RD hepatobiliary formatted Flashcards
- 10cm pancreatic cyst (cystic mass) in a young patient (25 years). (Incidental with no calcifications). Most likely is
a. Serous
b. Mucinous
c. Solid pseudopapillary
d. Insulinoma
e. Gastrinoma
c. Solid pseudopapillary T Young age suggests solid pseudopapillary neoplasm with predominate cystic degeneration. RG 2011 – F»M (9:1), young adult (mean age 25); typically large (mean 9cm); 30% have calcifications. Against this is no mention of solid components or haemorrhage
.1. 10cm pancreatic cyst (cystic mass) in a young patient (25 years). (Incidental with no calcifications). Most likely is (Lim DDx p208) (SK)
a. Serous F mean age 65 years; multiple small cysts (cut orange); maybe at this age if they had VHL?
b. Mucinous F mean age 40-60 years; smaller number of larger (> 2cm) cysts
c. Solid pseudopapillary T Young age suggests solid pseudopapillary neoplasm with predominate cystic degeneration. RG 2011 – F»M (9:1), young adult (mean age 25); typically large (mean 9cm); 30% have calcifications. Against this is no mention of solid components or haemorrhage.
d. Insulinoma F 4th-6th decades; usually small & hypervascular solid
e. Gastrinoma F 4th-5th decades; somewhat larger but hypervascular solid
- A small diverticulum arises from the common bile duct, separate from the ampulla. Which is the correct classification?
a. I
b. II
c. III
d. IV
e. V
b. II
- Woman on HRT is jaundiced, with abnormal LFTs and non-dilated ducts on ultrasound. (LAS – liver normal echogenicity). Most likely cause:
a. Steatohepatitis
b. Cholestasis
c. Hepatocellular necrosis
B: Cholestasis.
*LW: Estrogen therapy can induce a clinically cholestatic liver injury during first few cycles, insideous onset with jaundice, elevated liver enzymes, with bland intra hepatic cholestasis and biopsy showing little inflammation or necrosis. Thus favoured answer is B - cholestasis given Hx stating HRT, jaundice, abnormal LFTs and normal liver echogenicity.
b. Cholestasis ?T = systemic retention of bilirubin, bile salts & cholesterol due to inadequate biliary elimination of these solutes. Results from hepatocellular dysfunction or biliary obstruction. In this patient intrahepatic cholestasis could account for the findings.
3. Woman on HRT is jaundiced, with abnormal LFTs and non-dilated ducts on ultrasound. (LAS – liver normal echogenicity). Most likely cause: (SK)
a. Steatohepatitis ?T NASH = hepatocytes filled with fat vacuoles with inflammatory infiltrates -> probably wrong -> liver would be echogenic
b. Cholestasis ?T = systemic retention of bilirubin, bile salts & cholesterol due to inadequate biliary elimination of these solutes. Results from hepatocellular dysfunction or biliary obstruction. In this patient intrahepatic cholestasis could account for the findings.
c. Hepatocellular necrosis ?T in the setting of hepatitis?Robbins says “estrogen replacement therapy” can cause a cholestatic liver injury.No other reference anywhere for effects of HRT on the liver – apart from a number saying it can reduce risks of type 2 DM and improve LFTs.Robbins p860: Individuals with simple steatosis are generally asymptomatic. AST & ALT elevated in 90% of patients with NASH.
- Middle aged woman with pancreatic head mass. Least likely to be a?
a. Solid pseudopapillary neoplasm
b. Serous cystadenoma
c. Mucinous cystic neoplasm
d. Islet cell tumour
e. Pseudocyst
a. Solid & pseudopapillary neoplasm F age < 35 years (rare in adults)
- Middle aged woman with pancreatic head mass. Least likely to be a?
a. Solid & pseudopapillary neoplasm F age < 35 years (rare in adults)
b. Serous cystadenoma mean age 65 years; multiple small cysts; favours the pancreatic head
c. Mucinous cystic neoplasm mean age 40-60 years; smaller number of larger (> 2cm) cysts; favours the pancreatic body/tail
d. Islet cell tumour 4th-6th decades; usually small & hypervascular solid
e. Pseudocyst
- Young woman. CT triple phase. Arterial and PV phase, heterogenous enhancement. Us heterogenous. Most likely
a. adenoma
b. FNH
c. HCC
A – adenoma = T young females on OCP; heterogenous rapid enhancement (hyperdense arterially, but often isodense on pre-con, PV & delayed phases); heterogenous/variable at US
A – adenoma = T young females on OCP; heterogenous rapid enhancement (hyperdense arterially, but often isodense on pre-con, PV & delayed phases); heterogenous/variable at US
B – FNH = F young females, homogenous arterial enhancement (except central scar); US homogenously hypoechoic except for central scar
C – HCC = F – early enhancement +/- central necrosis; typically echogenic at US; can be radiologically identical to adenoma, but less common in young patients without cirrhosis
- Patient with diarrhoea. Hypokalaemia. Pan shows arterial and PV base enhancing mass. Most likely.
a. Gastrinoma
b. VIPoma
c. Somastotinoma
B = VIPoma = WHDA syndrome – watery diarrhoea, hypokalaemia, achlorhydria A = gastrinoma = 2nd most common islet cell neoplasm; causes ZES (diarrhoea, PUD, but no hypokalaemia) B = VIPoma = WHDA syndrome – watery diarrhoea, hypokalaemia, achlorhydria C = Somatostatinoma = Diabetes, diarrhoea, cholelithiasis
- Definition of segment 4a.
