Ice-ball Volume Research Articles

Comparison of Probe Materials for Tissue Cryoablation: Operational Properties of Metal and Sapphire Cryoprobes

Typical probes that are used for cryosurgical applications are manufactured from metals, since such materials as copper and brass feature high thermal conductivity at low temperatures and enable rapid growth of an ice ball in living tissues. Due to a favorable combination of properties, sapphire could be also widely used for tissue cryoablation. In this paper, a sapphire probe is experimentally compared with metal ones. Using a gel-based biotissue phantom, an ice ball volume and phantom temperatures in control points are analyzed for the considered probe materials aimed at revealing the advantages of using sapphire for cryosurgery. Next, the impact of probe-tissue contact on the sample and probe surface is studied. The experimental results and qualitative comparison of the considered cryoprobes demonstrate the abilities of the sapphire one for faster tissue freezing, reaching lower temperatures and featuring less damage of its contact surface and adjacent tissues, justifying a potential of sapphire as a material for tissue cryosurgery .

Renal mass cryoablation: Melting time analysis of radiographic ice-ball after 5-minute active thawing by using serial ultrasound

ObjectiveCryoneedles removal before sufficient thawing may lead to tissue damage and bleeding. We analyzed melting time of radiographic ice-ball in renal percutaneous cryoablation (PCA) using ultrasound. Materials and methodsConsecutive 27 patients who underwent PCA using cryoneedles of 2–4 for the renal mass (median size, 1.9 cm; range, 1.1–4.1 cm) were evaluated. Reconstructed CT images obtained during freezing were used to measure radiographic ice-ball volume. After completing final freezing, 5-min active thawing and following passive thawing were performed. Melting time of radiographic ice-ball during the thawing was analyzed by serial ultrasound examination. Melting time was defined as the time of complete disappearance of intrarenal posterior acoustic shadowing generated by radiographic ice-ball, which was analyzed by two independent radiologists. The relationship between total melting time and radiographic ice-ball volume was also analyzed by Spearman’s rank correlation. ResultsMedian radiographic ice-ball volume was 30.5 cm3 (range, 26.6–37.3 cm3). After 5-min active thawing, radiographic ice-ball needed additional passive thawing of median 8-min or 9-min for complete melting in analyses of two independent radiologists, respectively (p > 0.05). The range of total melting time during active and passive thawing was 9-min-to-15-min for both radiologists, respectively. A positive correlation was found between total melting time and radiographic ice-ball volume (Spearman’s rho, 0.644 and 0.479 for radiologist 1 and 2). ConclusionIn our PCA protocol, radiographic ice-ball needed approximately 10-min passive thawing after 5-min active thawing for complete melting. This may help determine safe removal time of cryoneedles.

Comparison of Double-Freeze versus Modified Triple-Freeze Pulmonary Cryoablation and Hemorrhage Volume Using Different Probe Sizes in an In Vivo Porcine Lung

PurposeTo determine size of ablation zone and pulmonary hemorrhage in double-freeze (DF) vs modified triple-freeze (mTF) cryoablation protocols with different probe sizes in porcine lung. Materials and MethodsIn 10 healthy adult pigs, 20 pulmonary cryoablations were performed using either a 2.4-mm or a 1.7-mm probe. Either conventional DF or mTF protocol was used. Serial noncontrast CT scans were performed during ablations. Ablation iceball and hemorrhage volumes were measured and compared between protocols and probe sizes. ResultsWith 1.7-mm probe, greater peak iceball volume was observed with DF compared with mTF, although difference was not statistically significant (16.1 mL ± 1.9 vs 8.8 mL ± 3.6, P = .07). With 2.4-mm probe, DF and mTF produced similar peak iceball volumes (14.0 mL ± 2.8 vs 14.6 mL ± 2.7, P = .88). Midcycle hemorrhage was significantly larger with DF with the 1.7-mm probe (94.3 mL ± 22.2 vs 19.6 mL ± 2.1, P = .02) and with both sizes combined (93.2 mL ± 17.5 vs. 50.9 mL ± 12.6, P = .048). Rate of hemorrhage increase was significantly higher in DF (10.4 mL/min vs 5.1 mL/min, P = .003). End-cycle hemorrhage was visibly larger in DF compared with mTF across probe sizes, although differences were not statistically significant (P = .14 for 1.7 mm probe, P = .18 for 2.4 mm probe, and P = .07 for both probes combined). Rate of increase in hemorrhage during the last thaw period was not statistically different between DF and mTF (3.0 mL/min vs 2.8 mL/min, P = .992). ConclusionsmTF reduced rate of midcycle hemorrhage compared with DF. With mTF, midcycle hemorrhage was significantly smaller with 1.7-mm probe; although noticeably smaller with 2.4-mm probe, statistical significance was not achieved. Iceball size was not significantly different across both protocols and probe types.

