Intravoxel incoherent motion and diffusion tensor imaging of early renal fibrosis induced in a murine model of streptozotocin induced diabetes.

INTRODUCTION: To assess if parameters in intravoxel incoherent motion (IVIM) and diffusion tensor imaging (DTI) can be used to evaluate early renal fibrosis in a mouse model of diabetic nephropathy. MATERIALS & METHODS: In a population of 38 male CD1 mice (8weeks old, 20-30g), streptozotocin induced diabetes was created in 20 mice via a single intraperitoneal injection of streptozotocin at 150mg/kg, while 18 mice served as control group. IVIM parameters were acquired at 0, 12 and 24weeks after injection of streptozotocin using a range of b values from 0 to 1200s/mm2. DTI parameters were obtained using 12 diffusion directions and lower b values of 0, 100 and 400s/mm2. DTI and IVIM parameters were obtained using region of interests drawn over the renal parenchyma. Histopathological analysis of the right kidney was performed in all mice. Results were analyzed using an unpaired t-test with P<0.05 considered statistically significant. RESULTS: Renal cortex fractional anisotropy (FA) was significantly lower in the diabetes group at week 12 as compared with the control group. Renal cortex apparent diffusion coefficient and tissue diffusivity were significantly higher in the diabetes group at week 12 compared with the control group at 12weeks. Blood flow was significantly decreased at the renal medulla at 24weeks. Histopathological analysis confirmed fibrosis in the diabetes group at 24weeks. CONCLUSION: FA is significantly reduced in diabetic nephropathy. FA might serve a potential role in the detection and therapy monitoring of early diabetic nephropathy.

Imaging appearances for recurrent nasopharyngeal carcinoma and post-salvage nasopharyngectomy.

Nasopharyngeal carcinoma (NPC) is a head and neck neoplasm that occurs in endemic numbers among people of southern Chinese descent. External beam radiation to the nasopharyngeal bed and primary draining lymph node echelons is the mainstay of treatment with concurrent cisplatin-based chemotherapy for more advanced disease. Detection of residual and/or recurrent NPC has important clinical implications, as salvage protocols are available. The review aims to increase awareness of the imaging features of NPC recurrences at local and distant sites using computed tomography (CT), magnetic resonance imaging (MRI), and positron-emission tomography (PET). Important changes in imaging seen in patients after nasopharyngectomy are also discussed.

Assessment of tumor blood flow distribution by dynamic contrast-enhanced CT.

A distinct feature of the tumor vasculature is its tortuosity and irregular branching of vessels, which can translate to a wider dispersion and higher variability of blood flow in the tumor. To enable tumor blood flow variability to be assessed in vivo by imaging, a tracer kinetic model that accounts for flow dispersion is developed for use with dynamic contrast-enhanced (DCE) CT. The proposed model adopts a multiple-pathway approach and allows for the quantification of relative dispersion in the blood flow distribution, which reflects flow variability in the tumor vasculature. Monte Carlo simulation experiments were performed to study the possibility of reducing the number of model parameters based on the Akaike information criterion approach and to explore possible noise and tissue conditions in which the model might be applicable. The model was used for region-of-interest analysis and to generate perfusion parameter maps for three patient DCE CT cases with cerebral tumors, to illustrate clinical applicability.

Interpretation and applicability of empirical tissue enhancement metrics in dynamic contrast-enhanced MRI based on a multiple pathway model.

Computer simulations based on a physiologically realistic tracer kinetic model with multiple pathways was used to provide insights on the applicability and interpretation of tissue enhancement metrics such as the maximum slope, peak enhancement and area under curve, commonly used in dynamic contrast-enhanced (DCE) MRI. Results show that physiological conditions of the tissue that could affect the accuracy of the maximal slope method include a high blood flow, increased variability of flow within the vasculature or a low vascular volume. Interestingly, changes in permeability and interstitial volume might not affect the accuracy of the maximal slope method. Time-to-peak and peak value of the tissue enhancement curve are not strictly properties of the tissue alone, and they cannot be linearly related to intrinsic tissue parameters such as blood flow, blood volume, capillary permeability, interstitial volume and mean transit time. Similar to the normalized initial area under tissue concentration curve, an alternative estimate of the total tracer distribution volume can be simply given by the ratio of tracer concentration in the tissue and artery sampled at the final DCE scan.

