Percutaneous MR Imaging–Guided Cryoablation of Small Renal Masses in a 3-T Closed-Bore MR Imaging Environment: Initial Experience

Purpose

To assess the feasibility of percutaneous magnetic resonance (MR) imaging–guided cryoablation of small renal masses (SRMs) in a 3-T environment and to evaluate intraprocedural imaging, procedural safety, and initial outcomes.

Magnetic Resonance Imaging–Guided Vacuum-Assisted Breast Biopsy: An Initial Experience in a Community Hospital

Objective

To evaluate the effectiveness in diagnosing mammographically and sonographically occult breast lesions by using magnetic resonance imaging (MRI) guided vacuum-assisted breast biopsy in patients who presented to a community-based hospital with a newly established breast MRI program.

Methods

The records of 142 consecutive patients, median age of 55 years, who had undergone MRI-guided biopsy at our institution between July 2006 and July 2007 were reviewed. From these patients, 197 mammographically and sonographically occult lesions were biopsied at the time of discovery. The pathology was then reviewed and correlated with the MRI findings.

Results

Cancer was present and subsequently discovered in 8% of the previously occult lesions (16/197) or 11% of the women studied (16/142). Of the cancerous lesions, 56% were invasive carcinomas (9/16) and 44% were ductal carcinomas in situ (7/16). Fourteen percent of the discovered lesions (28/197) were defined as high risk and included atypical ductal hyperplasia, atypical lobular hyperplasia, lobular carcinoma in situ, and radial scar. In total, occult cancerous and high-risk lesions were discovered in 22% of the found lesions (44/197) or 31% of the women who underwent MRI-guided biopsy (44/142).

Conclusions

This study demonstrated that detection of cancerous and high-risk lesions can be significantly increased when an MRI-guided biopsy program is introduced at a community-based hospital. We believe that as radiologists gain confidence in imaging and histologic correlation, community-based hospitals can achieve similar rates of occult lesion diagnosis as those found in data emerging from academic institutions.     

Mistargeting after Fusion Imaging–Guided Percutaneous Radiofrequency Ablation of Hepatocellular Carcinomas

PurposeTo evaluate the incidence and causes of mistargeting after fusion imaging–guided percutaneous radiofrequency (RF) ablation of hepatocellular carcinomas (HCCs).Materials and MethodsBetween September 2011 and March 2013, 955 HCCs in 732 patients were treated with percutaneous RF ablation. Among them, ablation of 551 HCCs was accomplished under fusion imaging guidance, and seven mistargetings were noted in seven patients (male-to-female ratio = 6:1; mean age, 60.1 y; range, 47–73 y). The incidence of mistargeting and the cause of liver disease in the patients with mistargeting were evaluated. The causes of mistargeting were assessed according to the following classification: small size of HCC, subcapsular location, subphrenic location, confusion with pseudolesions, poor conspicuity of HCC, poor sonographic window, and poor electrode path.ResultsThe incidence of mistargeting after fusion imaging–guided RF ablation was 1.3% (7 of 551). All patients with mistargeting were hepatitis B virus carriers. The most common cause of mistargeting was the small size of HCC (100%; 7 of 7), followed by confusion with surrounding pseudolesions (85.7%; 6 of 7), subcapsular (71.4%; 5 of 7) and subphrenic locations (71.4%; 5 of 7), poor conspicuity of the HCC (71.4%; 6 of 7), poor sonographic window (28.6%; 2 of 7), and poor electrode path (28.6%; 2 of 7).ConclusionsThe incidence of mistargeting after fusion imaging–guided RF ablation was 1.3%. The most common cause of mistargeting was the small size of HCC, followed by confusion with surrounding pseudolesions, subcapsular and subphrenic locations, and poor conspicuity of the HCC.     

