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British Journal of Radiology [journal]
- Efficacy of Dose Escalation on TCP, Recurrence and Second Cancer Risks: A Mathematical Study. [JOURNAL ARTICLE]
- Br J Radiol 2014 Sep 11.:20140377.
Objective: We investigate the effects of conventional and hypo-fractionation protocols by modeling TCP,tumor recurrence time, and examine their impact on second cancer risks. The main objectives of this study include the following: a) incorporate tumor recurrence time and second cancer risks into the TCP framework and analyze the effects of variable doses, b) investigate an efficient protocol to reduce the risk of a secondary malignancy while maximizing disease free survival and tumor control. Methods: A generalized mathematical formalism is developed that incorporates recurrence and second cancer risk models into the TCP dynamics. Results: Our results suggest that the TCP and relapse time are almost identical for conventional and hypo-fractionated regimens, however, second cancer risks resulting from hypo-fractionation were reduced by 22% when compared to the second cancer risk associated with a conventional protocol. Hypo-fractionated regimen appears to be sensitive to dose escalation and the corresponding impact on tumor recurrence time, and reduction in second cancer risk. The reduction in second cancer risk is approximately 20% when the dose is increased from 60 Gy to 72 Gy in a hypo-fractionated protocol. Conclusion: Our results suggest that hypo-fractionation may be a more efficient regimen in the context of TCP, relapse time and second cancer risks. Overall, our study demonstrates the importance of including a second cancer risk model in designing an efficient radiation regimen. Advances in knowledge: The impact of various fractionation protocols on TCP and relapse in conjunction with second cancer risks is an important clinical question that is as yet unexplored.
- Effective radiation dose and eye lens dose in dental cone beam CT: effect of field of view and angle of rotation. [Journal Article]
- Br J Radiol 2014 Oct; 87(1042):20130654.
To quantify the effect of field of view (FOV) and angle of rotation on radiation dose in dental cone beam CT (CBCT) and to define a preliminary volume-dose model.Organ and effective doses were estimated using 148 thermoluminescent dosemeters placed in an anthropomorphic phantom. Dose measurements were undertaken on a 3D Accuitomo 170 dental CBCT unit (J. Morita, Kyoto, Japan) using six FOVs as well as full-rotation (360°) and half-rotation (180°) protocols.For the 360° rotation protocols, effective dose ranged between 54 µSv (4 × 4 cm, upper canine) and 303 µSv (17 × 12 cm, maxillofacial). An empirical relationship between FOV dimension and effective dose was derived. The use of a 180° rotation resulted in an average dose reduction of 45% compared with a 360° rotation. Eye lens doses ranged between 95 and 6861 µGy.Significant dose reduction can be achieved by reducing the FOV size, particularly the FOV height, of CBCT examinations to the actual region of interest. In some cases, a 180° rotation can be preferred, as it has the added value of reducing the scan time. Eye lens doses should be reduced by decreasing the height of the FOV rather than using inferior FOV positioning, as the latter would increase the effective dose considerably.The effect of the FOV and rotation angle on the effective dose in dental CBCT was quantified. The dominant effect of FOV height was demonstrated. A preliminary model has been proposed, which could be used to predict effective dose as a function of FOV size and position.
- Radiotherapy treatment of non-melanoma skin cancer- A survey of current UK practice and commentary. [JOURNAL ARTICLE]
- Br J Radiol 2014 Sep 5.:20140501.
Objectives: In the on-going absence of available trial data a national survey was carried out to provide details on radiotherapy treatment strategy for NMSC. Methods: A survey was performed of clinical oncologists treating NMSC. Respondents were asked for basic information on workload as well as a proposed treatment strategy for various clinical scenarios for patients of varying fitness. Results: A total of 43 completed and 20 partially completed surveys were received. There was a wide variation in the workload and additional disease sites respondents had responsibility for. KV radiotherapy was available to 81%. Respondents' approach was affected by the fitness of patient, with longer fractionation regimes proposed for younger, fitter patients and shorter or non-standard fractionations more likely for the infirm elderly. Four daily fractionation regimes (18-20Gy in 1 fraction, 35Gy in 5 fractions, 45Gy in 10 fractions and 55Gy in 20 fractions) were most commonly suggested. There was a large degree of variation in non-standard fractions proposed with significant potential differences in radiobiological effect. Concern over the use of kV photons on skin over cartilage was apparent as was a reluctance to use radiotherapy in areas of increased risk of poor wound healing. Conclusions: The survey results largely showed practice to be in line with available published evidence. The variation seen in some areas, such as non-standard fractionation, would benefit from the publication of local outcomes to achieve a more consistent approach. Advances in knowledge: Provides information on national practice. Identifies variation, particularly within widespread use of non-standard fractionation.
