Computed tomographic colonography:Hope or hype?

Computed tomographic colonography (CTC) is a promising emerging technology for imaging of the colon. This concise review discusses the currently available data on CTC technique,test characteristics,acceptance,safety,cost-effectiveness,follow-up strategy,and extracolonic findings. In summary,CTC technique is still evolving,and further research is needed to clarify the role of automated colonic insufflation,smooth-muscle relaxants,intravenous and oral contrast,soft-ware rendering,and patient positioning. Currently,full bowel preparation is still required to achieve optimal results. The sensitivity for detecting large polyps (> 1 cm) can be as high as 85%,with specificity of up to 97%. These test characteristics are almost comparable to those of conventional colonoscopy. Patient acceptance of CTC is generally higher than that for colonoscopy,especially in patients who have never undergone either procedure. CTC is generally safe,although uncommon instances of colonic perforation have been documented. In terms of cost-effectiveness,most decision analyses have concluded that CTC would only be cost-effective if it were considerably cheaper than conventional colonoscopy. The proper follow-up strategy for small polyps or incidental extracolonic findings discovered during CTC is still under debate. At present,the exact clinical role of virtual colonoscopy still awaits determination. Even though widespread CTC screening is not available today,in the future there may eventually be a role for this technology. Technological advances in this area will undoubtedly continue,with multi-detector row CT scanners allowing thinner collimation and higher reso-lution images. Stool-tagging techniques are likely to evolve and may eventually allow for low-preparation CTC. Perceptual and fatigue-related reading errors can potentially be minimized with the help of computer-aided detection software. Further research will define the exact role of this promising technology in our diagnostic armamentarium.

Findings on intraprocedural non-contrast computed tomographic imaging following hepatic artery embolization are associated with development of contrast-induced nephropathy

BACKGROUND Contrast-induced nephropathy(CIN)is a reversible form of acute kidney injury that occurs within 48-72 h of exposure to intravascular contrast material.CIN is the third leading cause of hospital-acquired acute kidney injury and accounts for 12%of such cases.Risk factors for CIN development can be divided into patientand procedure-related.The former includes pre-existing chronic renal insufficiency and diabetes mellitus.The latter includes high contrast volume and repeated exposure over 72 h.The incidence of CIN is relatively low(up to 5%)in patients with intact renal function.However,in patients with known chronic renal insufficiency,the incidence can reach up to 27%.AIM To examine the association between renal enhancement pattern on non-contrast enhanced computed tomographic(CT)images obtained immediately following hepatic artery embolization with development of CIN.METHODS Retrospective review of all patients who underwent hepatic artery embolization between 01/2010 and 01/2011(n=162)was performed.Patients without intraprocedural CT imaging(n=51),combined embolization/ablation(n=6)and those with chronic kidney disease(n=21)were excluded.The study group comprised of 84 patients with 106 procedures.CIN was defined as 25%increase above baseline serum creatinine or absolute increase≥0.5 mg/dL within 72 h post-embolization.Post-embolization CT was reviewed for renal enhancement patterns and presence of renal artery calcifications.The association between noncontrast CT findings and CIN development was examined by Fisher’s Exact Test.RESULTS CIN occurred in 11/106(10.3%)procedures(Group A,n=10).The renal enhancement pattern in patients who did not experience CIN(Group B,n=74 with 95/106 procedures)was late excretory in 93/95(98%)and early excretory(EE)in 2/95(2%).However,in Group A,there was a significantly higher rate of EE pattern(6/11,55%)compared to late excretory pattern(5/11)(P<0.001).A significantly higher percentage of patients that developed CIN had renal artery calcifications(6/11 vs 20/95,55%vs 21%,P=0.02).CONCLUSION A hyperdense renal parenchyma relative to surrounding skeletal muscle(EE pattern)and presence of renal artery calcifications on immediate post-HAE noncontrast CT images in patients with low risk for CIN are independently associated with CIN development.

