Paul Humphries

Pediatric and Adolescent Lymphoma: Comparison of Whole-Body STIR Half-Fourier RARE MR Imaging with an Enhanced PET/CT Reference for Initial Staging

PURPOSE To compare the diagnostic performance of rapid whole-body anatomic magnetic resonance (MR) staging of pediatric and adolescent lymphoma to an enhanced positron emission tomographic (PET)/computed tomographic (CT) reference standard. MATERIALS AND METHODS Ethical permission was given by the University College London Hospital ethics committee, and informed written consent was obtained from all participants and/or parents or guardians. Thirty-one subjects (age range, 7.3-18.0 years; 18 male, 11 female) with histologically proved lymphoma were prospectively recruited. Pretreatment staging was performed with whole-body short inversion time inversion-recovery (STIR) half-Fourier rapid acquisition with relaxation enhancement (RARE) MR imaging, fluorine 18 fluorodeoxyglucose PET/CT, and contrast agent-enhanced chest CT. Twenty-six subjects had posttreatment PET/CT and compromised our final cohort. Eleven nodal and 11 extranodal sites per patient were assessed on MR imaging by two radiologists in consensus, with a nodal short-axis threshold of >1 cm and predefined extranodal positivity criteria. The same sites were independantly evaluated by two nuclear medicine physicians on PET/CT images. Disease positivity was defined as a maximum standardized uptake value >2.5 or nodal size >1 cm. An unblinded expert panel reevaluated the imaging findings, removing perceptual errors, and derived an enhanced PET/CT reference standard (taking into account chest CT and 3-month follow-up imaging) against which the reported and intrinsic performance of MR imaging was assessed by using the kappa statistic. RESULTS There was very good agreement between MR imaging and the enhanced PET/CT reference standard for nodal and extranodal staging (kappa = 0.96 and 0.86, respectively) which improved following elimination of perceptual errors (kappa = 0.97 and 0.91, respectively). The sensitivity and specificity of MR imaging (following removal of perceptual error) were 98% and 99%, respectively, for nodal disease and 91% and 99%, respectively, for extranodal disease. CONCLUSION Whole-body STIR half-Fourier RARE MR imaging of pediatric and adolescent lymphoma can accurately depict nodal and extranodal disease and may provide an alternative nonionizing imaging method for anatomic disease assessment at initial staging.

Quantitative diffusion weighted MRI: A functional biomarker of nodal disease in Hodgkin lymphoma?

PURPOSE This study explores the relationship between MRI Apparent Diffusion Coefficient (ADC) and PET Standardized Uptake Value (SUV) measurements in pediatric Hodgkin lymphoma. METHODS Sixteen patients (mean age 15.4 yrs, 8 male) with proven Hodgkin lymphoma were recruited and staged using PET-CT, anatomical MRI and additional 1.5T diffusion weighted imaging (DWI) prior to and following chemotherapy. Pre-treatment lymph nodes and anatomically paired post-treatment residual tissue located on MRI were matched to the corresponding PET-CT. Region of interest (ROI) analysis was used to extract quantitative measurements. Mean ADC (ADC(mean)) and maximum SUV (SUV(max)) were recorded and correlation assessed using Spearman statistics. RESULTS Fifty-three ROIs were sampled. Pre- and post-treatment ADC(mean) ranged from 0.77 × 10(−3) to 1.79 × 10(−3) (median 1.15 × 10(−3) mm(2)s(−1)) and 1.08 × 10(−3) to 3.18 ×10(−3) (median 1.88 × 10(−3) mm(2)s(−1)), and SUV(max) from 2.60 to 25.4 (median 8.85 mg/ml) and 1.00 to 3.50 mg/ml (median 1.90 mg/ml). Median post-treatment ADC(mean) was higher, and median SUV(max) lower than pretreatment values (p < 0.0001). There was an inverse correlation between pre-treatment ADC(mean) and SUV(max) (p = 0.005) and between fractional change ([post-treatment – pre-treatment]/pre-treatment)in ADC(mean) and SUV(max) (p =0.002). CONCLUSION Our results confirm a strong reciprocal relationship between nodal ADC(mean) and SUV(max) in Hodgkin lymphoma;supporting the potential application of quantitative DWI as a functional biomarker of disease.