- MDCT Features of Succinate Dehydrogenase (SDH)-Deficient Gastrointestinal Stromal Tumors. [JOURNAL ARTICLE]
- Br J Radiol 2014 Sep 5.:20140476.
Purpose: To describe the MDCT features and metastatic pattern of succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumors (GISTs). Materials and Methods: In this IRB-approved, HIPAA-compliant study, we retrospectively identified 34patients (20women; mean age 34years, range, 12-59) with histopathology-confirmed SDH-deficient GIST who were seen at our institution from 1999 through 2012. MDCT of primary tumor in eight patients and follow-up imaging in all 34 patients over median follow-up of106 months (IQR, 52-175 months) was reviewed by two radiologists in consensus. Clinical information was extracted from electronic medical record. Results: Primary tumor in all 34 patients was located in stomach. Mean tumor size (n=8) was 9.6cm (range 8-14cm). Primary tumors were lobulated, variable in growth pattern, hypo- (1/8) to isodense (7/8) and similar in enhancement to skeletal muscle. Two were multifocal, 4/8 had necrosis and 1/8 had hemorrhage. Tumor rupture with hemoperitoneum and tumor-bowel fistula was noted in one patient each. During follow-up, 12/34 patients developed tumor in surgical bed and 28/34 patients developed metastases. Most common sites of metastases were liver (24/34), peritoneum (20/34) and lymph nodes (18/34). Carney triad and Carney-Stratakis syndrome were noted in 5/34 and 1/34 patients respectively. At the time of writing, six patients have deceased at median interval of 109months (IQR, 54-126months) Conclusion: SDH-deficient GISTs occur in young patients, commonly arise in stomach, can be multifocal, and may be associated with Carney triad or Carney-Stratakis syndrome. They frequently metastasize to lymph nodes in addition to liver and peritoneum, and are associated with indolent course despite metastatic spread.
- Assessing and ensuring patient safety during breath-holding for radiotherapy. [JOURNAL ARTICLE]
- Br J Radiol 2014 Sep 5.:20140454.
objectives: While there is recent interest in using repeated deep inspiratory breath-holds, or prolonged single breath-holds, to improve radiotherapy delivery, breath-holding has risks. There are no published guidelines for monitoring patient safety and there is little clinical awareness of the pronounced blood pressure rise and the potential for gradual asphyxia that occur during breath-holding. We describe the blood pressure rise during deep inspiratory breath-holding with air and test whether it can be abolished simply by preoxygenation and hypocapnia. methods: We measured blood pressure, oxygen saturation (SpO2) and heart rate in 12 healthy, untrained subjects performing breath-holds. Results: Even for deep inspiratory breath-holds with air, blood pressure rose progressively (e.g., mean systolic pressure rose from 133±5 mmHg to 175±8 mmHg at breakpoint, P<0.005 and in 2 subjects it reached 200 mmHg). Preoxygenation and hypocapnia prolonged breath-hold duration and prevented the development of asphyxia, but failed to abolish the pressure rise. The pressure rise was not at function of breath-hold duration and was not signalled by any fall in heart rate (remaining at resting levels of 72±2 b.p.m). Conclusions: Colleagues should be aware of the progressive blood pressure rise during deep inspiratory breath-holding that so far is not easily prevented. In breast cancer patients scheduled for breath-holds, we recommend routine screening for heart, cardiovascular, renal and cerebrovascular disease, routine monitoring of patient blood pressure and SpO2 during breath-holding and requesting patients to stop if systolic pressure rises consistently above 180 mmHg and or SpO2 falls below 94%.
