Role of transrectal ultrasound guided salvage cryosurgery for recurrent prostate carcinoma after radiotherapy

Despite improvements in treatment of localized prostate cancer, local recurrence remains a significant problem. A total of 46 patients with proven local cancer recurrence following external beam radiotherapy entered a prospective clinical trial using ultrasound-guided cryosurgery to ablate the residual prostate gland. Persistent complications included one urethra-rectal fistula, incontinence (2), retention (3), and treatment induced erectile dysfunction (7). Using the PSA definitions for biochemical failure as PSA>or=0.3 ng/ml, the Kaplan-Meier plots showed the incidence of patients to be free of biochemical recurrence at 51 and 44% at 1 and 2 y, respectively. For a PSA>or=1.0, the values at 1 and 2 y were 72 and 58%.

Prospective trial of cryosurgical ablation of the prostate: five-year results

OBJECTIVES

To determine in a prospective pilot study the safety and efficacy of cryosurgical ablation for localized prostate carcinoma.

METHODS

A total of 87 cryosurgical procedures were performed on 76 consecutive patients between December 1994 and February 1998. All patients had histologically proved adenocarcinoma of the prostate, with prostate-specific antigen (PSA) readings of less than 30 ng/mL. Clinical evaluations, PSA determinations, and patient self-reported quality-of-life questionnaires (functional assessment of cancer treatment-prostate; FACT-P) were used to determine biochemical and clinical disease-free status and complications. Patients had a mean follow-up of 50 months (minimum 36).

RESULTS

Follow-up biopsies were performed in 73 patients, and 72 were negative for malignancy after one or more treatments. Ten patients required two treatments and 1 patient required three treatments. The 5-year overall and cancer-specific survival rate was 89% (95% confidence interval, 83% to 97%) and 98.6% (95% confidence interval, 96% to 100%), respectively. The undetectable PSA rate (less than 0.3 ng/mL) for low-risk patients (n = 13) was 60% at 5 years; for moderate-risk patients (n = 23), it was 77%, and for high-risk patients (n = 40), 48%. The corresponding percentage of patients with a PSA level less than 1.0 ng/mL at 5 years was 75%, 89%, and 76%. Sloughing occurred in 3 patients (3.9%), incontinence in 1 (1.3%), and testicular abscess in 1 (1.3%). At 3 years, 18 (47%) of 38 patients capable of unassisted intercourse at the time of cryosurgery had resumed sexual intercourse, 5 spontaneously and 13 with sildenafil or prostaglandin.

CONCLUSIONS

The results of this prospective evaluation show cryosurgery to be both a safe and an effective option in the treatment of localized prostate cancer.

Analysis of early failure of tunneled hemodialysis catheters

OBJECTIVE

Tunneled hemodialysis catheters are often placed by the interventional radiology service using sonographic guidance and fluoroscopy for safe and optimal placement. The aim of this study was to determine the causes of early failure (<or=7 days) of these catheters in our practice.

SUBJECTS AND METHODS

Data were prospectively collected for 639 radiologically placed tunneled hemodialysis catheters. The reason for catheter removal was recorded in each case. Tips of removed catheters were routinely sent for microbial culture.

RESULTS

Fifty-two (8.1%) of 639 catheters were removed within 7 days of insertion. Six (0.9%) of these had completed their purpose and had not failed; these were not included in the study. Of the 46 catheters having early failure, six (0.9%) were clotted and 12 (1.9%) were suspected of being infected, only three of which had a proven catheter-related infection. Twenty-eight catheters (4.4%) were removed for other reasons. In this group, the most common reasons were poor tip position (n = 9) and catheter replacement over a guidewire into a preexisting fibrin sheath (n = 8). Only two failed because of poor tip orientation. Other reasons for failure were kinked or pinched catheters (n = 4) and bleeding (n = 3), including one exsanguination, and two unknown reasons.

CONCLUSION

By paying careful attention to catheter tip position, searching diligently for the presence of a fibrin sheath when catheter exchanges are made over a wire, and better investigating presumed catheter infection, we could reduce the early failure rate by more than half, from 46 cases to 20 cases (nine cases of suspected infection were in fact not infected).

Radiologic placement of central venous catheters: rates of success and immediate complications in 3412 cases

OBJECTIVE

To determine the success and immediate complication rates associated with 3412 central venous catheter placements performed in an interventional radiology suite.

METHODS

Success and immediate complication rates were prospectively recorded for 3412 consecutive patients who had central venous catheters radiologically placed at a tertiary care centre between July 1993 and October 2000. The indication for placement and the insertion site were also recorded.

