Artificial intelligence-based analysis of whole-body bone scintigraphy: The quest for the optimal deep learning algorithm and comparison with human observer performance

PURPOSE

Whole-body bone scintigraphy (WBS) is one of the most widely used modalities in diagnosing malignant bone diseases during the early stages. However, the procedure is time-consuming and requires vigour and experience. Moreover, interpretation of WBS scans in the early stages of the disorders might be challenging because the patterns often reflect normal appearance that is prone to subjective interpretation. To simplify the gruelling, subjective, and prone-to-error task of interpreting WBS scans, we developed deep learning (DL) models to automate two major analyses, namely (i) classification of scans into normal and abnormal and (ii) discrimination between malignant and non-neoplastic bone diseases, and compared their performance with human observers.

MATERIALS AND METHODS

After applying our exclusion criteria on 7188 patients from three different centers, 3772 and 2248 patients were enrolled for the first and second analyses, respectively. Data were split into two parts, including training and testing, while a fraction of training data were considered for validation. Ten different CNN models were applied to single- and dual-view input (posterior and anterior views) modes to find the optimal model for each analysis. In addition, three different methods, including squeeze-and-excitation (SE), spatial pyramid pooling (SPP), and attention-augmented (AA), were used to aggregate the features for dual-view input models. Model performance was reported through area under the receiver operating characteristic (ROC) curve (AUC), accuracy, sensitivity, and specificity and was compared with the DeLong test applied to ROC curves. The test dataset was evaluated by three nuclear medicine physicians (NMPs) with different levels of experience to compare the performance of AI and human observers.

RESULTS

DenseNet121_AA (DensNet121, with dual-view input aggregated by AA) and InceptionResNetV2_SPP achieved the highest performance (AUC = 0.72) for the first and second analyses, respectively. Moreover, on average, in the first analysis, Inception V3 and InceptionResNetV2 CNN models and dual-view input with AA aggregating method had superior performance. In addition, in the second analysis, DenseNet121 and InceptionResNetV2 as CNN methods and dual-view input with AA aggregating method achieved the best results. Conversely, the performance of AI models was significantly higher than human observers for the first analysis, whereas their performance was comparable in the second analysis, although the AI model assessed the scans in a drastically lower time.

CONCLUSION

Using the models designed in this study, a positive step can be taken toward improving and optimizing WBS interpretation. By training DL models with larger and more diverse cohorts, AI could potentially be used to assist physicians in the assessment of WBS images.

Diagnostic performance of prone-only myocardial perfusion imaging versus coronary angiography in the detection of coronary artery disease: A systematic review and meta-analysis

STUDY DESIGN

Although prone position is considered as a complementary protocol in myocardial perfusion imaging (MPI), there is no consensus on its capability to find coronary artery disease (CAD), independently. The primary aim of this review was to report pooled sensitivity and specificity for prone position MPI in detection of CAD. In addition, the results were compared to the supine position's performance.

METHODS

Electronic bibliographic databases, The Cochrane Library, Web of Science (Science and Social Science Citation Index), Scopus, PubMed, and EMBASE until the end of June 2020 were searched. Studies were included based on the inclusion criteria of (1) evaluated the prone position MPI, (2) defined CAD with coronary angiography (CAG), using the threshold of ≥ 50% stenosis, (3) Adequate data were provided to extract the diagnostic performance. QUADAS-2 tool was utilized to assess the quality of included studies. Pooled sensitivity and specificity were calculated for prone and supine positions, separately. The hierarchical summary ROC curves were also drawn.

RESULTS

Ten individual studies with the data of the 1490 patients for the prone position and 1138 patients for the supine position were included. Pooled sensitivity and specificity for the prone position were 83% and 79%, respectively. These results were calculated for the supine position as the sensitivity of 86% and specificity of 67%. The pooled sensitivity and specificity of the prone position in detecting the right coronary artery territory defects were 70% and 84%, in turn.