- Diffusion Tensor Imaging in Evaluation of Thigh Muscles in Patients with Polymyositis and Dermatomyositis. [JOURNAL ARTICLE]
- Br J Radiol 2014 Sep 3.:20140261.
Objectives: To explore the diffusion tensor imaging (DTI) characteristics of thigh muscles in patients with polymyositis (PM) and dermatomyositis (DM). Methods: 12 patients with known PM/DM and 10 healthy volunteers were enrolled in this study. Both DTI and conventional MR sequences were performed on both thighs of all subjects. ADC, fractional anisotropy (FA) and three eigenvalues were compared between the PM/DM group and the healthy group. One-way ANOVA and Student's t-test were used for statistical analyses with a significance of P<0.05. Results: In the healthy group, the vastus intermedias muscle showed the highest ADC value and the gracilis muscle showed the lowest ADC value. These results were statistically significant when compared to other muscles (P<0.05). The gracilis, semitendinosus and semimembranosus muscles showed higher FA values than the other three thigh muscles (P<0.05). Mean ADC value and three eigenvalues of edematous muscles in PM/DM group were higher on average, and showed a statistically significant difference when compared to unaffected muscles (non-edematous muscles in patients) and normal muscles (P<0.05). There was no statistical difference in mean FA value between edematous muscles and normal muscles. Mean ADC, FA and three eigenvalues in unaffected muscles (in patients) showed no statistical differences from those in normal muscles (P>0.05). Conclusions: DTI can be used to quantitatively evaluate the anisotropic diffusion characteristics of muscles in PM/DM patients.
- Implementation of a Target Volume Design Function for Intrafractional Range Variation in a Particle Beam Treatment Planning System. [JOURNAL ARTICLE]
- Br J Radiol 2014 Aug 29.:20140233.
Introduction: Treatment planning for charged particle therapy in the thoracic and abdominal regions should take account of range uncertainty due to intrafractional motion. Here, we developed a design tool (4Dtool) for the target volume (field-specific target volume = FTV), which accounts for this uncertainty using 4DCT. Methods & Materials: Target and normal tissue contours were input manually into a treatment planning system (TPS). These data were transferred to the 4Dtool via PACS. Contours at the reference phase were propagated to other phases by deformable image registration. FTV was calculated using 4DCT on the 4Dtool. The TPS displays FTV contours using DICOM files imported from the PACS. These treatment parameters on the CT image at the reference phase were then used for dose calculation on the TPS. The tool was tested in single clinical case randomly selected from patients treated at our center for lung cancer. Results: In this clinical case, calculation of dose distribution with the 4Dtool resulted in the successful delivery of carbon-ion beam at the reference phase of 95% of the prescribed dose to the CTV. Application to the other phases also provided sufficient dose to the CTV. Conclusions: The 4Dtool software allows the design of the target volume with consideration to intrafractional range variation and is now in routine clinical use at our institution. Advances in knowledge: our alternative technique represents a practical approach to 4D treatment planning within the current state of charged particle therapy.
- The utility of atlas-assisted segmentation in the male pelvis is dependent on the inter-observer agreement of the structures segmented. [JOURNAL ARTICLE]
- Br J Radiol 2014 Aug 29.:20140299.
Objectives: To investigate the relationship between the ability of atlas based auto-segmentation to reduce outlining time in the male pelvis (body, bladder, rectum, femoral heads, prostate and seminal vesicles) and the inter-observer agreement in the delineation of these structures. To examine any increase of the inter-observer agreement with the use of an auto-segmentation tool. Methods: We created atlases in the Elekta ABAS system and recorded the time to delineate the above structures on 8 patients with and without its aid. We also measured the inter-observer agreement in the structure definitions using several metrics (Dice's Similarity Coefficient (DSC), Mean Distance to Conformity, Percentage Volume Difference) with and without its aid. Results: There is a high degree of correlation between the time saving with the use of ABAS and the degree of inter-observer agreement (r=0.90 for DSC). This indicates that for structures where inter-observer agreement is low (DSC<0.65) then ABAS does not reduce outlining time. We found that the inter-observer agreement is increased with ABAS only for the prostate. Conclusions: Outlining time saved in the male pelvis is highly correlated with the inter-observer agreement of the structures. Only for the prostate does the use of ABAS significantly reduce the amount of inter-observer variation in contouring. Advances in Knowledge: The use of auto-segmentation software increases the outlining time for structures where inter-observer agreement is low. Any increase in the inter-observer agreement in contouring with the aid of such software may be limited to those structures where there is currently mid-range agreement between observers.