RESULTS

The most common indication for both short- and long-term venous access was hemodialysis, and the right internal jugular vein was the most common site for catheter insertion. Placement was successful for 98.8% of tunnelled lines and 99.3% of temporary catheters. The rate for immediate complications (including pneumothorax, air emboli, bleeding and arterial puncture) for tunnelled catheter placements was 3.8% and for temporary catheter placements was 1.6%; no major complications were documented.

CONCLUSION

Our results lend further evidence to the claim that the success and immediate complication rates of radiologically placed central venous catheters compare favourably with blind placement and surgical placement of central venous catheters.

A model for the time dependent three-dimensional thermal distribution within iceballs surrounding multiple cryoprobes

A time dependent three-dimensional finite difference model of iceball formation about multiple cryoprobes has been developed and compared to experimental data. Realistic three-dimensional probe geometry is specified and the number of cryoprobes, the cryoprobe cooling rates, and the locations of the probes are arbitrary inputs by the user. The simulation accounts for observed longitudinal thermal gradients along the cryoprobe tips. Thermal histories for several points around commercially available cryoprobes have been predicted within experimental error for one, three, and five probe configurations. The simulation can be used to generate isotherms within the iceball at arbitrary times. Volumes enclosed by the iceball and any isotherms may also be computed to give the ablative ratio, a measure of the iceball's killing efficiency. This ratio was calculated as the volume enclosed by a critical isotherm divided by the total volume of the iceball for assumed critical temperatures of -20 and -40 degrees C. The ablative ratio for a single probe is a continuously decreasing function of time but when multiple probe configurations are used the ablative ratio increases to a maximum and then essentially plateaus. Maximum values of 0.44 and 0.55 were observed for three and five probe configurations, respectively, with an assumed critical temperature of -20 degrees C. Assuming a critical temperature of -40 degrees C, maximum ablative ratios of 0.21 and 0.3 for three and five probe configurations, respectively, were observed.

Flounder antifreeze peptides increase the efficacy of cryosurgery

Type I antifreeze protein (AFP) from the winter flounder (Pseudopleuronectes americanus) was used as an adjuvant to cryosurgery of subcutaneous tumors of Dunning AT-1 rat prostate cells grown in Copenhagen rats. The cryosurgical procedure was performed with a commercially available cryosurgery device (CRYO-HIT, Galil Medical) with clinically relevant single- and double-freeze protocols. Injury was assessed with the alamar blue indicator of metabolic activity. The assay gave anomalous results when used to assess the extent of injury immediately following the procedure, underestimating the extent of injury. However, a double-freeze procedure with antifreeze protein present was found to give significantly better ablation than a double-freeze without AFP or a single-freeze with or without AFP.

Histological findings in the prostate two years following cryosurgical ablation

We examined the pathological findings from prostatic whole mounts obtained at post-mortem, 2 years following cryosurgical ablation of the prostate (CSAP), to evaluate the presence or absence of residual benign or malignant tissue. Whole prostates were obtained from two patients at post-mortem, in which the cause of death was not related to prostate cancer. The patients had received CSAP 24 and 30 months earlier, as the primary treatment for prostate cancer. Complete ablation of the gland was demonstrated in one case, with some residual viable benign glands in the transitional zone in the second case. These results suggest that localized prostate cancer can be successfully eradicated by CSAP.

Image-guided central venous catheter placement for apheresis in allogeneic stem cell donors

Peripheral blood stem cell harvest by apheresis is an increasingly important procedure utilized in the treatment of many malignancies. Whether autologous or allogeneic, it is frequently performed via peripheral access because of concern over major complications associated with central venous catheter placement. This study was to determine the safety and success, complications and premature failure rates for radiolocally placed ultrasound-guided non-tunneled central venous catheters placed for apheresis in a donor (allogeneic) population. One hundred central venous catheters were placed in ninety-one individuals for allogeneic stem cell harvest. Procedural success and complications relating to placement were noted in all. In 97 cases the number of needle passes required for venous cannulation and whether this was achieved with a single wall puncture was noted. Duration of catheterization and reason for removal were recorded in all cases. All catheters were placed by a right transjugular route. Venous cannulation and functioning line placement was achieved in every case; 92/97 (95%) required only a single needle pass and 84/97 (87%) only a single wall puncture. There were no placement related complications; 94 catheters were removed the same day with the remainder removed within 48 hr. All completed apheresis. Our study demonstrates the safe use of central venous catheters for apheresis in normal donors if ultrasound guidance is used for the puncture and the duration of catheterization is short.

