Image-guided radiotherapy of the prostate using daily CBCT: the feasibility and likely benefit of implementing a margin reduction

Objective:

To investigate whether planning target volume (PTV) margins may be safely reduced in radiotherapy of localized prostate cancer incorporating daily online tube potential-cone beam CT (CBCT) image guidance and the anticipated benefit in predicted rectal toxicity.

Methods:

The prostate-only clinical target volume (CTV₂) and rectum were delineated on 1 pre-treatment CBCT each week in 18 randomly selected patients. By transposing these contours onto the original plan, dose–volume histograms (DVHs) for CTV₂ and the rectum were each calculated and combined, for each patient, to produce a single mean DVH representative of the dose delivered over the treatment course. Plans were reoptimized using reduced CTV₂ to PTV₂ margins and the consequent radiobiological impact modelled by the tumour control probability (TCP) and normal tissue complication probability (NTCP) of the rectum.

Results:

All CBCT images were deemed of sufficient quality to identify the CTV and rectum. No loss of TCP was observed when plans using the standard 5-mm CTV₂ to PTV₂ margin of the centre were reoptimized with a 4- or 3-mm margin. Margin reduction was associated with a significant decrease in rectal NTCP (5–4 mm; p < 0.05 and 5–3 mm; p < 0.01).

Conclusion:

Using daily online image guidance with CBCT, a reduction in CTV₂ to PTV₂ margins to 3 mm is achievable without compromising tumour control. The consequent sparing of surrounding normal tissues is associated with reduced anticipated rectal toxicity.

Advances in knowledge:

Margin reduction is feasible and potentially beneficial. Centres with image-guided radiotherapy capability should consider assessing whether margin reduction is possible within their institutes.Adenocarcinoma of the prostate accounts for >10,000 deaths in the UK each year.¹ External beam radiotherapy is a potentially curative treatment option for localized disease but is associated with a risk of acute and late side effects, as a consequence of radiation effects on surrounding normal tissues. The rectum is the critical dose-limiting structure, and there is a close relationship between the radiation dose received and subsequent risk of late toxicity.² Late effects, including diarrhoea, incontinence, tenesmus and bleeding can have a significant impact on quality of life.³A course of radical radiotherapy is delivered over more than 7 weeks but is usually planned on a single planning CT scan. This introduces geometric uncertainty such that the initial planning scan is unlikely to be representative of the position of the prostate or normal structures throughout the course of treatment. The anatomical proximity of the prostate and mid-rectum means that rectal distension, secondary to gaseous or faecal filling, is the major contributor to prostate motion. Studies using implanted fiducial markers,^4,5 serial CT scans⁶ and ultrasound⁷ demonstrate prostatic displacements of up to 20 mm.⁸ The position of the prostate gland in relation to bony landmarks is also seen to change in an unpredictable way.⁹ To ensure adequate dose coverage of the tumour, a safety margin is added to the clinical target volume (CTV) to accommodate for positional uncertainties called the planning target volume (PTV). A larger CTV to PTV margin results in the irradiation of a larger volume of normal tissue within the high-dose envelope.Image-guided radiotherapy (IGRT) uses images taken at the time of treatment to assess the accuracy of patient set-up, allowing real-time correction to be made if required. Its aim is to reduce the geometric uncertainties that occur between planning and delivery of radiotherapy. Strategies in current use include ultrasound,¹⁰ megavoltage CT (TomoTherapy®; Accuray, Sunnyvale, CA),¹¹ CBCT^12,13 and implanted fiducial markers.^14,15In this study, all patients were treated using intensity-modulated radiotherapy (IMRT) with daily online IGRT using tube potential-cone beam CT (CBCT). Our aim was to generate and assess new margin strategies based on the premise that the reduction in geometric uncertainty afforded by IGRT may permit PTV margin reduction without unacceptably compromising tumour control.IGRT reduces positional uncertainty but does not eliminate interfractional set-up variation. In order to more accurately assess the actual doses delivered to the pelvic organs, pre-treatment CBCT images were used to delineate the prostate and rectum in the treated position. Dose–volume histograms (DVHs) for the CBCT-outlined structures were estimated by transposing these contours onto the original plan and using them to sample the original dose distribution. These were compared with the DVHs of the original plan and to the DVHs created using reduced margins with corresponding dose distributions generated by reoptimization. Data were evaluated using radiobiological modelling of the tumour control probability (TCP) and normal tissue complication probability (NTCP) of the rectum to assess whether margin reduction could be achieved safely and the likely benefit in terms of spared rectal toxicity anticipated from such a strategy.     

Obscure gastrointestinal bleeding: diagnostic performance of 64-section multiphase CT enterography and CT angiography compared with capsule endoscopy

Objective:

To compare the diagnostic capabilities between capsule endoscopy (CE) and multislice CT (MSCT) enterography in combination with MSCT angiography for assessment of obscure gastrointestinal bleeding (OGIB).

Methods:

A total of 127 patients with OGIB were looked at in this study. 82 patients (aged 42.7 ± 19.1 years; 34 males) were assigned to receive MSCT diagnosis and 67 patients to (aged 53.9 ± 16.2 years; 28 males) receive CE diagnosis. Among them, 22 patients (aged 54.1 ± 19.1 years; 12 males) received both examinations. Oral isotonic mannitol and intramuscular injection of anisodamine were performed; non-ionic contrast (iopromide, 370 mg I ml⁻¹) was intravenously administered; and then multiphase scanning was conducted at arterial, small intestinal and portal venous phases in MSCT. The results were compared with findings of reference standards including double balloon enteroscopy, digital subtraction angiography, intraoperative pathological examination and/or clinical diagnosis.

Results:

Administration of anisodamine markedly increased the satisfaction rate of bowel filling (94.67% vs 28.57%; p < 0.001) but not the diagnostic yield (p = 0.293) of MSCT. Compared with MSCT, CE showed an improved overall diagnostic yield (68.66% vs 47.56%; p = 0.010), which was also observed in overt bleeding patients (i.e. patients with continued passage of visible blood) (76.19% vs 51.02%; p = 0.013) and in patients aged younger than 40 years of age (85% vs 51.28%; p = 0.024). However, CE had similar positive rates to MSCT (p > 0.05). Among the 22 cases in whom both examinations were conducted, CE showed no significantly different diagnostic capability compared with MSCT (p = 0.4597).

Conclusion:

Both CE and MSCT are safe and effective diagnostic methods for OGIB.

Advances in knowledge:

CE is preferred for overt bleeding or patients aged younger than 40 years. The combined use of CE and MSCT is recommended in OGIB diagnosis.Obscure gastrointestinal bleeding (OGIB), which accounts for approximately 5% of all gastrointestinal haemorrhage cases,¹ is defined as persistent or recurring gastrointestinal bleeding without an obvious aetiology after gastroduodenoscopy and colonoscopy.^2,3 Based on the presence or absence of clinically evident bleeding, OGIB could be divided into occult (no visible blood) and overt (continued passage of visible blood, such as haematemesis, melaena or haematochezia) bleeding.^3,4 OGIB frequently occurs in the small bowel and is caused by small bowel diseases such as intestinal erosions, ulcers, vascular anomaly, gastrointestinal tumours and inflammatory bowel and parasitic diseases.^5,6Multiple diagnostic techniques have been developed to elucidate the causes of OGIB. Among them, two non-invasive technologies, capsule endoscopy (CE) and multislice CT (MSCT) markedly improved the ability to determine the causes of OGIB by allowing the visualization of the gastrointestinal tract.^2,3,6 CE is able to obtain direct visualization of mucosal surface of the entire small intestine.^4,7,8 However, capsule retention remains a major risk of CE diagnosis.^4,9–11 In addition, the visual field restriction limits the value of CE in diagnosis of umbilicate or extraluminal lesions, since the small bowel is difficult to evaluate owing to its large length and tortuous course.^4,10 Conversely, MSCT, including MSCT angiography (MSCTA), MSCT enteroclysis and MSCT enterography (MSCTE), has full capacity to depict the extraintestinal lesions, owing to the combination of the advantages of enteral volume challenge with the ability of cross-sectional imaging.^4,12 Yet, substantial patient radiation exposure is one of the major disadvantages of MSCT diagnosis.^3,13 Careful preparation is also needed before examination.¹⁴ Considering that both CE and MSCT have advantages and disadvantages, a limited number of published data have compared the two diagnostic tools in patients with OGIB.^4,6,15–17 However, most of these studies did not refer to MSCTA, and apparently different results were obtained owing to the advancement of the two technologies. Thus, an updated and comprehensive comparison is required.Hence, we compared the diagnostic capability of MSCTE in combination with MSCTA with CE in patients suffering from OGIB. In this study, MSCTE and MSCTA technologies performed with a 64-slice spiral CT scanner were combined by non-contrast-enhanced scanning after oral administration of a neutral enteric contrast material (isotonic mannitol, 2.5%) and the intramuscular injection of anisodamine to restrain enterocinesia, and the following multiphase scanning at arterial, small intestinal and portal venous phases followed the intravenous infusion of non-ionic iodinated contrast material (iopromide, 370 mg I ml⁻¹). In addition, the influences of the clinical bleeding pattern and age on the diagnostic capability were also investigated.     

