J Zhang

Whole-Body Diffusion-Weighted Imaging: The Added Value to Whole-Body MRI at Initial Diagnosis of Lymphoma

OBJECTIVEnThe objective of our study was to evaluate the diagnostic performance of conventional whole-body MRI without and with diffusion-weighted imaging (DWI) in the detection of known (18)F-FDG-avid lymphomas. The conventional whole-body MRI protocol consisted of a T2-weighted sequence and a T2-weighted spectral attenuated inversion recovery (SPAIR) sequence with frequency-selective fat suppression. The second protocol used the same sequences as the first protocol but also included DWI.nnnSUBJECTS AND METHODSnSeventeen patients with pathologically confirmed, newly diagnosed, untreated lymphoma were recruited. T2-weighted and T2-weighted SPAIR images were evaluated first, separate from the DW images, and then were evaluated with the DW images. We used (18)F-FDG PET/CT as the standard of reference. True-positive, false-positive, and false-negative values were evaluated on a per-lesion basis. Tumor staging based on T2-weighted and T2-weighted SPAIR imaging without DWI and then with DWI was compared using the Ann Arbor staging system.nnnRESULTSnTrue-positive lesions were increased from 89% to 97%, false-positive lesions were increased from 3% to 6%, and false-negative lesions were decreased from 11% to 3% by the addition of DWI. Diagnostic sensitivity was significantly increased (p = 0.002) by adding DWI. Lesions detected on DWI but not on T2-weighted and T2-weighted SPAIR imaging were located in renal (n = 1), paraaortic (n = 6), and pelvic (n = 3) lymph nodes. On DWI, 47% of the lesions (n = 55) were more conspicuous than on T2-weighted and T2-weighted SPAIR imaging; most of these lesions (58%, n = 32) were from lymph nodes in the pelvic or abdominal regions and bone marrow. No difference was found between T2-weighted and T2-weighted SPAIR imaging without DWI and T2-weighted and T2-weighted SPAIR imaging with DWI in lymphoma staging, being consistent with PET/CT in 88% of the patients (n = 15).nnnCONCLUSIONnThe addition of DWI to conventional whole-body MRI sequences enhanced lesion conspicuity and improved diagnostic accuracy for lymphomas. With technical optimization, whole-body MRI with DWI, as a nonionizing imaging modality, may potentially be useful as an alternative method to PET/CT in the management of malignant lymphoma.

Quantitative Assessment of Diffusion-Weighted MR Imaging in Patients with Primary Rectal Cancer: Correlation with FDG-PET/CT

PurposeThe aim of the study was to assess correlations between parameters on diffusion-weighted imaging and 2-deoxy-2-[18F]fluoro-d-glucose–positron emission tomography/computed tomography (FDG-PET/CT) in rectal cancer.ProceduresThirty-three consecutive patients with pathologically confirmed rectal adenocarcinoma were included in this study. Apparent diffusion coefficient (ADC) maps were generated to calculate ADCmean (average ADC), ADCmin (lowest ADC), tumor volume, and total diffusivity index (TDI). PET/CT exams were performed within 1xa0week of magnetic resonance imaging. Standardized uptake values (SUVs) were normalized to the injected FDG dose and body weight. SUVmax (maximum SUV), SUVmean (average SUV), tumor volume, and total lesion glycolysis (TLG) were calculated using a 50% threshold.ResultsSignificant negative correlations were found between ADCmin and SUVmax (ru2009=u2009−0.450, pu2009=u20090.009), and between ADCmean and SUVmean (ru2009=u2009−0.402, pu2009=u20090.020). A significant positive correlation was found between TDI and TLG (ru2009=u20090.634, pu2009<u20090.001).ConclusionThe significant negative correlations between ADC and SUV suggest an association between tumor cellularity and metabolic activity in primary rectal adenocarcinoma.

Radiation dose and cancer risk in retrospectively and prospectively ECG-gated coronary angiography using 64-slice multidetector CT.

