Use of computed tomography (CT) in medicine comes with the responsibility of its appropriate (wise) and safe (gentle) application to obtain required diagnostic information with the lowest possible ...dose of radiation. CT provides useful information that may not be available with other imaging modalities in many clinical situations in children and adults. Inappropriate or excessive use of CT should be avoided, especially if required information can be obtained in an accurate and time-efficient manner with other modalities that require a lower radiation dose, or non-radiation-based imaging modalities such as ultrasonography and magnetic resonance imaging. In addition to appropriate use of CT, the radiology community also must monitor scanning practices and protocols. When appropriate, high-contrast regions and lesions should be scanned with reduced dose, but overly zealous dose reduction should be avoided for assessment of low-contrast lesions. Patients' cross-sectional body size should be taken into account to deliver lower radiation dose to smaller patients and children. Wise use of CT scanning with gentle application of radiation dose can help maximize the diagnostic value of CT, as well as address concerns about potential risks of radiation. In this article, key concepts in CT radiation dose are reviewed, including CT dose descriptors; radiation doses from CT procedures; and factors and technologies that affect radiation dose and image quality, including their use in creating dose-saving protocols. Also discussed are the contributions of radiation awareness campaigns such as the Image Gently and Image Wisely campaigns and the American College of Radiology Dose Index Registry initiatives.
Microwave ablation is the most recent development in the field of tumor ablation. The technique allows for flexible approaches to treatment, including percutaneous, laparoscopic, and open surgical ...access. With imaging guidance, the tumor is localized, and a thin (14.5-gauge) microwave antenna is placed directly into the tumor. A microwave generator emits an electromagnetic wave through the exposed, noninsulated portion of the antenna. Electromagnetic microwaves agitate water molecules in the surrounding tissue, producing friction and heat, thus inducing cellular death via coagulation necrosis. The main advantages of microwave technology, when compared with existing thermoablative technologies, include consistently higher intratumoral temperatures, larger tumor ablation volumes, faster ablation times, and an improved convection profile. Microwave ablation has promising potential in the treatment of primary and secondary liver disease, primary and secondary lung malignancies, renal and adrenal tumors, and bone metastases. The technology is still in its infancy, and future developments and clinical implementation will help improve the care of patients with cancer.
To retrospectively evaluate effectiveness, follow-up imaging features, and safety of microwave ablation in 50 patients with intraparenchymal pulmonary malignancies.
This HIPAA-compliant study was ...approved by the institutional review board; informed consent was waived. From November 10, 2003, to August 28, 2006, 82 masses (mean, 1.42 per patient) in 50 patients (28 men, 22 women; mean age, 70 years) were percutaneously treated in 66 microwave ablation sessions. Each tumor was ablated with computed tomographic (CT) guidance. Follow-up contrast material-enhanced CT and positron emission tomographic (PET) scans were reviewed. Mixed linear modeling and logistic regression were performed. Time-event data were analyzed (Kaplan-Meier survival estimates and log-rank statistic). All event times were the time to a patient's first event (alpha level = .05, all analyses).
At follow-up (mean, 10 months), 26% (13 of 50) of patients had residual disease at the ablation site, predicted by using index size of larger than 3 cm (P = .01). Another 22% (11 of 50) of patients had recurrent disease resulting in a 1-year local control rate of 67%, with mean time to first recurrence of 16.2 months. Kaplan-Meier analysis yielded an actuarial survival of 65% at 1 year, 55% at 2 years, and 45% at 3 years from ablation. Cancer-specific mortality yielded a 1-year survival of 83%, a 2-year survival of 73%, and a 3-year survival of 61%; these values were not significantly affected by index size of larger than 3 cm or 3 cm or smaller or presence of residual disease. Cavitation (43% 35 of 82 of treated tumors) was associated with reduced cancer-specific mortality (P = .02). Immediate complications included pneumothorax (Common Terminology Criteria for Adverse Events CTCAE grades 1 18 of 66 patients and 2 eight of 66 patients), hemoptysis (four of 66 patients), and skin burns (CTCAE grades 2 one of 66 patients and 3 one of 66 patients).
Microwave ablation is effective and may be safely applied to lung tumors. (c) RSNA, 2008.
Objectives
To define effectiveness and safety of CT-guided radiofrequency ablation (RFA) of renal tumours and prognostic indicators for treatment success.
Methods
Patients with a single treatment of ...a solitary, biopsy-proven renal tumour with intent to cure over a 14-year period were included (n = 203). Probability of residual disease over time, complication rates and all-cause mortality were assessed in relation to multiple variables.