Cone-Beam Computed Tomography–Guided Percutaneous Radiologic Gastrostomy

The purpose of this study was to investigate the feasibility of a flat-detector C-arm–guided radiographic technique (cone-beam computed tomography [CBCT]) for percutaneous radiologic gastrostomy (PRG) insertion. Eighteen patients (13 men and 5 women; mean age 62 years) in whom percutaneous endoscopic gastrostomy (PEG) had failed underwent CBCT-guided PRG insertion. PEG failure or unsuitability was caused by upper gastrointestinal tract obstruction in all cases. Indications for gastrostomy were esophageal and head and neck malignancies, respectively. Before the PRG procedure, initial C-arm CBCT scans were acquired. Three- and 2-dimensional soft-tissue reconstructions of the epigastrium region were generated on a dedicated workstation. Subsequently, gastropexy was performed with T-fasteners after CBCT-guided puncture of the stomach bubble, followed by insertion of an 14F balloon-retained catheter through a peel-away introducer. Puncture of the stomach bubble and PRG insertion was technically successful in all patients without alteration of the epigastric region. There was no malpositioning of the tube or other major periprocedural complications. In 2 patients, minor complications occurred during the first 30 days of follow-up (PRG malfunction: n = 1; slight infection: n = 1). Late complications, which were mainly tube disturbances, were observed in 2 patients. The mean follow-up time was 212 days. CBCT-guided PRG is a safe, well-tolerated, and successful method of gastrostomy insertion in patients in whom endoscopic gastrostomy is not feasible. CBCT provides detailed imaging of the soft tissue and surrounding structures of the epigastric region in one diagnostic tour and thus significantly improves the planning of PRG procedures.     

Can Iterative Reconstruction Improve Imaging Quality for Lower Radiation CT Perfusion? Initial Experience

BACKGROUND AND PURPOSE:Initial results using IR for CT of the head showed satisfactory subjective and objective imaging quality with a 20–40% radiation dose reduction. The aim of our study was to compare the influence of IR and FBP algorithms on perfusion parameters at standard and lowered doses of CTP.MATERIALS AND METHODS:Forty patients with unilateral carotid stenosis post–carotid stent placement referred for follow-up CTP were divided into 2 groups (tube currents were 100 mAs in group A and 80 mAs in group B). Datasets were reconstructed with IR and FBP algorithms; and SNRs of gray matter, white matter, and arterial and venous ROIs were compared. CBF, CBV, and MTT means and SNRs were evaluated by using linear regression, and qualitative imaging scores were compared across the 2 algorithms.RESULTS:The mean effective radiation dose of group B (2.06 mSv) was approximately 20% lower than that of group A (2.56 mSv). SNRs for ROIs in the dynamic contrast-enhanced images were significantly higher than those for the FBP images. Correlations of the SNRs for CBF, CBV, and MTT across the 2 algorithms were moderate (R² = 0.46, 0.23, and 0.44, respectively). ROIs in gray matter rather than the IR algorithm predicted increasing SNRs in all CBF, CBV, and MTT maps. Two cases of significant restenosis were confirmed in both algorithms. CBV, CBF, and MTT imaging scores did not differ significantly across algorithms or groups.CONCLUSIONS:Lower dose CTP (20% below normal dose) without IR can effectively identify oligemic tissue in poststenting follow-up. IR does not alter the absolute values or increase the SNRs of perfusion parameters. Other methods should be attempted to improve SNRs in settings with low tube currents.