Femoral neck shaft angle width is associated with hip-fracture risk in males but not independently of femoral neck bone density

Objective:

To investigate the specificity of the neck shaft angle (NSA) to predict hip fracture in males.

Methods:

We consecutively studied 228 males without fracture and 38 with hip fracture. A further 49 males with spine fracture were studied to evaluate the specificity of NSA for hip-fracture prediction. Femoral neck (FN) bone mineral density (FN-BMD), NSA, hip axis length and FN diameter (FND) were measured in each subject by dual X-ray absorptiometry. Between-mean differences in the studied variables were tested by the unpaired t-test. The ability of NSA to predict hip fracture was tested by logistic regression.

Results:

Compared with controls, FN-BMD (p < 0.01) was significantly lower in both groups of males with fractures, whereas FND (p < 0.01) and NSA (p = 0.05) were higher only in the hip-fracture group. A significant inverse correlation (p < 0.01) was found between NSA and FN-BMD. By age-, height- and weight-corrected logistic regression, none of the tested geometric parameters, separately considered from FN-BMD, entered the best model to predict spine fracture, whereas NSA (p < 0.03) predicted hip fracture together with age (p < 0.001). When forced into the regression, FN-BMD (p < 0.001) became the only fracture predictor to enter the best model to predict both fracture types.

Conclusion:

NSA is associated with hip-fracture risk in males but is not independent of FN-BMD.

Advances in knowledge:

The lack of ability of NSA to predict hip fracture in males independent of FN-BMD should depend on its inverse correlation with FN-BMD by capturing, as the strongest fracture predictor, some of the effects of NSA on the hip fracture. Conversely, NSA in females does not correlate with FN-BMD but independently predicts hip fractures.Hip fracture is the worst osteoporotic fracture with regard to cost^1,2 and adverse consequences,^3,4 so its prevention by checking for the related fracture risk factors is an important goal. Although low bone mineral density (BMD) is generally recognized as the main risk factor for hip fracture,^5,6 there is growing evidence that other bone characteristics, such as proximal femur geometry (PFG) parameters, are implicated in determining the risk profile for hip fracture.^7,8 This evidence, however, mainly derives from studies carried out in females,^9–13 whereas contradictory results characterize studies carried out in males.^14–20 Authors'' opinions seem to vary widely about the ability of the neck shaft angle (NSA), one of the PFG factors, to predict osteoporotic hip fractures in males,^14–16,21 whereas its association with the risk of hip fracture in females^10,11,14,22 is generally accepted. Gender differences in the hip anatomy²³ have been put forward as a possible explanation for the different relationship of NSA with the hip-fracture risk between genders, whereas geographic and racial differences²⁴ among the examined male populations have been advocated as a possible cause of authors'' discrepancies on the relationship between NSA and the hip-fracture risk in males.This topic is therefore still under debate, and further studies are required to clarify the association of the NSA with hip-fracture risk in males. The authors of the current study contribute to this topic by studying the relationship between NSA and the hip fragility fracture in a sample of white Italian males.     

The challenge of segmental small bowel motility quantitation using MR enterography

Objective:

Analysis of “cine” MRI using segmental regions of interest (ROIs) has become increasingly popular for investigating bowel motility; however, variation in motility in healthy subjects both within and between scans remains poorly described.

Methods:

20 healthy individuals (mean age, 28 years; 14, males) underwent MR enterography to acquire dynamic motility scans in both breath hold (BH) and free breathing (FB) on 2 occasions. Motility data were quantitatively assessed by placing four ROIs per subject in different small bowel segments and applying two measures: (1) contractions per minute (CPM) and (2) Jacobian standard deviation (SD) motility score. Within-scan (between segment) variation was assessed using intraclass correlation (ICC), and repeatability was assessed using Bland–Altman limits of agreement (BA LoA).

Results:

Within-scan segmental variation: BH CPM and Jacobian SD metrics between the four segments demonstrated ICC R = 0.06, p = 0.100 and R = 0.20, p = 0.027 and in FB, the CPM and Jacobian SD metrics demonstrated ICC R = −0.26, p = 0.050 and R = 0.19, p = 0.030. Repeatability: BH CPM for matched segments ranged between 0 and 14 contractions with BA LoA of ±8.36 and Jacobian SD ranged between 0.09 and 0.51 with LoA of ±0.33. In FB data, CPM ranged between 0 and 10 contractions with BA LoA of ±7.25 and Jacobian SD ranged between 0.16 and 0.63 with LoA = ±0.28.

Conclusion:

The MRI-quantified small bowel motility in normal subjects demonstrates wide intersegmental variation and relatively poor repeatability over time.

Advances in knowledge:

This article presents baseline values for healthy individuals of within- and between-scan motility that are essential for understanding how this process changes in disease.Dynamic “cine” MRI acquired during MR enterography is increasingly utilized to assess bowel motility in a range of conditions, notably inflammatory bowel disease and enteric dysmotility syndromes.^1–4 Analysis of the data remains primarily subjective in clinical routine, but the ability to apply quantitative techniques makes this a potentially powerful methodology to explore gastrointestinal physiology in disease as well as an emerging application as a biomarker for drug efficacy.^5–7Despite the growing literature, a consensus has yet to be reached as to the best method of quantitatively analysing small bowel data and indeed a range of motility metrics are proposed.^2,3,8–12 The most commonly used metric is the change in luminal diameter at a fixed anatomical position through the time series. By tracking bowel diameter, a characteristic curve can be produced with the number of contractions expressed per minute (CPM) to give an intuitive and broadly accepted metric for small bowel motility (SBM).^{2–4,9,11,13–15} To date, several studies have reported a relationship between CPM and dysmotility in disease, either compared with a histopathological standard or “normal” reference bowel loops.^2–4,12 An array of additional metrics derived both from bowel diameter measures and more abstract processing techniques have further been implemented with varying degrees of effectiveness in disease and health.^{2,4,5,8,10,14,16}Although intuitively attractive, the robustness of assessing overall enteric motility using only an isolated loop of bowel has received relatively little attention to date irrespective of the precise metric applied. It is unclear how representative the selected bowel loops are of overall SBM and if normal motility intrinsically differs between bowel segments, for example, between the jejunum and ileum. Furthermore, the repeatability of single loop metrics, even in normal individuals, is not well described, knowledge of which is vital if segmental analysis is to be used to diagnose, guide treatment and monitor enteric pathology.The purpose of this study is to explore segmental variation in SBM in healthy volunteers measured using two commonly reported small bowel metrics [CPM and Jacobian standard deviation (SD)] looking at (1) within-scan motility variation between different segments and (2) between-scan variation (repeatability) across two time points.     

Radiographers' professional knowledge regarding parameters and safety issues in plain radiography: a questionnaire survey

Objective:

To review the knowledge of radiographers and examine the possible sociodemographic and situational contributors to this knowledge.

Methods:

A questionnaire survey was devised and distributed to a cohort of 120 radiographers. Each questionnaire contained two sections. In the first section, background data, including sex, age, highest academic level, grade point average (GPA), length of time from graduation, work experience as a radiographer and the status of previous refresher course(s), were collected. The second section contained 17 multiple-choice questions concerning radiographic imaging parameters and safety issues.

Results:

The response rate was 63.8%. In univariate analytic model, higher academic degree (p < 0.001), higher GPA (r² = 0.11; p = 0.001), academic workplace (p = 0.04) and taking previous refresher course(s) (p = 0.01) were significantly associated with higher knowledge score. In multivariate analytic model, however, higher academic degree (B = 1.62; p = 0.01), higher GPA (B = 0.50; p = 0.01) and taking previous refresher course(s) (B = −1.26; p = 0.03) were independently associated with higher level of knowledge. Age, sex, length of time from graduation and work experience were not associated with the respondents'' knowledge score.