Feasibility of Subtraction Coronary Computed Tomographic Angiography and Influencing Factor Analysis: a Retrospective Study

Objective To investigate the feasibility of subtraction coronary computed tomographic(CT)angiography(SubCCTA)to decline calcium artifacts and improve diagnostic accuracy in the presence of coronary calcification and analyze the factors that influence SubCCTA.Methods A total of 294 patients suspected of having coronary artery diseases underwent coronary computed tomographic angiography(CCTA)and SubCCTA.Coronary stenoses were blindly evaluated by two experienced radiologists,which were compared with invasive coronary angiography(ICA).Multiple statistical indexes were adopted to analyze the value of SubCCTA for the diagnosis of calcium stenoses.Results The diagnosable rate of SubCCTA was 67.2%(n=197),and the non-diagnosable rate was 32.8%(n=97).Using SubCCTA,the false positive rate decreased from 56.5%to 17.4%,and the corresponding diagnostic accuracy was increased from 83.6%to 92.9%.Univariate logistic regression analysis showed that height(OR=1.029,95%CI=1.001–1.058),weight(OR=1.025,95%CI=1.004–1.046),left ventricular size(OR=1.018,95%CI=1.007–1.030),cardiothoracic ratio(OR=39.917,95%CI=1.244–1281.098),the average heart rate(OR=0.866,95%CI=0.836–0.896)and heart rate range(OR=0.882,95%CI=0.853–0.912)might be the factors influencing SubCCTA.Conclusion This study suggested that SubCCTA could help improve diagnostic accuracy in the presence of calcium plaques.Moreover,several factors were discovered for the first time to possibly influence SubCCTA,which will be helpful in improving the subtracted image quality.

Serial computed tomographic findings and specific clinical features of pediatric COVID-19 pneumonia:A case report

BACKGROUND A series of recent cases of pneumonia in Wuhan,Hubei Province,China,was caused by the 2019 novel coronavirus[2019-nCoV,also called severe acute respiratory syndrome(SARS)-CoV-2].The World Health Organization officially named the disease as coronavirus disease 2019(COVID-19).With the global spread of COVID-19,similar cases have appeared in other areas of China,and there are a few reports of pediatric patients with COVID-19 pneumonia.CASE SUMMARY A 7-year-old girl was diagnosed with COVID-19 and presented with irregular fever,sore throat and diarrhea.Chest computed tomography revealed patchy consolidation and ground-glass opacities in multiple areas.The lesions were mainly distributed in the bronchial bundles or subpleural areas of both lungs,particularly in the right lower lobe.The patient also presented with diarrhea,mild kidney injury,and live coronavirus was found in her feces.She was given antiviral agents(lopinavir and ritonavir),and follow-up detection showed that these abnormalities were markedly decreased within 3 d.CONCLUSION The clinical symptoms and prognosis of COVID-19 in pediatric patients may be different from those in adult patients,and the fecal–oral transmission of SARSCoV-2 should be considered.

Multi-scale characterizations of colon polyps via computed tomographic colonography

Texture features have played an essential role in the field of medical imaging for computer-aided diagnosis.The gray-level co-occurrence matrix(GLCM)-based texture descriptor has emerged to become one of the most successful feature sets for these applications.This study aims to increase the potential of these features by introducing multi-scale analysis into the construction of GLCM texture descriptor.In this study,we first introduce a new parameter-stride,to explore the definition of GLCM.Then we propose three multi-scaling GLCM models according to its three parameters,(1)learning model by multiple displacements,(2)learning model by multiple strides(LMS),and(3)learning model by multiple angles.These models increase the texture information by introducing more texture patterns and mitigate direction sparsity and dense sampling problems presented in the traditional Haralick model.To further analyze the three parameters,we test the three models by performing classification on a dataset of 63 large polyp masses obtained from computed tomography colonoscopy consisting of 32 adenocarcinomas and 31 benign adenomas.Finally,the proposed methods are compared to several typical GLCM-texture descriptors and one deep learning model.LMS obtains the highest performance and enhances the prediction power to 0.9450 with standard deviation 0.0285 by area under the curve of receiver operating characteristics score which is a significant improvement.