IR has been shown to be an effective reconstruction method for improving imaging quality at low radiation doses in CT of the chest and abdomen.^1–3 Current IR techniques attempt to formulate image reconstruction as an optimization problem in both signal space and imaging space. The noisiest measurements are given low weight in the iterative process by an intensive computerized process and, therefore, contribute very little to the final image.⁴ Initial results by using IR for CT of the head showed satisfactory subjective and objective imaging quality with a 20%–40% radiation dose reduction.^3,5,6 An integrated IR algorithm iDose⁴ (Philips Healthcare, Best, the Netherlands) has recently been developed, which consists of the following 2 de-noising components: an iterative maximum likelihood-type sinogram restoration method based on Poisson noise distribution and a local structure model fitting on image data that iteratively decreases the uncorrelated noise. In clinical practice, the users can adjust the image noise by inputting a parameter called “iDose level.”⁷In 2009, the FDA raised concern about the radiation dose accompanying brain CTP in daily neurovascular examinations.⁸ CTP has been widely used to evaluate hemodynamic changes in the brains of patients with stenotic-occlusive diseases and those with subarachnoid hemorrhage.^9,10 In combination with CT angiography, it serves as an excellent triage tool for patients with acute ischemic insults who may benefit from thrombolytic therapy within and beyond the therapeutic time window.^11,12 With quick acquisition processes and lower radiation doses, CTP serves as a potential peritherapeutic hemodynamic monitoring tool for patients with neurovascular disorders.There are 2 approaches to lowering radiation doses during CTP. Prolonged scanning intervals can reduce the dose by 25%–58%, depending on the frequency of sampling on the time-attenuation curve. For a fixed sampling frequency, the radiation dose of diagnostic-qualitative MTT mapping can be decreased to 58.3%.^13,14 For an alternative sampling frequency in the arterial and venous phases, the maximum interval to provide an absolute CBF value is 1.5 seconds in the arterial phase and 3 seconds in the venous phase, resulting in a dose reduction of approximately 38%.^14–16 Keeping the kilovolt(peak) at the level of 80 is recommended to provide the best contrast-to-noise ratio for CTP.¹⁷ These temporal variables dominate the SNRs in CTP.¹⁶ Lowering the tube current is the second method used to decrease the radiation dose. Its influence on hemodynamic parameters such as CBV, CBF, and MTT is not well-understood. The aim of this study was to explore the effects of IR on the imaging quality of primary enhanced images and color maps of hemodynamic parameters in CTP in a setting of lower tube currents.     

Safety and Therapeutic Efficacy of Complete or Near-Complete Ablation of Symptomatic Uterine Fibroid Tumors by MR Imaging–Guided High-Intensity Focused US Therapy

PurposeTo evaluate the safety and therapeutic efficacy of magnetic resonance (MR) imaging–guided high-intensity focused ultrasound (US) ablation of symptomatic uterine fibroid tumors with an immediate nonperfused volume (NPV) ratio of 80% or more.Materials and MethodsA total of 79 women with 117 uterine tumors were treated with MR-guided high-intensity focused US ablation. Immediate NPV, complications, and therapeutic efficacy (tumor volume reduction ratio and symptom severity score [SSS] decrease at 3-mo follow-up) were retrospectively assessed. Statistical comparisons of the frequency of complications and therapeutic efficacy were performed between patients with NPV ratios of at least 80% and less than 80%.ResultsTechnical success was achieved in 93.7% of cases (n = 74) of cases, and the immediate NPV ratio was 62.7% ± 25.5. Twenty-four patients exhibited an NPV ratio of at least 80% (89.7% ± 5.8), and 50 patients showed an NPV ratio of less than 80% (49.8% ± 20.7). All complications were minor in severity, and the incidences were not significantly different between groups (P > .05). The 3-month volume reduction ratio was significantly greater in patients with an NPV ratio of at least 80% (0.43 ± 0.17) than in those with an NPV ratio of less than 80% (0.20 ± 0.26; P = .002), although the decreases in SSS were not significantly different (20.9 ± 19.6 vs 12.1 ± 10.1; P = .097).ConclusionsIn MR-guided high-intensity focused US ablation of symptomatic uterine fibroid tumors, achievement of an immediate NPV ratio of at least 80% is safe, with greater tumor volume shrinkage compared with cases with a lower NPV ratio.     

Percutaneous CT–Guided Sympathicolysis with Radiofrequency for the Treatment of Palmar Hyperhidrosis

Purpose

To evaluate the benefits of computed tomography (CT)–guided percutaneous sympathicolysis with radiofrequency in patients with primary palmar hyperhidrosis (PPHH) in terms of safety, patient satisfaction, and short- and long-term efficacy.

Frequency and Risk Factors of Various Complications After Computed Tomography–Guided Radiofrequency Ablation of Lung Tumors