Suppression of high-density artefacts in x-ray CT images using temporal digital subtraction with application to cryotherapy

Image guidance in cryotherapy is usually performed using ultrasound. Although not currently in routine clinical use, x-ray CT imaging is an alternative means of guidance that can display the full 3D structure of the iceball, including frozen and unfrozen regions. However, the quality of x-ray CT images is compromised by the presence of high-density streak artefacts. To suppress these artefacts we applied temporal digital subtraction (TDS). This TDS method has the added advantage of improving the grey scale contrast between frozen and unfrozen tissue in the CT images. Two sets of CT images were taken of a phantom material, cryoprobes and a urethral warmer (UW) before and during the cryoprobe freeze cycle. The high density artefacts persisted in both image sets. TDS was performed on these two image sets using the corresponding mask image of unfrozen material and the same geometrical configuration of the cryoprobes and the UW. The resultant difference image had a significantly reduced artefact content. Thus TDS can be used to significantly suppress or eliminate high-density CT streak artefacts without reducing the metallic content of the cryoprobes. In vivo study needs to be conducted to establish the utility of this TDS procedure for CT assisted prostate or liver cryotherapy. Applying TDS in x-ray CT guided cryotherapy will facilitate estimation of the number and location of all frozen and unfrozen regions, potentially making cryotherapy safer and less operator dependent.

A semi-empirical treatment planning model for optimization of multiprobe cryosurgery

A model is presented for treatment planning of multiprobe cryosurgery. In this model a thermal simulation algorithm is used to generate temperature distribution from cryoprobes, visualize isotherms in the anatomical region of interest (ROI) and provide tools to assist estimation of the amount of freezing damage to the target and surrounding normal structures. Calculations may be performed for any given freezing time for the selected set of operation parameters. The thermal simulation is based on solving the transient heat conduction equation using finite element methods for a multiprobe geometry. As an example, a semi-empirical optimization of 2D placement of six cryoprobes and their thermal protocol for the first freeze cycle is presented. The effectiveness of the optimized treatment protocol was estimated by generating temperature-volume histograms and calculating the objective function for the anatomy of interest. Two phantom experiments were performed to verify isotherm locations predicted by calculations. A comparison of the predicted 0 degrees C isotherm with the actual iceball boundary imaged by x-ray CT demonstrated a spatial agreement within +/-2 mm.

Extraprostatic biopsy improves the staging of localized prostate cancer

OBJECTIVE

To evaluate the role and safety of biopsy of the seminal vesicles and neurovascular bundles in determining the pathologic stage of prostatic carcinoma.

METHODS

Eighty-one consecutive patients were enrolled in a comprehensive cryosurgical biopsy protocol that included sextant intraprostatic plus extraprostatic biopsy. The pathologic stage, determined after biopsy, was compared with the clinical stage, determined by digital rectal examination (DRE) and transrectal ultrasonographic (TRUS) evaluation. As well, complication rates for these patients were compared with rates for a separate group that underwent sextant intraprostatic biopsy alone.

RESULTS

Of the 81 patients, 61 (75%) were confirmed to have cancer by biopsy. None of these patients was considered to have extraprostatic extension by clinical evaluation (DRE and TRUS), but 16 of 61 (26%) were identified to have extraprostatic cancer in the seminal vesicles (8 of 61, 13%) or in the neurovascular bundles (8 of 61, 13%) by extraprostatic biopsy. There was no significant difference in the complication rates between sextant intraprostatic biopsy and sextant intraprostatic plus extraprostatic biopsy (p>0.97).

CONCLUSIONS

Extraprostatic biopsy identifies extension of carcinoma in a large proportion of patients in whom clinical evaluation by DRE and TRUS indicates organ-confined disease. Extraprostatic biopsy is therefore warranted as routine evaluation before surgery in order to correctly stage prostatic carcinoma and select appropriate therapy.

Quality-of-life outcomes for men treated with cryosurgery for localized prostate carcinoma

BACKGROUND

Cryosurgery was introduced as an alternative to radiotherapy or radical prostatectomy in the mid-1960s. Although it met the primary objective of achieving local control, it was largely abandoned due to a high incidence of complications. Technologic advances in the areas of imaging and urethral warming have renewed interest in this treatment methodology. The aim of the current study was to determine the quality of life of men enrolled in a Phase II clinical trial of cryosurgery for the treatment of localized prostate carcinoma.

METHODS

Men were administered the Functional Assessment of Cancer Treatment-Prostate (FACT-P) prior to their treatment and at 6 weeks and 3, 6, and 12 months posttreatment.

RESULTS

By 12 months after cryosurgery, most of the FACT-P subscales had returned to pretreatment levels, following a decline in well-being immediately after cryosurgery. There were two exceptions to this general trend: At 12 months, impairments in social/family well-being and sexual function still remained. The average time to return to work after therapy was 3 weeks. Stay in hospital after treatment was limited to 1 day for 94% of the participants. Compared with men who received the standard treatments of radical prostatectomy and radical radiotherapy, men treated with cryosurgery appeared to have a similar quality of life, with perhaps the exception of decreased sexual function.