CONCLUSION

In the suspicion for the CAD, prone position with comparable sensitivity and higher specificity can be an acceptable alternative to the supine position as the standard method. Also, in the cases of possible defects in the RCA territory, prone position showed to be a superior standard.

Determination of the value of albumin, anti-thrombin III, fibrinogen and D-dimer factors in the diagnosis of asymptomatic pulmonary embolism in patients with nephrotic syndrome

BACKGROUND

Thromboembolism is one of the most important and dangerous complications of nephrotic syndrome. This study aimed to determine the value of albumin, anti-thrombin III, fibrinogen and D-dimer factors in the prediction of asymptomatic pulmonary embolism in patients with nephrotic syndrome in non-remission period.

METHODS

Plasma levels of albumin, anti-thrombin III, fibrinogen and D-dimer were assessed in 30 nephrotic children in non-remission period (including new case-patient or relapse period), and the results were compared with chest X-ray and lung perfusion scintigraphy (Q scan).

RESULTS

The mean age of patients was 6.22 ± 3.5 years (range 2-12 years). Of patients, 23.3% had abnormal findings in perfusion scan suggestive of pulmonary emboli despite absence of any respiratory manifestations. Median plasma albumin and anti-thrombin III levels in patients with asymptomatic pulmonary embolism were lower than in patients without pulmonary embolism. Also, median fibrinogen and D-dimer levels in patients with asymptomatic pulmonary embolism were higher than in patients without pulmonary embolism, with no statistically significant differences between sex, age, hemoglobin and hematocrit of patients and lung perfusion scan results.

CONCLUSION

Patients with abnormal blood levels of albumin (< 3.5 g/dl), anti-thrombin III (< 80 ml/dl), fibrinogen (> 400 ml/dl) and D-dimer (> 0.5 μg/dl) underwent CXR/Q scan and were treated with heparin if there was pulmonary embolism.

Role of Technetium-99m-Ethylenedicysteine in the Calculation of Differential Renal Function: A Comparison Study with Dimercaptosuccinic Acid Renal Scintigraphy

Purpose of the Study:

The aim of our study was to compare the technetium-99m (Tc-99m)-ethylenedicysteine (EC) renography calculation of differential renal function (DRF) with this measurement using Tc-99m-dimercaptosuccinic acid (DMSA) scintigraphy.

Materials and Methods:

Patients referred to our department were included in our study, and both DMSA and EC scans were performed for each patient according to the standard imaging protocols. A checklist was filled for each patient. Statistical analysis was performed using correlation and regression methods.

Results:

Forty-two patients (mean age: 3.6 ± 3.4 years), including 32 boys and 10 girls, participated in our study. The results of EC scintigraphy were significantly correlated with the values of DMSA scintigraphy (P < 0.001). Performing linear regression, EC renography significantly (P < 0.001) predicted the DRF as it was calculated by DMSA scintigraphy (R² = 0.92, P < 0.001). This test was significant in both male and female subgroups (P < 0.001).

Conclusions:

Overall, our study findings were similar to the reported results in the other reviewed studies, showing that Tc-99m-EC can be considered as an alternative for DMSA scintigraphy, providing interchangeable results.

CAD system based on B-mode and color Doppler sonographic features may predict if a thyroid nodule is hot or cold

OBJECTIVES

The aim of this study was to evaluate if the analysis of sonographic parameters could predict if a thyroid nodule was hot or cold.

METHODS

Overall, 102 thyroid nodules, including 51 hyperfunctioning (hot) and 51 hypofunctioning (cold) nodules, were evaluated in this study. Twelve sonographic features (i.e., seven B-mode and five Doppler features) were extracted for each nodule type. The isthmus thickness, nodule volume, echogenicity, margin, internal component, microcalcification, and halo sign features were obtained in the B-mode, while the vascularity pattern, resistive index (RI), peak systolic velocity, end diastolic velocity, and peak systolic/end diastolic velocity ratio (SDR) were determined, based on Doppler ultrasounds. All significant features were incorporated in the computer-aided diagnosis (CAD) system to classify hot and cold nodules.