Results
Mean tumour size was 2.5 cm (range 1.0–6.0). Mean follow-up was 34.1 months (range 1–131). There was an increase in likelihood of residual disease for tumours ≥3.5 cm (P < 0.05), clear cell subtype of renal cell carcinoma (P ≤ 0.005) and maximum treatment temperature ≤70 °C (P < 0.05). There was a decrease in likelihood of residual disease for exophytic tumours (P = 0.01) and no difference based on age, gender, tumour location or type of radio freqency (RF) electrode used. Major complications occurred in 3.9 %. Median post-treatment survival was 7 years for patients with tumours <4 cm, and 5-year overall survival was 80 %. Probability of minor complication increased with tumour size (P = 0.03), as did all-cause mortality (P = 0.005).
Conclusions
CT-guided RFA is safe and effective for early-stage renal cancer, particularly for exophytic tumours measuring <3.5 cm. Overall 5-year survival with tumours <4 cm is comparable to partial nephrectomy.
Key points
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Prognostic indicators for success of CT-guided RFA of renal tumours are reported.
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Tumour size ≥3.5 cm confers an increased risk for residual tumour.
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Clear cell renal cell carcinoma subtype confers increased risk for residual tumour.
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Tmax <70 °C within the ablation zone confers increased risk for residual tumour.
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Exophytic tumours have a lower probability of residual disease.
The majority of patients with lung cancer present with metastatic disease. Chronic inflammation and subsequent activation of nuclear factor-κB (NF-κB) have been associated with the development of ...cancers. The RelA/p65 subunit of NF-κB is typically associated with transcriptional activation. In this report we show that RelA/p65 can function as an active transcriptional repressor through enhanced methylation of the BRMS1 (breast cancer metastasis suppressor 1) metastasis suppressor gene promoter via direct recruitment of DNMT-1 (DNA (cytosine-5)-methyltransferase 1) to chromatin in response to tumor necrosis factor (TNF). TNF-mediated phosphorylation of S276 on RelA/p65 is required for RelA/p65-DNMT-1 interactions, chromatin loading of DNMT-1 and subsequent BRMS1 promoter methylation and transcriptional repression. The ability of RelA/p65 to function as an active transcriptional repressor is promoter specific, as the NF-κB-regulated gene cIAP2 (cellular inhibitor of apoptosis 2) is transcriptionally activated whereas BRMS1 is repressed under identical conditions. Small-molecule inhibition of either of the minimal interacting domains between RelA/p65-DNMT-1 and RelA/p65-BRMS1 promoter abrogates BRMS1 methylation and its transcriptional repression. The ability of RelA/p65 to directly recruit DNMT-1 to chromatin, resulting in promoter-specific methylation and transcriptional repression of tumor metastasis suppressor gene BRMS1, highlights a new mechanism through which NF-κB can regulate metastatic disease, and offers a potential target for newer-generation epigenetic oncopharmaceuticals.
As multidetector CT has come to play a more central role in medical care and as CT image quality has improved, there has been an increase in the frequency of detecting "incidental findings," defined ...as findings that are unrelated to the clinical indication for the imaging examination performed. These "incidentalomas," as they are also called, often confound physicians and patients with how to manage them. Although it is known that most incidental findings are likely benign and often have little or no clinical significance, the inclination to evaluate them is often driven by physician and patient unwillingness to accept uncertainty, even given the rare possibility of an important diagnosis. The evaluation and surveillance of incidental findings have also been cited as among the causes for the increased utilization of cross-sectional imaging. Indeed, incidental findings may be serious, and hence, when and how to evaluate them are unclear. The workup of incidentalomas has varied widely by physician and region, and some standardization is desirable in light of the current need to limit costs and reduce risk to patients. Subjecting a patient with an incidentaloma to unnecessary testing and treatment can result in a potentially injurious and expensive cascade of tests and procedures. With the participation of other radiologic organizations listed herein, the ACR formed the Incidental Findings Committee to derive a practical and medically appropriate approach to managing incidental findings on CT scans of the abdomen and pelvis. The committee has used a consensus method based on repeated reviews and revisions of this document and a collective review and interpretation of relevant literature. This white paper provides guidance developed by this committee for addressing incidental findings in the kidneys, liver, adrenal glands, and pancreas.
The standard treatment of stage I non-small cell lung cancer (NSCLC) is surgical resection. Some patients are poor surgical candidates due to severe comorbid medical conditions. Radiotherapy alone ...has historically been used in this patient population with limited success. Radiofrequency ablation (RFA) is an image-guided, thermally mediated ablative technique recently applied to lung tumors. Combination therapy with both these treatments has not been previously performed. We report our experience with combined CT-guided RFA and conventional radiotherapy in 24 medically inoperable patients with a minimum of 2-year study follow-up in surviving patients.
Twenty-four consecutive, medically inoperable patients with biopsy-proven, stage I NSCLC were treated with CT-guided RFA followed by radiotherapy to a dose of 66 Gy. RFA was performed with a single or cluster cool-tip F electrode; 21 patients were staged before therapy using fluorodeoxyglucose-positron emission tomography.