The value of three-dimensional computed tomographic angiography in the early diagnosis and treatment of spontaneous subarachnoid hemorrhage (616 cases report)

Objective To evaluate the clinical value of three dimensional computerized tomography angiography in the diagnosis and treatment of spontaneous subarachnoid hemorrhage. Methods 616 cases were diagnosed as suspected intracranial aneurysms in 3D CTA system. Computed tomographic scans and CTA studies were

Noninvasive three-dimensional computed tomographic angiography in preoperative detection of intracranial arteriovenous malformations

Obejctive To assess the value of noninvasive three dimensional computed tomographic angiography (3D CTA) in preoperative detection of intracranial arteriovenous malformations (AVMs) Methods A prospective evaluation at a single institute over a 2 year period included 23 patients suspected of intracranial AVMs All patients underwent 3D CTA and digital subtraction angiography (DSA) Results from both procedures were compared Results 3D CTA imaging provided excellent visualization of intracranial AVMs The false positive error and false negative error were zero in our sample The details of arterial supply (numerical measure, orientation, caliber and routing) and vascular nidus (size, morphosis and location) provided by 3D CTA images were the same as DSA and the details of venous drainage were an approximate match Additionally, 3D CTA can depict tridimensional anatomical information for AVMs and their relationship to adjacent structures, a function not possible with DSA This assisted the surgeons in making better surgical planning and reduced trauma As a non invasive course, there were no related complications in the course of 3D CTA processing Conclusions DSA is still regarded as the gold standard for intracranial AVMs detection The modality of 3D CTA is accurate, noninvasive, nearly risk free and low price; we could routinely use it instead of or as a supplement to DSA, in the preoperative detection of suspected intracranial AVMs and postoperative radiological follow up 3D CTA adds tridimensional aspect and assists the surgeon in a the more accurate therapeutic scheme Preliminary data suggest that 3D CTA is playing a favorable role in the assessment of patients with intracranial AVMs

Impact of Clinical Guideline Recommendations on the Application of Coronary Computed Tomographic Angiography in Patients with Suspected Stable Coronary Artery Disease

Background： Coronary computed tomographic angiography （CCTA） has been widely used in patients who are at intemaediate risk for having stable coronary artery disease （SCAD）, and 2013 European Society of Cardiology Guidelines on the Management of SCAD （2013G） recommended the appropriate application of CCTA. However, 2013G has not been subjected to systematic analyses for subsequent impact on clinical practice. Methods： A total of 5320 patients suspected with SCAD were enrolled and scheduled for CCTA from March 2013 to September 2014. For each patient, pretest probability of SCAD was calculated according to updated Diamond-Forrester model （UDFM）. Appropriate CCTA or appropriate stress test was determined as described in the 2013G. A generalized estimating equation model was used to determine the trends in the half-monthly rate of appropriate CCTA. Results： Overall, only 61.37% of patients received appropriate CCTA, and there was insignificant change over time （P = 0.8701）. The application of CCTA in patients who should have had a stress test accounted for most of the inappropriate CCTA before （22.29%） or after （19.98%） the publication of the 2013G. In all patients or any subgroup, no significant change in the adjusted half-monthly rate of appropriate CCTA was found after the publication of the 2013G （odds ratio, 1.002; 95% confidence interval, 0.982-1.021; P = 0.8678）. Conclusions： These findings suggest that the 2013G have not, to date, been fully incorporated into clinical practice, and the clinical utilization of CCTA remains unreasonable to some extent.

Coronary Computed Tomographic Angiography for Suspected Stable Coronary Artery Disease： Gap Between the 2013 European Society of Cardiology Guideline Recommendations and Clinical Practice

Coronary computed tomographic angiography （CCTA） as a noninvasive diagnostic technique for the evaluation of coronary anatomy is widely used clinically. Its advantages include high sensitivity and specificity for the diagnosis of present of coronary artery lesions and lesion characteristics,

Understanding the predictive value and methods of risk assessment based on coronary computed tomographic angiography in populations with coronary artery disease:a review

Risk assessment in coronary artery disease plays an essential role in the early identification of high-risk patients.However,conventional invasive imaging procedures all require long intraprocedural times and high costs.The rapid development of coronary computed tomographic angiography(CCTA)and related image processing technology has facilitated the formulation of noninvasive approaches to perform comprehensive evaluations.Evidence has shown that CCTA has outstanding performance in identifying the degree of stenosis,plaque features,and functional reserve.Moreover,advancements in radiomics and machine learning allowmore comprehensive interpretations of CCTA images.This paper reviews conventional as well as novel diagnostic and risk assessment tools based on CCTA.