RESULTS

Among all sonographic features, only isthmus thickness, nodule volume, echogenicity, RI, and SDR were significantly different between hot and cold nodules. Based on these features in the training dataset, the CAD system could classify hot and cold nodules with an area under the curve (AUC) of 0.898. Also, in the test dataset, hot and cold nodules were classified with an AUC of 0.833.

CONCLUSIONS

2D sonographic features could differentiate hot and cold thyroid nodules. The CAD system showed a great potential to achieve it automatically.

KEY POINTS

• Cold nodules represent higher volume (p = 0.005), isthmus thickness (p = 0.035), RI (p = 0.020), and SDR (p = 0.044) and appear hypoechogenic (p = 0.010) in US. • Nodule volume with an AUC of 0.685 and resistive index with an AUC of 0.628 showed the highest classification potential among all B-mode and Doppler features respectively. • The proposed CAD system could distinguish hot nodules from cold ones with an AUC of 0.833 (sensitivity 90.00%, specificity 70.00%, accuracy 80.00%, PPV 87.50%, and NPV 75.00%).

Fragmented QRS on surface electrocardiogram as a predictor of perfusion defect in patients with suspected coronary artery disease undergoing myocardial perfusion imaging

Background

Fragmented QRS (FQRS) on surface electrocardiogram (ECG) is associated with the presence of myocardial scar tissue and may have prognostic value after certain ischemic events. We aimed to examine the anatomical correlation of FQRS with the presence of perfusion abnormalities in patients with suspected coronary artery disease (CAD).

Methods

Patients without a known history of CAD, who were referred for myocardial perfusion imaging (MPI) between January 2016 and May 2016, were enrolled. The presence of FQRS on surface ECG was evaluated. The presence of FQRS, number of leads with FQRS, and the location of FQRS as well as patient characteristics were compared in patients with normal versus abnormal MPI. Multivariate model was constructed to identify independent factors associated with perfusion defect.

Results

One hundred four women and 94 men were enrolled. Fragmentation of anterior, lateral, and inferior leads was detected in 13 (6.5%), 17 (8.5%), and 36 (18.1%) subjects, respectively. MPI was normal in 134 (67.6%) patients. FQRS was significantly more common in patients with abnormal MPI (p < 0.001). Age (odds ratio [OR]: 1.05 [1.02–1.08]; p = 0.001), number of the leads presenting FQRS (OR: 1.46 [1.12–1.92] p = 0.006), and diabetes (OR: 2.33 [1.16–4.69]; p = 0.018) were independent predictors of the presence of perfusion defect on MPI.

Conclusion

In the absence of known CAD, FQRS is associated with the presence of perfusion abnormalities. Incorporating FQRS in diagnostic armamentarium may aid us in selecting patients who may benefit from MPI.

COMPARE CPM-RMI Trial: Intramyocardial Transplantation of Autologous Bone Marrow-Derived CD133+ Cells and MNCs during CABG in Patients with Recent MI: A Phase II/III, Multicenter, Placebo-Controlled, Randomized, Double-Blind Clinical Trial

This article published in Cell J (Yakhteh), Vol 20, No 2, Jul-Sep 2018, on pages 267-277, four affiliations (1, 4, 5, and 10) were changed based on authors request.

COMPARE CPM-RMI Trial: Intramyocardial Transplantation of Autologous Bone Marrow-Derived CD133+ Cells and MNCs during CABG in Patients with Recent MI: A Phase II/III, Multicenter, Placebo-Controlled, Randomized, Double-Blind Clinical Trial

Objective:

The regenerative potential of bone marrow-derived mononuclear cells (MNCs) and CD133⁺ stem cells in the heart varies in terms of their pro-angiogenic effects. This phase II/III, multicenter and double-blind trial is designed to compare the functional effects of intramyocardial autologous transplantation of both cell types and placebo in patients with recent myocardial infarction (RMI) post-coronary artery bypass graft.