Conclusion:

Academic background is a robust indicator of a radiographer''s professional knowledge. Refresher courses and regular knowledge assessments are highly recommended.

Advances in knowledge:

This is the first study in the literature that examines professional knowledge of radiographers in terms of technical and safety issues in plain radiography. Academic degree, GPA and refresher courses are independent predictors of this knowledge. Regular radiographer professional knowledge checks may be recommended.The Joint Commission on Accreditation of Healthcare Organizations mandates “processes that are designed to ensure that the competency of all staff members is assessed, maintained, demonstrated and improved on an ongoing basis.” Tests with practical questions that reflect the knowledge required to perform daily examinations have been proposed as effective tools to attain this purpose. The results enable us to take on existing blemishes and improve the competency.¹Medical imaging, as a field with growing complexity and increasing impact on diagnosis, plans of management and patient health status,² is a good example of raised requirements for competency.^3–8Knowledge assessment may be useful for detecting possible weaknesses in an organization and spotlighting existing educational flaws and shortcomings.⁹ According to some reports, knowledge assessment takes priority over checking competency,^7,10 particularly in professions that are completely mediated by technology.¹¹In addition, although clinical education is the mainstay for developing skills, it has been shown that the combination of practical and theoretical education would lead to a significantly better outcome in the field of teaching. This integrated approach of using both knowledge and practice in education enables the trainee to work more competently and be prepared to take responsibility in his/her future career.¹²Although radiography using film for imaging the internal organs of the body has been introduced for over a century,¹³ it is still among the most widespread and useful imaging modalities all over the world. Radiographers are generally in charge of radiological equipment, imaging examination and frequently nursing care.^7,14,15Incompetent radiographers could render radiographic examinations suboptimal. A poor radiographic technique, in turn, may lead to unnecessary exposures to X-radiation, poor image quality, repeated views and examinations, patient discomfort or further injury because of poor positioning and the possibility of a missed diagnosis or misdiagnosis.¹⁶Furthermore, a rapid shift from conventional to fully digitized radiology departments, along with rapidly evolving changes in healthcare administration¹⁷ entails knowledgeable, up-to-date radiographers who utilize the technology.¹⁸Except for very limited number of studies that have described radiographers'' self-reported competency^7,16 and the level of awareness pertaining to the protection against radiation,^19,20 to the best of our knowledge, there is no study in the literature regarding radiographers'' level of knowledge with a dedicated focus on technical parameters and safety in plain radiography.This study sets out to examine knowledge amongst a cohort of radiographers and to investigate possible association of some sociodemographic and situational factors with the level of this knowledge.     

Medial temporal lobe atrophy in Alzheimer's disease/mild cognitive impairment with depression

Objective:

Depression is common in patients with Alzheimer''s disease (AD) and mild cognitive impairment (MCI). Patients with depression have an earlier onset and rapid progression of cognitive decline. Medial temporal lobe atrophy (MTA) is common in AD and MCI, and some degree of atrophy is found in almost all patients. In the present study, an attempt was made to know if MTA is more common in patients with AD/MCI with depression than those without it.

Methods:

Patients reporting to the outpatient department of a neurology centre of a tertiary care hospital were recruited for the present study. After initial general physical and neurological examination, they were evaluated using National Institute of Neurological and Communicative Disorders and Stroke and Related Disorders Association criteria for diagnosis of AD. Clinical Dementia rating scale was used for the diagnosis of MCI. Cornell scale for depression in dementia (CSDD) was used.

Results:

We found 20 cases with depression as per CSDD out of a sample of 37 patients (male:female = 30:7). There were 26 patients with AD and 11 with MCI. The mean age of all patients was 72.33 ± 6.45 years. The mean mini mental status examination score was 19.00 ± 6.73. The mean time since diagnosis was 4.19 ± 3.26 years. The mean Scheltens visual rating scale score for right MTA was 2.08 ± 0.95 and was 2.05 ± 0.94 for the left. Both scores did not differ statistically when analyzed using paired t-test (p > 0.05). However, difference in those with depression (2.36 ± 0.95) from those without depression (1.60 ± 0.74) was significant (p < 0.05).

Conclusion:

MTA scores were higher in those with AD/MCI with depression than those without it.Depression¹ is common in patients with Alzheimer''s disease (AD) and mild cognitive impairment (MCI). Relationship between depression and cognitive decline is a complex one, and depression is both an aetiological risk factor² and comorbidity for dementia.³ Incidence and prevalence of depressive symptoms in MCI range from 15% in population-based studies to 44% in hospital-based studies.⁴ Likewise, up to two-thirds of patients with AD have been reported to have depression.⁵ Because in many studies, depression has been seen to be an early manifestation of AD, it has been suggested that it may represent a continuum⁴ from depression to MCI to AD (late-life depression → MCI → AD). Two recent meta-analyses have found that a history of depression approximately doubles an individual''s risk for subsequent dementia in general and AD in particular.⁶ Depression is known to be neurotoxic to medial temporal lobe structures and can contribute to their atrophy.^7–9 Atrophy is more so, when depression is severe or recurrent⁷ and medial temporal lobe atrophy (MTA) has a temporal association with depression.⁹ Continued treatment of depression has been shown to protect the hippocampus from the ill effects of depression.¹⁰ Although volumetric method could be a preferred mode of measuring the hippocampal volume in AD, qualitative rating of MTA is a good alternative.¹¹ Visual rating of the hippocampal volume^12–14 can be carried out using Scheltens et al¹⁵ rating scale that is based on the width of the choroid fissure, the width of the temporal horn and the height of hippocampal formation and is a quantitative scale.     

Diffusion-weighted MRI in the follow-up of chronic periaortitis

Objective:

To evaluate the usefulness of diffusion-weighted MRI (DWI) for the assessment of the intraindividual follow-up in patients with chronic periaortitis (CP) under medication.

Methods:

MRI data of 21 consecutive patients with newly diagnosed untreated disease were retrospectively examined before and after medical therapy, with a median follow-up of 16 weeks. DWI parameters [b800 signal, apparent diffusion coefficient (ADC) values] of the CP and psoas muscle were analysed together with the extent and contrast enhancement. Pre- and post-treatment laboratory inflammation markers were acquired parallel to each MR examination.

Results:

Statistically significant lower b800 signal intensities (p ≤ 0.0001) and higher ADC values (p ≤ 0.0001) were observed after medical treatment within the fibrous periaortic tissue. Extent and contrast enhancement of the CP showed also a statistically significant decrease (p ≤ 0.0001) in the follow-up examinations, while the control parameters within the psoas muscle showed no differences.

Conclusion:

DWI seems to be a useful method for the evaluation of response to treatment without contrast agents. The technique may be helpful in the assessment of disease activity to guide further therapeutic strategies.

Advances in knowledge:

DWI detects significant differences in the intraindividual follow-up of CP under medical therapy.Chronic periaortitis (CP) is a proliferating fibroinflammatory disease of the perivascular retroperitoneal space and aortic wall.^1–4 Owing to adventitial inflammation, some recent theories consider CP as a large vessel vasculitis.⁵ Clinical manifestations of CP include idiopathic retroperitoneal fibrosis, inflammatory aortic aneurysm and perianeurysmal retroperitoneal fibrosis.^2,6,7 The three manifestations with very similar histopathological characteristics are distinguished by the diameter of the abdominal aorta and concomitant ureteral affection.^1,3,7Specific clinical symptoms are caused by extrinsic compression of the ureters or retroperitoneal veins, resulting in hydronephrosis, oliguria, lower extremity oedema and deep vein thrombosis.^1,8Under medical treatment with steroids, CP has a good prognosis.⁷ Today tamoxifen is suggested as a safe and effective therapeutic alternative, and immunosuppressive drugs can be considered in patients with suboptimal responses to these drugs or multiple relapses.^9–11CT and MRI are the modalities of first choice for diagnosis and follow-up of CP.^1,7,12 The fibrotic para-aortic tissue shows significant contrast uptake in gadolinium-enhanced MRI.^12–14 Dynamic contrast-enhanced MRI was suggested for the assessment of the disease activity.^15,16 However, in cases with impaired renal function (e.g. by ureteral compression), gadolinium-independent imaging methods should be preferred owing to the potential development of a nephrogenic systemic fibrosis.¹⁷Diffusion-weighted MRI (DWI) is a non-contrast MR modality that has been successfully applied for the assessment of retroperitoneal masses, inflammatory abdominal aortic aneurysms and for the differentiation between retroperitoneal fibrosis and malignant retroperitoneal neoplasms.^18–21DWI indicates restricted diffusion of water, for example caused by a high cellularity in malignant disease or active inflammation. The apparent diffusion coefficient (ADC) is a quantitative parameter for the level of restricted diffusion, which is calculated from the signals of different diffusion gradients (b-values).²²In the context of untreated CP diffusion-weighted MRI may detect restricted inflammation as a sign of high cellularity caused by active inflammation.There are no data for the evaluation of intraindividual follow-up and the response to treatment by DWI of CP so far. Therefore, the aim of the present study was to analyse differences in DWI signals during follow-up in patients with CP before and after treatment. In addition, we sought to elucidate the potential of DWI in the therapy monitoring of CP.     

