We report percutaneous cryoablation of spine tumors in 7 consecutive patients (5 men, 2 women mean age, 47 years; range, 17-68 years) by using intraprocedural image monitoring of ice ball margins to ...protect adjacent neural elements. Complete tumor ablation was achieved in all patients without neurologic complication. Pain relief was achieved in 4 of 5 (80%) patients; the patient with persistent pain was later found to have enlarging metastases at other sites.
Aim To assess single-breath-hold combined positron-emission tomography/computed tomography (PET/CT) for accuracy of tumour image registration and projected ablation volume overlap in patients ...undergoing percutaneous PET/CT-guided tumour-ablation procedures under general anaesthesia. Materials and methods Eight patients underwent 12 PET/CT-guided tumour-ablation procedures to treat 20 tumours in the lung, liver, or adrenal gland. Using breath-hold PET/CT, the centre of the tumour was marked on each PET and CT acquisition by four readers to assess two- (2D) and three-dimensional (3D) spatial misregistration. Overlap of PET and CT projected ablation volumes were compared using the Dice similarity coefficient (DSC). Interobserver differences were assessed with repeated measure analysis of variance (ANOVA). Technical success and local progression rates were noted. Results Mean tumour 2D PET/CT misregistrations were 1.02 mm (range 0.01–5.02), 1.89 (0.03–7.85), and 3.05 (0–10) in the x , y , and z planes. Mean 3D misregistration was 4.4 mm (0.36–10.74). Mean projected PET/CT ablation volume DSC was 0.72 (±0.19). No significant interobserver differences in 3D misregistration ( p =0.73) or DSC ( p =0.54) were observed. Technical success of ablations was 100%; one (5.3%) of 19 tumours progressed. Conclusion Accurate spatial registration of tumours and substantial overlap of projected ablation volumes are achievable when comparing PET and CT acquisitions from single-breath-hold PET/CT. The results suggest that tumours visible only at PET could be accurately targeted and ablated using this technique.
Purpose: Patients with favorable‐risk prostate cancer may be attracted to focal therapy aimed at the dominant intraprostatic lesion as a middle ground between the morbidity of full gland treatment ...and the uncertainty of observation. The various approaches involve isotopes having different energies implying different dosimetric characteristics. This work seeks to determine if choice of isotope makes a substantial difference in the fraction of prostate that may be implanted as a function of implant volume and rectal dose limit. Methods: Representations of prostate, urethra and rectum were generated from MR scans as part of an IRB approved medical record review of patients with confirmed low risk prostate cancer. Anatomic structures were digitized on a 2.5 × 2.5 × 5.0 mm grid. Focal implants were simulated by placement of a single source. All prostate points 5 mm or further from a sensitive structure were considered as potential implant location. Dose distributions were calculated for implants of 125I, 109Pd and 192Ir. The fraction of potential implant locations that respected normal tissue constraints (rectum: 10–100% of Rx, urethra 100–200% of Rx) as a function of prescription radius was recorded. Results: The fraction of the prostate implantable for a given prescription radius primarily depends on the normal tissue dose limits that are to be respected with a secondary dependence on isotope. Prescription radius less than 1 cm and rectal dose constraints greater than 50% of prescription dose allow a substantial portion of the gland to be considered for a focal implant. Detailed results are presented as a function of normal tissue constraints and prescription radius. Conclusion: While isotope choice does affect the implantable volume, the effect is secondary to the choice of prescription parameters. Choice of focal brachytherapy approach may be made based on consideration of duration of irradiation or clinical concerns. NIH P41 EB015898
To describe the cryoablation of liver tumors by using a percutaneous approach and intraprocedural magnetic resonance (MR) imaging monitoring and to assess the feasibility and safety of the procedure.
...Fifteen hepatic tumors (mean diameter, 2.9 cm) in 12 patients were treated (18 total cryoablations). Fourteen were metastases and one was a hemangioma; all were proved at biopsy. By using a 0.5-T open MR imaging system, cryoneedles were placed and lesions ablated by using real-time monitoring. Clinical signs and symptoms were assessed and laboratory tests performed. Intraprocedural depictions of iceballs were compared with contrast material-enhanced MR imaging-based estimates of cryonecrosis that were obtained 24 hours after cryoablation.