Dynamic contrast-enhanced MRI of neuroendocrine hepatic metastases: A feasibility study using a dual-input two-compartment model.

Neuroendocrine hepatic metastases exhibit various contrast uptake enhancement patterns in dynamic contrast-enhanced MRI. Using a dual-input two-compartment distributed parameter model, we analyzed the dynamic contrast-enhanced MRI datasets of seven patient study cases with the aim to relate the tumor contrast uptake patterns to parameters of tumor microvasculature. Simulation studies were also performed to provide further insights into the effects of individual microcirculatory parameter on the tumor concentration-time curves. Although the tumor contrast uptake patterns can be influenced by many parameters, initial results indicate that hepatic blood flow and the ratio of fractional vascular volume to fractional interstitial volume may potentially distinguish between the patterns of neuroendocrine hepatic metastases.

Oligodendroglial tumor chemotherapy using "decreased-dose-intensity" PCV: a Singapore experience.

The authors propose "decreased-dose-intensity" PCV (procarbazine, lomustine [CCNU], and vincristine) chemotherapy for Asian patients with oligodendroglial tumors. In this study, all seven patients with oligodendroglioma (OD) and eight with anaplastic oligodendroglioma (AO) had objective responses or stable disease. Median progression-free survival was greater than 29 months (OD) and 36.5 months or greater (AO); 86% of patients with OD and 63% with AO remain progression-free. Twenty-four Common Toxicity Criteria Grade 3/4 adverse events were noted.

Metastatic angiosarcoma to the thyroid.

BACKGROUND: Angiosarcoma (AS) in non-alpine areas is exceptionally rare, and so is metastatic AS to the thyroid. The difficulties and controversies associated with its diagnosis and management are highlighted in this case report. METHOD: Case report. RESULTS: A Chinese gentleman with AS metastatic to the thyroid presented a year after radiotherapy to his scalp AS. There was rapid expansion of the metastasis over 2 weeks and invasion of the pyriform fossa caused dysphagia and haemoptysis. The diagnosis was established by paraffin histology of the tumour post-hemithyroidectomy, after repeated fine-needle aspiration cytology was not diagnostic. Patient opted for external beam radiotherapy to the pyriform fossa instead of pharyngolaryngectomy. Residual pyriform tumour was treated with brachytherapy delivered via nasogastric tube. Unfortunately, the patient died 4 months later due to cardiac failure which was unrelated to his oncologic condition. CONCLUSION: AS metastatic to the thyroid is possible. The unexpectedly acute presentation and difficulties associated with diagnosis and management are highlighted. A useful method of delivering brachytherapy to the pyriform fossa is described.

Clinics in diagnostic imaging (85). Mandible osteoradionecrosis complicated by infection.

Mandibular osteoradionecrosis is a rare but well-known complication that may be seen in patients with head and neck tumours following radiation therapy. A 42-year-old man presented with painful soft tissue swelling and a discharging sinus over the right mandible. Radiographs showed osteolytic destruction. Computed tomography confirmed bony destruction and fragmentation, as well as signs of soft tissue infection. The diagnosis of mandible osteoradionecrosis complicated by infection was confirmed by biopsy and surgically. The clinical and imaging features of osteoradionecrosis are highlighted.

Radiologists' detection of mammographic abnormalities with and without a computer-aided detection system.

The aim of this study was to to evaluate the role of a computer-aided program (CAD) in assisting detection of mammographic lesions by radiologists not specifically trained in mammography and its potential utility in breast screening. Mammograms were evaluated by radiologists not specifically trained in mammography first without, and then with, the CAD. Finally, the mammograms were evaluated by experienced mammographers who formed the reference standard. Two hundred and ninety four breasts were studied. In 257 breasts (87.4%), the CAD system did not help with the detection of abnormalities. It assisted radiologists in detecting abnormalities in 21 breasts (7.1%) with potential for detecting abnormalities in a further 13 breasts (4.4%). Only in three cases (1%) did it cause confusion in interpretation. There is overall increased sensitivity in detecting mammographic abnormalities with the aid of the CAD system from 74.4 to 87.2%, which is statistically significant. However, it failed to detect suspicious abnormalities in 71 breasts (24.1%). The CAD system improved detection of suspicious mammographic abnormalities by radiologists who are not specifically trained in mammography. However, there is also a substantial failure to detect suspicious mammographic features that cautions against over-reliance on the system, emphasizing its role as a second reader at best.

