Aravind S. Ravi Kumar

The segmental distribution and clinical significance of colorectal fluorodeoxyglucose uptake incidentally detected on PET-CT.

BackgroundUnexpected focal colorectal fluorodeoxyglucose (FDG) uptake is becoming a common clinical dilemma with the increasing utilization of positron emission tomography (PET). These findings may subsequently reveal malignant or premalignant pathology. AimIn addition to reporting the prevalence of clinically significant colonic pathology associated with unexpected focal FDG uptake, this study analysed the correlation between pathological colonic segments with those reported on the FDG-PET scan. MethodsThe reports of 2071 consecutive PET-computed tomography (PET-CT) scans performed in a calendar year were reviewed. Information regarding subsequent patient investigation and management was collected from medical records. The segments harbouring foci of unexpected bowel FDG uptake were compared against the eventual outcome(s) of the endoscopic and pathological investigations. ResultsAmong the 62 individual patients represented, 37 (60%) were investigated further. Clinically unsuspected neoplasms were found in 68% of those investigated, including 10 diagnosed with carcinoma. In addition, an unknown bowel lymphoma and 19 colonic adenomas were discovered. The positive predictive value for pathology was higher in the proximal colon than the distal colon. The segments in which the pathological findings were identified correlated well with those reported as abnormal on PET-CT. ConclusionUnexpected bowel FDG uptake on PET-CT is associated with a high incidence of neoplastic pathology. In particular, focal FDG uptake in the proximal colon is associated with a high positive predictive value for neoplasm. The location of pathology is strongly concordant with endoscopic findings.

Optical Differentiation Between Malignant and Benign Lymphadenopathy by Grey Scale Texture Analysis of Endobronchial Ultrasound Convex Probe Images

BACKGROUND Morphologic and sonographic features of endobronchial ultrasound (EBUS) convex probe images are helpful in predicting metastatic lymph nodes. Grey scale texture analysis is a well-established methodology that has been applied to ultrasound images in other fields of medicine. The aim of this study was to determine if this methodology could differentiate between benign and malignant lymphadenopathy of EBUS images. METHODS Lymph nodes from digital images of EBUS procedures were manually mapped to obtain a region of interest and were analyzed in a prediction set. The regions of interest were analyzed for the following grey scale texture features in MATLAB (version 7.8.0.347 [R2009a]): mean pixel value, difference between maximal and minimal pixel value, SEM pixel value, entropy, correlation, energy, and homogeneity. Significant grey scale texture features were used to assess a validation set compared with fluoro-D-glucose (FDG)-PET-CT scan findings where available. RESULTS Fifty-two malignant nodes and 48 benign nodes were in the prediction set. Malignant nodes had a greater difference in the maximal and minimal pixel values, SEM pixel value, entropy, and correlation, and a lower energy (P < .0001 for all values). Fifty-one lymph nodes were in the validation set; 44 of 51 (86.3%) were classified correctly. Eighteen of these lymph nodes also had FDG-PET-CT scan assessment, which correctly classified 14 of 18 nodes (77.8%), compared with grey scale texture analysis, which correctly classified 16 of 18 nodes (88.9%). CONCLUSIONS Grey scale texture analysis of EBUS convex probe images can be used to differentiate malignant and benign lymphadenopathy. Preliminary results are comparable to FDG-PET-CT scan.

Comparison of objective criteria and expert visual interpretation to classify benign and malignant hilar and mediastinal nodes on 18-F FDG PET/CT

There is widespread adoption of FDG‐PET/CT in staging of lung cancer, but no universally accepted criteria for classifying thoracic nodes as malignant. Previous studies show high negative predictive values, but reporting criteria and positive predictive values varies. Using Endobronchial ultrasound transbronchial needle aspiration (EBUS‐TBNA) results as gold standard, we evaluated objective FDG‐PET/CT criteria for interpreting mediastinal and hilar nodes and compared this to expert visual interpretation (EVI).

FDG PET/CT appearance of benign pilomatricoma.

A 56-year-old patient was referred for FDG PET/CT with a right preauricular lymph node fine-needle biopsy, suggesting poorly differentiated carcinoma and no obvious primary lesion. There was intense FDG uptake in the right preauricular nodule. The node was excised, and formal histology demonstrated a benign pilomatricoma rather than malignancy. Pilomatricoma is uncommon in adults and an unusual cause for marked FDG uptake, likely due to foreign body inflammation. Pilomatricoma can be either benign or malignant. The marked FDG uptake demonstrated in our patient with benign pilomatricoma also suggests that FDG PET cannot reliably grade this rare condition.

Correlation of various published radionuclide glomerular filtration rate estimation techniques and proposed paediatric normative data.