Abstract No. 406 - Single center experience with percutaneous CT-guided cryoablation of renal neoplasms

No. 406 Single center experience with percutaneous CTguided cryoablation of renal neoplasms M.M. Ali, C.R. Fedele, A. Graif, O.M. Tahir, A. Froush, C.J. Grilli, D.J. Agriantonis, K.M. Lie, G. Kimbiris, M.J. Garcia, D. Leung; Department of Radiology, Christiana Care Health System, Newark, DE Purpose: To evaluate safety and efficacy of CT-guided cryoablation of renal neoplasms and identify factors predictive of clinical success. Materials and Methods: A retrospective analysis was undertaken of patients treated with CT-guided cryoablation between December 2008 and August 2013 at a single center. Chart and image review was performed to evaluate technical success and adverse events for the procedure as well as survival and freedom from recurrence on follow up. In addition, multivariable analysis was performed to identify predictors of clinical success, including CT volumetric analysis of the lesion and ice-ball using Tera-Recon 3D reconstruction software. Results: Ninety-six renal neoplasms in 89 consecutive patients (55 male, mean age 67 years) were enrolled in the study. The mean lesion diameter was 2.73 cm (range 1-6.5 cm), with a mean lesion volume of 14.6 cm. The mean number of probes required for treatment was 2.74. 52 lesions demonstrated medullary involvement (54.1%). Hydrodissection was required in 13 lesions (14%) due to proximity of bowel loops.Technical success was achieved in 95 of the 96 lesions (99%). Major bleeding occurred in 3 patients requiring transfusions. There was a single 30-day mortality not directly related to complications from the procedure.Mean follow-up was 13 months (range 1-48 months). Local recurrence was noted in 3 of 89 patients (3.4%) while secondary lesions in the contralateral kidney were seen in two patients (2.2%).The mean ratio of iceball volume to lesion volume at the index procedure was 1.22 in patients with recurrent lesions and 2.07 in patients without recurrences (p 1⁄4 0.028). None of the other analyzed variables yielded significant findings Conclusion: Percutaneous CT-guided cryoablation is a safe and effective procedure for the treatment of renal neoplasms. An ice-ball to lesion volumetric ratio of o 1.5 may be indicative of potential future recurrence.

Percutaneous MR-guided cryoablation of prostate cancer: initial experience

We report our initial experience and the technical feasibility of transperineal prostate cryoablation under MR guidance. Percutaneous MR-guided cryoablation was performed in 11 patients with prostatic adenocarcinoma contraindicated for surgery (mean age: 72 years, mean Gleason score: 6.45, mean prostate-specific antigen (PSA): 6.21 ng/ml, T1-2c/N0/M0, mean: prostate volume 36.44 ml). Free-hand probe positioning was performed under real-time MR imaging. Four to seven cryoprobes were inserted into the prostate, depending on gland volume. The ice ball was monitored using real-time and high-resolution BLADE multi-planar imaging. Patients were followed at 1, 3, 6, 9 and 12 months after the procedure with serum PSA level and post-ablation MRI. Prostate cryoablation was technically feasible in 10/11 patients. The ice ball was clearly and sharply visualised in all cases as a signal-void area. Mean ice-ball volume was 53.3 ml. Mean follow-up was 15 months (range: 1-25). Mean PSA nadir was 0.33 ng/ml (range: 0.02-0.94 ng/ml). Mean hospitalisation was 5 days (range: 3-13). Complications included a urethro-rectal fistula, urinary infection, transient dysuria and scrotal pain. MR-guided prostate cryoablation is feasible and promising, with excellent monitoring of the ice ball. Future perspectives could include the use of MR guidance for focal prostate cancer cryotherapy. • Magnetic resonance allows precise positioning of cryoprobes with real-time imaging. • High-resolution MRI allows excellent monitoring of the developing ice ball. • Cryoablation of prostate cancer under MR guidance is technically feasible. • Further work will refine the procedure and make it even safer.

Are Multiple Cryoprobes Additive or Synergistic in Renal Cryotherapy?