There were 14 women and 10 men (median age, 76 years; range, 58 to 85 years). The histologic subtypes were squamous cell (n = 13), adenocarcinoma (n = 5), and undifferentiated (n = 6). All patients received RFA followed by three-dimensional conformal radiotherapy. There were no treatment-related deaths or grade 3/4 toxicities. Pneumothorax requiring chest tubes developed in three patients (12.5%). At a mean follow-up period of 26.7 months (range, 6 to 65 months), 14 patients (58.3%) died, with cumulative survival rates of 50% and 39% at the end of 2 years and 5 years, respectively. Ten of the deaths were cancer related. Two patients had local recurrence (8.3%), while nine patients had systemic metastatic disease. Three patients died of respiratory failure with no evidence of active disease, and one patient died of a cerebrovascular accident at 18-month follow-up. Pleural effusions developed after treatment in six patients (25%), which proved to be malignant in one patient.
RFA followed by conventional radiotherapy is feasible in this population of medically inoperable stage I NSCLC patients. Procedural complication rates are low, and no additional major toxicities were seen despite the addition of RFA. Local control and survival rates appear to be better than with radiotherapy alone.
To review the recurrence patterns in patients with primary non-small cell lung cancer (NSCLC) treated with percutaneous image-guided radiofrequency (RF) ablation.
This retrospective review was ...institutional review board approved and HIPAA compliant. Informed consent was waived. Data from all patients with primary NSCLC who underwent lung RF ablation from January 1998 to January 2008 were reviewed. Ninety-one patients were identified. Ten patients with no posttreatment imaging results and two patients with multiple treated lung cancers were excluded. There were 79 tumors in 79 patients (mean age, 75 years). Mean tumor size was 2.5 cm (range, 1-5.5 cm). Fifteen (19%) tumors were central, and 64 (81%) tumors were peripheral. Nineteen (24%) patients underwent adjuvant external beam radiation, and nine (11%) patients underwent concomitant brachytherapy. Correlation of computed tomography and positron emission tomography imaging studies with biopsy results, tumor size, location, and stage was performed. Patterns of recurrence were classified as local, intrapulmonary, nodal, mixed (local and nodal), and distant.
Forty-five (57%) patients demonstrated no evidence of recurrence at follow-up imaging (range, 1-72 months; mean, 17 months). Recurrence was seen in 34 (43%) patients (range, 2-48 months; mean, 14 months). Recurrence after RF ablation was local in 13 (38%), intrapulmonary in six (18%), nodal in six (18%), mixed in two (6%), and distant metastases in seven (21%) cases. Median disease-free survival was 23 months. Sex, tumor location, and radiation therapy were not associated with risk of recurrence. Increasing tumor size (P = .02) and stage (P = .007) were related to risk of recurrence.
The most common pattern of recurrence was local, which suggests that more aggressive initial RF ablation and adjuvant radiation may offer improvement in outcomes. Continued follow-up imaging is needed because new recurrences were seen throughout the 2 years following treatment.
To document the utilization of radiologic imaging in pregnant patients at one academic institution during a 10-year period (1997-2006).
The study was approved by the hospital institutional review ...board and was compliant with HIPAA. Informed consent was waived. At the authors' institution, pregnant patients exposed to radiation during imaging are recorded in a database compiled by the medical physics department. The authors retrospectively reviewed this database to document the number of patients, number of each type of imaging examination, date of the examination, and the estimated radiation dose to the fetus from 1997 to 2006. The authors searched the institution's medical records to obtain the total number of deliveries by year as a control for the total pregnant patient population.
During the 10-year period, 5270 examinations were performed in 3285 pregnant patients (mean age, 28 years). The number of patients and examinations increased from 237 patients undergoing 331 studies in 1997 to 449 patients undergoing 732 examinations in 2006, an increase of 89% in patients and 121% in examinations. The total number of pregnant patients measured by deliveries increased 7%--from 8661 in 1997 to 9264 in 2006. Utilization rates (examinations per 1000 deliveries) of all radiologic examinations increased 107% from 1997 to 2006. The number of conventional radiographic examinations increased by an average of 7% per year, nuclear medicine examinations by 12% per year, and computed tomographic (CT) examinations by 25% per year. The average estimated fetal radiation exposure per examination was 0.43 mGy (range, 0.01-22.5 mGy) for conventional radiography, 4.3 mGy (range, 0.01-43.9 mGy) for CT, and 0.40 mGy (range, 0.01-7.7 mGy) for nuclear medicine examinations.
For the comparison of 1997 to 2006, the radiologic utilization rate in pregnant patients increased by 107% from 1997 to 2006. The greatest increase was in CT.
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