Hepatic radiofrequency ablation: in vivo and ex vivo comparisons of 15-gauge (G) and 17-G internally cooled electrodes

Objective:

To compare the performance of the 15-G internally cooled electrode with that of the conventional 17-G internally cooled electrode.

Methods:

A total of 40 (20 for each electrode) and 20 ablation zones (10 for each electrode) were made in extracted bovine livers and in in vivo porcine livers, respectively. Technical parameters, three dimensions [long-axis diameter (Dl), vertical-axis diameter (Dv) and short-axis diameter (Ds)], volume and the circularity (Ds/Dl) of the ablation zone were compared.

Results:

The total delivered energy was higher in the 15-G group than in the 17-G group in both ex vivo and in vivo studies (8.78 ± 1.06 vs 7.70 ± 0.98 kcal, p = 0.033; 11.20 ± 1.13 vs 8.49 ± 0.35 kcal, p = 0.001, respectively). The three dimensions of the ablation zone had a tendency to be larger in the 15-G group than in the 17-G group in both studies. The ablation volume was larger in the 15-G group than in the 17-G group in both ex vivo and in vivo studies (29.61 ± 7.10 vs 23.86 ± 3.82 cm³, p = 0.015; 10.26 ± 2.28 vs 7.79 ± 1.68 cm³, p = 0.028, respectively). The circularity of ablation zone was not significantly different in both the studies.

Conclusion:

The size of ablation zone was larger in the 15-G internally cooled electrode than in the 17-G electrode in both ex vivo and in vivo studies.

Advances in knowledge:

Radiofrequency ablation of hepatic tumours using 15-G electrode is useful to create larger ablation zones.Radiofrequency ablation (RFA) is the most widely used local ablation technique for the management of primary and metastatic liver tumours. However, previous studies have reported that RFA showed a relatively higher local tumour progression rate than did hepatic resection.^1,2 One of the most important factors affecting local tumour progression was insufficient tumour-free ablation margin of hepatic parenchyma around the tumour margin.^3–6Several strategies have been developed to obtain sufficient ablation margin. In the aspect of RFA techniques, overlapping technique and combined treatment with transcatheter arterial chemoembolization can be used.^7–9 Another strategy is to use switching monopolar, bipolar or multipolar modes to deliver radiofrequency (RF) energy more efficiently.^10,11 Sufficient ablation margin can also be achieved by more efficient electrodes: internally cooled electrode increases the size of ablation zone by preventing charring around the electrode tip.^12,13 Perfusion electrodes can also enlarge the ablation zone by increasing electrical conductance and thermal conductivity.^14–16The diameter of an electrode is also known to be associated with the size of the ablation zone. Theoretically, as the diameter of an electrode becomes larger, the contact surface of the electrode with the surrounding tissue becomes bigger, thereby increasing the active electric field.^17,18 As a result, an electrode with a larger diameter is likely to create a larger ablation zone. In a previous study, Goldberg et al¹⁷ reported that the extent of coagulation necrosis by RFA increases as the diameter of an electrode increases through an in vivo experimental study. However, this study was performed with an electrode without an internal cooling system. Recently, a clinical study comparing therapeutic efficacy and safety between 15-G and 17-G internally cooled electrodes of RFA for hepatocellular carcinoma was published.¹⁹ According to that study, the 15-G internally cooled electrode created a larger ablation volume than did the 17-G electrode. However, the study was limited by selection bias owing to the retrospective study design. In addition, the ablation protocol was not exactly the same between the two groups. Therefore, the issue whether an internally cooled electrode with a larger diameter creates a larger ablation volume should be verified with ex vivo and in vivo experimental studies.The purpose of this experimental study was to compare the performance of the 15-G internally cooled RF electrode with that of the conventional 17-G electrode in both ex vivo and in vivo studies.     

Walking on thin ice! Identifying methamphetamine “drug mules” on digital plain radiography

Objective:

The purpose of this study was to retrospectively evaluate the sensitivity, specificity and accuracy of identifying methamphetamine (MA) internal payloads in “drug mules” by plain abdominal digital radiography (DR).

Methods:

The study consisted of 35 individuals suspected of internal MA drug containers. A total of 59 supine digital radiographs were collected. An overall calculation regarding the diagnostic accuracy for all “drug mules” and a specific evaluation concerning the radiological appearance of drug packs as well as the rate of clearance and complications in correlation with the reader''s experience were performed. The gold standard was the presence of secured drug packs in the faeces.

Results:

There were 16 true-positive “drug mules” identified. DR of all drug carriers for Group 1 (forensic imaging experienced readers, n = 2) exhibited a sensitivity of 100%, a mean specificity of 76.3%, positive predictive value (PPV) of 78.5%, negative predictive value (NPV) of 100% and a mean accuracy 87.2%. Group 2 (inexperienced readers, n = 3) showed a lower sensitivity (93.7%), a mean specificity of 86%, a PPV of 86.5%, an NPV of 94.1% and a mean accuracy of 89.5%. The interrater agreement within Group 1 was 0.72 and within Group 2 averaged to 0.79, indicating a fair to very good agreement.

Conclusion:

DR is a valuable screening tool in cases of MA body packers with huge internal payloads being associated with a high diagnostic insecurity. Diagnostic insecurity on plain films may be overcome by low-dose CT as a cross-sectional imaging modality and addressed by improved radiological education in reporting drug carriers on imaging.

Advances in knowledge:

Diagnostic signs (double-condom and halo signs) on digital plain radiography are specific in MA “drug mules”, although DR is associated with high diagnostic insecurity and underreports the total internal payload.For the past decade, significant worldwide manufacturing of amphetamine-type stimulants has been reported to the United Nations Office on Drugs and Crime, Vienna, Austria, with a predominance of methamphetamine (MA) and its derivatives, which are also known as “syabu” or “ice”, throughout East and South East Asia.¹ In this region, the use of this synthetic drug is more prevalent than that of cocaine or heroin, which are more common in relatively developed areas, such as Europe and the USA.² During the course of this development, an increase in the number of drug carriers being intercepted by law enforcement at the borders of Malaysia has been observed. Drug carriers or “drug mules” are generally referred to as a human harbouring internal illicit drug packet(s). Internal body concealment of illegal drugs is one of the methods used to smuggle this illicit drug across the border.^3,4 “Drug mules” are generally known as body packers.^5,6 However, for correct terminology, one should differentiate between the terms body packer, body pusher and body stuffer. A body packer swallows a large amount of specially prepared drug packets to smuggle the packets in their gastrointestinal tract across a national border.^5,6 A body pusher hides a few containers in easily accessible body cavities, such as the rectum or vagina. Body stuffers, including traffickers and users, ingest intentionally small amounts of loosely wrapped drug pellets (typically initially hidden in the mouth), usually immediately before an unexpected encounter with law enforcement.^5–10The generally accepted radiological examination is a plain abdominal radiograph in the supine projection.^4–6 This technique is widely available at a low cost and is a simple method of detecting drug-filled packets within the alimentary tract. Radiation exposure to the patient is relatively moderate. In the literature, the detection rate for drug-filled packets is highly variable, and sensitivities from 58.3% to 90% have been reported.^4,5,11 Hence, plain abdominal radiography is a flawed screening method for identifying “drug mules”. Examining the bowel for foreign bodies, such as drug containers with variable sizes and radiodensities, is problematic, even for an experienced radiologist because the drug-filled packets may have an appearance similar to that of stool and gas and may be superimposed. Specific appearances described in the literature, such as the “double-condom”, “halo” and “rosette” signs, may be diagnostic for drug packages but are not necessarily so.^{4–6,11–13} Other modalities employed worldwide for the identification of body packers include CT, ultrasound, MRI and low-dose linear slit digital radiography (LSDR or LODOX®; Lodox Systems, Johannesburg, South Africa).^4,5,14–18Recent research has mainly concentrated on cocaine and heroin drug trafficking, which occurs predominantly in Western countries.^{3,4,6,7,11,14,19} There is little research on the accuracy of plain abdominal radiography in MA drug carriers, although there has been a significant increase of MA in Asia, accompanied by draconian legal measures in cases of drug trafficking.^1,2 The purpose of this study was to retrospectively evaluate the sensitivity, specificity and accuracy of plain abdominal digital radiography (DRL) for identifying the internal payloads of MA in “drug mules”.     