- Prediction of pathologic complete response of breast cancer patients undergoing neoadjuvant chemotherapy: usefulness of Breast MRI computer-aided detection. [JOURNAL ARTICLE]
- Br J Radiol 2014 Aug 27.:20140142.
Purpose: The purpose of this study is to evaluate usefulness of MR CAD in patients undergoing neoadjuvant chemotherapy for prediction of tumor's pathologic complete response. Objective: 148 breast cancer patients (mean age: 47.3, range: 29-72 years) who underwent neoadjuvant chemotherapy included our study. They had taken MRI before and after neoadjuvant chemotherapy, and pathologic result reviewed as gold standard. Methods: Computer-generated kinetic features for each lesion were recorded, and features analyzed included "threshold enhancement" at 50% and 100% minimum thresholds; degree of initial peak enhancement; and enhancement profiles composed of lesion percentages of washout, plateau, and persistent enhancement. Final pathologic size and character of tumor was correlated with post-chemotherapy mammography, ultrasonography and MR CAD findings. Kruskal-Wallis test and intraclass correlation coefficient (ICC) were used to analysis. Results: We divided 148 patients as complete pathologic response group and non-complete pathologic response group. Complete pathologic response was defined as no histopathologic evidence of any residual invasive cancer cells in the breast or axillary lymph nodes. 39 patients showed complete pathologic response, 109 patients showed non-complete pathologic response. Between enhancement profiles of MR CAD, plateau proportion of tumor was significantly correlated with tumor's pathologic response (mean proportion of plateau on complete pathologic response group was 27%, p-value=0.007). Conclusion: When plateau proportion of tumor is high on MR CAD, we can predict non-complete pathologic response of neoadjuvant chemotherapy. Advances in knowledge: MR CAD can be a useful tool for the assessment of response to neoadjuvant chemotherapy and prediction of pathologic result.
- Diffusion-Weighted MR Imaging in Early Assessment of Tumor Response to Radiotherapy in high-risk Prostate Cancer. [JOURNAL ARTICLE]
- Br J Radiol 2014 Aug 27.:20140359.
Objectives: The objective of this study was to assess the efficacy of diffusion-weighted MRI (DWI) in monitoring the response to radiotherapy in high-risk prostate cancer. Materials and Methods: This retrospective study included 78 patients with high-risk prostate cancer undergoing 3.0 T MRI (supplemented by DWI) before and after Intensity Modulated Radiotherapy (IMRT). Based on follow-up clinical exams, patients were divided into two groups: the recurrence group (patients suffered biochemical/clinical recurrence within 3 years, n=13) and non-recurrence group (patients with over 3-years of recurrence-free, n=65). The apparent diffusion coefficient?ADC?values pre- and post-IMRT were compared between these two groups. The receiver-operating characteristics (ROC) analysis was carried out to investigate the discriminatory capability for pre- and post-IMRT ADC values. Results: The overall ADC values were 1.04± 0.18×10(-3)mm(2)/s for prostate cancers before IMRT, and 1.45± 0.15×10(-3)mm(2)/s after IMRT (P<0.001). A statistically significant difference in post-IMRT ADC values was noted between patients with and without recurrence (1.27 ± 0.14×10-3 mm(2)/s vs. 1.49 ± 0.12×10(-3)mm(2)/s, P<0.001), though there was no statistical difference between them in pre-IMRT ADC values (1.00 ± 0.17×10(-3)mm(2)/s vs. 1.05 ± 0.18×10(-3)mm(2)/s, P=0.31). ROC curve analysis revealed that the post-IMRT ADC values could help identify patients suffering recurrences (area under the curve 0.88, P<0.001) Conclusions: Marked increase in ADC values was observed in prostate cancer after radiotherapy, especially in good responders. DWI is a valuable tool for monitoring the response to radiotherapy. Advances in knowledge: This study examined the relationship between ADC changes and tumor response to treatment in prostate cancer.