Chetan Patel

The role of DMSA scans in evaluation of the correlation between urinary tract infection, vesicoureteric reflux, and renal scarring.

Abstract The correlation between urinary tract infection (UTI), vesicoureteric reflux (VUR) and renal scarring was studied in 89 patients (177 renal units; 1 solitary kidney) during the period 1997–2000. There were 63 males and 26 females; ages ranged from neonates to 14 years. UTI was diagnosed on the basis of a positive urine culture, VUR was diagnosed and graded by micturating cystourethrogram (MCU), and renal scarring was assessed by technetium 99 m Tc-dimercaptosuccinic acid (DMSA) scan. Ultrasonography (US) was done to evaluate renal tract dilatation and other structural abnormalities. A follow up DMSA scan was performed approximately 6 months after the initial scan. VUR was present in 106 of the 171 renal units in which it was studied and absent in 65 units. The majority of the VUR was grade V. Renal scars were seen in 90 of 177 renal units at presentation and in 72 of the 163 renal units studied at follow-up. Some information was lacking in 31 patients; hence, the correlation between UTI, VUR, and renal scarring was done in 58 patients. The majority of the suspected scars at presentation were not seen at follow-up, but most of the established scars persisted. Only 2 renal units showed scars for the first time on follow-up. On US, approximately 50% of normal kidneys showed either suspicious or established scars on DMSA scan, and patients with bilateral abnormality on US showed renal scars. Renal scars were seen in 15 of 23 children without VUR, 17 of 18 with unilateral VUR, and 16 of 17 with bilateral VUR. Thus, there is a cause-and-effect relationship between UTI and renal scarring that is made worse by VUR. DMSA scans have been shown to be the most reliable method of assessing renal scarring, and an abnormal US scan showing upper-tract dilatation or a structural abnormality may have a predictive value in the detection of renal scarring.

Comparative Accuracy of Ct Attenuation-corrected and Non–attenuation-corrected Spect Myocardial Perfusion Imaging

Objective: The aim of the present study was to evaluate whether computed tomography based-attenuation correction (CT-AC) provides any advantage over non–attenuation-corrected (NAC) images for qualitative and quantitative analysis of single photon emission tomography (SPECT) myocardial perfusion imaging (MPI). Methods: We retrospectively evaluated data of 171 patients who underwent stress rest MPI SPECT/CT as per standard protocol. Angiography done within ±3 months of MPI was taken as reference standard. Two readers independently evaluated CT-AC and NAC images. Receiver operating characteristic curve analysis was done using ≥50% and ≥70% stenosis as cutoff. The size and severity of perfusion defects were also compared on CT-AC and NAC images. Results: For both readers, the area under the receiver operating characteristic curve was larger for CT-AC images than for NAC images at both ≥50% and ≥70% cutoff, but the difference was not significant. CT-AC images had significantly lower sensitivity for detecting right coronary artery disease compared with NAC (29% vs. 50% for reader 1 and 25.8% vs. 43.2% for reader 2). However, the specificity improved with CT-AC. Inferior defects were significantly smaller in CT-AC than NAC (P = 0.0002), with no significant difference for anterior defects (P = 0.544). There was significant variation in severity between CT-AC and NAC images for both overall (P = 0.001) as well as for inferior defects (P = 0.0007), but not for anterior defects (P = 0.279). Conclusion: In our study, the CT-based AC improved the specificity but decreased the sensitivity leading to nonsignificant improvement in overall diagnostic accuracy of Tc-99m sestamibi/tetrofosmin MPI.

Left ventricular ejection fraction and volumes on rest gated 201Tl perfusion SPECT: comparison with two-dimensional echocardiography.

BackgroundRest gated 201Tl images are considered to be of poor count statistics due to lower energy and low photon flux of 201Tl in addition to increased attenuation and low dose that can be administered. We compared the left ventricular ejection fraction (LVEF), end diastolic (EDV) and end systolic volume (ESV) obtained on 4 h gated rest 201Tl myocardial perfusion single photon emission computed tomography (SPECT) with those obtained by two-dimensional echocardiography (2-D ECHO) in patients with known or suspected coronary artery disease (CAD). MethodsEighty-two consecutive patients who underwent gated 201Tl stress–rest myocardial perfusion SPECT and 2-D ECHO were studied. The gated thallium images were processed with Siemens e-soft autocardiac processor and LVEF, EDV and ESV were evaluated using Emory Cardiac Toolbox. The same parameters were also assessed on the 2-D ECHO using the modified Simpson method for comparison. ResultsOut of 82 rest gated images, one study was excluded because of poor count statistics. In 81 (99%) patients there was good linear correlation with 2-D ECHO values and rest gated 201Tl SPECT images for EDV, ESV and LVEF. Pearsons correlation co-efficient (r value) for EDV, ESV and LVEF between the two methods was 0.78, 0.79 and 0.88, respectively. A Bland–Altman plot showed close agreement with LVEF but not for EDV and ESV. ConclusionThese results suggest that the 4 h rest gated 201Tl study gives a reliable value for the LVEF compared to 2-D ECHO and can be used in routine clinical practice.