Multidetector CT imaging features of solid pseudopapillary tumours of the pancreas in male patients: distinctive imaging features with female patients

Objective:

To describe multidetector CT imaging features of solid pseudopapillary tumours (SPTs) in male patients and to compare these imaging features with those found in female patients.

Methods:

The institutional review board approved this retrospective study. We included the CT images of 72 patients (M:F = 12:60; mean age, 35.0 years) diagnosed with SPT by histology. CT images were reviewed on the following: location of the tumour, maximal diameter, shape, margin and the fraction of the tumour composition. Statistical differences in CT imaging features were analysed.

Results:

Male patients with SPTs were significantly older than female patients (42.4 years vs 33.4 years, p = 0.0408) and the mean size of the SPTs in male patients was larger (6.3 cm vs 4.6 cm, p = 0.0413) than that of SPTs in female patients. Lobulated shape of the SPTs was most frequent in male patients, whereas oval shape was most frequent in female patients (p = 0.0133). SPTs in male patients tended to have a solid component (p = 0.0434). Progressive enhancement in the solid portion of the tumour was seen in 9 (81.8%) of 11 SPTs in male patients and in 30 (79.0%) of 38 SPTs in female patients on multiphasic CT.

Conclusion:

The imaging features of SPTs in male patients usually appeared as a somewhat large-sized solid mass with a lobulated margin and progressive enhancement. These imaging features may help to differentiate SPTs from other pancreatic tumours for their proper management.

Advances in knowledge:

SPTs in male patients appear as somewhat large-sized solid masses with lobulated margins, and this form occurs more frequently in older male patients than in female patients.Solid pseudopapillary tumour (SPT) of the pancreas is a rare low-grade malignant neoplasm accounting for only 1–2% of all pancreatic tumours.^1–3 Synonyms for this neoplasm include solid and cystic tumours, solid and papillary epithelial neoplasms, solid cystic papillary tumour, papillary cystic neoplasm, papillary cystic epithelial neoplasm, papillary cystic tumour or Frantz''s tumour.^3,4SPT is known to occur preferentially in young females and has a favourable prognosis. The characteristic imaging features of SPTs include encapsulation, solid and cystic components and peripheral calcification.^1,3,4 Although the imaging characteristics of SPTs have been well described in recent years,^3,5 it remains uncertain if the features of SPT occurring in males differ from those in females.Machado et al⁶ and Takahashi et al⁷ described distinctive clinicopathological characteristics of SPTs occurring in males. The purpose of this study was to describe multidetector CT (MDCT) imaging features of SPTs in male patients and to compare these features with those of female patients.     

Quantitative pixelwise myocardial perfusion maps from first-pass perfusion MRI

Objective:

To calculate and evaluate absolute quantitative myocardial perfusion maps from rest first-pass perfusion MRI.

Methods:

10 patients after revascularization of myocardial infarction underwent cardiac rest first-pass perfusion MRI. Additionally, perfusion examinations were performed in 12 healthy volunteers. Quantitative myocardial perfusion maps were calculated by using a deconvolution technique, and results were compared were the findings of a sector-based quantification.

Results:

Maps were typically calculated within 3 min per slice. For the volunteers, myocardial blood flow values of the maps were 0.51 ± 0.16 ml g⁻¹ per minute, whereas sector-based evaluation delivered 0.52 ± 0.15 ml g⁻¹ per minute. A t-test revealed no statistical difference between the two sets of values. For the patients, all perfusion defects visually detected in the dynamic perfusion series could be correctly reproduced in the maps.

Conclusion:

Calculation of quantitative perfusion maps from myocardial perfusion MRI examinations is feasible. The absolute quantitative maps provide additional information on the transmurality of perfusion defects compared with the visual evaluation of the perfusion series and offer a convenient way to present perfusion MRI findings.

Advances in knowledge:

Voxelwise analysis of myocardial perfusion helps clinicians to assess the degree of tissue damage, and the resulting maps are a good tool to present findings to patients.MRI is widely used for the evaluation of myocardial perfusion. Advantages of perfusion MRI are a higher spatial resolution compared with positron emission tomography (PET)^1,2 and single photon emission CT³ and the lack of exposure to radiation. Great efforts have been made to use MRI for quantitative evaluation of myocardial perfusion in the past years.^4,5 In clinical routine, however, evaluation of MRI perfusion examinations is performed by the visual analysis of the acquired images depicting areas remaining hypo-intense during the passage of the contrast agent bolus. One main reason for not quantifying myocardial perfusion is the sometimes-excessive user interaction time required for manual segmentation of the acquired images in the quantification process.If myocardial perfusion is quantified, in most studies, the high spatial resolution of the acquired MR images is not maintained. Instead, a sector-based evaluation is performed.^6,7 First attempts have been made to calculate myocardial perfusion maps to evaluate regional myocardial perfusion.^3,8–10 However, until now, these studies were performed in animals^8–10 or perfusion was only evaluated semiquantitatively.³ Recently, our group has published an automatic post-processing tool for quantitative perfusion evaluation.¹¹ That study focused on the automation of post-processing but confined itself on sectors of the myocardium. The next and consequent step is to evolve this technique to work on a pixel-by-pixel basis. Therefore, it was the goal of this study to develop and test a method that calculates pixelwise quantitative perfusion maps from myocardial perfusion MRI examinations. These maps might help the clinician in making a diagnosis by decreasing the number of images to be examined, because a pixelwise quantitative perfusion map demonstrates the information of a whole series of images obtained in a first-pass perfusion examination clearly arranged.     

Diffusion-weighted imaging vs STIR turbo SE imaging: capability for quantitative differentiation of small-cell lung cancer from non-small-cell lung cancer

Objective:

To compare the capability of differentiation of small-cell lung cancer (SCLC) from non-SCLC (NSCLC) between diffusion-weighted imaging (DWI) and short tau inversion recovery (STIR) turbo spin-echo imaging.

Methods:

The institutional review board of Kobe University Hospital, Kobe, Japan, approved this study, and written informed consent was obtained from each patient. 49 patients with NSCLC (30 males and 19 females; mean age, 66.8 years) and 7 patients with SCLC (5 males and 2 females; mean age, 68.6 years) enrolled and underwent DWI and STIR. To quantitatively differentiate SCLC from NSCLC, apparent diffusion coefficient (ADC) values on DWI and contrast ratios (CRs) between cancer and muscle on STIR were evaluated. ADC values and CRs were then compared between the two cell types by Mann–Whitney''s U-tests, and the diagnostic performances were compared by McNemar''s test.

Results:

There were significant differences of mean ADC values (p < 0.001) and mean CRs (p = 0.003). With adopted threshold values, the specificity (85.7%) and accuracy (85.7%) of DWI were higher than those of STIR (specificity, 63.3%; p = 0.001 and accuracy, 66.1%; p = 0.001). In addition, the accuracy of combination of both indexes (94.6%; p = 0.04) could significantly improve as compared with DWI alone.

Conclusion:

DWI is more useful for the differentiation of SCLC from NSCLC than STIR, and their combination can significantly improve the accuracy in this setting.