Materials and Methods:

This was a phase II/III, randomized, double-blind, placebo-controlled trial COMPARE CPM-RMI (CD133, Placebo, MNCs - recent myocardial infarction) conducted in accordance with the Declaration of Helsinki that assessed the safety and efficacy of CD133 and MNCs compared to placebo in patients with RMI. We randomly assigned 77 eligible RMI patients selected from 5 hospitals to receive CD133⁺ cells, MNC, or a placebo. Patients underwent gated single photon emission computed tomography assessments at 6 and 18 months post-intramyocardial transplantation. We tested the normally distributed efficacy outcomes with a mixed analysis of variance model that used the entire data set of baseline and between-group comparisons as well as within subject (time) and group×time interaction terms.

Results:

There were no related serious adverse events reported. The intramyocardial transplantation of both cell types increased left ventricular ejection fraction by 9% [95% confidence intervals (CI): 2.14% to 15.78%, P=0.01] and improved decreased systolic wall thickening by -3.7 (95% CI: -7.07 to -0.42, P=0.03). The CD133 group showed significantly decreased non-viable segments by 75% (P=0.001) compared to the placebo and 60% (P=0.01) compared to the MNC group. We observed this improvement at both the 6- and 18-month time points.

Conclusion:

Intramyocardial injections of CD133⁺ cells or MNCs appeared to be safe and efficient with superiority of CD133+ cells for patients with RMI. Although the sample size precluded a definitive statement about clinical outcomes, these results have provided the basis for larger studies to confirm definitive evidence about the efficacy of these cell types (Registration Number: NCT01167751).

Predictive quantitative sonographic features on classification of hot and cold thyroid nodules

PURPOSE

This study investigated the potentiality of ultrasound imaging to classify hot and cold thyroid nodules on the basis of textural and morphological analysis.

METHODS

In this research, 42 hypo (hot) and 42 hyper-function (cold) thyroid nodules were evaluated through the proposed method of computer aided diagnosis (CAD) system. To discover the difference between hot and cold nodules, 49 sonographic features (9 morphological, 40 textural) were extracted. A support vector machine classifier was utilized for the classification of LNs based on their extracted features.

RESULTS

In the training set data, a combination of morphological and textural features represented the best performance with area under the receiver operating characteristic curve (AUC) of 0.992. Upon testing the data set, the proposed model could classify the hot and cold thyroid nodules with an AUC of 0.948.

CONCLUSIONS

CAD method based on textural and morphological features is capable of distinguishing between hot from cold nodules via 2-Dimensional sonography. Therefore, it can be used as a supplementary technique in daily clinical practices to improve the radiologists' understanding of conventional ultrasound imaging for nodules characterization.

From in-silico immunogenicity verification to in vitro expression of recombinant Core-NS3 fusion protein of HCV

BACKGROUND AND OBJECTIVE

Hepatitis C virus (HCV) is a serious global health burden. There is no effective vaccine against HCV and new direct acting antivirals (DAAs) are so expensive and virtually unavailable to the public. Therefore, seeking for therapeutic or prophylactic vaccines is exigent and reliever.

METHODS

The secondary and tertiary structures of the recombinant Core-NS3 (rC-N) fusion protein of HCV and its B and T-cells epitopes were evaluated with bioinformatics software. Cloning and in vitro expression of rC-N were performed by pET24a(+) and E.coli BL21-DE3 expression host, respectively. The recombinant protein purification was done by affinity chromatography method and then identified by Western blotting using anti-His monoclonal antibody.

RESULTS

The sequences of rC-N protein consist of 1-118 amino acid parts of Core and 1095-1384 amino acids of NS3 were connected by a flexible linker (AAY) with proteasome cleavable site. The expressed and purified 46.7292 kDa rC-N protein had antigenic value up to threshold and conservancy found in this chimeric protein. Ramchandran Plot analysis represented that most residues were fallen in favourable regions. It also interacted with both type I and II major histocompatibility complex (MHC I, II) molecules. The rC-N had antigenic behaviour to create T cell responses.