Structural Abnormalities of the Female Reproductive Tract

The true incidence of structural abnormalities of the female reproductive tract in paediatric and adolescent patients is difficult to determine. The term “structural abnormality” encompasses a wide spectrum of anatomical anomalies, which, depending on the precise anomalies present, have a varied temporal and clinical presentation. Imaging assessment of these abnormalities often requires a multi-modality approach with the methods employed being modified depending on the clinical presentation and age of the patient. Classification of structural genital abnormalities is not standardized, with several different schema proposed. Ultimately good communication between clinical and radiological multidisciplinary team members is vital to ensure that there is unambiguous interpretation of the spectrum of abnormalities in a given patient and best care delivered.

MRI in the assessment of congenital vaginal anomalies

AIM To assess accuracy of magnetic resonance imaging (MRI) for the delineation of morphological abnormalities of the vagina in patients with congenital anomalies of the genito-urinary tract. MATERIALS AND METHODS Fifty-one patients (median age 19 years; range 12-40 years) were studied. All were consecutively referred for MRI to assess genital tract anatomy, between 1996 and 2004, from a clinic specializing in congenital abnormalities of the urogenital tract. All patients were assessed clinically and underwent MRI. Images were reviewed retrospectively by an experienced radiologist. Where there was discordance between clinical and radiological findings a consensus diagnosis was achieved by the gynaecologists and radiologists reviewing all of the clinical and radiological evidence together, including assessment of vaginal length. RESULTS The clinical data were incomplete for five women and the images non-diagnostic in two cases; consequently, 44 of 51 women had complete datasets and could be evaluated. Vaginas were abnormal in 30 of the 44 patients. There was discordance between the clinical and imaging findings at the initial review in three of the 44 cases (6.8%). After consensus review, and with the inclusion of measurement of the vaginal length on MRI, the MRI and clinical findings were concordant in all cases. The initial discordance was due to two vaginal dimples not being appreciated on MRI and one case in which presence of vaginal tissue proximal to a mid-segment obstruction was not appreciated clinically. CONCLUSION MRI is an accurate method of imaging vaginal anomalies. However, to achieve reliable results the radiologist requires details of previous surgery and the vaginal length must be measured.

Dynamic contrast-enhanced MRI improves accuracy for detecting focal splenic involvement in children and adolescents with Hodgkin disease.

BackgroundAccurate assessment of splenic disease is important for staging Hodgkin lymphoma.ObjectiveThe purpose of this study was to assess T2-weighted imaging with and without dynamic contrast-enhanced (DCE) MRI for evaluation of splenic Hodgkin disease.Materials and methodsThirty-one children with Hodgkin lymphoma underwent whole-body T2-weighted MRI with supplementary DCE splenic imaging, and whole-body PET-CT before and following chemotherapy. Two experienced nuclear medicine physicians derived a PET-CT reference standard for splenic disease, augmented by follow-up imaging. Unaware of the PET-CT, two experienced radiologists independently evaluated MRI exercising a locked sequential read paradigm (T2-weighted then DCE review) and recorded the presence/absence of splenic disease at each stage. Performance of each radiologist was determined prior to and following review of DCE-MRI. Incorrect MRI findings were ascribed to reader (lesion present on MRI but missed by reader) or technical (lesion not present on MRI) error.ResultsSeven children had splenic disease. Sensitivity/specificity of both radiologists for the detection of splenic involvement using T2-weighted images alone was 57%/100% and increased to 100%/100% with DCE-MRI. There were three instances of technical error on T2-weighted imaging; all lesions were visible on DCE-MRI.ConclusionsT2-weighted imaging when complemented by DCE-MRI imaging may improve evaluation of Hodgkin disease splenic involvement.

Atypical abdominal paediatric lymphangiomatosis: diagnosis aided by diffusion-weighted MRI

We report a 4-year-old child with a mesenteric mass, which on ultrasound, CT and conventional MRI appeared solid, raising lymphoma as a possible diagnosis. Diffusion weighted MRI (DW-MRI), however, suggested a low-cellularity lesion, making lymphoma less likely. Biopsy confirmed lymphangioma. DW-MRI may be a useful adjunct to conventional imaging, even in the abdomen.