CONCLUSIONS

The quality-of-life outcomes of this study support the current renewed interest in cryosurgery. The severe impairments reported in other studies were not seen in this sample. In fact, it appeared that all aspects of the participants' well-being had returned to pretreatment levels by 12 months, with the exception of sexual function.

Value of frontal caval measurement in the placement of inferior vena cava filters

OBJECTIVE

Inferior vena cavae (IVC) can be of unusual geometry, often having odd shapes and being oriented (in long axes) away from the horizontal plane. However, after insertion of a filter, most IVC adopt a circular cross-section. The objective of this study was to determine if the IVC diameter estimated by frontal measurement (cavogram equivalent) reflects the true circular diameter of the infrarenal vena cava. Diameter estimation is clinically important in the correct selection of a filter, because mega cavae (diameter 28 mm or greater) require a particular filter.

METHODS

The infrarenal IVC was measured on computed tomographic (CT) scans in 136 patients. The frontal diameter was recorded as that which would be obtained by a cavogram. Corrected circular diameter was obtained by mapping the circumference of each cross-section on CT to a straight line and calculating diameter from circumference.

RESULTS

The average frontal caval diameter was 20.5 (standard deviation 3.7) mm, whereas the average corrected circular diameter was 23.0 (standard deviation 3.4) mm. By frontal measurements, 6 IVC diameters were 28.0 mm or greater. Similarly, by corrected circular diameter, 6 IVC diameters were 28.0 mm or greater. However, of the 6 mega cavae extrapolated to cavograms, only 3 corresponded to mega cavae when corrected for true circular diameter. Yet, of the 6 mega cavae identified by corrected circular diameter measurement, 3 were not identified by frontal diameter assessment. Of the 6 patients with true mega cavae, 2 were being evaluated for right lower quadrant pain, 2 for lymphoma, 1 for a pelvic mass, and 1 for staging of a head and neck cancer.

CONCLUSIONS

Cavograms can over- or underestimate the true diameter of an IVC, and may thus lead to incorrect filter choice. It is recommended that a sonogram or CT scan be obtained to visualize the IVC in cases of suspected mega cava, and that true circular diameters be used for selection and placement of IVC filters.

Should anticoagulant therapy be stopped or reversed before venous intervention?

PURPOSE

To determine the safety of venous intervention and the incidence of complications in patients undergoing venous interventional radiological procedures while receiving anticoagulant therapy.

METHOD

Data were collected prospectively for a 1-year period. One hundred patients receiving anticoagulant therapy underwent interventional radiological procedures requiring venous cannulation. Of these, 87 had documented prolonged bleeding times. There were 50 inferior vena cavograms obtained and filters placed (29 transfemoral, 21 transjugular), and 50 transfemoral pulmonary angiogram obtained, all in patients with thrombo-embolic disease who were receiving anticoagulant therapy. In most cases venous access was achieved with real-time sonographic guidance.

RESULTS

Venous access was gained in all patients in all groups. There were 41/50 filter placements and 46/50 pulmonary angiograms performed in the patients with prolonged clotting times in or above the therapeutic range. There were no cases of arterial puncture and no cases of venous bleeding either during or after the procedures. No other complications were recorded.

CONCLUSION

Venous intervention in patients receiving therapeutic anticoagulation is safe, with no complications reported in our series. There is no need to discontinue anticoagulant therapy in patients with life-threatening thrombo-embolic disease. Real-time sonographic guidance greatly facilitates venous cannulation and avoids inadvertent arterial puncture.

Radiologic placement of tunneled central catheters: rates of success and of immediate complications in a large series

OBJECTIVE

The objective was to examine the success and immediate complication rates in a large series of radiologically placed tunneled central venous catheters.

SUBJECTS AND METHODS

We prospectively recorded the success and immediate complication rates in 880 consecutive radiologically placed tunneled central venous catheters. We also recorded the indication for placement, the success of placement, the number of passes required, and whether a double- or single-wall puncture occurred.

RESULTS

Hemodialysis was the most common indication for long-term venous access. Venous access was successful in all patients, and catheter placement was successful in 99.4% of patients, with only five failed placements. All patients in whom placement was initially unsuccessful underwent successful placement the same day. All catheters were placed using real-time sonographic guidance. Most were placed in an internal jugular vein, with 87.4% requiring only a single needle pass. The immediate complication rate was only 4.0%, and no major complications occurred.

CONCLUSION

To our knowledge, this series is the largest for which the immediate complication and success rates for radiologically placed central venous catheters have been reported. Our results suggest that radiologic placement of tunneled central venous catheters is a safe and effective alternative to surgery.