To investigate the relationship between multiple cryoprobes was investigated to determine whether they work in an additive or synergistic fashion in an in vivo animal model because 1.47 mm (17-gauge) cryoprobes have been introduced to the armamentarium for renal cryotherapy. Laparoscopic-guided percutaneous cryoablation was performed in both renal poles of 3 pigs using 3 IceRod cryoprobes. These 12 cryolesions were compared with 12 cryolesions using a single IceRod cryoprobe. Each cycle consisted of two 10-minute freeze cycles separated by a 5-minute thaw. The iceball volume was measured using intraoperative ultrasonography. The kidneys were harvested, and cryolesion surface area was calculated. The lesions were fixed and excised to obtain a volume measurement. Statistical analysis was used to compare the single probe results multiplied by 3 to the multiple probe group for iceball volume, cryolesion surface area, and cryolesion volume. The iceball volume for the first freeze cycle for the single cryoprobe multiplied by 3 was 8.55 cm3 compared with 9.79 cm3 for the multiple cryoprobe group (P=.44) and 10.01 cm3 versus 16.58 cm3 for the second freeze (P=.03). The cryolesion volume for the single cryoprobe multiplied by 3 was 11.29 cm3 versus 14.75 cm3 for the multiple cyroprobe group (P=.06). The gross cryolesion surface area for the single cryoprobe multiplied by 3 was 13.14 cm2 versus 13.89 cm2 for the multiple probe group (P=.52). The cryolesion created by 3 simultaneously activated 1.47-mm probes appears to be larger than that of an additive effect. The lesions were significantly larger as measured by ultrasonography and nearly so (P=.06) as measured by the gross cryolesion volume.

Correction of susceptibility-induced GRE phase shift for accurate PRFS thermometry proximal to cryoablation iceball

The susceptibility contrast between frozen and unfrozen tissue disturbs the local magnetic field in the proximity of the ice-ball during cryotherapy. This effect should be corrected for in real time to allow PRFS-based monitoring of near-zero temperatures during intervention. Susceptibility artifacts were corrected post-processing, using a rapid numerical algorithm. The difference in bulk magnetic susceptibility between frozen and non-frozen tissue was approximated to be uniform over the ice-ball volume and was determined from the isothermal principle applied to the phase-transition frontier of compartments. Subsequently, the magnetic perturbation field was calculated rapidly in 3D using a Fourier-convolution. Experimental studies were performed for two scenarios: tissue defrosting in a water bath and induction of an ice-ball by a MR-compatible cryogenic probe. The susceptibility artifacts yielded PRFS temperature errors as high as 10-12°C proximal to the ice-ball, positive or negative depending on the relative orientation of the position vector from the B(o) direction. These effects were fully corrected for to within the noise range. The susceptibility-corrected PRFS temperature values were consistent with the phase-transition isothermal condition, irrespective of the local orientation of the position vector. By implementing on-line the post processing algorithm, PRFS MRT may be used as a safety tool for non-invasive and accurate monitoring of near-zero temperatures during MR-guided clinical cryotherapy.

Impact of Pneumoperitoneum on Renal Cryotherapy

Pneumoperitoneum is known to decrease blood flow to the kidney during laparoscopy. We investigated if this change in blood flow would increase the size of the cryolesion. Twelve Yorkshire swine underwent laparoscopy-guided percutaneous cryoablation of the upper and lower pole of each kidney at four randomized pneumoperitoneum pressures (10, 15, 20, and 25 mm Hg). Cryolesions were made with a 1.47-mm IceRod (Galil Medical, Plymouth Meeting, PA). Each site underwent two 10-minute freeze cycles separated by a 5-minute active thaw with pressurized helium gas. At the conclusion of each freeze cycle, the iceball volume was measured with intraoperative ultrasound. After completion of the four cryolesions, the kidneys were harvested, and the cryolesion surface area was calculated. The lesions were fixed in 10% buffered formalin and then excised with a 1-mm margin to obtain a volume measurement using fluid displacement. Iceball volume was 3.41, 2.85, 3.44, and 2.36 cm(3) for freeze cycle 1 (p = 0.16) and 3.67, 3.34, 4.88, 3.95 cm(3) for freeze cycle 2 (p = 0.20) at 10, 15, 20, and 25 mm Hg, respectively. Cryolesion volume by fluid displacement was 4.06, 3.77, 3.97, and 3.93 cm(3) (p = 0.86) and cryolesion surface area was 4.55, 4.38, 4.39, and 4.20 cm(2) (p = 0.71) at 10, 15, 20, and 25 mm Hg, respectively. In this study, pneumoperitoneum pressure between 10 and 25 mm Hg did not affect iceball size as measured by intraoperative ultrasound, cryolesion volume by fluid displacement, or cryolesion surface.