CONCLUSION

The results indicated that conserved rC-N protein had the ability to induce T-cell-mediated immune responses and it could be utilized as a therapeutic vaccine candidate against HCV (Tab. 3, Fig. 4, Ref. 40).

Solitary metastasis of gastric cancer to fibula: a case report

Gastric cancer is one of the most common and most fatal neoplasms in human. Its skeletal metastasis is less frequent, particularly when solitary. The objective of this article is to represent a case of solitary fibular metastasis from this cancer not reported before based on Medline search.

Risk factor investigation for cardiovascular health through WHO STEPS approach in Ardabil, Iran

Objectives:

Reliable evidence is the keystone for any noncommunicable disease (NCD) prevention plan to be initiated. In this study we carried out a risk factor investigation based on the WHO Stepwise approach to Surveillance (STEPS).

Methods:

The study was conducted on 1000 adults between 15 and 64 years of age living in Ardabil province, north-west Iran during 2006, based on the WHO STEPS approach to surveillance of risk factors for NCD. At this stage only the first and second steps were carried out. Data were collected through standard questionnaires and methods analyzed using STATA version 8 statistical software package.

Results:

29.0% of men and 2.6% of women were current daily tobacco smokers. The mean number of manufactured cigarettes smoked per day was 18.9 among current daily smokers. Smoking was most prevalent among men of low-income families and those of lower education. The mean body mass index (BMI) was 26.6 kg/m², and was significantly correlated with systolic blood pressure. 58.9% were overweight or obese; 18.0% had raised blood pressure and 3.7% had isolated systolic hypertension. The mean number of servings of fruit consumed per day was 1.1; 33.1% had low levels of activity. Combined risk factor analysis showed that 4.1% of participants were in the low-risk group (up to 5.1% among men and 3.2% among women). Those in the high-risk group comprised 25.6% in the 25- to 44-year age group and 49.7% in the 45- to 64-year age group. Mean BMI increased by age in both sexes at least at the first three decades of adult life.

Conclusion:

Based on observed status of risk for cardiovascular health, burden of cardiovascular diseases is expected to increase if an effective prevention strategy is not undertaken.

Hard Ticks on Domestic Ruminants and their Seasonal Population Dynamics in Yazd Province, Iran

BACKGROUND

Ticks are the main vectors for transmission of different pathogens to human and animals. This survey was performed to find out distribution of ticks, which infested the domestic ruminants in Yazd Province, central Iran during year 2008-2009.

METHODS

A total number of 30 villages from both mountainous (20%) and plateau (80%) regions of the province were selected randomly. Ticks were colleted from the body of infested animals and transported to the laboratory of Medical Entomology, School of Public Health, Tehran University of Medical Sciences and then were identified to space level using valid identification key.

RESULTS

A total of 583 hard ticks were collected. The ticks were classified into three genera and 7 species including: Hyalomma dromedarii (55.92%), Hy. marginatum (13.20%), Hy. anatolicum (9.78%), Hy. detritum (4.98%), Hy. asiaticum (3.94%), Rhipicephalus sanguineus (11.84%), and Dermacentor marginatus (0.34%). The highest seasonal activities occurred in summer. The prevalence of the Ixodidae ticks was more evident in plateaus area in Yazd Province. Among the hosts including: cow, goat, sheep and camel, the ticks that collected from camel was more prevalent. The ratio of male was more than female ticks. Hyalomma. dromedarii was the predominant tick species and accounted for 55.92% of the ticks.

CONCLUSION

Some of the collected ticks may play an important role for transmission of vector borne disease to human; therefore, the results of this study will provide a clue for vectors of tick-borne diseases in the region for local authorities for implementation of disease control.

