Musculoskeletal Interventional Radiology: Radiofrequency Ablation

Histotripsy Ablation of Bone Tumors: Feasibility Study in Excised Canine Osteosarcoma Tumors

Osteosarcoma (OS) is a primary bone tumor affecting both dogs and humans. Histotripsy is a non-thermal, non-invasive focused ultrasound method using controlled acoustic cavitation to mechanically disintegrate tissue. In this study, we investigated the feasibility of treating primary OS tumors with histotripsy using a 500-kHz transducer on excised canine OS samples harvested after surgery at the Veterinary Teaching Hospital at Virginia Tech. Samples were embedded in gelatin tissue phantoms and treated with the 500-kHz histotripsy system using one- or two-cycle pulses at a pulse repetition frequency of 250 Hz and a dosage of 4000 pulses/point. Separate experiments also assessed histotripsy effects on normal canine bone and nerve using the same pulsing parameters. After treatment, histopathological evaluation of the samples was completed. To determine the feasibility of treating OS through intact skin/soft tissue, additional histotripsy experiments assessed OS with overlying tissues. Generation of bubble clouds was achieved at the focus in all tumor samples at peak negative pressures of 26.2 ± 4.5 MPa. Histopathology revealed effective cell ablation in treated areas for OS tumors, with no evidence of cell death or tissue damage in normal tissues. Treatment through tissue/skin resulted in generation of well-confined bubble clouds and ablation zones inside OS tumors. Results illustrate the feasibility of treating OS tumors with histotripsy.

Current updates in image-guided musculoskeletal interventions

Image-guided musculoskeletal interventions are frequently done in clinical practice. Even then, the literature regarding their effectiveness is relatively scarce. Image guidance adds value over the conventional landmark-based approach and should be preferred. We hereby try to list the commonly performed procedures along with the current practice guidelines regarding their clinical indications and periprocedural care.

Effectiveness and reliability of traditional open surgery in atypical localizations of osteoid osteoma

Objectives

This study aims to evaluate traditional open surgery results of osteoid osteomas (OOs) in atypical localizations and explore whether open surgery can be a safe alternative in localizations where radiofrequency ablation (RFA) may not be suitable.

Patients and methods

A total of 26 patients (20 males, 6 females; mean age 23.3±14.2 years; range, 4 to 65 years) having OO in atypical localizations between January 2008 and January 2017 were retrospectively evaluated. All patients underwent traditional open surgery under anesthesia. All patients were followed-up, and their clinical success and complications were evaluated. The pain intensity was assessed using the visual analog scale (VAS).

Results

The postoperative first year VAS score was 0.2±0.5 (range, 0-2) (p<0.005). None of the patients showed any complications. No recurrences were reported at the end of the first year. All patients were relieved from pain due to OO in atypical localizations.

Conclusion

Although RFA has been accepted as the preferred treatment for OO, traditional open surgery may still be used for OO in atypical localizations yielding perfect clinical results with fewer complications. It is a safe alternative for localizations such as carpal bones, distal ulna, hand and foot where RFA complications can be seen more frequently. In these localizations, traditional open surgery can be recommended as the first treatment choice.

Therapeutic exercise and radiofrequency in the rehabilitation project for hip osteoarthritis pain

BACKGROUND

Severe hip osteoarthritis is responsible for disabling pain and functional impairment of the joint. Although total hip arthroplasty (THA) is a successful treatment, some patients have multiple comorbidities that represent contraindications for THA. Conventional drug therapies are often ineffective or responsible for numerous side effects. For these patients, it is difficult to draw up an acceptable rehabilitation path, as the main limitation is intense pain. New rehabilitation strategies that relieve pain and improve articular function need to be developed. The combination of traditional treatments such as education and therapeutic exercise with innovative, minimally-invasive therapies such as continuous radiofrequency (CRF) appears to reduce hip pain by determining the neurolysis of the joint.