CT evaluation of nasolacrimal relapse of nasopharyngeal carcinoma.

AIM: The aim of the current study was to elucidate the anatomy of the nasolacrimal apparatus using computed tomography (CT), and to investigate the CT findings suggestive of recurrent nasopharyngeal carcinoma (NPC) involving the nasolacrimal apparatus. MATERIALS AND METHODS: CT images of five patients with clinical or radiological findings suggestive of recurrent NPC who presented with nasolacrimal involvement were reviewed. Involvement of the lacrimal fossa, nasolacrimal canal (NLC), and adjacent anatomic structures including orbit and sinonasal cavities were noted. RESULTS: CT in all patients demonstrated findings of NLC invasion and ostiomeatal complex obliteration. Four of the five patients showed medial canthal mass or pre-septal thickening, ethmoid bulla opacification and inferior nasal meatal involvement. CONCLUSION: Knowledge of the anatomy of the nasolacrimal apparatus using CT is critical for evaluating images for tumour recurrence at this site. NLC invasion, a medial canthal mass and pre-septal thickening are important primary indicators for potential involvement of the nasolacrimal apparatus by recurrent NPC. Secondary signs suggesting this distinct form of relapse are obliteration of ostiomeatal channel, ethmoid bulla opacification and inferior nasal meatus involvement.

Neurological changes following radiation therapy for head and neck tumours.

Radiation therapy is widely used in the treatment of head and neck tumours either as a primary form of treatment or a supplementary modality. Although the benefits of radiation therapy are well established, this treatment modality is not without untoward consequences and complications. The intent of this paper is to highlight the neurological complications that may follow the treatment for head and neck malignancies, in particular, following radiation therapy for nasopharyngeal carcinoma.

Diffusion weighted MR imaging in acute stroke: the SGH experience.

Cerebrovascular accident (CVA) is a leading cause of death and disability in many countries. Diffusion-weighted (DW) magnetic resonance (MR) imaging has been reported to be useful in the detection of acute strokes and as an investigative tool evaluating the therapeutic effects of neuroprotective and thrombolytic agents. The objectives of this study are to share our experience using the commercially available isotropic DW scan in imaging of acute stroke, assess its usefulness over conventional T2-weighted (T2W) scans in a busy clinical radiology unit and highlight it pitfalls. We found the rapid sub-minute DW technique well suited for ill and restless stroke patients and superior to T2W scans in many ways. It was highly sensitive to acute ischaemic lesions, made lesions easily identifiable and readily differentiated the acute lesion from a background of multiple chronic infarcts. However, there are potential pitfalls in the evaluation of small hyperacute posterior fossa strokes and venous infarcts. The major strength of this MR technique lies in its ability to diagnose hyperacute strokes and thence the potential for therapeutic thrombolysis, but unfortunately patients qualifying for the "therapeutic window" were a minority. More efforts need to be focused on public education in order for this powerful imaging modality to find its true value and contribute to viability of an effective thrombolytic programme.

Correlation of the apparent diffusion coefficient and the creatine level in early ischemic stroke: a comparison of different patterns by magnetic resonance.

It has been reported that reduction of the apparent diffusion coefficient (ADC) after stroke can persist for several days, after which the ADC increases gradually to an abnormally high level. We evaluated ADC values of stroke lesions and compared the results to the cellular density of the lesion by means of the creatine (Cre) level. This two-parameter estimation is of particular relevance in ascertaining the underlying cellular status. Lesion-to-contralateral ADC ratios (ADCn) were obtained based on diffusion-weighted echo-planar and fast spin-echo imaging. Single-voxel localized spectroscopy was used for quantification of cerebral metabolites in infarcted regions. Their levels were also compared to that in homotopic contralateral regions. Fifteen patients with ischemic stroke were examined at times ranging from 18-88 hours following the onset of symptoms. In the stroke lesion, there was a significant correlation between the ADC and the Cre level showing that the higher the cell density the lower the ADC value. For ADCn vs. the lesion Cre concentration and the lesion-to-contralateral Cre ratio (Cre(n)), the strengths of relationship were R2 = 0.70 and 0.58, respectively. It is concluded that ADC is a good reflection of cell density. Greatly lowered ADC values occur within the context of a stable cellularity. ADC and the Cre level have complementary roles in the characterization of stroke lesion with regard to the sequential stage.