This study aimed to estimate the radiation dose and cancer risk to adults in England, the USA and Hong Kong associated with retrospectively and prospectively electrocardiogram (ECG)-gated coronary computed tomography angiography (CTA) using currently practised protocols in Hong Kong. The doses were simulated using the ImPACT spreadsheet. For retrospectively ECG-gated CTA with pitches of 0.2, 0.22 and 0.24, the effective doses were 27.7, 23.6 and 20.7 mSv, respectively, for males and 23.6, 20.0 and 18.8 mSv, respectively, for females. For prospectively ECG-gated CTA, the effective dose was 3.7 mSv for both males and females. A table of lifetime attributable risks (LAR) of cancer incidence was set up for the English population for the purpose of estimating cancer risk induced by low-dose radiation exposure, as previously reported for US and Hong Kong populations. From the tables, the LAR of cancer incidence for a representative 50-year-old subject was calculated for retrospectively ECG-gated CTA to be 0.112% and 0.227% for English males and females, respectively, 0.103% and 0.228% for US males and females, respectively, and was comparatively higher at 0.137% and 0.370% for Hong Kong males and females, respectively; for prospectively ECG-gated CTA, the corresponding values were calculated to be 0.014% and 0.035% for English males and females, respectively, and 0.013% and 0.036% for US males and females, respectively, and again were higher at 0.017% and 0.060% for Hong Kong males and females, respectively. Our study shows that prospectively ECG-gated CTA reduces radiation dose and cancer risks by up to 87% compared with retrospectively ECG-gated CTA.

Spectrum of 18F-FDG PET/CT Appearances in Peritoneal Disease

OBJECTIVEnThe objective of our study was to illustrate the spectrum of appearances of peritoneal diseases on (18)F-FDG PET/CT, show the usefulness of fused FDG PET/CT as a diagnostic tool for the peritoneum, and discuss the pitfalls in FDG PET/CT interpretation of peritoneal disease.nnnCONCLUSIONnMalignant and benign diseases may have peritoneal involvement, which can manifest as various imaging patterns on FDG PET/CT. Awareness of these patterns and of potential interpretation issues is important to optimize diagnostic accuracy.

Dynamic contrast‐enhanced MRI of primary rectal cancer: Quantitative correlation with positron emission tomography/computed tomography

To assess the correlations between parameters measured on dynamic contrast‐enhanced magnetic resonance imaging and 18F‐fluorodeoxyglucose positron emission tomography (FDG‐PET) in rectal cancer.

18F-FDG-PET-CT imaging findings of recurrent intracranial haemangiopericytoma with distant metastases

A 42-year-old woman presented with local recurrence and distant lung and liver metastases 7 years after resection of a primary intracranial haemangiopericytoma. Whole-body (18)F-fluoro-2-deoxy-d-glucose (FDG)-positron emission tomography (PET)-CT scan showed no increased uptake in local recurrence or distant metastases except for a focus of increased FDG uptake within a hepatic metastasis. The hypermetabolic area correlated with an intratumoral hypoenhancing area on the CT scan. PET-CT scan may be useful to allow further understanding of the tumour.

Combined use of 18F-FDG PET/CT, DW-MRI, and DCE-MRI in treatment response for preoperative chemoradiation therapy in locally invasive rectal cancers.

We investigated if 18F-FDG PET/CT, DW-MRI, and DCE-MRI are able to predict preoperative chemoradiation therapy (CRT) response in patients with T3-4 rectal adenocarcinomas. MRI and PET/CT scans were performed within 1 week, at baseline, early midtreatment (2 weeks of CRT), and posttreatment (6 weeks after completing CRT). Responders (n = 4) and nonresponders (n = 4) were defined according to tumor regression grade by histology. Only SUVmax (P = 0.030) at early midtreatment could significantly differentiate between responders and nonresponders, suggesting that 18F-FDG PET/CT may be effective to predict early treatment response compared with DW-MRI and DCE-MRI in T3-4 rectal cancer.

PET/CT appearance of intestinal Behcet disease.

Behcet disease is a multisystem, chronic relapsing vasculitis of unknown etiology. Gastrointestinal involvement occurs in 10% to 40%, usually affecting the terminal ileum and cecum. Radiologic appearances resemble inflammatory and neoplastic diseases, with differential diagnoses including: Crohn disease, carcinoma, lymphoma, typhlitis, tuberculosis, and amebiasis. While computed tomography (CT) and magnetic resonance imaging appearances have been described, the F-18 fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET)/CT appearance of intestinal Behcet disease has not been previously reported. FDG-PET, coregistered with CT, was useful in this case to aid lesion detection, and for determining the extent of disease for treatment planning. The case also highlights the need for awareness of this condition as a rare benign cause for false-positive diagnosis in the assessment for malignancy, with potential avoidance of unnecessary surgery.