Advances in knowledge:

Pulmonary MRI, including DWI and STIR, had a potential of the suggestion of the possibility as SCLC.Lung cancer is the most common cause of cancer-related death among both males and females worldwide.¹ Lung cancers are divided into non-small-cell cancer (NSCLC) and small-cell lung cancer (SCLC), and the differentiation between SCLC and NSCLC is important in clinical practice because their therapeutic strategies, clinical course and prognoses are different.² In general, SCLC is usually determined with extensive hilar and mediastinal lymphadenopathy,³ and these cancers are mainly treated by chemotherapy or chemoradiotherapy.^2,4On the other hand, 5–10% of patients with SCLC were diagnosed as having solitary pulmonary nodules.^5,6 In this situation, the assessments of distant metastases before treatment play an important role in deciding the treatment. At present, although there are some different reports for patients with NSCLC regarding the assessment of distant metastases before surgery,^7–9 it is important to assess the distant metastases of these patients with SCLC because SCLC is known for its rapid doubling time, high growth fraction and early development of metastatic disease.^10–12 If patients with SCLC are diagnosed at Stage I or possibly Stage II, clinicians consider their treatment as surgery and/or neoadjuvant chemotherapy.^13–15 Therefore, the differentiation between SCLC and NSCLC and the suggestion of the possibility of SCLC may be important in routine clinical practice. However, the differentiation of SCLC from NSCLC is difficult on CT and positron emission tomography (PET) or PET/CT,^5,6,16 and fiberoptic bronchoscopy and percutaneous biopsy are recommended, although their diagnostic sensitivities range from 67% to 100%.^17–19Recently, the image quality and diagnostic capability of chest MRI has improved because of the advancement of MR systems and sequences, and short tau inversion recovery (STIR) turbo spin-echo (SE) imaging and diffusion-weighted imaging (DWI) have been reported as useful in differentiating malignant nodules and lymph nodes from benign ones in several articles.^20–25 Meanwhile, the utilities of chest MRI, including STIR and DWI, have been reported,²⁶ and, in addition, meta-analysis report for pulmonary nodules by means of DWI have been published.²⁷ However, to the best of our knowledge, there have been only reports of chest DWI regarding the differentiation between SCLC and NSCLC,²² but no major studies have reported a direct comparison of the use of DWI and STIR in chest MRI for the assessment of differentiation between SCLC and NSCLC. We hypothesized that both DWI and STIR were useful MR sequences for differentiation of SCLC from NSCLC and their combination might improve the differentiation capabilities. The aim of this study was to evaluate the diagnostic performances of DWI and STIR for differentiating between SCLC and NSCLC.     

Investigation into the radiobiological consequences of pre-treatment verification imaging with megavoltage X-rays in radiotherapy

Objective:

The aim of this study was to investigate the effect of pre-treatment verification imaging with megavoltage X-rays on cancer and normal cell survival in vitro and to compare the findings with theoretically modelled data. Since the dose received from pre-treatment imaging can be significant, the incorporation of this dose at the planning stage of treatment has been suggested.

Methods:

The impact of imaging dose incorporation on cell survival was investigated by clonogenic assay of irradiated DU-145 prostate cancer, H460 non-small-cell lung cancer and AGO-1522b normal tissue fibroblast cells. Clinically relevant imaging-to-treatment times of 7.5 and 15 min were chosen for this study. The theoretical magnitude of the loss of radiobiological efficacy due to sublethal damage repair was investigated using the Lea–Catcheside dose protraction factor model.

Results:

For the cell lines investigated, the experimental data showed that imaging dose incorporation had no significant impact on cell survival. These findings were in close agreement with theoretical results.

Conclusion:

For the conditions investigated, the results suggest that allowance for the imaging dose at the planning stage of treatment should not adversely affect treatment efficacy.

Advances in knowledge:

There is a paucity of data in the literature on imaging effects in radiotherapy. This article presents a systematic study of imaging dose effects on cancer and normal cell survival, providing both theoretical and experimental evidence for clinically relevant imaging doses and imaging-to-treatment times. The data provide a firm foundation for further study into this highly relevant area of research.Radiotherapy is in a period of rapid scientific and clinical development. With the introduction of adaptive radiotherapy¹ and the increasing use of high-precision techniques,² there has been an increased requirement for verification imaging. Verification imaging can be carried out using megavoltage portal beams, kilovoltage planar fields or cone beam CT (CBCT) using kilovoltage or megavoltage beams. Dependent on the imaging technique employed, the dose required to acquire an image of adequate quality can vary significantly. Whilst doses ranging from a few centigrays to 10 cGy are required for megavoltage portal imaging and CBCT, doses in the order of megagrays are typically required to obtain an image of adequate quality using kilovoltage planar imaging.³ The choice of imaging modality is dictated by the available technology, with megavoltage portal imaging being the most established imaging option. However, with the addition of on-board kilovoltage imaging systems, kilovoltage imaging options are becoming much more widespread both for their improved image contrast and reduced patient dose.⁴Associated with this increasing imaging dose burden are concerns regarding the increased risk of deterministic and stochastic effects due to increased radiation exposure.^3,5–7 Whilst it is important to quantitatively determine the long-term effects of increased concomitant exposures, it is equally important to determine any potential changes to the effectiveness of the therapeutic dose.^5,8–10Low-dose biological phenomena such as adaptive responses^11–13 and bystander signalling^14–17 hold the potential to significantly alter the response of cells to radiation and thus treatment efficacy. However, since these effects tend to occur over a period of hours, it is unlikely that they will have any significant impact with regard to imaging in the treatment room.¹⁸ By contrast, sublethal damage repair that can occur over a period of minutes may be of significance in radiotherapy when the dose delivered from imaging beams is incorporated with the prescribed therapeutic dose at the treatment planning stage.^9,10,19–22The effect of imaging dose incorporation was previously reported in a preliminary study by Yang et al.¹⁰ In particular, they showed an unexpected 12.6% increase in cell survival when H460 cells were exposed to a pre-treatment imaging dose of 5 cGy followed by a therapeutic dose of 200 cGy, they attributed their findings to increased cell proliferation. The results suggest that the delivery of a fraction of the therapeutic dose by imaging beams presents a potential issue since the time from imaging to delivery of the treatment can be of the order of 5–20 min, having a negative impact on treatment efficacy owing to low-dose biological phenomena¹⁶ or sublethal damage repair that may be initiated during this time.^9,19 Although the need for imaging dose incorporation is justified, the potential to affect treatment efficacy should be determined.To investigate the radiobiological impact of imaging dose incorporation, a series of experiments were conducted in vitro, where the imaging doses were incorporated with the prescribed treatment dose for different human cell lines. As megavoltage portal imaging is the most widely used type of imaging for verification and as it delivers a higher dose, the study was carried out using 6 MV beams for both the imaging and treatment components. The theoretical magnitude of this effect and its impact on cell survival was quantified using radiobiological modelling based on the Lea–Catcheside dose protraction factor²³ as a comparison to the experimental data.     

Repeatability of quantitative metrics derived from MR diffusion tractography in paediatric patients with epilepsy

Objective:

To quantify the test–retest repeatability of mean diffusivity (MD) and fractional anisotropy (FA) derived from diffusion tensor imaging (DTI) tractography in a cohort of paediatric patients with localization-related epilepsy.

Methods:

30 patients underwent 2 DTI acquisitions [repetition time/echo time (ms), 7000/90; flip, 90°; b-value, 1000 s mm⁻²; voxel (mm), 2 × 2 × 2]. Two observers used Diffusion Toolkit and TrackVis (www.trackvis.org) to segment and analyse the following tracts: corpus callosum, corticospinal tracts, arcuate fasciculi, inferior longitudinal fasciculi and inferior fronto-occipital fasciculi. Mean MD and mean FA were calculated for each tract. Each observer independently analysed one of the DTI data sets for every patient.

Results:

Segmentation identified all tracts in all subjects, except the arcuate fasciculus. There was a highly consistent relationship between repeated observations of MD (r = 0.993; p < 0.0001) and FA (r = 0.990; p < 0.0001). For each tract, coefficients of variation ranged from 0.9% to 2.1% for MD and from 1.5% to 2.8% for FA. The 95% confidence limits (CLs) for change ranged from 2.8% to 6% for MD and from 4.3% to 8.6% for FA. For the arcuate fasciculus, Cohen''s κ for agreement between the observers (identifiable vs not identifiable) was 1.0.

Conclusion:

We quantified the repeatability of two commonly utilized scalar metrics derived from DTI tractography. For an individual patient, changes greater than the repeatability coefficient or 95% CLs for change are unlikely to be related to variability in their measurement.