Anti-inflammatory effects of probiotic yogurt in inflammatory bowel disease patients

Our aim was to assess anti-inflammatory effects on the peripheral blood of subjects with inflammatory bowel disease (IBD) who consumed probiotic yogurt for 1 month. We studied 20 healthy controls and 20 subjects with IBD, 15 of whom had Crohn's disease and five with ulcerative colitis. All the subjects consumed Lactobacillus rhamnosus GR-1 and L. reuteri RC-14 supplemented yogurt for 30 days. The presence of putative regulatory T (T(reg)) cells (CD4(+) CD25(high)) and cytokines in T cells, monocytes and dendritic cells (DC) was determined by flow cytometry from peripheral blood before and after treatment, with or without ex vivo stimulation. Serum and faecal cytokine concentrations were determined by enzyme-linked immunosorbent assays. The proportion of CD4(+) CD25(high) T cells increased significantly (P = 0.007) in IBD patients, mean (95% confidence interval: CI) 0.84% (95% CI 0.55-1.12) before and 1.25% (95% CI 0.97-1.54) after treatment, but non-significantly in controls. The basal proportion of tumour necrosis factor (TNF)-alpha(+)/interleukin (IL)-12(+) monocytes and myeloid DC decreased in both subject groups, but of stimulated cells only in IBD patients. Also serum IL-12 concentrations and proportions of IL-2(+) and CD69(+) T cells from stimulated cells decreased in IBD patients. The increase in CD4(+) CD25(high) T cells correlated with the decrease in the percentage of TNF-alpha- or IL-12-producing monocytes and DC. The effect of the probiotic yogurt was confirmed by a follow-up study in which subjects consumed the yogurt without the probiotic organisms. Probiotic yogurt intake was associated with significant anti-inflammatory effects that paralleled the expansion of peripheral pool of putative T(reg) cells in IBD patients and with few effects in controls.

Cryotherapy in the treatment of pyogenic granuloma

BACKGROUND

Pyogenic granuloma is a benign, acquired, proliferative vascular lesion of the skin and mucous membranes. Many different treatments have been used for pyogenic granuloma with variable success rates.

OBJECTIVE

To evaluate the efficacy of cryotherapy in the treatment of pyogenic granuloma.

METHODS

In a prospective observational study, 135 patients with pyogenic granuloma were treated with cryotherapy using liquid nitrogen. The patients were followed up every 3 weeks until 3 months after disappearance of the lesion.

RESULTS

Complete resolution of the pyogenic granuloma was achieved in all patients after a mean of 1.58 treatments (range, 1-4 treatments). At the end of follow-up period, there was a flat imperceptible scar, smaller than the treated lesion, in 16 patients (11.8%). A hypertrophic scar, 3 mm in diameter, was observed in one patient. Hypopigmentation was observed in seven patients (5.1%). No other complication or side-effect was recorded in the study.

CONCLUSIONS

We believe that pyogenic granuloma can be treated simply and effectively with cryotherapy.

Ethylenedicysteine versus diethylenetriamine pentaacetic acid as the carrier of technetium Tc 99m in diuretic renography for patients with upper urinary tract obstruction

INTRODUCTION

L,L-ethylenedicysteine (EC) is a new carrier of technetium Tc 99m (99mTc) with a lower affinity to plasma albumin in comparison with diethylenetriamine pentaacetic acid (DTPA). We compared 99mTc-EC scan with 99mTc-DTPA scan in diuretic renography for patients with obstructive uropathy.

MATERIALS AND METHODS

Thirty-three patients with upper urinary tract obstruction were randomly selected and underwent diuretic renographies by 99mTc-EC and 99mTc-DTPA. The counts of radioisotope per pixel in the target (the kidney) and background tissues as well as the clearance half-life of these two radiopharmaceuticals were measured and compared.

RESULTS

Mean counts of radioisotope per pixel in the target tissue was not different between 99mTc-EC and 99mTc-DTPA scans, but in the background tissue, it was less for 99mTc-EC (P = .003). Target-background ratio was higher for 99mTc-EC scan (3.80 +/- 2.11 versus 2.48 +/- 1.39; P < .001). Renal clearance half-life of radioisotope was shorter for 99mTc-EC scan than 99mTc-DTPA scan (58.15 +/- 15.17 minutes versus 78.65 +/- 19.99 minutes; P = .033). The results were similar for uremic patients (with a serum creatinine level > 2mg/dL).