A simplified method of gastropexy for transgastric enterostomy

Radiological placement of gastrostomy tubes was first described in 1983. Percutaneous gastropexy to facilitate gastrostomy placement was reported in 1986. Debate has continued to this day regarding the necessity of gastric fixation. We describe our technique of a simplified gastropexy to facilitate transgastric enterostomy and advocate its more widespread use.

Transrectal ultrasound-guided biopsy of the prostate: relation between ASA use and bleeding complications

OBJECTIVE

To determine the relation between ASA ingestion and the incidence of bleeding complications after transrectal ultrasound (TRUS)-guided biopsy of the prostate.

METHODS

Overall, 1810 patients with suspected prostate disease were followed after biopsy. ASA use was determined before the procedure. A TRUS-guided sextant biopsy was performed and patients were contacted immediately and by follow-up telephone call to determine whether there were any immediate or delayed bleeding complications.

RESULTS

Overall, 46 subjects (2.5%) had bleeding complications. Of the 54 subjects reporting current use of ASA, 2 (3.7%) had such complications. This difference was not significant.

CONCLUSION

There was no evidence of an association between the use of ASA and postbiopsy bleeding complications.

Apheresis: another indication for radiologically placed central venous catheters

OBJECTIVE

Apheresis is an important technique, used increasingly for a variety of conditions. It is sometimes performed via peripheral access because of concern over major complications associated with central venous catheter (CVC) placement. This study was to determine the safety and success of radiologic placement of CVCs for apheresis.

METHODS

Data were collected prospectively for 278 CVCs placed under real-time sonographic or fluoroscopic guidance in the radiology department. Complications were noted in all cases; the number of passes required for venipuncture and whether this was achieved with a single wall puncture were noted in 265 cases; duration of catheterization and reason for removal of the catheter were recorded in all cases. The study group included 83 donors providing peripheral blood stem cells for allogeneic transplant.

RESULTS

CVCs were successfully placed in all patients, 269 in the internal jugular and 9 in the femoral vein. In 87% of cases, only a single pass was required, and in 80% of cases venipuncture was achieved with a single anterior wall puncture. There was inadvertent but clinically insignificant arterial puncture in 6 cases (2%). In no case did this prevent CVC placement. Most catheters (211/274, 77%) were removed the same day. Only 3 catheters were removed prematurely (1%), 1 because of infection and 2 because of clotting. There was 1 case of venous bleeding.

CONCLUSION

CVCs are safe for apheresis if real-time sonographic guidance is used for the puncture, guide wire and catheter placement are confirmed fluoroscopically, and the duration of catheterization is short.

Considerations during clinical operation of two commercially available cryomachines

BACKGROUND AND OBJECTIVES

Advances in the technology of cryomachines in the last 10 years have led to the development of both liquid nitrogen and argon-based Joule-Thompson cryomachines. Theoretical and practical evaluation of the CMS Accuprobe and the ENDOcare CRYOcare was performed as respective examples of these technologies.

METHODS

Thermal gradients were calculated about both probes for the best case scenario of probe surface temperature equaling that of the cryogen used. Also, experimental evaluation in gelatin phantoms was performed with five probe arrays.

RESULTS

Theoretically, a liquid nitrogen-cooled probe provides only a slight advantage over one cooled with liquid argon. However, the experimental performance evaluation demonstrated that the CRYOcare system creates an iceball faster with steeper internal temperature gradients than the Accuprobe. Further, temperature outputs from the Accuprobe were shown to be in error, likely due to the position of the thermocouple within the probe.

CONCLUSIONS

Cryomachine performance is determined more by technological innovations than by cryogen temperature. Thermocouple monitoring is urged for users of the Accuprobe.

Outcome and safety of transrectal US-guided percutaneous cryotherapy for localized prostate cancer

OBJECTIVES

To assess the effectiveness and safety of ultrasound (US)-guided cryotherapy as a primary treatment for localized prostate cancer.

MATERIALS AND METHODS

A prospective study of percutaneous transrectal US (TRUS)-guided cryotherapy was performed on 71 patients with T1-T3, N0, M0 prostatic cancer: 10 patients underwent two or more procedures. All cases were newly diagnosed and patients had no previous treatment for cancer. For all patients, TRUS biopsies were performed at 5-6 months. Patients were monitored at 6 weeks; 3, 6, 9, and 12 months; and twice yearly thereafter for prostate specific antigen (PSA) levels, complications, and clinical evidence of residual disease.