Advances in knowledge:

Reproducibility of these metrics will aid in the design of future studies and might one day be used to guide management in patients with epilepsy.Epilepsy is a common neurological condition defined by recurrent unprovoked seizures that affects 1% of the population, including 1 in 200 children.^1,2 Unlike in adults, developmental lesions predominate as the source of seizures in children; in particular, focal cortical dysplasia is the most common anatomical substrate for intractable epilepsy in the paediatric population.³ A high proportion of epilepsies occurring in the setting of cortical malformations are pharmacoresistant,⁴ highlighting the importance of alternative management strategies. In appropriately selected patients who fail medical management, surgical resection of the dysplastic cortex can be curative. In such cases, pre-operative identification and complete resection of the structural lesion are important prognostic factors.^5,6 Decision making surrounding the pursuit of invasive alternatives is rarely straightforward, however, and in practice relies heavily on supplementary information provided by novel diagnostic techniques.Although surgical management is an attractive option for many patients with focal seizures, medical therapy continues to be adopted as the “safe” strategy in a significant portion of this population. However, there is good evidence to suggest that ongoing seizures and treatment with antiseizure medication might be associated with progressive alterations in white matter integrity.^7–9 Furthermore, these same ongoing processes can contribute to progressive functional decline.^10,11 As such, the ability to confidently identify progression of network alterations in an individual patient with epilepsy, whether on the basis of ongoing seizure activity, antiseizure medication or both, would be of great value to informed decision making surrounding potential surgical intervention.With the advent of diffusion-weighted imaging (DWI), the microstructural properties of a tissue of interest can be non-invasively probed at a spatial scale that is otherwise unattainable using even the most advanced structural MR techniques. Diffusion tensor imaging (DTI) is a variation on the theme of DWI, which quantifies water motion in three orthogonal dimensions and, therefore, is better able to capture the anisotropic tendencies of diffusion in highly organized tissues, such as cerebral white matter.¹² Numerous scalar metrics can be derived from the tensor; the most commonly referenced are mean diffusivity (MD) and fractional anisotropy (FA). MD provides a measure of overall incoherent motion within a voxel without regard for direction and reflects tissue organization at the cellular level.¹³ Increased MD is a common manifestation of white matter pathology of diverse aetiology.^14–16 By contrast, FA provides a measure of the degree to which a single direction of water motion dominates overall diffusivity in a voxel. As such, FA has been shown to be a relatively robust measure of white matter integrity.^17–21 Diffusion tractography is an extension of DTI in which the directional tendencies of water diffusion are used to create three-dimensional representations of white matter tracts based on their structural coherence.^22,23 In many instances, the functional role of the constructed pathways is at least in part known, which enables assessment of brain parenchymal abnormalities in terms of functional systems.^16,24DTI and diffusion tractography already occupy a prominent place in epilepsy research, and they are increasingly used to guide clinical management of epilepsy patients.^7,25–30 Although preliminary results are promising, a thorough understanding of the test–retest reproducibility of metrics derived from DTI will be crucial to the widespread application of this technique. Such knowledge would inform the design of both cross-sectional and longitudinal studies, including appropriate sample size selection. Furthermore, the clinical utility of such quantitative techniques will be predicated on an understanding of their intrinsic variability at the level of the individual. In particular, an understanding of what represents true difference at the individual level will be required to ascribe significance to changes in these metrics that occur in an individual patient. To date, however, the reproducibility of quantitative metrics derived from tractography has not been widely studied and, in particular, there are very few data from either the paediatric or epilepsy populations.³¹ The goal of this study, therefore, was to measure the repeatability of MD and FA derived from DTI tractography in a cohort of paediatric patients with localization-related epilepsy.     

Reduction of radiation exposure by lead curtain shielding in dedicated extremity cone beam CT

Objective:

A dedicated extremity cone beam CT (CBCT) was introduced recently, and is rapidly becoming an attractive modality for extremity imaging. This study aimed to evaluate the effectiveness of a curtain-shaped lead shielding in reducing the exposure of patients to scattered radiation in dedicated extremity CBCT.

Methods:

A dedicated extremity CBCT scanner was used. The lead shielding curtain was 42 × 60 cm with 0.5-mm lead equivalent. Scattered radiation dose from CBCT was measured using thermoluminescence dosimetry chips at 20 points, at different distances and directions from the CT gantry. Two sets of scattered radiation dose measurements were performed before and after installation of curtain-shaped lead shield, and the percentage reduction in dose in air was calculated.

Results:

Mean radiation exposure dose at measured points was 34.46 ± 48.40 μGy without curtains and 9.67 ± 4.53 μGy with curtains, exhibiting 71.94% reduction (p = 0.000). The use of lead shielding curtains significantly reduced scattered radiation at 0.5, 1.0 and 1.5 m from the CT gantry, with percent reductions of 84.8%, 58.0% and 35.5%, respectively (p = 0.000, 0.000 and 0.002). The percent reduction in the diagonal (+45°, −45°) and vertical forward (0°) directions were 86.3%, 83.1% and 77.7%, respectively, and were statistically significant (p = 0.029, 0.020 and 0.041).

Conclusion:

Shielding with lead curtains suggests an easy and effective method for reducing patient exposure to radiation in extremity CBCT imaging.

Advances in knowledge:

Lead shielding curtains are an effective technique to reduce scattered radiation dose in dedicated extremity CBCT, with higher dose reduction closer to the gantry opening.Plain radiographic examinations are routinely used in initial evaluation of bony injuries, but superimposition of structures and other inherent problems associated with this technique cause misdiagnosis.¹ CT is widely used for more detailed evaluation of suspected injuries in extremities. Multidetector CT (MDCT) can provide medical practitioners with detailed morphological information on osseous and soft-tissue structures.More recently, cone beam CT (CBCT) has been introduced for extremity imaging.² This application offers an attractive alternative with high spatial resolution, which enables detailed visualization of osseous structures, easy installation owing to its smaller size, and relatively low radiation dose compared with conventional MDCT scanners.^3–7 There are an increasing number of papers reporting various clinical applications of CBCT, such as in CT angiography and in weight-bearing imaging.^8,9 Like other imaging modalities using ionizing radiation, reducing patient radiation dose is an important issue.¹⁰ Patient radiation exposure can be largely categorized into the following two categories: (1) radiation dose within the field of view (FOV) and (2) scattered radiation extending beyond the FOV area. Although radiation dose within FOV has been a major concern regarding patient dose, we cannot neglect the out-of-field radiation that can affect radiosensitive organs such as the gonads and the thyroid gland in extremities imaging.Several approaches exist for reducing scattered radiation, including decreasing the overall radiation dose by adjusting the radiation source and shielding. Decreasing radiation exposure dose within FOV results in reduced out-of-FOV radiation because scattered radiation is positively correlated to the entrance surface dose.¹¹ However, a certain amount of radiation dose is necessary within the FOV for maintaining image quality. Therefore, there are limitations on reducing the scattered radiation by adjusting the radiation source. Shielding materials can be placed between the radiation source and the areas where protection is needed for further reducing the out-of-field radiation. Various methods have been developed for reducing the scattered radiation, for example, lead apron, lead shield and radio-absorbable drape in the setting of fluoroscopy-guided procedures.^12,13 However, there are no standardized methods for reducing the scattered radiation to patients in extremity scanning using mobile dedicated extremity CBCT.Therefore, we proposed a curtain-shaped radiation-absorbing material hung at the gantry outlet. The goal of this study was to evaluate the effectiveness of curtain-shaped lead shielding technique for reducing the radiation exposure in dedicated extremity CBCT.     

Stage T3a renal cell carcinoma: staging accuracy of CT for sinus fat,perinephric fat or renal vein invasion

Objective:

To study the accuracy of CT for staging T3a (TNM 2009) renal cell carcinoma (RCC).

Methods:

Unenhanced and nephrographic phase CT studies of 117 patients (male:female = 82:35; age range, 21–86 years) with T1–T3a RCC were independently reviewed by 2 readers. The presence of sinus or perinephric fat, or renal vein invasion and tumour characteristics were noted.