Ultrashort intracorporeally maneuverable cryoprobes for laparoscopic renal cryoablation in the porcine model

To determine the feasibility and efficacy of laparoscopic renal cryosurgery using a novel ultrathin ultrashort intracorporeal cryoprobe in a porcine model. Novel cryoprobes 4 cm in length and 1.5 mm in diameter were manipulated intracorporeally after insertion via a designated 15 mm laparoscopic port. Renal cryoablative lesions were induced laparoscopically in four 40 kg female piglets. We correlated between intraoperative temperature, ice ball geometry, intraoperative ultrasonographic properties, and histology. Laparoscopic manipulation of the cryoprobes was straightforward. No port site bleeding occurred during insertion, freezing, thawing or upon removal of the probes. The 0 degrees C, -20 degrees C, and -40 degrees C isotherms were measured at 6, 8, and 12 mm from the probe circumferentially. Ice-ball volume stabilization as determined by ultrasound occurred after 10 min of activation. Lower temperatures were reached after 10 min of probe activation as compared with 5 min (ice ball diameter 30 mm, DeltaT = 13-21 degrees C). Using a second 10-min-long freeze cycle resulted in a 14-22 degrees C lower temperature within the ice ball compared to a single cycle. Full coagulative necrosis was noted in the areas between the inserted probes with an additional 1-2 mm circumferential rim of severe tubular damage and apoptosis. Our novel cryoprobe can be used effectively and conveniently in laparoscopic renal cryosurgery. Considering the size of the cryogenic lesion, using a cluster of probes may be advisable.

Hepatic vascular inflow occlusion enhances tissue destruction during cryoablation of porcine liver 1

Background Local recurrences after cryoablation of liver tumors have been reported at rates from 5% to 44% and can be caused by inadequate coverage of the tumor by the frozen region. Hepatic vascular inflow occlusion may facilitate ablation by enlarging the size of the frozen region and the tissue necrosis induced by freezing. Few studies have documented these effects of inflow occlusion during liver cryoablation. Materials and methods Two cryolesions were induced in the liver of 12 pigs in a standardized set-up. Vascular inflow occlusion was used in six pigs during freezing. Two freeze cycles were performed at each location. Ice-ball volume was estimated by intraoperative magnetic resonance imaging. Cryolesion volume was estimated from histopathologic examination of the lesions 4 days after ablation. Results The median volume of ice-balls produced during inflow occlusion was 107% larger than for ice-balls produced without occlusion ( P < 0.001). The median volume of cryolesions made during inflow occlusion was 195% larger than for cryolesions induced without occlusion ( P < 0.001). The geometry of the ice-balls was more regular if produced during inflow occlusion than if not. The ice-balls produced during the second freeze cycle were 17% and 20% larger than the ice-ball produced during the first freeze for lesions made with ( P = 0.01) and without ( P = 0.03) inflow occlusion. Conclusions Hepatic vascular inflow occlusion enables freezing of larger volumes of liver tissue andincreases the volume of tissue necrosis induced during cryoablation of porcine liver.

Intraoperative contrast-enhanced MR-imaging as predictor of tissue damage during cryoablation of porcine liver.

This study evaluate intraoperative Magnetic Resonance Imaging (MRI) as predictor of tissue damage following cryoablation of porcine liver with and without concomitant hepatic vascular inflow occlusion. Inflow occlusion was used during freezing in 6 of 12 pigs included. The volumes of the procedural ice-balls were estimated from MR images. Immediately after thawing contrast (MnDPDP) enhanced MRI was performed to estimate the volume of the cryolesion. Four days after ablation MRI was repeated of the in-vivo and the ex-vivo liver. Photography was performed of the sliced liver specimens to estimate the volumes of the lesions. The intraoperative volume of the cryolesion as shown by contrast enhanced MRI corresponded well to the ice-ball volume for lesions made without vascular occlusion (difference 0.3 +/- 0.9 cm(3), p = 0.239). For lesions made during occlusion the volume of the intraoperative cryolesion was larger than the corresponding ice-ball (difference 7.5 +/- 3.3 cm(3), p = 0.003). The volume of the cryolesions as estimated from histopathology four days after freezing and contrast enhanced MRI immediately after freezing corresponded well for lesions made with (difference -2.6 +/- 4.5 cm(3), p = 0.110) and without vascular occlusion (difference -0.5 +/- 2.3 cm(3), p = 0.695). Intraoperative MnDPDP-enhanced MRI of the cryolesion is predictive of the tissue damage induced during cryoablation of porcine liver. The procedural ice-ball is not, if induced during inflow occlusion.

Percutaneous cryoablation of colorectal liver metastases: potentiated by two consecutive freeze–thaw cycles

Cryoablation may be beneficial for selected patients with liver tumours. Two freeze–thaw cycles at the same location have been recommended during treatment as this potentiate the effect of ablation in experimental studies. However, single freeze ablations are used by some as double freeze procedures are time-consuming and have been associated with increased risk of complications. Estimation of ice-ball volume is difficult using regularly used monitoring techniques. Magnetic resonance imaging, however, allows excellent and multiplanar visualisation of the frozen region during ablation. We comment on the effect of double freeze cycles in regard to ice-ball volume as estimated from magnetic resonance imaging during percutaneous cryoablation of colorectal liver metastases. The ice-ball volume at the end of the second freeze cycle was median 42% larger than the volume at the end of the first freeze. Double freeze cycles may thus facilitate tumour destruction.