Objective To retrospectively determine the frequency and risk factors of various side effects and complications after percutaneous computed tomography–guided radiofrequency (RF) ablation of lung tumors. Methods We reviewed and analyzed records of 112 treatment sessions in 57 of our patients (45 men and 12 women) with unresectable lung tumors treated by ablation. Risk factors, including sex, age, tumor diameter, tumor location, history of surgery, presence of pulmonary emphysema, electrode gauge, array diameter, patient position, maximum power output, ablation time, and minimum impedance during ablation, were analyzed using univariate and multivariate analyses. Results Total rates of side effects and minor and major complications occurred in 17%, 50%, and 8% of treatment sessions, respectively. Side effects, including pain during ablation (46% of sessions) and pleural effusion (13% of sessions), occurred with RF ablation. Minor complications, including pneumothorax not requiring chest tube drainage (30% of sessions), subcutaneous emphysema (16% of sessions), and hemoptysis (9% of sessions) also occurred after the procedure. Regarding major complications, three patients developed fever >38.5°C; three patients developed abscesses; two patients developed pneumothorax requiring chest tube insertion; and one patient had air embolism and was discharged without neurologic deficit. Univariate and multivariate analyses suggested that a lesion located ≤1 cm of the chest wall was significantly related to pain (p < 0.01, hazard index 5.76). Risk factors for pneumothorax increased significantly with previous pulmonary surgery (p < 0.05, hazard index 6.1) and presence of emphysema (p <0.01, hazard index 13.6). Conclusion The total complication rate for all treatment sessions was 58%, and 25% of patients did not have any complications after RF ablation. Although major complications can occur, RF ablation of lung tumors can be considered a safe and minimally invasive procedure.     

Percutaneous Computed Tomography–guided High-Dose-Rate Brachytherapy Ablation of Breast Cancer Liver Metastases: Initial Experience with 80 Lesions

PurposeTo analyze initial experience with computed tomography–guided high-dose-rate brachytherapy (CT-HDRBT) ablation of breast cancer liver metastases (BCLM).Materials and MethodsBetween January 2008 and December 2010, 37 consecutive women with 80 liver metastases were treated with CT-HDRBT in 56 sessions. Mean age was 58.6 years (range, 34–83 y). Treatment was performed by CT-guided applicator placement and high-dose-rate brachytherapy with an iridium-192 source. The mean radiation dose was 18.57 Gy (standard deviation 2.27). Tumor response was evaluated by gadoxetic acid–enhanced liver magnetic resonance (MR) imaging performed before treatment, 6 weeks after treatment, and every 3 months thereafter.ResultsTwo patients were lost to follow-up; the remaining 35 patients were available for MR imaging evaluation for a mean follow-up time of 11.6 months (range 3–32 mo). Mean tumor diameter was 25.5 mm (range 8–74 mm). Two (2.6%) local recurrences were observed after local tumor control for 10 months and 12 months. Both local progressions were successfully retreated. Distant tumor progression (new metastases or enlargement of nontreated metastases) occurred during the follow-up period in 11 (31.4%) patients. Seven (20%) patients died during the follow-up period. Overall survival ranged from 3–39 months (median 18 months).ConclusionsCT-HDRBT is a safe and effective ablative therapy, providing a high rate of local tumor control in patients with BCLM.     

Initial Experience with CT–Guided High-Dose-Rate Brachytherapy in the Multimodality Treatment of Neuroendocrine Tumor Liver Metastases

Purpose

To evaluate efficacy of computed tomography (CT)–guided high-dose-rate brachytherapy (HDRBT) of neuroendocrine liver metastases (NELM) with the goal of local tumor control (LTC).

Endoscopic or Percutaneous Biliary Drainage for Klatskin Tumors?

PurposeControversy exists regarding the preferred biliary drainage technique in patients with Klatskin tumors because few comparative studies exist. This study compared outcomes of endoscopic biliary drainage (EBD) and percutaneous transhepatic biliary drainage (PTBD).Materials and MethodsConsecutive patients (N = 129) with Klatskin tumors treated with initial EBD or PTBD were identified, and their clinical histories were retrospectively reviewed. The primary endpoint was the time to therapeutic success (TTS), defined as the time between the first drainage and a total bilirubin measurement of 40 μmol/L or lower.ResultsEBD was the first biliary decompression procedure performed in 87 patients; PTBD was performed first in 42. Technical success rates (78% with EBD vs 98% with PTBD; P = .004) and therapeutic success rates (49% vs 79%, respectively; P = .002) were significantly lower in the EBD group than in the PTBD group. Forty-four patients in the EBD group (51%) subsequently underwent PTBD before therapeutic success was achieved or antitumoral treatment was started. Median TTSs were 61 days in the EBD group and 44 days in the PTBD group, and multivariate analysis showed a hazard ratio of 0.63 (95% confidence interval, 0.41–0.99; P = .045). In patients treated with surgery or chemotherapy with or without radiation therapy, median times to treatment were 76 and 68 days in the EBD and PTBD groups, respectively (P = .76). Cholangitis occurred in 25% and 21% of patients in the EBD and PTBD groups, respectively (P = .34).ConclusionsPTBD should be seriously considered for biliary decompression when treating patients with Klatskin tumor.     