Pediatric lymphoma: metabolic tumor burden as a quantitative index for treatment response evaluation

ObjectiveMetabolic tumor burden (MTB) incorporates the advantages of the existing indices: the metabolic volume of the lesion calculated by size-dependent thresholding on positron emission tomography–computed tomography (PET–CT) along with its aggressiveness as determined by standardized uptake value (SUV). This study was conducted to investigate whether MTB can be used as an objective index for monitoring therapy response in pediatric lymphoma.MethodsForty-two pediatric patients (35 male and 7 female) with histologically proven lymphomas (26 Hodgkin’s and 16 non-Hodgkin’s) were evaluated. MTB was assessed in baseline, early interim (after 2 cycles) and post-therapy PET–CT studies using RT_Image software. Size-dependent thresholding based on a phantom study conducted at our institute was used for the calculation of metabolic tumor volume (MTV). MTB was given as the product of MTV and the SUVmean. Summation of MTB from all lesions gave the whole body MTB. Baseline, early interim and post-therapy SUVmax and whole body MTB of the partial and complete response group were compared.ResultsOf 42 patients, 37 had complete response and 5 had partial response at the end of therapy based on clinical, CECT and bone marrow biopsy findings. SUVmax showed an overall reduction of 87.4% while MTB showed a reduction of 96.4% between baseline and early interim PET–CT scan. Similarly, SUVmax showed an overall reduction of 95.2% while MTB showed a reduction of 99.6% between baseline and post-therapy scan. There was significant difference between MTB of partial response and complete response group at baseline and early interim PET–CT (p 0.031 and 0.012, respectively). No such significant difference was found for SUVmax.ConclusionWhole body MTB appears to be useful quantitative parameter for the assessment of treatment response using PET–CT in pediatric lymphoma patients.

Renal function and structure in subacute hepatic failure.

Background and Aims: Subacute hepatic failure (SHF) is a fatal complicaton of acute viral hepatitis. Renal failure has been implicated as the main cause of death in this disease. However, renal functional and structural evaluation in such patients have not been performed. The present prospective study evaluated the renal functional and structural abnormalities in patients with subacute hepatic failure.

Effect of duration of fasting and diet on the myocardial uptake of F-18-2-fluoro-2-deoxyglucose (F-18 FDG) at rest

Context: Patterns of myocardial fluoro-2-deoxyglucose (FDG) uptake with respect to duration of fasting and dietary modifications. Aim: We observed the effect of duration of fasting and diet on the myocardial uptake pattern of F-18 FDG in patients routinely referred for oncological evaluation and no previous history of Coronary Artery Disease (CAD). Settings and Design: Prospective study. Subjects and Methods: A total of 153 patients (M: 81, F: 72; mean age: 47 ± 15 years; mean blood glucose level (mBG) 105 ± 23 mg/dl) were randomly divided in three groups. Group A: 4-6 h fasting; Group B: Overnight fasting (12–14 h); Group C: Low carbohydrate and fat rich diet for 2 days coupled with overnight fasting prior to the positron emission tomography (PET) scan. FDG uptake was classified as following: 1) homogeneous uptake, 2) heterogeneous uptake, and 3) ‘no uptake’ in the left ventricular (LV) myocardium. FDG PET study was performed as standard protocol for oncological conditions. Statistical Analysis Used: Descriptive statistics, Chi-square test or Fishers exact test, and Spearmans rank correlation tests were applied. Results: We observed the ‘no uptake’ pattern in five (10%), 28 (55%), and 39 (77%), ‘heterogeneous’ pattern in 20 (39%), 14 (28%), and seven (14%), and ‘homogeneous’ pattern in 26 (51%), nine (18%), and five (10%) patients in Group A, B, and C, respectively. There was statistically significant difference of myocardial uptake pattern between group A and B (P < 0.0001), between group A and C (P < 0.0001), and between Group B and C (P = 0.023). The mBG was 102, 105, and 111 mg/dl in ‘no uptake’, heterogeneous, and homogeneous uptake pattern, respectively, (P = 0.103). Also, within each group the mBG was not related to the uptake pattern. Conclusion: Both restricted diet and duration of fasting play an important role in determining the pattern and suppression of myocardial F-18 FDG uptake. Overnight fasting and restricted diet together suppress myocardial FDG uptake more than overnight fasting alone, which suppresses uptake more than 4-h fasting.

Diagnostic value of 18F-FDG PET/CT in paediatric neuroblastoma: comparison with 131I-MIBG scintigraphy.