RESULTS

Follow-up from 10 to 36 months was available for 70 of 71 patients; one patient died of unrelated disease. Initially, 10 of 69 patients had positive postcryotherapy biopsy results. After repeated treatment, nine of these 10 patients had negative biopsy results and one patient had no follow-up. Overall, 68 of 69 patients had negative biopsy results. At 1 year, 43 of 64 (67%) had an undetectable PSA level. Two patients had proven metastases. Complications include three cases with urethral sloughing requiring transurethral resection of the prostate (TURP). One patient had orchitis. Two patients had persistent incontinence, one as the result of a TURP. There was no death, acute serious morbidity, or fistula formation. Impotence was universal at 6 months, but many patients demonstrated late recovery.

CONCLUSION

Cryoablation is an imaging-guided percutaneous intervention for prostate cancer that can safely yield disease-free status in a high percentage of patients with localized disease.

Image-guided central venous catheters for apheresis

Apheresis is an increasingly important procedure in the treatment of a variety of conditions, sometimes performed via peripheral access because of concern over major complications associated with central venous catheter (CVC) placement. This study sought to determine the safety and success for ultrasound and fluoroscopically guided, non-tunneled dual lumen CVCs placed for apheresis. Prospective data collection was made of 200 attempted CVC placements in the radiology department utilizing real time sonographic guidance. The complications relating to placement were noted in all and the number of passes required for venepuncture and whether a single wall puncture was achieved was recorded in 185 cases. Duration of catheterization and reason for line removal were recorded in all. Our study group included 71 donors providing peripheral blood stem cells for allogeneic transplant. CVCs were successfully placed in all patients, 191 lines in the internal jugular and seven in the femoral vein. 86.5% required only a single pass and 80.5% with only anterior wall puncture. Inadvertent but clinically insignificant arterial puncture occurred in six (3%) cases. In no case did this prevent line placement. There were no other procedure-related complications. 173 (87.4%) catheters were removed the same day. No catheters were removed prematurely. There was one case of prolonged venous bleeding. Our study demonstrates the safety of central venous catheters for apheresis provided that duration of catheterization is short and real-time sonographic guidance is used for the puncture, and guide wire and catheter placement are confirmed fluoroscopically.

A model for the time-dependent thermal distribution within an iceball surrounding a cryoprobe

The optimal cooling parameters to maximize cell necrosis in different types of tissue have yet to be determined. However, a critical isotherm is commonly adopted by cryosurgeons as a boundary of lethality for tissue. Locating this isotherm within an iceball is problematic due to the limitations of MRI, ultrasound and CT imaging modalities. This paper describes a time-dependent two-dimensional axisymmetric model of iceball formation about a single cryoprobe and extensively compares it with experimental data. Thermal histories for several points around a CRYOprobe are predicted to high accuracy (5 degrees C maximum discrepancy). A realistic three-dimensional probe geometry is specified and cryoprobe temperature may be arbitrarily set as a function of time in the model. Three-dimensional temperature distributions within the iceball, predicted by the model at different times, are presented. Isotherm locations, as calculated with the infinite cylinder approximation, are compared with those of the model in the most appropriate region of the iceball. Infinite cylinder approximations are shown to be inaccurate when applied to this commercial probe. Adopting the infinite cylinder approximation to locate the critical isotherm is shown to lead the user to an overestimate of the volume of target tissue enclosed by this isotherm which may lead to incomplete tumour ablation.

X-ray CT monitoring of iceball growth and thermal distribution during cryosurgery

X-ray CT is able to image the internal architecture of frozen tissue. Phantoms of distilled water, a saline-gelatin mixture, lard and a calf liver-gelatin suspension cooled by a plastic tube acting as a long liquid nitrogen cryoprobe were used to study the relationship between Hounsfield unit (HU) values and temperature. There is a signature change in HU value from unfrozen to completely frozen tissue. No discernible relation exists between temperature in a completely frozen tissue and its HU value for the temperature range achieved with commercial cryoprobes. However, such a relation does exist in the typically narrow region of phase change and it is this change in HU value that is the parameter of concern for quantitative monitoring of the freezing process. Calibration of temperature against change in HU value allows a limited set of isotherms to be generated in the phase change region for direct monitoring of iceball growth. The phase change temperature range, mid-phase change temperature and the absolute value of HU change from completely frozen to unfrozen tissue are shown to be sensitive to the medium. Modelling of the temperature distribution within the region of completely frozen phantom using the infinite cylinder solution to the Fourier heat equation allows the temperature history of the phantom to be predicted. A set of isotherms, generated using a combination of thermal modelling and calibrated HU values demonstrates the feasibility of routine x-ray CT assisted cryotherapy. Isotherm overlay will be a major aid to the cryosurgeon who adopts a fixed target temperature as the temperature below which there is a certainty of ablation of the diseased tissue.