AIM

The aim of our study was to describe the reduction in pain and improvements in joint function when CRF is combined with the therapeutic exercise in rehabilitation of patients with severe hip osteoarthritis.

DESIGN

Case series study.

SETTING

Rehabilitation service outpatients.

POPULATION

Twenty-five patients with severe hip osteoarthritis causing disabling pain and with contraindications to THA, and for whom conventional drug therapies were ineffective or responsible for numerous side effects.

METHODS

The study design included: initial clinical-functional assessment using the Harris Hip Score (HHS), the Numeric Rating Scale (NRS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC); a pre-lesion anaesthetic block; hip neuroablation with CRF; a three-week kinesitherapy protocol (3 sessions per week); two further assessments using the same scales one month (T1) and six months (T2) after CRF.

RESULTS

Improvements at T1 and T2 follow-ups, after CRF (P=0.000) were recorded for articular pain and function. However, results at T2 were worse than those at T1 (P=0.000).

CONCLUSIONS

CRF combined with therapeutic exercise in rehabilitation of severe hip osteoarthritis is an attractive option for significant pain relief as it allows patients to carry out kinesitherapy more easily.

CLINICAL REHABILITATION IMPACT

CRF could represent a valid alternative in the rehabilitation of patients with severe hip osteoarthritis especially when other therapeutic approaches are unworkable.

Procedural Treatments for Knee Osteoarthritis: A Review of Current Injectable Therapies

Knee osteoarthritis is a common painful degenerative condition affecting the aging Canadian population. In addition to pain and disability, osteoarthritis is associated with depression, comorbid conditions such as diabetes, and increased caregiver burden. It is predicted to cost the Canadian healthcare system $7.6 billion dollars by 2031. Despite its high cost and prevalence, controversy persists in the medical community regarding optimal therapies to treat knee osteoarthritis. A variety of medications like nonsteroidal anti-inflammatories and opioids can cause severe side effects with limited benefits. Total knee arthroplasty, although a definitive management, comes with risk such as postoperative infections, revisions, and chronic pain. Newer injectable therapies are gaining attention as alternatives to medications because of a safer side effect profile and are much less invasive than a joint replacement. Platelet-rich plasma is beginning to replace the more common injectable therapies of intra-articular corticosteroids and hyaluronic acid, but larger trials are needed to confirm this effect. Small studies have examined prolotherapy and stem cell therapy and demonstrate some benefits. Trials involving genicular nerve block procedures have been successful. As treatments evolve, injectable therapies may offer a safe and effective pathway for patients suffering from knee osteoarthritis.

Acute myonecrosis on MRI: etiologies in an oncological cohort and assessment of interobserver variability

OBJECTIVE

To determine the etiologies of myonecrosis in oncology patients and to assess interobserver variability in interpreting its MRI features.

MATERIALS AND METHODS

Pathology records in our tertiary cancer hospital were searched for proven myonecrosis, and MRIs of affected regions in those patients were identified. MRI reports that suggested myonecrosis were also identified. Each MRI was reviewed independently by 2 out of 6 readers to assess anatomical site, size, and signal intensities of muscle changes, and the presence of the previously reported stipple sign (enhancing foci within a region defined by rim enhancement). The stipple sign was assessed again, weeks after a training session. Cohen kappa and percentage agreement were calculated. Medical records were reviewed for contemporaneous causes of myonecrosis.

RESULTS

MRI reports in 73 patients suggested the diagnosis of myonecrosis; pathological proof was available in another 2. Myonecrosis was frequently associated with radiotherapy (n = 34 patients, 45 %); less frequent causes included intraoperative immobilization, trauma, therapeutic embolization, ablation therapy, exercise, and diabetes. Myonecrosis usually involved the lower extremity, the pelvis, and the upper extremity; mean size was 13.0 cm. The stipple sign was observed in 55-100 % of patients at first assessment (κ = 0.09-0.42; 60-80 % agreement) and 55-100 % at second (κ = 0.0-0.58; 72-90 % agreement). Enhancement surrounded myonecrosis in 55-100 % patients (κ = 0.03-0.32; 58-70 % agreement).