Role of magnetic resonance imaging and magnetic resonance angiography in patients with hemifacial spasm.

Vascular compression of the facial nerve is a well recognized cause of hemifacial spasm (HFS). In this study, we described the magnetic resonance imaging (MRI) and three-dimensional magnetic resonance angiography (MRA) techniques used and findings in 34 patients with hemifacial spasm. A vascular abnormality, defined as a vessel seen in close proximity, touching or compressing the facial nerve, was identified in 22 of the 25 patients (88%) who had both MRI and MRA studies. Vessels identified were anterior inferior cerebellar artery (59.2%), posterior inferior cerebellar artery (13.6%), vertebral artery (18.2%) and basilar artery (4.5%). All vascular abnormalities were ipsilateral to the side of the HFS. Only 3 of the 12 controls (25%) had a vascular abnormality in both MRI and MRA studies. One of the 9 HFS patients (11.1%) who had MRI only had an ipsilateral vascular abnormality. There is a role for combined MRI and MRA studies in the non-invasive evaluation of patients with HFS.

Computed tomographic and magnetic resonance imaging findings in paranasal sinus involvement in nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) may spread to the paranasal sinuses. This retrospective study describes the features of paranasal sinus involvement in NPC on computed tomography (CT) and magnetic resonance imaging (MRI). One hundred and fourteen patients with histologically proven NPC underwent staging with both CT and MRI. Maxillary sinus infiltration was demonstrated on MRI in 10 patients; sphenoid sinus infiltration in 24 patients; and, ethmoid sinus involvement in 4 patients. CT could separate inflammatory changes from tumour in all maxillary sinuses but is less helpful in the sphenoid and ethmoid sinuses. Contrast-enhanced MRI could differentiate tumour from inflammatory changes in all sinuses. Using MRI as the standard, the rates of CT separating tumour from inflammation are: maxillary sinus (100%), sphenoid sinus (43%) and ethmoid sinus (25%). Histological confirmation of tumour involvement in the paranasal sinuses is not available. It is important to separate sinusitis from tumour infiltration as prognosis and treatment planning may be affected.

Clinics in diagnostic imaging (17). Chronic eosinophilic pneumonia (CEP).

A 24-year-old Chinese woman presented with cough, chest pain, weight loss, low grade fever and bronchial breath sounds on auscultation. The diagnosis of chronic eosinophilic pneumonia was made on characteristic systemic and pulmonary clinical manifestations, blood eosinophilia and the striking chest radiographic appearance. This rare, idiopathic but benign condition responds well to corticosteroid treatment and the long term prognosis is excellent. The typical chest radiographic pattern of 'photographic negative of pulmonary oedema' in this condition is emphasised.

Modified barium swallow examination in dysphagic stroke patients.

UNLABELLED: Aspiration in dysphagic stroke patients is common and causes significant morbidity and mortality. Bedside clinical assessment of aspiration risk is often unreliable, particularly in patients with silent aspiration. Twenty-five dysphagic stroke patients clinically assessed to have borderline risk of aspiration were studied using a Modified Barium Swallow (MBS) examination. MBS revealed definite aspiration of liquids in 6 patients (24%) and semisolids in 4 patients (16%). Combined clinical and MBS assessment revealed an additional 12 patients (48%) had problems swallowing liquids and 5 patients (20%) semisolids due to reasons other than aspiration. In total, oral feeding of liquids were contraindicated in 18 patients (72%) and semisolids in 9 patients (36%). IN CONCLUSION: (1) In dysphagic stroke patients assessed clinically to have borderline risk of aspiration, MBS can distinguish those who aspirate from those who do not. MBS can also identify patients with other swallowing problems which expose them to potential aspiration. (2) Aspiration risk with food of various consistencies can be clearly defined, thus guiding the choice of food consistency and safe feeding methods.

Nasopharyngeal carcinoma with intracranial spread: CT and MR characteristics.