Numerical Simulation of Flow Behavior in Basilar Bifurcation Aneurysms Based on 4-Dimensional Computed Tomography Angiography

Initiation, growth, and rupture of cerebral aneurysms are caused by hemodynamic factors. It is extensively accepted that the cerebral aneurysm wall is assumed to be rigid using computational fluid dynamics (CFD). Furthermore, fluid-structure interactions have been recently applied for simulation of an elastic cerebral aneurysm model. Herein, we examined cerebral aneurysm hemodynamics in a realistic moving boundary deformation model based on 4-dimensional computed tomographic angiography (4D-CTA) obtained by high time-resolution using numerical simulation. The aneurysm of the realistic moving deformation model based on 4D-CTA at each phase was constructed. The effect of small wall deformation on hemodynamic characteristics might be interested. So, four hemodynamic factors (wall shear stress, wall shear stress divergence, oscillatory shear index and residual residence time) were determined from the numerical simulation, and their behaviors were assessed in the basilar bifurcation aneurysm.

Evaluation of recurrence in gastric carcinoma: Comparison of contrast-enhanced computed tomography and positron emission tomography/computed tomography

AIM To compare the value of contrast-enhanced abdominal computed tomography(CT) and fluorodeoxyglucose(FDG) positron emission tomography/computed tomography(PET/CT) for detecting gastric carcinoma recurrence.METHODS We retrospectively examined data from 2475 patients who underwent both contrast-enhanced abdominal CT and FDG PET/CT for the surveillance of gastric carcinoma curative resection. Patients had an interval of less than 1 mo between their CT and PET/CT scans. Sixty patients who had recurrence were enrolled. Among 1896 patients who did not have recurrence, 60 were selected by simple random sampling. All CT and PET/CT images were reviewed retrospectively by two reviewers blinded to all clinical and pathologic information except curative resection due to gastric carcinoma. RESULTS The pathological stage of the recurrence group was statistically significantly higher than that of the control group(P < 0.001). In the 60 patients who had recurrence, there were 79 recurrent lesions. Fortyfour patients had only one location of recurrence, 13 patients had two locations, and 3 patients had three. In the detection of patient-based overall recurrence, no statistically significant differences existed between the two modalities(P = 0.096). However, for peritoneal carcinomatosis, CT had a statistically significantly higher sensitivity compared to PET/CT(96% vs 50%, P = 0.001). Adenocarcinoma was the most common type of gastric carcinoma. On the pathology-based analysis, CT also had a statistically significantly higher sensitivity compared to PET/CT(98% vs 80%, P = 0.035).CONCLUSION Contrast-enhanced CT was superior to PET/CT in the detection of peritoneal carcinomatosis and pathologic type of adenocarcinoma.

Imaging characteristics of a rare case of monostotic fibrous dysplasia of the sacrum:A case report

BACKGROUND Fibrous dysplasia(FD)is a common benign intramedullary fibro-osseous lesion.Involvement of the spine is rare,with the literature including only case reports,and cases of monostotic FD(MFD)in the sacrum are extremely rare.A correct preoperative diagnosis of spinal MFD is important for clinicians to select proper treatment.CASE SUMMARY We retrospectively assessed a case report of MFD in the sacrum.This patient was examined by computed tomography(CT)and magnetic resonance imaging(MRI),and the diagnosis was confirmed by pathology.A review of the literature was performed to analyze the imaging characteristics and differential diagnoses of spinal MFD.For our patient,the CT scan showed the lesion to be expansile,with ground glass opacity and a sclerotic rim.On MRI,the lesion showed iso-low signal intensity on T1WI and iso-high signal intensity on T2WI.A low signal rim was found on T1WI and T2WI.Our patient was treated by posterior focal excision,decompression,bone grafting,fusion and pedicle screw fixation.A satisfactory result was achieved,with pain disappearance.No complications had occurred at the 1-year follow up.CONCLUSION MFD is an expansile osteolytic change.Ground glass opacity and a sclerotic margin are obvious characteristics.The lesion often involves the vertebral body and posterior element.Knowledge of these imaging characteristics of spinal FD could be helpful for diagnosis and prevent unnecessary procedures.