CT–Guided Microwave Ablation of 45 Renal Tumors: Analysis of Procedure Complexity Utilizing a Percutaneous Renal Ablation Complexity Scoring System

Purpose

To develop a scoring system that stratifies complexity of percutaneous ablation of renal tumors.

Percutaneous Cryoablation of Metastatic Lesions from Non–Small-Cell Lung Carcinoma: Initial Survival,Local Control,and Cost Observations

PurposeTo assess feasibility, complications, local tumor recurrences, overall survival (OS), and estimates of cost effectiveness for multisite cryoablation (MCA) of oligometastatic non–small-cell lung cancer (NSCLC).Materials and MethodsA total of 49 computed tomography- and/or ultrasound-guided percutaneous MCA procedures were performed on 60 tumors in 31 patients (19 women and 12 men) with oligometastatic NSCLC. Average patient age was 65 years. Tumor location was grouped according to common metastatic sites. Median OS was determined by Kaplan–Meier method and defined life-years gained (LYGs). Estimates of MCA costs per LYG were compared with established values for systemic therapies.ResultsTotal numbers of tumors and cryoablation procedures for each anatomic site were as follows: lung, 20 and 18; liver, nine and seven; superficial, 12 and 11; adrenal, seven and seven; paraaortic/isolated, two and two; and bone, 10 and seven. A mean of 1.6 procedures per patient were performed, with a median clinical follow-up of 11 months. Major complication and local recurrence rates were 8% (four of 49) and 8% (five of 60), respectively. Median OS for MCA was 1.33 years, with an estimated 1-year survival rate of approximately 53%. MCA appeared cost-effective even when added to the cost of best supportive care or systemic regimens, with an adjunctive cost-effectiveness ratio of $49,008–$87,074.ConclusionsMCA was associated with very low morbidity and local tumor recurrence rates for all anatomic sites, and possibly increased OS. Even as an adjunct to systemic therapies, MCA appeared cost-effective for palliation of oligometastatic NSCLC.     

Iron-Oxide Nanocluster Labeling of Clostridium novyi-NT Spores for MR Imaging–Monitored Locoregional Delivery to Liver Tumors in Rat and Rabbit Models

PurposeTo label Clostridium novyi-NT spores (C. novyi-NT) with iron oxide nanoclusters and track distribution of bacteria during magnetic resonance (MR) imaging-monitored locoregional delivery to liver tumors using intratumoral injection or intra-arterial transcatheter infusion.Materials and MethodsVegetative state C. novyi-NT were labeled with iron oxide particles followed by induction of sporulation. Labeling was confirmed with fluorescence microscopy and transmission electron microscopy (TEM). T2 and T2* relaxation times for magnetic clusters and magnetic microspheres were determined using 7T and 1.5T MR imaging scanners. In vitro assays compared labeled bacteria viability and oncolytic potential to unlabeled controls. Labeled spores were either directly injected into N1-S1 rodent liver tumors (n = 24) or selectively infused via the hepatic artery in rabbits with VX2 liver tumors (n = 3). Hematoxylin-eosin, Prussian blue, and gram staining were performed. Statistical comparison methods included paired t-test and ANOVA.ResultsBoth fluorescence microscopy and TEM studies confirmed presence of iron oxide labels within the bacterial spores. Phantom studies demonstrated that the synthesized nanoclusters produce R2 relaxivities comparable to clinical agents. Labeling had no significant impact on overall growth or oncolytic properties (P >.05). Tumor signal-to-noise ratio (SNR) decreased significantly following intratumoral injection and intra-arterial infusion of labeled spores (P <.05). Prussian blue and gram staining confirmed spore delivery.ConclusionsC. novyi-NT spores can be internally labeled with iron oxide nanoparticles to visualize distribution with MR imaging during locoregional bacteriolytic therapy involving direct injection or intra-arterial transcatheter infusion.