ObjectiveThe aim of this study is to assess the comparability and interchangeability of the radionuclide glomerular filtration rate (GFR) using different published techniques, and propose normative data for paediatrics. MethodsA total of 476 paediatric oncology patients aged 2–17 years, referred between January 2001 and December 2008 for GFR estimation, were reviewed for any potential cause of renal impairment. Sixty-nine patients met the stringent inclusion criteria, and were included in the study. GFR estimation was carried out using either technetium-99m diethylene triamine penta-acetic acid (99mTc-DTPA) or chromium-51 EDTA (51Cr-EDTA). Multiple GFR results were calculated from the same blood sample data (counts/min/ml), according to previously published GFR estimation techniques using one to three blood samples. These techniques were slope–intercept, slope-only and half life. For slope–intercept techniques, GFR was normalized to body surface area or extracellular fluid volume. ResultsThe GFR values obtained using different techniques were highly variant. The intraclass correlation (ICC) for different methods was moderate (ICC=0.56–0.66). A reliable empiric formula to allow conversion of GFR values from one technique to another could not be derived because of this variability, with some exceptions. 51Cr-EDTA yielded the same or lower variability than 99mTc-DTPA. The British Nuclear Medicine Society-recommended method had the lowest coefficient of variation, with a mean value of 116 (SD 22) normalized to 1.73 m2 for 51Cr-EDTA using two samples. ConclusionThe GFR values obtained from different calculation techniques are not readily interchangeable or comparable, with some exceptions. For both 99mTc-DTPA and 51Cr-EDTA, the British Nuclear Medicine Society-recommended technique appears to be the most robust, with the least coefficient of variation.

Potential for truncating the scan length of restaging FDG-PET/CT after chemoradiotherapy in head and neck squamous cell carcinoma.

BackgroundFluorine-18 fluorodeoxyglucose PET/computed tomography (CT) is now routinely used for staging and monitoring treatment response in head and neck squamous cell carcinoma (HNSCC). Although most patients with HSNCC have locoregional disease, distant metastases are relatively uncommon and occur predominantly in the lungs. AimTo explore the potential of a limited scan range from the skull vertex to lung bases, viz. an ‘above diaphragm’ scan, as an adequate examination for assessment of disease following chemoradiotherapy. MethodsA retrospective review of 240 patients with HNSCC both staged and monitored after therapy with 18F-fluorodeoxyglucose PET/CT was conducted. Patients with previous HNSCC, unknown primary and known distant metastatic disease were excluded. Patients with positive PET/CT findings below the neck on the posttherapy study were confirmed on either follow-up clinical or radiological findings. ResultsA total of 196 (81.7%) patients had nodal disease at PET/CT staging. Unrelated findings were present in 50 (20.8%) patients, including five colonic neoplasms and two second malignancies. After an average of 6.4 months after staging, 13 patients (5.4%) demonstrated progression to distant metastases on the posttherapy PET/CT. All patients demonstrated intrapulmonary metastases. Two patients had additional liver metastases, which would not have impacted on the overall management. No patient demonstrated isolated disease below the diaphragm. ConclusionA limited ‘above-diaphragm’ scan for early assessment following chemoradiotherapy may be safely considered. The benefits of this tailored approach flow onto both the health system and the patients as it can improve resource allocation by increasing scanner availability and patient throughput and reduces cumulative patient radiation exposure.

FDG-PET/CT in evaluation and prognostication of primary prostate lymphoma

A 76-year-old man was incidentally diagnosed with prostate lymphoma following transurethral resection of the prostate for prostatism. Staging F-18 fluorodeoxyglucose (FDG) positron emission tomography/ computed tomography (PET/CT) revealed markedly increased FDG uptake in the prostate, with no evidence of other disease. Following combination chemotherapy, restaging FDG-PET/CT demonstrated a complete metabolic response. The patient subsequently achieved prolonged remission on followup. Because of its rarity, FDG-PET in predicting outcome after therapy has not been validated for primary prostate lymphoma. This case highlights the potential of FDG-PET/CT in not only evaluation of disease extent but also prognostication of primary lymphoma of the prostate.

Tumor Thrombus in the Great Veins from Papillary Carcinoma of the Thyroid: 131I Scan Findings

Tumor invasion of great veins and forming thrombus is a rare complication in papillary carcinoma of thyroid. Contrast computed tomography, ultrasound, and positron emission tomography scan can demonstrate the thrombus but will not help to diagnose the nature of the thrombus. Demonstration of the cause of the thrombus by (131)I scan is possible because tumor tissue in the vein will be iodine avid, but simple thrombus will not.

Grey scale texture analysis of endobronchial ultrasound mini probe images for prediction of benign or malignant aetiology.

Expert analysis of endobronchial ultrasound mini probe (EBUS‐MP) images has established subjective criteria for discriminating benign and malignant disease. Minimal data are available for objective analysis of these images. The aim of this study was to determine if greyscale texture analysis could differentiate between benign and malignant lung lesions.

18F-FDG uptake in multiple splenic foci on PET/CT: an unusual case of visceral leishmaniasis.

A previously well 48-year-old male patient presented with several months of weight loss, fever, massive hepatosplenomegaly, and pancytopenia. A provisional diagnosis of lymphoma could not be confirmed on blind lymph node or bone marrow biopsies. Referral for 18F-FDG PET was made to identify an appropriate biopsy site. Focal uptake in multiple splenic lesions was seen, with normal FDG uptake elsewhere in the body. Splenectomy was then performed and histology revealed leishmaniasis, with no evidence of lymphoma. Focally FDG avid splenic deposits have never been reported in leishmaniasis and were likely due to nodular red pulp expansion.