MR imaging-guided percutaneous cryotherapy resulted in no serious complications and no clinically important changes in serum liver enzymes or creatinine or myoglobin levels. Intraprocedural MR imaging demonstrated iceballs as sharply marginated regions of signal loss that expanded and engulfed tumors. The maximal iceball size was 4.9 x 2.2 x 2.2 cm with the use of one cryoneedle and 6.0 x 5.6 x 4.9 cm with three cryoneedles. Intraprocedural iceball depictions correlated well with postprocedural cryonecrosis estimates.
MR imaging-guided percutaneous cryotherapy of liver tumors is feasible and safe. MR imaging can be used to estimate cryotherapy effects and guide therapy intraprocedurally.
Purpose: To evaluate the use of a non‐rigid registration method for improved intra‐operative target definition in 125‐I permanent prostate implants. Methods: The validation dataset was created from ...10 MRI‐guided prostate biopsy patients with both diagnostic (with endorectal coil) and intra‐procedural (without endorectal coil) 3 Tesla MRI scans under an IRB approved protocol. A biomechanical‐based probabilistic non‐rigid registration method was adapted to register diagnostic to intra‐procedural images by matching the contoured prostate boundaries. The probabilistic framework provides a collection of prostate configurations under deformation, or a marginal probability map for a given location to be identified as inside the prostate by the registration. The marginal probability map was compared to the intra‐procedural prostate contour. 125‐I treatment plans were generated for the intra‐procedural scans. Results: In two cases we find that ∼5% of the prostate volume within the 50th percentile of the marginal deformed probability is not included in the intra‐procedural contour, and 3–4% of the intra‐procedural prostate volume is not included in any of the deformed configurations. Different regions of the prostate have varying uncertainties; preliminary results show margins of 1–2 mm near mid‐gland and 3–4 mm around the apex. We present geometric uncertainties and the resulting variation of dosimetric quantities in the base, mid‐gland, apex and peripheral zone of the prostate. Conclusions: We study the feasibility of using a probabilistic non‐rigid registration method for supplementing intra‐procedural images with diagnostic MR images. The method is evaluated geometrically and dosimetrically, which quantifies the method's ability to provide intra‐procedural estimation of the accuracy of the deformed configurations. This method will be applied to registration of diagnostic MR with intra‐procedural transrectal ultrasound images to improve visualization of the prostate apex and substructure, which could provide improved prostate boundary definitions with uncertainty margins to guide the development of intra‐operative brachytherapy treatment plans.
This work was supported by NIH grants 1U41RR019703‐01A2, 1R01CA111288‐01A1,P01‐CA67165,andU01CA151261.
We report the findings of a transperineal magnetic resonance image (MRI) guided biopsy of the prostate in a man with increasing prostate specific antigen who was not a candidate for a transrectal ...ultrasound guided biopsy.
Using an open configuration 0.5 Tesla MRI scanner and pelvic coil, a random sextant sample was obtained under real time MRI guidance from the peripheral zone of the prostate gland as well as a single core from each MRI defined lesion. The patient had previously undergone proctocolectomy for ulcerative colitis and, therefore, was not a candidate for transrectal ultrasound guided biopsy. Prior attempts to make the diagnosis of prostate cancer using a transurethral approach were unsuccessful.
The random sextant samples contained benign prostatic hyperplasia, whereas Gleason grade 3 + 3 = 6 adenocarcinoma was confirmed in 15% and 25% of the 2 cores obtained from the MRI targeted specimens of 2 defined lesions. The procedure was well tolerated by the patient.
Transperineal MRI guided biopsy is a new technique that may be useful in detecting prostate cancer in men with increasing prostate specific antigen who are not candidates for transrectal ultrasound guided biopsy.
In this tutorial article, the concepts of correlation and regression are reviewed and demonstrated. The authors review and compare two correlation coefficients, the Pearson correlation coefficient ...and the Spearman rho, for measuring linear and nonlinear relationships between two continuous variables. In the case of measuring the linear relationship between a predictor and an outcome variable, simple linear regression analysis is conducted. These statistical concepts are illustrated by using a data set from published literature to assess a computed tomography-guided interventional technique. These statistical methods are important for exploring the relationships between variables and can be applied to many radiologic studies.
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