T1‐weighted MR image contrast around a cryoablation iceball: A phantom study and initial comparison with in vivo findings

Abstract

The hyperintense rim around the iceball in fast T1w GRE images corresponded to cooled but nonfreezing temperatures (<20 °C) proximal to the frozen zone. The same image contrast was observed both in a phantom study as well as in vivo in the human prostate during cryotherapy. Potentially, monitoring of this rim could be useful in order to maintain a safe margin from at-risk tissues during MR-guided prostate cryoablation procedures.

Percutaneous MR-guided focal cryoablation for recurrent prostate cancer following radiation therapy: retrospective analysis of iceball margins and outcomes

“…Cryoablation was performed using an MR-compatible cryoablation device (MRI-SeedNet; Galil Medical, Yokneam, Israel). Two 10-min freezing cycles separated by 2-min passive and 1-min active thaw were applied under continuous T1-weighted gradient echo MR monitoring [ 21 , 22 ]. The intraprocedural images were used to modulate the size and shape of the iceball by regulating the gas flow to each individual cryoprobe so as to cover the entire tumour while avoiding contact between the iceball and rectal wall.…”

MRI for Noninvasive Thermometry

“…Recently interest has also revived in the use of MR-thermometry for monitoring cryoablations [24,136] and the temperature of adipose tissue [37,55,74,81,137]. When T 1 is used to monitor ablations of fatty tissue such as breast, water must be suppressed [138] or water and fat signals separated [55,77] for improved accuracy.…”

“…The most commonly treated tissue is the liver; however with advances in equipment for delivery of thermal energy [5,7,11,14,28,[30][31][32], accurate temperature monitoring, image reconstruction and automation [3,4,6,8,9,[11][12][13][15][16][17][23][24][25], the possibilities are expanding. Emerging applications include local drug-delivery [112][113][114], epilepsy treatment [9], quality control of red blood cells [115], iron mapping [116], diagnosis of multiple sclerosis [117], and brain abnormalities [118,119] and identification of iron-oxide labelled stem cells [120].…”

In-bore MRI interventions

“…Iceball growth can be monitored in near real time with T1 weighted gradient echo imaging [62]. Overduin et al [63] reported that a hyperintense rim is seen progressing at the margins caused by shortening of T1 and seen in cooled (less than 20 8C) but as yet nonfreezed margin. MR thermography information is less accurate from cooling tissue and is therefore not routinely used.…”