Unfavorable Outcome of Percutaneous Coronary Intervention for Coronary Heart Disease with Rare Severe Pericoronary Fat Stranding

Background: Pericoronary fat stranding (PCFS) is a novel noninvasive imaging sign of coronary inflammation, and has important implications for cardiovascular risk stratification, and the outcome of percutaneous coronary intervention (PCI) for coronary heart disease patients with pericoronary fat stranding remains unknown. Aim: We report two rare cases of PCI-treated coronary heart disease patients with severe PCFS. Case Presentation: This is the first report of two rare cases of PCI for patients with coronary heart disease surrounded by severe PCFS. We demonstrated that the outcome in these cases is poor, and in-stent restenosis or occlusion occurs rapidly within 2- 6 months following PCI. However, Case 2 underwent coronary artery bypass grafting after the rapid occurrence of in-stent occlusion, and the bypass graft remained intact over the 5 years following coronary artery bypass grafting. Conclusion: Coronary artery bypass grafting rather than PCI may be appropriate for coronary heart disease patients with severe PCFS.

Time-dependent Changes in CT of Radiation-induced Liver Injury:A Preliminary Study in Gastric Cancer Patients

In this study, the time-dependent changes on dynamic computed tomograph (CT) of radiation-induced liver injury in gastric cancer patients was examined.The CT images of 52 gastric cancer patients who had received chemoradiotherapies were reviewed on the PACS system.Dynamic CT scan was performed in all the subjects.Our results showed that 18 patients were found to have radiation-induced liver injury.The CT findings of radiation-induced liver injury in gastric cancer patients tend to show up one month after radiation treatment.The damaged area was of low density on all three phases, and then it was enhanced on portal vein phase or delay phase.The focal radiation reaction of liver without basic disease vanished 9-11 months later after treatment.We are led to conclude that dynamic CT is of help in the diagnosis of CRT-induced liver injury, and it may be the method of choice for following up the whole course of the CRT-induced liver injury, i.e., form hepatic damage to healing.The classification of CT findings we recommend can avoid the influence of technological factors, and thereby serve as a better guide for treatment of CRT-induced liver injury.

Angio-Computed Tomograph-Guided Immediate Lipiodol Computed Tomograph for Diagnosis of Small Hepatocellular Carcinoma Lesions during Transarterial Chemoembolization

Background： The diagnosis and treatment of small hepatocellular carcinoma （HCC） play a vital role in the prognosis of patients with HCC. The purpose of our study was to evaluate anglo-computed tomography （angio-CT）-guided immediate lipiodol CT （a CT scan performed immediately after transarterial chemoembolization [TACE]） in the diagnosis of potential HCCs ≤1 cm in diameter. Methods： This study retrospectively analyzed 31 patients diagnosed with HCCs after routine imaging （contrast-enhanced CT or magnetic resonance imaging） or pathologic examinations with undefined or undetermined tumor lesions （diameter 〈1 cm） from February 2016 to September 2016. After TACE guided by digital subtraction angiography of the angio-CT system, potential HCC lesions with a diameter ≤1 cm were diagnosed by immediate lipiodol CT. The number of well-demarcated lesions was recorded to calculate the true positive rate. The correlation between the number of small HCCs detected by immediate lipiodol CT and the size of HCC lesions （diameter 〉1 cm） diagnosed preoperatively was analyzed 1 month after TACE. A paired t-test was used to analyze differences in liver function. Pearson analysis was used to analyze correlation. Chi-square test was used to compare the rates. Results： Fifty-eight lesions were detected on preoperative routine imaging examinations in 31 patients including 15 lesions with a diameter ≤ 1 cm. Ninety-one lesions were detected on immediate lipiodol CT, of which 48 had a diameter ≤ 1 cm. After 1 month, CT showed that 45 lesions had lipiodol deposition and three lesions had lipiodol clearance. Correlation analysis showed that the number of small HCCs detected by lipiodol CT was positively correlated with the size of HCC lesions diagnosed by conventional imaging examination （R^2 - 0.54, P 〈 0.05）. Conclusion： Immediate lipiodol CT may be a useful tool in the diagnosis of potential HCC lesions with a diameter of ≤1 cm.