CONCLUSION

Target-background ratio of radiopharmaceutical uptake rates in diuretic renography was a good indicator of the higher resolution of 99mTc-EC than 99mTc-DTPA scan. We also demonstrated the faster clearance of 99mTc-EC than 99mTc-DTPA. This results in less radiation that is especially useful in children. To our opinion, 99mTc-EC can better depict the kidneys in comparison with 99mTc-DTPA.

The first rapid onset optic neuritis after measles–rubella vaccination: case report

During the largest mass campaign for measles-rubella (MR) vaccination 33,000,000 people with an age range of 5-25 years were vaccinated in Iran. Some complications were encountered, including a rare case of optic neuritis. In the past 30 years of medical literature, five cases of optic neuritis have been reported but all of them were developed at least 8 days after vaccination. We are supposed to report the first case of rapid onset optic neuritis in which the complication came out just in few hours in a 16 years old boy.

Manufacture and quality of iron-fortified yogurt

Yogurts (nonfat and low fat) were manufactured and fortified with 10, 20, and 40 mg of iron/kg of yogurt. Growth of starter culture bacteria and nonstarter culture bacteria as well as lipid oxidation of the yogurts were monitored over 30 d of storage at 4 degrees C. Sensory characteristics of the yogurts were determined during that time by a trained panel of judges, and consumer panels were used to test acceptability of iron-fortified yogurt. Counts of Lactobacillus delbrueckii ssp. bulgaricas and Streptococcus thermophilus after 1 d of storage in iron-fortified skim yogurts were 7.0 x 10(8) cfu/ml, which were not significantly different from numbers in unfortified yogurts. Counts decreased to 2.5 x 10(8) and 1.9 x 10(8) cfu/ml for L. delbrueckii ssp. bulgaricus and S. thermophilus, respectively, after 30 d of storage. Fortifying yogurt with iron did not support the growth of Pseudomonas fluorescens or Escherichia coli. No significant increases in chemical oxidation, as measured using the thiobarbituric acid assay, were detected as a consequence of iron fortification. Trained panelists scored all yogurts for oxidized, metallic, bitter, and other off-flavors in the range of "not perceptible" to "very slightly perceptible". Iron-fortified yogurts had slightly higher oxidized flavor scores than did the control yogurt. There was no increase in metallic, bitter, or other off-flavors. The consumer panel did not detect any significant differences in the appearance, mouthfeel, flavor, or overall quality between fortified and unfortified flavored yogurts. All yogurt samples were liked by the consumer panelists, suggesting that yogurt is a suitable vehicle for iron fortification.

Survival of Lactobacillus acidophilus and Bifidobacterium bifidum in ice cream for use as a probiotic food

Probiotic ice cream was made by fermenting a standard ice cream mix with Lactobacillus acidophilus and Bifidobacterium bifidum cultures and then freezing the mix in a batch freezer. Survival of the L. acidophilus and B. bifidum, as well as beta-galactosidase activity, was monitored during 17 wk of frozen storage at -29 degrees C. After freezing of the fermented mix, bacterial counts were 1.5 x 10(8) cfu/ml for L. acidophilus and 2.5 x 10(8) cfu/ml for B. bifidum. Seventeen weeks after freezing, these counts had decreased to 4 x 10(6) and 1 x 10(7) cfu/ml, respectively. During the same period, beta-galactosidase activity decreased from 1800 to 1300 units/ml. Probiotic ice cream was prepared at pH 5.0, 5.5, and 6.0 to determine consumer preferences and was compared with standard Utah State University "Aggie" ice cream. All samples were strawberry-flavored and were evaluated by 88 judges. The preferred pH of probiotic ice cream, based on overall acceptance, was pH 5.5. We demonstrated that probiotic ice cream is a suitable vehicle for delivering beneficial microorganisms such as L. acidophilus and B. bifidum to consumers. The bacteria can be grown to high numbers in ice cream mix and remain viable during frozen storage.