type	Liquid pressure (psi)	Spray height (mm)	DV0.1 (µm)	D32 (µm)	DV0.5 (µm)	DV0.9 (µm)	Average velocity (m/sec)
Straight orifice open end	19	8	48	79	91	155	115
			44	65	85	148	115
Offset radial orifice	19	4	32	55	65	121	25
			33	57	67	124	23
In−line radial orifice	19	3	34	60	73	136	23

Figure 9 Open-end catheter droplet size (D_V0.5) across spray plume.

Notes: Blue (square data points)/green (diamonds) are Spray 1; red (circles)/yellow (triangles) are Spray 2.

Figure 10 Radial catheter laser sheet imaging showing droplet counts as a function of position (inset image in lower right corner shows enlarged center pattern image. Inset scale not shown).

Figure 11 Core probe measurement system to determine LN₂ cryospray output.

Figure 12 Schematic of cavity test fixture for a 6 mm lumen diameter.

Figure 13 NBT stain identifies cryothermic effects by staining nontreated cells (dark blue), whereas treated cells remain unstained.

Note: Stain changes color based on viable cell energy production.^19,22
Abbreviation: NBT, nitro blue tetrazolium.

Figure 14 Catheter terminal temperature versus lumen size.

Figure 15 Representative porcine model distal trachea.

Note: Purple line (open arrow) depicts essentially circumferential MCS treatment effect.
Abbreviation: MCS, Metered Cryospray^™.

Figure 16 Correlation of HTNT gel temperatures with DOI.

Notes: The DOI is determined by looking at the contour lines. For example, the “1” data point (a 14s spray with a gel temperature of 3°C) falls between the 0.1 and 0.25 mm DOI lines; therefore, in a human, it would be expected to see a DOI between 0.1 and 0.25 mm. The “2” data point is a DOI between 0.25 and 0.5 mm. The “3” data point falls between 0.5 and 0.75 mm, and the “4” data point is on the line at 0.5 mm.
Abbreviations: DOI, depth of injury; HTNT, high-temperature nontoxic; Poly., polynomial fit.

Table 4 Ballistic gel length of injury measurements

Lumen diameter (mm)	Approximate length of injury (mm)
6	4–6
8	5–7
10	7
12	7–8
18	9–12

Figure 17 Length of injury measurements of MCS in an 8 mm diameter of HTNT gel.

Abbreviations: HTNT, high-temperature nontoxic; MCS, Metered Cryospray^™.

Figure 18 Centered spray (left) and off-center spray (right) final temperature profiles in HTNT gel with a 12 mm lumen.

Notes: Actual catheter position is denoted with a bold X. Small x markers indicate locations of embedded thermocouples on rings of 0.25, 0.75, and 3 mm depth relative to the lumen surface. Color scales are in °C.
Abbreviation: HTNT, high-temperature nontoxic.

CoadJEPractical pathology perspectives for minimally invasive hyperthermic medical devicesProc SPIE20117901112

 Google Scholar

RuppCCNagelTCSwanlundDJBischofJCCoadJECryothermic and hyperthermic treatments of human leiomyomata and adjacent myometrium and their implications for laparoscopic surgeryJ Am Assoc Gynecol Laparosc200310909812555001

 PubMedGoogle Scholar