CT angiography of pulmonary embolism using a 64 slice multi-detector scanner

Background Multi-detector computed tomography （MDCT） has already been the first line investigation method for diagnosis of pulmonary embolism （PE）. Reducing the amount of contrast medium used during CT scanning could decrease the incidental rate of adverse reactions. Our study amied to evaluate the image quality of pulmonary arteries using 64 slice multi-detector CT with small volumes of contrast media injection. Methods Forty nonconsecutive patients without PE or other lung diseases were randomly assigned to two groups. Group A underwent CT scanning with 16×1 .25 mm collimation and a 70 ml contrast injection, while group B had CT with 64×0.625 mm collimation and 20 ml of contrast injection. Two readers independently depicted the segmental and subsegmental pulmonary arteries. Reasons we could not analyze the pulmonary artery or that led to misdiagnosis of pulmonary embolism were evaluated, including the degree of contrast enhancement of the main pulmonary artery, and factors that caused misdiagnosis of PE （flow-related artifacts, partial volume artifact, beam-hardening artifacts and enhancement of pulmonary vein）. The independent samples t-test, Mann-Whitney U test and Pearson chi-square test were applied. Results There were no significant differences in image quality of segmental and subsegmental arteries between the two groups. No significant difference was found for factors that made pulmonary arteries non-analyzable or in the misdiagnosis of PE, except the degree of contrast enhancement. Conclusion 64×0.625 mm collimation with 20 ml contrast injection could depict the pulmonary arteries well.

Virtual reality system for diagnosis and therapeutic planning of cerebral aneurysms

Background The virtual reality （VR） system can provide the neurosurgeon to intuitively interact with and manipulate the three dimensional （3-D） image similarly to manipulate a real object.it was seldom reported that the system was used in diagnosis and treatment of cerebral aneurysms.This study aimed to investigate the application of VR system in diagnosis and therapeutic planning of cerebral aneurysms.Methods A total of 24 cases of cerebral aneurysms were enrolled in this study from 2006 to 2008, which diagnosed by 3-D digital subtraction angiography （3D-DSA） or VR-based computed tomography angiographies （CTA）.The VR system and 3D-DSA system were used to observe and measure aneurysms and the adjacent vessels.The data of observation and measurements were compared between VR image and 3D-DSA image.All the patients underwent surgical plan and simulated neurosurgical procedures in the VR system.Results There were 28 aneurysms detected in VR system and 3D-DSA system.The VR system generated clear and vivid 3-D virtual images which clearly displayed the location and size of the aneurysms and their precise anatomical spatial relations to the parent arteries and skull.The location, size and shape of the aneurysms and their anatomical relationship with the adjacent vessels were similar between 3-D virtual image and 3D-DSA, but the spatial relationship between aneurysms and skull only been displayed by VR system.This VR system also could simulate simple surgical procedures and surgical environments.Conclusions The VR system can provide a highly effective way to provide precise imaging details as same as 3D-DSA system and assist the diagnosis of cerebral aneurysms with virtual 3-D data based on CTA.It significantly enhances the chosen therapeutic strategy of cerebral aneurysms.

The association of the uterine motion with bladder volume during radiotherapy in gynecological malignancies

Aim:This study was performed to assess the extent of interfraction uterine motion during radiotherapy for cervical cancer and uterine body carcinoma while maintaining a strict bladder filling protocol.Methods:Twenty-four patients with cervical cancer or uterine body carcinoma who were treated on a linear accelerator,were recruited.During the course of external beam radiotherapy,cone beam computed tomographic scans were taken,once at the start of treatment and then weekly until the completion of the radiotherapy course.Patients were instructed to maintain a strict bladder filling protocol.After negating the effect of patient’s setup error by offline cone beam computed tomographic imaging,the position of the uterus was defined in the clinical target volume.Then the position of the uterus was compared in the following weekly scans.The position of the uterus was also correlated with the position and the filling of the bladder.This change in uterus position was measured separately in the anterioposterior(AP),superioinferior(SI),and lateral directions.Results:According to calculations based on weekly imaging,The mean values of shift in AP,SI,and lateral directions were respectively 0.67,0.29,and 0.23 The mean extent of motion in the uterine position on a daily basis for individual patients ranged from-2.28 to+1.3 in AP,-0.56 to+0.71 in SI,and from-0.6 to+0.45 in lateral directions.Conclusion:At least once a week cone beam computed tomography might be necessary to minimize the geometrical miss and deliver the planned doses to the target tissue and normal structure provide best results with minimum toxicity by maintaining a bladder volume of about 100 mL and an empty rectum during the whole course of treatment.The daily anatomical shift and contour of the patients maintaining a bladder volume of approximately 100 mL with an empty rectum may result in asymmetrical conforming to the planning target volume and hence appropriate and adequate planning target volume margins are required.