CONCLUSION

Myonecrosis in oncology patients usually occurred after radiotherapy, and less commonly after intraoperative immobilization, trauma, therapeutic embolization, ablation therapy, exercise, or diabetes. Although interobserver variability for MRI features of myonecrosis exists (even after focused training), a combination of findings facilitates diagnosis and conservative management.

Radiofrequency thermo-ablation of PVNS in the knee: initial results

INTRODUCTION

Pigmented villonodular synovitis (PVNS) is normally treated by arthroscopic or open surgical excision. We present our initial experience with radiofrequency thermo-ablation (RF ablation) of PVNS located in an inaccessible location in the knee.

MATERIALS

Review of all patients with histologically proven PVNS treated with RF ablation and with at least 2-year follow-up.

RESULTS

Three patients met inclusion criteria and were treated with RF ablation. Two of the patients were treated successfully by one ablation procedure. One of the three patients had a recurrence which was also treated successfully by repeat RF ablation. There were no complications and all patients returned to their previous occupations following RF ablation.

CONCLUSION

In this study we demonstrated the feasibility of performing RF ablation to treat PVNS in relatively inaccessible locations with curative intent. We have also discussed various post-ablation imaging appearances which can confound the assessment for residual/recurrent disease.

Ultrasound-guided radiofrequency ablation of early breast cancer in a resection specimen: lessons for further research

PURPOSE

To assess the feasibility and effectiveness of radiofrequency ablation (RFA) in breast cancer, using different histopathologic staining methods to evaluate tissue viability.

MATERIALS AND METHODS

In twenty patients with unifocal small (≤1, 5 cm) invasive ductal carcinoma, ultrasound-guided RFA was performed immediately after surgery. Cell viability was assessed using cytokeratin 8 (CK 8) and nicotinamide adenine dinucleotide diaphorase (NADHD) in addition to hematoxylin-eosin (HE).

RESULTS

At histopathological examination, ex vivo RFA resulted in complete cell death of the target lesion in 17/20 patients. In two cases viable ductal carcinoma in situ (DCIS) was found just outside the completely ablated lesion.

CONCLUSION

RFA of small invasive breast cancer seems to be a feasible treatment option. Both NADHD and CK 8 demonstrate a clear and comparable demarcation between viable and non-viable tissue. A high level of accuracy is required in proper positioning of the needle electrode and a "hot retraction" is mandatory.

Irreversible electroporation ablation: is all the damage nonthermal?

PURPOSE

To determine whether high-dose irreversible electroporation (IRE) ablation induces thermal effects in normal liver tissue.

MATERIALS AND METHODS

Animal care and use committee approval was obtained prior to the experiments. IRE ablation (n = 78) was performed by a single four-person team in vivo in 22 porcine livers by applying electric current to two 1.3-cm-diameter circular flat-plate electrodes spaced 1 cm apart. Cardiac-gated IRE pulses (n = 40-360) were systematically applied at varying voltages (1500-2900 V). End temperatures at the ablation zone center were measured and were correlated with ablation time, energy parameters, and resultant treatment effect as determined at gross pathologic and histopathologic examination. Temperatures were then monitored at the center and periphery of four ablations created by using a four-electrode IRE array (3000 V, 90 pulses per electrode pair). Data were analyzed by using multivariate analysis of variance with multiple comparisons and/or paired t tests and regression analysis, as appropriate.