PURPOSE: Nasopharyngeal carcinoma (NPC) frequently spreads intracranially. We compare CT and MRI in identifying intracranial spread and reexamine the route of infiltration. METHOD: One hundred fourteen consecutive patients with proven NPC were evaluated prospectively with T1-, T2-weighted, contrast-enhanced MRI and CT. RESULTS: MRI showed 35 (31%) patients with middle cranial fossa involvement. Twenty-nine (25%) patients had cavernous sinus infiltration, while six (5%) showed only dural thickening. The most common route of spread is through the foramen ovale (FO) (12/35 patients, 34%), followed by skull base destruction (6/35 patients, 17%), foramen lacerum (FL) (6/35 patients, 17%), sphenoid sinus (6/35 patients, 17%), and combined FO and FL (5/35 patients, 14%). Using MRI as a standard, CT demonstrated the following involvement: cavernous sinus in 26 of 29 (90%) patients, FO in 9 of 12 patients, skull base in 6 of 6 patients, FO and FL in 3 of 5 patients, FL in 6 of 6 patients, sphenoid sinus in 6 of 6 patients and dura in 0 of 18 patients. CONCLUSION: It is believed that NPC most commonly spreads intracranially via the FL or by direct erosion. Perineural spread through the FO is an important route, which explains why with CT evidence of cavernous sinus involvement there may be no skull base erosion. These findings are best seen on MRI.

MRI features of cervical nodal necrosis in metastatic disease.

Magnetic resonance imaging (MRI) is increasingly used to evaluate head and neck tumours but its place in the assessment of nodal metastasis is still unclear. This study compares the MRI findings with the computed tomography (CT) sign of nodal necrosis in 114 patients with confirmed nasopharyngeal carcinoma (NPC). Ninety-one (80%) patients showed neck node enlargement on both MRI and CT. Thirty-one (34%) of these patient with lymphadenopathy showed nodal necrosis. Seventy-two necrotic nodes were seen on CT. Using CT as the standard, the sensitivity and specificity of individual MRI sequences are as follows: T1-weighted (36%, 100%), T2-weighted (47%, 98%) and enhanced T1 (67%, 100%). In combination (when one or more sequences are positive), the sensitivity and specificity are as follows: T1 and T2-weighted (60%, 99%), T1-weighted and enhanced scan (67%, 100%) and T1-, T2-weighted and enhanced scan (78%, 99%). Only 26 (36%) nodes with nodal necrosis could be recognised on T1-weighted MRI as an area of low signal intensity. Paradoxically, eleven (15%) nodes, showed slightly hyperintense necrotic areas. Contrast enhanced MRI showed 48 (67%) NN thus improving detection rate. High signal intensity with or without a rim of lower signal intensity could be seen in 39 (54%) nodes on T2-weighted images. Five nodes (7%), curiously showed low signal necrotic centres. Ideally, staging of the primary tumour and nodes should be performed using a single modality. The tumour is often more advantageously evaluated by MRI. However, CT should be considered if MRI findings of nodal involvement are equivocal.

Retropharyngeal lymphadenopathy in nasopharyngeal carcinoma.

PURPOSE: This study reports the incidence, numer, size and distribution of enlarged lateral retropharyngeal (LRP) nodes in patients with nasopharyngeal carcinoma (NPC). MATERIALS AND METHODS: One-hundred and fourteen patients with histopathologically proven NPC were staged prospectively with magnetic resonance imaging (MRI) and computed tomography (CT). T1-weighted, gadolinium-DTPA enhanced, T2-weighted images and CT were obtained. RESULTS: Ninety-one (80%) patients showed enlargement of both LRP and cervical nodes. LRP lymphadenopathy was detected in 59 (65%) of these 91 patients. A total of 347 neck nodes were identified. There were 72 enlarged LRP nodes (average 13 mm, range 6-34 mm). Sixteen groups of fused nodes were also seen (average 24 mm, range 15-40 m). Thirty-two patients (35%) with cervical lymphadenopathy showed no LRP lymphadenopathy. LRP nodes were seen at the following levels: C1, 35 (49%) nodes; C1/C2, 23 (32%); C2, 13 (18%) and C2/C3, one (1%). It is not known if all these nodes are due to metastasis or hyperplasia as no histopathological proof is available. CONCLUSION: LRP lymphadenopathy may be seen in up to 65% of NPC patients with neck node enlargement. All the retropharyngeal nodes were located in the lateral group. Although medial retropharyngeal nodes are mentioned in the literature, they were not seen in this study. LRP nodes should be documented when surgical resection is contemplated in malignancy of the head and neck.