US-guided puncture of the internal jugular vein: complications and anatomic considerations

PURPOSE

To examine success and complication rates for ultrasound (US)-guided cannulation of the internal jugular vein (IJV) in comparison with blind techniques and to present the variations in anatomy of the IJV.

MATERIALS AND METHODS

Data were prospectively collected for 869 cases of sonographically guided cannulation of the IJV. In all cases, the side of the puncture, procedural success or failure, and any immediate complications were recorded. In 764 (88%) cases, the number of passes required and whether a single- or double-wall puncture was used were recorded. In 690 (79%) cases, IJV diameter and depth were recorded, while its relationship to the common carotid artery (CCA) was noted in 659 (76%) cases.

RESULTS

Cannulation was successful in 868 (99.9%) cases. Complications occurred in 20 (2.3%) cases. Eighty-seven percent of cannulations were achieved with one pass and 83% with a single-wall puncture. Success at first pass was significantly correlated with right-sided puncture and the diameter of the IJV. In 5.5% of cases, the IJV lay medial to the CCA, making successful cannulation with use of the landmark technique unlikely.

CONCLUSIONS

US-guided cannulation of the IJV is superior to blind techniques, increasing the success rate and incidence of first pass cannulation and reducing the incidence of complications.

Use of a moratorium to achieve consistent liquid nitrogen cryoprobe performance

BACKGROUND AND OBJECTIVES

During liver cryosurgical procedures, the authors observed seriously inconsistent rates of iceball growth implying inconsistent probe cooling rates. This inconsistency can lead to several problems, most importantly, loss of precision and reliability in freezing the chosen volume of tissue. The observation led to investigation of the performance of the cryosurgery machine.

METHODS

The performance of the Cryotech LCS 3000 with different moratorium periods was investigated. Freezing was performed in a gelatin phantom with thermocouple monitoring at the probe tip.

RESULTS

It was determined that a moratorium period between unit filling and clinical use essentially eliminates the uncertainty in probe performance. The need for this arises from the design of the system. A full liquid nitrogen tank does not have the necessary pressure required to induce effective freezing. A partially filled tank increases vapor pressure in the storage dewar driving more liquid nitrogen through the probes, thus allowing a more reliable and faster freeze.

CONCLUSION

The simple measure of introducing a moratorium period between filling the dewar with liquid nitrogen and its use in surgery allows partial evaporation of the nitrogen and enhances cryoprobe performance. This protocol modification may reduce the chance of inconsistent probe performance thus making liver cryosurgery more reliable.

Correlation between thermosensor temperature and transrectal ultrasonography during prostate cryoablation

OBJECTIVE

To determine if the adequacy of freezing in the neurovascular bundle region of the prostate during prostate cryotherapy can be monitored by transrectal ultrasonography (TRUS).

PATIENTS AND METHODS

The study group consisted of 11 patients undergoing TRUS-guided prostate cryotherapy. The actual temperature in the gland was monitored with thermosensors placed in each prostatic neurovascular bundle. The 2 cryo-operators, working together and blinded to the actual temperature, used sonographic observations to estimate the temperature at the neurovascular bundles every 2 minutes until they believed that the gland was adequately frozen. The congruity between the estimated and measured temperatures was analyzed to determine if the operators could accurately monitor the progress of cryoablation by ultrasonography.

RESULTS

There were a total of 85 data points for which the operators thought tumoricidal cryo-injury had been achieved at the neurovascular bundles (temperature -20 degrees C or below). For these points the measured temperature was on average 6.0 degrees C warmer than the estimated temperature (standard deviation, 22). For operator estimates of -20 degrees C or below, the measured temperature was -20 degrees C or below for 37 (44%) data points, between -19 degrees C and 0 degree C for 32 (38%) and greater than 0 degree C for 16 (19%).

CONCLUSIONS

The operators were not able to accurately predict subzero temperatures at the neurovascular bundle region by TRUS evaluation. Moreover, the bias and magnitude of the error were significant and might lead to inadequate freezing of the prostate during attempted cryoablation.

Cryosurgery for malignant tumours of the liver

OBJECTIVE

To evaluate the safety and efficacy of ultrasound-guided cryosurgery to treat malignant tumours of the liver.

DESIGN

A prospective nonrandomized trial. The follow-up was complete and ranged from 8 to 35 months.

SETTING

A university-affiliated hospital.

PATIENTS

Ten patients with secondary malignant tumours of the liver; 1 with primary hepatoma.

INTERVENTIONS

Computed portography for preoperative staging; laparotomy and ultrasonographic examination of the liver; cryosurgical ablation of liver tumours with or without a concomitant resection. Thirteen procedures were performed on 11 patients.

MAIN OUTCOME MEASURES

Preoperative morbidity, disease-free and overall survival.