RESULTS

Temperature rose above the 34°C baseline after IRE in all flat-plate experiments and correlated linearly (R(2) = 0.39) with IRE "energy dose" (product of voltage and number of pulses) and more tightly in univariate analysis with both voltage and number of pulses. Thus, mean temperatures as high as 86°C ± 3 (standard deviation) were seen for 2500 V and 270 pulses. Ablations of 90 pulses or more at 2500 V produced temperatures of 50°C or greater and classic gross and histopathologic findings of thermal coagulation (pyknotic nuclei and streaming cytoplasm). For lower IRE doses (ie, 2100 V, 90 pulses), temperatures remained below 45°C, and only IRE-associated pathologic findings (ie, swollen sinusoids, dehydrated cells, and hemorrhagic infiltrate) were seen. For the four-electrode arrays, temperatures measured 54.2°C ± 6.1 at the electrode surfaces and 38.6°C ± 3.2 at the ablation zone margin.

CONCLUSION

In some conditions of high intensity, IRE can produce sufficient heating to induce "white zone" thermal coagulation. While this can be useful in some settings to increase tumor destruction, further characterization of the thermal profile created with clinical electrodes and energy parameters is therefore needed to better understand the best ways to avoid unintended damage when ablating near thermally sensitive critical structures.

Thermal ablation a comparison of thermal dose required for radiofrequency-, microwave-, and laser-induced coagulation in an ex vivo bovine liver model

RATIONALE AND OBJECTIVES

To compare thermal dosimetry metrics for specified diameters of coagulation achieved using three different ablation energy sources.

MATERIALS AND METHODS

204 ablations measuring 20, 30, or 40 +/- 2 mm were created in an ex-vivo bovine liver model using 1) 2.5 cm cluster RF electrodes (n = 114), 2) 3 cm microwave antennas (n = 45), and 3) 3 cm laser diffusing fibers (n = 45). Continuous temperature monitoring was performed 5-20 mm from the applicators to calculate: a) the area under the curve (AUC), b) cumulative equivalent minutes at 43 degrees C (CEM43), and c) Arrhenius damage integral (Omega) for the critical ablation margin (DOC), with results compared by multivariate analysis of variance and regression analysis.

RESULTS

The end temperatures at the margin of coagulation varied, and was lowest for the RF cluster electrode (33-58 degrees C), higher for laser (52-72 degrees C), and covered the widest range for microwave (42-95 degrees C). These end temperatures correlated with applied energy, as linear functions (r(2) = 0.74-0.96). The total heat needed to achieve ablation (AUC) varied with applied energy and coagulation diameter as negative exponential (RF and laser) or negative power (microwave) functions (r(2) = 0.82-0.98). Similarly, CEM43 values varied exponentially with energy and distance (r(2) = 0.52-0.76) over a wide range of values (10(12)). Likewise, Omega varied not only based upon energy source and DOC, but also as a positive linear correlation to applied energy and with sigmoid correlation to duration of ablation (r(2) = 0.85-0.97).

CONCLUSION

Our study demonstrates that the thermal dosimetry of ablation is not based solely on a fixed end temperature at the margin of the coagulation zone. Thermal dosimetry is not constant, but dependent on the type and amount of energy applied and distance suggesting the need to take into account the rate of heat transfer for ablation dosimetry.

Future directions in percutaneous vertebroplasty

The first percutaneous vertebroplasty, used to treat a painful cervical haemangioma, was performed by a French team in 1984 and reported in the literature in 1987. This technique has rapidly become the standard of care for treatment of medically refractory painful vertebral compression fractures. Vertebral fractures usually become evident because of pain of varying intensity that reduces the patient's quality of life, producing functional limitations, depression, disability, height loss, spinal instability and kyphotic deformity associated with impaired lung capacity. Many diseases may underlie vertebral compression fractures, such as osteoporosis, trauma, neoplasms and haemangioma. Vertebroplasty, as derived from our experience and a review of the literature data, has more than 70%-90% effectiveness for short-term pain reduction and return to activity. The aim of this paper was to describe the state of the art of this spinal interventional radiology procedure and to examine the future directions of percutaneous vertebroplasty.