The joints in juvenile idiopathic arthritis

Juvenile idiopathic arthritis is the most common rheumatic entity in childhood. Imaging has become an important supplement to the clinical assessment of children with JIA. Radiographs still play an important role in the workup, and long-term follow-up in children with JIA, but are not sensitive to findings in the early disease stage. Both ultrasound and MRI are more sensitive to inflammatory changes than clinical assessment alone. However, the differentiation between normal findings and pathology can be challenging, particularly in early disease. The objective of this review is to discuss the role of imaging in JIA, describe the typical findings on different modalities and highlight the challenges we face regarding the reliability and accuracy of the different methods for imaging the joints in children with JIA.Key Points• Imaging is an important supplement to the clinical examination in JIA.• Ultrasound is more sensitive for detecting synovitis than clinical examination alone.• MRI can depict all relevant structures in joint inflammation.• The differentiation between normal variants and pathology is difficult in children.

Perineal Lipoma With Accessory Labioscrotal Fold and Penis-like Phallus in a Female Infant With Unilateral Renal Agenesis

We present a case of a female 46,XX infant with a perineal lipoma within an accessory labioscrotal fold containing a penis-like phallus, associated with contralateral renal agenesis and complete absence of Müllerian/paramesonephric structures. To our knowledge, this is the first report of perineal lipoma and accessory labioscrotal fold associated with urogenital abnormalities in a female. The case also has an exceptional penis-like phallus in the absence of Y chromosome material or evidence of virilization.

Diseases of the Peritoneum, Mesentery, and Omentum

Diseases involving the peritoneum, mesentery and omentum are numerous; they include among others, effusions and abscesses, consequences of intestinal malrotation and tumors. Many will be discovered during the work-up acute abdominal symptoms.

Accuracy of ADC estimates: response to letter by Priola et al. re Diffusion-weighted MRI of lymphoma: prognostic utility and implications for PET/MRI?

Dear Sir, We thank Priola et al. for clarifying an important point in relation to the use of apparent diffusion coefficient (ADC) estimates in our study [1] and agree with them that there are a number of factors that can affect quantitative ADC values. Priola et al. quite correctly point out that at low b-values (i.e. <200 s/mm) there is likely a perfusion component to the diffusion signal weighting. This is evidenced by the multi-exponential signal decay behaviour previously reported and indeed exploited by others to derive perfusion fractions from diffusion-weighted images [2, 3]. We agree that within our results the ADC estimates will have a perfusion component and our post-chemotherapy ADC changes could also reflect perfusion changes induced by treatment, although the degree of perfusion contribution remains uncertain. Concerning the difference in average ADC between Abdel Razek et al. [4] and our data, we do not agree with the explanation offered by Priola et al. that this is due to a difference in the highest b-value between the two studies (b500 vs b600) where the higher maximum b-value in the data of Abdel Razek et al. [4] results in reduced vascular contribution to the ADC signal. It is in fact the lowest bvalue that is important for perfusion weighting and both studies [1, 4] use a b0 image for ADC calculation. As a result both studies will have a contribution by intravoxel incoherent motion (IVIM) to the signal loss (from the b0 signal). We agree that at approximately b200most [perhaps all (dependent on the tissue)] of the signal loss caused by IVIM will have already occurred. Therefore any further signal loss caused by increasing the b-value is unlikely to be from spins within the vascular compartment. To reduce/eliminate IVIM contributions to ADC estimates one must exclude the b0 image from the ADC calculation. The difference in ADC estimates between our studies [1, 4] is therefore more likely a manifestation of the complex nature by which ADC values are derived and the variability that this induces (see below). We are in agreement with Priola et al. that obtaining accurate ADC estimates is important if we are to consider ADC for diagnosis and/or prognosis; however, we do not think that accounting for IVIM by choosing a non-zero lowest b-value signifies that the calculated ADC is more accurate (i.e. a better estimate of the ground truth ADC value within a region); it simply aims to reduce/eliminate the dependence of ADC upon the IVIM. Whether one wishes to remove this dependence should be governed by the pathology of interest as the IVIM componentmay itself be of importance for diagnosis/prognosis [2, 3, 5]. When considering accurate ADC estimation we need to consider a number of other factors. Firstly, there needs to be adequate signal to noise ratio (SNR) in the diffusion-weighted images used to derive ADC. From our experience where the SNR of images falls below a minimum of 6, errors in ADC estimates rapidly increase and can be as high as 80–90% at an SNR of 1 [6]. The number and spread of b-values used in calculating ADC is also important. Whilst authors report that mono-exponential decay behaviour can be ‘reasonably estimated’ by 2 or 3 b-values [7], the real diffusion signal decay curve in biological tissues is at least a bi-exponential or indeed more likely multi-exponential [8]. To accurately capture this the choice and number of b-values should ideally be adjusted This reply refers to the comment available at doi 10.1007/s00259-0132390-2.