RESULTS

Of 24 lesions frozen, the procedure on 4 lesions was considered a technical failure because of persistent disease. There were no perioperative deaths. One patient had a liver abscess that resolved with percutaneous drainage. One patient had a biliary fistula that resolved spontaneously, and one had a transient rise in the serum creatinine level. Of 11 patients treated, 7 had a recurrence in the liver (persistent disease in 2 and new liver metastases in 5); 2 of these patients died. One patient died of distant disease with no local recurrence. At the time of writing, one patient was alive with extrahepatic disease and no local recurrence and two were free of disease.

CONCLUSIONS

Cryosurgery of the liver is a relatively safe procedure that allows treatment of otherwise unresectable malignant disease. Proof of long-term benefit requires further experience and follow-up.

Ultrasound monitoring in cannulation of the internal jugular vein: anatomic and technical considerations

OBJECTIVE

To examine the effect of variations in anatomic features and operator experience on the success and complication rates of sonographically monitored cannulation of the internal jugular vein.

PATIENTS AND METHODS

The authors prospectively collected data for ultrasound-monitored cannulation of the internal jugular vein in 150 patients. In all cases the radiologist recorded the side of puncture, the number of passes needed, the number of vein punctures (one or two), whether the walls were opposed during puncture and any complications. For the last 80 patients the following information was also recorded: the distance from the skin to the internal jugular vein, the diameter of the vein with the Valsalva manoeuvre and the location of the vein relative to the carotid artery. All but three of the cannulations were performed by one of three radiologists, all of whom had at least 5 years of experience.

RESULTS

Cannulation was successful in all of the patients, and the first pass was successful in 133 (88.7%). These results are better than those of blind placement techniques reported in the literature. The only complications were hematoma and carotid puncture, which both occurred in the same two patients (1.3%). There was no significant difference among the radiologists in the number of passes needed (one-way analysis of variance, p > 0.05). The number of passes was independent of anatomic factors, including depth from skin, vein diameter or relative location. However, significantly more passes were needed for left-side punctures than for right-side punctures (Student t-test, p < 0.05).

CONCLUSIONS

Real-time ultrasound monitoring is superior to blind techniques in cannulation of the internal jugular vein because of its ease, accuracy and safety. Sonographic real-time monitoring minimizes the impact of anatomic factors on success and complication rates. It is a safe and efficacious approach that should be preferred in the placement of central lines.

Outpatient percutaneous nephrostomy

PURPOSE

To assess the feasibility of performing percutaneous nephrostomy (PCN) on an outpatient basis in a select group of patients.

MATERIALS AND METHODS

In 6 years, 60 PCN procedures were performed in a subgroup of 48 patients (22 men, 26 women) carefully selected from a larger group of 881 nephrostomy procedures in 589 patients. Exclusion criteria included hypertension; untreated urinary tract infection, coagulopathy, and staghorn calculi. Indications were calculus (n = 17), benign stricture (n = 10), and malignant ureteric obstruction (n = 21).

RESULTS

There was 100% technical success. Six of 48 patients (12%) were admitted within a week of PCN; there were no cost savings in these patients. Three of these patients (6%) were admitted as a direct consequence of PCN; one had sepsis, one had bleeding, and one was unable to manage the PCN tube. Outpatient treatment saved the cost of hospitalization in 42 patients (88%).

CONCLUSION

Outpatient PCN is feasible and safe in carefully selected patients and yields major cost savings because it precludes hospital admission.

Embolization of the uterine arteries before termination of a 15-week cervical pregnancy

The authors describe a patient with a 15-week cervical pregnancy after in-vitro fertilization. The pregnancy was safely aborted after preoperative embolization of the uterine arteries. Fertility was preserved.

Indium-111 chloride scintigraphy in adult osteomyelitis

Osteomyelitis is a common clinical problem that may be difficult to diagnose. We compared the performance of indium-111-labeled white cells ([111In]WBC) to 111In chloride ([111In]Cl) in two groups of adult patients suspected to have osteomyelitis or septic arthritis. Using [111In] WBC, 52 scans were performed on 51 patients. Nineteen patients had osteomyelitis. The sensitivity was 84% and specificity 82%. Using [111In]Cl, 48 scans were performed on 47 patients. Twelve had osteomyelitis. Sensitivity was 91%, and specificity was 89%. In each group, one false-negative study occurred in vertebral osteomyelitis. Three false-negative studies using [111In]WBC were due to failure to distinguish between combined bone and soft-tissue infection and soft-tissue infection alone. False-positive studies in both groups were due to overlying soft-tissue infection or inflammatory arthritis. Chi-squared test showed no significant difference in performance between the two agents. Indium-111 chloride is easier to prepare and use than [111In]WBC, which requires a time-consuming labeling process.