Results:

Median (range) tumour size was 5.5 (0.9–19.0) cm; and 46 (39%), 16 (14%) and 55 (47%) tumours were pT1, pT2 and pT3a RCC, respectively. The sensitivity/specificity for sinus fat, perinephric fat and renal vein invasion were 71/79%, 83/76% and 59/93% (Reader 1) and 88/71%, 68/72% and 69/91% (Reader 2) with κ = 0.41, 0.43 and 0.61, respectively. Sinus fat invasion was seen in 47/55 (85%) cases with T3a RCC vs 16/55 (29%) and 33/55 (60%) for perinephric fat and renal vein invasion. Tumour necrosis, irregularity of tumour edge and direct tumour contact with perirenal fascia or sinus fat increased the odds of local invasion [odds ratio (OR), 2.5–3.7; p < 0.05; κ = 0.42–0.61]. Stage T3a tumours were centrally located (OR, 3.9; p = 0.0009).

Conclusion:

Stage T3a RCC was identified with a sensitivity of 59–88% and specificity of 71–93% (κ = 0.41–0.61). Sinus fat invasion was the most common invasive feature.

Advances in knowledge:

Centrally situated renal tumours with an irregular tumour edge, inseparable from sinus structures or the perirenal fascia and CT features of tumour necrosis should alert the reader to the possibility of Stage T3a RCC (OR, 2.5–3.9).Current guidelines¹ recommend nephron-sparing procedures (either partial nephrectomy or ablation) for Stage T1a (<4 cm) renal cell carcinomas (RCCs), but the indications for nephron-sparing procedures are widening.² Successful surgical series have been reported with Stage T1b (<4–7 cm) tumours and even Stage T2 RCCs.³ Central location is not necessarily a barrier to good clinical outcome after partial nephrectomy,³ but nephron-sparing procedures are contraindicated for stage ≥T3a renal cancers.¹ Thus, prior accurate recognition of T3a stage is important, especially with central renal masses, as any pre-operative suspicion of local invasion should contraindicate nephron-sparing surgery or ablation.In the most recent TNM iteration, Stage T1 and T2 tumours are defined by tumour diameter (T1a, ≤4 cm; T1b, 4–7 cm; T2a, 7–10 cm; and T2b, ≥10 cm) and the absence of any local invasion. Stage T3a RCC was redefined to include invasion of either renal sinus or perinephric fat.⁴ Renal vein invasion [main renal vein and/or segmental (muscle-containing) branch invasion], without caval involvement, was downgraded from Stage T3b to Stage T3a, whilst adrenal invasion was upgraded from Stage T3a to Stage T4. Size is not a governing factor with ≥T3a tumours, and some renal masses <7 cm in diameter will be locally advanced. Nearly half of all pT3a RCCs (n = 309/623) in one study were <7 cm in diameter.⁵ Other studies have confirmed the poor prognostic significance of sinus fat or venous invasion in masses <7 cm, with a 4–6 times increased risk of cancer-related death.^6,7 Centrally located masses are more likely to demonstrate local invasion with positive surgical resection margins after partial nephrectomy,^8,9 and unrecognized sinus invasion may explain the recurrence of cancer, and subsequent death from metastatic disease, in some cases of presumed T1 RCCs.⁸However, in previous studies, CT staging has been variably accurate^10–18 for RCCs, and staging inaccuracies, usually understaging, are said to be most common with Stage T3a disease.^12,17 For venous invasion, the specificity and sensitivity have ranged between 58–97% and 32–96%,^10,14–16 and for perinephric infiltration, the figures have been 32–96% and 85–93%,^14–16 respectively. The CT accuracy for sinus fat invasion has not been previously investigated. The primary aim of this study was to define the accuracy of contrast-enhanced CT for identifying any of the three defining features of Stage T3a RCC, that is, sinus or perinephric fat invasion, or renal vein invasion. Secondary study objectives were to identify any tumour characteristics that increase the odds of T3a disease and may be used as accessory CT signs to alert the reader to an increased likelihood of local invasion by RCC.     

Early assessment of chronic kidney dysfunction using contrast-enhanced ultrasound: a pilot study

Objective:

We performed a prospective study to evaluate the value of contrast-enhanced (CE) ultrasound in quantitative evaluation of renal cortex perfusion in patients with chronic kidney dysfunction (CKD Stage I–II).

Methods:

The present study was approved by the institutional ethics committee. The study focused on 41 consecutive patients (males, 32; females, 9; mean age, 55.0 ± 5.0 years) with clinical suspicion of CKD (Stages I–II). For both kidneys, CE ultrasound was performed after intravenous bolus injection of 1.0 ml SonoVue® (Bracco Imaging S.p.A., Milan, Italy). Time–intensity curves (TICs) and quantitative indexes were created with Qlab software (Philips, Bothell, WA). 45 healthy volunteers were included as control group. All statistical analyses were performed with SPSS® v. 15.0 software package (SPSS, Chicago, IL). A difference was considered statistically significant with p < 0.05.

Results:

Patients with CKD (Stages I–II) had no obvious change in the shape of TICs. Among all quantitative indexes, the changes of area under the curve (AUC), derived peak intensity (DPI) and slope rate of elevation curve (A) were statistically significant (p < 0.05). DPI <12 dB, A >2 and AUC >1300 dB s had high utility in the evaluation of CKD, with 81%, 73% and 78% specificities and 76%, 73% and 77% sensitivities.

Conclusion:

CE ultrasound might be valuable in the early evaluation of CKD. AUC, A and DPI might be valuable quantitative indexes.

Advances in knowledge:

Quantitative CE ultrasound analysis can be used for the standardized and early evaluation of renal dysfunction.Throughout the world, chronic kidney dysfunction (CKD) is a growing health concern because of its increasing prevalence and incidence rate.¹ Since CKD primarily involves perfusion changes in the renal cortex, assessment of tissue perfusion is an important component for the evaluation of CKD.² Early and detailed visualizations of perfusion changes of the renal cortex yield information about organ viability and function, which would be crucial to make diagnosis and to initiate early drug therapy.³Different non-invasive imaging modalities, such as multidetector CT,⁴ positron emission tomography,⁵ MRI⁶ and single-photon emission CT with ^99mTc-diethylenetriamine pentaacetic acid⁷ are used in the quantifications of tissue perfusions. However, high costs, reduced availability, long examination periods, patients'' exposure to radiation or nuclear tracers limited clinical applications of these techniques.^4–7 Greyscale renal ultrasound combined with colour Doppler flow imaging (CDFI) had become the main non-invasive imaging methods for evaluating the renal anatomy and blood flow.⁸ However, CDFI parameters such as the resistance index (RI) and peak systolic velocity (PSV) provided only indirect macrovasculature parameters, which could not directly assess renal cortex perfusion and were of limited diagnostic use in the CKD.⁹ To date, there was no reliable, accurate and convenient method to determine renal blood perfusion in vivo, thereby leading to difficulty in early and accurate diagnosis of CKD.In recent years, low mechanical index (MI) real-time contrast-enhanced (CE) ultrasound has been proposed as an alternative imaging technique in this area.¹⁰ Because microbubbles are blood-pool agents, when injected intravenously, they remain entirely intravascular, mix uniformly with blood in the circulation and possess the same intravascular rheology as red blood cells.¹¹ The advantages of CE ultrasound include the absence of ionizing radiation or nephrotoxicity, and the widespread availability. When CE ultrasound is performed immediately after a non-conclusive ultrasound study, only a short time was needed to arrive at a final diagnosis.¹² CE ultrasound has been recently used as a new imaging technique for quantifying tissue perfusion changes in the liver,¹³ heart¹⁴ and kidney.¹⁵ The large blood supply of the kidney was a good base for contrast studies, as >90% of kidney blood flow supplied the renal cortex by the renal arterioles and capillaries.¹⁶ Since CE ultrasound microbubbles remain strictly inside the vessels, they can be viewed as blood-pool markers enabling functional imaging of the kidney.¹⁷ The increase in echo signal intensity after microbubble injection may be quantified by dedicated software packages to produce time–intensity curves (TICs). Enhancement-based representations had been used to assess unilateral kidney dysfunction such as in renal artery stenosis by a simple analysis of the tracer concentration curve.¹⁸ These features made low MI CE ultrasound a promising technique in evaluation of renal cortex perfusion.The purpose of this initial study was to evaluate the feasibility of CE ultrasound to assess renal cortex tissue perfusion in the early stages of CKD (Stages I–II) by means of TICs. The diagnostic efficacy gained by quantitative CE ultrasound was compared with that of renal arterial PSV and RI measured by CDFI.