PurposeThe aim of the study was to evaluate the diagnostic value of fluorine-18 fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) in paediatric patients with neuroblastoma (NB) and compare the results with iodine-131 metaiodobenzylguanidine (131I-MIBG) scintigraphy. MethodsData on 40 paediatric patients (age, 5.5±5.6 years; male, 32; female, eight) with histopathologically proven NB who underwent 18F-FDG PET/CT (staging, 21 patients; restaging/response monitoring, 19 patients) were retrospectively evaluated. 131I-MIBG scintigraphy data were available for 28/40 patients (median interval, 15 days; staging, 20 patients; restaging/response monitoring, eight patients). 131I-MIBG scintigraphy and 18F-FDG PET/CT images were evaluated by two nuclear medicine physicians in consensus and in separate sessions. Histopathology (n=50 lesions) and/or clinical/imaging follow-up (n=90 lesions) data were taken as the reference standard. ResultsPatient-wise sensitivity, specificity, positive-predictive value, negative-predictive value and accuracy of 18F-FDG PET/CT were 100, 50, 91.89, 100 and 92.50%, respectively. A total of 140 lesions (primary, 37; lymph node, 31; bone, 50; bone marrow, 15; and others, seven) were detected on PET/CT. In 28 patients undergoing both imaging studies, the sensitivity, specificity, positive-predictive value, negative-predictive value and accuracy of 18F-FDG PET/CT were 100, 60, 92, 100 and 92.80%, respectively, and those of 131I-MIBG were 95.65, 60, 91.67, 75 and 89.20%, respectively. In these 28 patients, PET/CT detected 107 lesions (primary, 25; lymph node, 22; bone/bone marrow, 56; and others, four) and 131I-MIBG scintigraphy detected 74 lesions (primary, 24; lymph node, five; and bone/bone marrow, 45). On a patient-based comparison there was no significant difference between 18F-FDG PET/CT and 131I-MIBG (P=1.000), but 18F-FDG PET/CT was superior to 131I-MIBG on a lesion-based comparison (P<0.0001). Although no difference was noted for primary lesions (P=1.000), PET/CT was superior to 131I-MIBG scintigraphy for the detection of lymph nodal (P=0.001) and bone/bone marrow lesions (P=0.007). Conclusion18F-FDG PET/CT shows high accuracy in paediatric patients with NB and demonstrates more lesions as compared with 131I-MIBG scintigraphy.

False-Negative and False-Positive Results in FDG-PET and PET/CT in Breast Cancer

PET and PET/CT has been used for the management of breast cancer for initial staging, monitor the treatment response, detect recurrences, and predict tumor behavior. It has found to be useful in detecting primary breast cancer in patients with large primary tumors. However, it has not been used routinely for early diagnosis of primary breast cancer due to certain limitations. In this article, the authors discuss various important factors that can lead to false-negative and false-positive results in PET and PET/computed tomography imaging used for the diagnosis of primary breast cancer.

Quantitative assessment of cardiac mechanical dyssynchrony and prediction of response to cardiac resynchronization therapy in patients with nonischaemic dilated cardiomyopathy using gated myocardial perfusion SPECT.

ObjectiveThe aim of the study was to evaluate gated myocardial perfusion SPECT (GMPS) in the prediction of response to cardiac resynchronization therapy (CRT) in nonischaemic dilated cardiomyopathy patients. Patients and methodsThirty-two patients (23 men, mean age 57.5±12.1 years) with severe heart failure, who were selected for CRT implantation, were prospectively included in this study. Patients with coronary heart disease and structural heart diseases were excluded. 99mTc-MIBI GMPS and clinical evaluation were performed at baseline and 3 months after CRT implantation. In GMPS, first-harmonic fast Fourier transform was used to extract a phase array using commercially available software. Phase standard deviation (PSD) and phase histogram bandwidth (PHB) were used to quantify cardiac mechanical dyssynchrony (CMD). Left ventricular ejection fraction was evaluated. ResultsAt baseline evaluation the mean NYHA class was 3.3±0.5, left ventricular ejection fraction was 23.2±5.3% and mean QRS duration was 150.3±18.2 ms. PSD was 55.8±19.2° and PHB was 182.1±75.8°. At 3-month follow-up, 22 patients responded to CRT with improvement in NYHA class by more than 1 grade and in ejection fraction by more than 5%. Responders had significantly larger PSD (63.6±16.6 vs. 38.7±12.7°) and PHB (214.8±63.9 vs. 110.2±43.5°) compared with nonresponders. Receiver-operating characteristic curve analysis demonstrated 86% sensitivity and 80% specificity at a cutoff value of 43° for PSD and 86% sensitivity and 80% specificity at a cutoff value of 128° for PHB in the prediction of response to CRT. ConclusionBaseline PSD and PHB derived from GMPS are useful for prediction of response to CRT in nonischaemic dilated cardiomyopathy patients.

Detection of coronary artery disease by stress thallium scintigraphy in diabetic patients.

We investigated the efficacy of exercise stress thallium in the diagnosis of coronary artery disease in patients with diabetes mellitus. Forty-three patients with known diabetes and suspected of having coronary artery disease were included in the study. All the patients underwent coronary angiography, 24 had significant coronary artery stenosis and 19 had normal coronaries. Out of the 24 patients with a positive angiographic finding, thallium scintigraphy was positive in 21 patients (sensitivity, 87.5%); and false negative in only three of the 24 patients. Out of the 19 patients with normal angiography findings, 16 patients had a normal thallium scan (specificity, 84.2%) and the remaining three had a positive thallium scan. This gives thallium scintigraphy a positive predictive value of 87.5% and negative predictive value of 84.2% when compared with coronary angiography. The findings of this study suggest that stress thallium scintigraphy is a useful modality in screening of coronary artery disease in diabetic patients.