above portal vein, between middle and left hepatic vein
patient with cholangiocarcinoma extends beyond right and left hepatic ducts a. type 1 b 2 c. 3a d. 3 b e. 4
e. 4
Bismuth-Corlette classification — Cancers arising in the perihilar region have been further classified according to their patterns of involvement of the hepatic ducts (the Bismuth-Corlette classification):
- Tumor of CHD below the confluence of the left and right hepatic ducts (Type I)
- Tumor of CHD reaching the confluence (Type II)
- Tumors occluding the common hepatic duct and either the right or left hepatic duct (Types IIIa and IIIb, respectively)
- Tumors that are multicentric, or that involve the confluence and both the right and left hepatic ducts (Type IV)
Classified based on anatomy and radiography
- Peripheral (10%) Intrahepatic; proximal to secondary biliary radicles
- Perihilar (50%) Klatskin tumor: Hilar tumor involving the confluence of hepatic ducts
- Distal (40%) Extrahepatic; distal CBD
May arise as short stricture or small polypoid mass
- A 45 year old man has a 3 cm homogenous pancreatic mass. 3 lesions are present in the liver. A lesion in segment IV measures 2cm, is well circumscribed and an-echoic with posterior acoustic enhancement. A lesion in segment VI measures 3cm and is heterogenous in appearance. A lesion in segment VIII measures 2cm, is well circumscribed and an-echoic with posterior acoustic enhancement. The referring oncologist needs tissue for diagnosis. Which of the following is most appropriate:
a. Imaging guided biopsy of the segment IV lesion.
b. Imaging guided biopsy of the segment VI lesion.
c. Imaging guided biopsy of the segment VIII lesion.
d. Imaging guided biopsy of the pancreas.
e. Progress CT in 3 months
b. Imaging guided biopsy of the segment VI lesion. T may be a pancreatic NET with mets?, alternatively pancreatic adenocarcinoma
*LW:
Biopsying a liver lesion easier to do than transcolemic FNA of the pancreatic mass.
Furthermore, risk, although accuracy is still undetemrined, in peritoneal seeding with FNA biopsy of pancreas, and accurracy is also relatively reduced.
It is an accepatable method to prove non surgical candidate in pancreatic Ca.
ERCP brushings or endoluminal US biopsy are methods with higher accuracy.
–> thus why segment VI lesion image guided biopsy is answer, and will likely confirm metastatic pancreatic ca.
*AJL - Biopsying the pancreatic mass will tell you its a cancer (which we kind of already know) but will not tell you if there is metastatic disease.
Biopsying the bad looking liver lesion will tell you if there is metastatic disease or not which is the real clinical question. (overall I agree with the above but just providing an explanation)
- Which of the following CT sequences will be most informative if looking for a hepatoma:
a. CT with biliary contrast
b. CT with IV contrast in the arterial phase
c. CT with IV contrast in the portal venous phase
d. CT with IV contrast at a 10 minute delay
e. CT with no IV contrast
b. CT with IV contrast in the arterial phase T best for detection – early enhancement during arterial phase.
- -> HCC
- A 45 year-old woman presents with 3 incidental liver lesions which are hyperechoic on ultrasound and measure between 3-5cm. They MOST LIKELY represent:
a. Mulitfocal HCC
b. Focal nodular hyperplasia
c. Adenoma
d. Metastasis
e. Haemangioma.
d. Metastasis T most common liver mass in adults; echogenic if hypervascular mets, calcified mets
e. Haemangioma.T 80% in females (more common postmenopause); 2nd most common liver mass after metastases; echogenic; usually solitary
Without any history of malignancy, go E haemangioma?
- A 45 year-old woman presents with 3 incidental liver lesion which are hyperechoic on ultrasound and measure between 3-5cm. They MOST LIKELY represent:
a. Mulitfocal HCC T but unlikely without Hx of cirrhosis
b. Focal nodular hyperplasia F usually homogenously hypoechoic
c. Adenoma F variable US, classically hyperechoic with central anechoic areas
d. Metastasis T most common liver mass in adults; echogenic if hypervascular mets, calcified mets
e. Haemangioma.T 80% in females (more common postmenopause); 2nd most common liver mass after metastases; echogenic; usually solitary
- A middle age male presents for staging CT scan of cholangiocarcninoma, which involves the primary confluence but not the secondary confluence. Which grade?
a. I
b. II
c. IIIA
d. IIIB
e. IV
b. II
Bismuth-Corlette classification — Cancers arising in the perihilar region have been further classified according to their patterns of involvement of the hepatic ducts (the Bismuth-Corlette classification):
- Tumors below the confluence of the left and right hepatic ducts (Type I)
- Tumors reaching the confluence (Type II)
- Tumors occluding the common hepatic duct and either the right or left hepatic duct (Types IIIa and IIIb, respectively)
- Tumors that are multicentric, or that involve the confluence and both the right or left hepatic duct (Type IV)
- Pancreatic mass in 50 year old female, 9cm, mural nodule on MRI, Ca++ in wall on CT, most correct
a. Mucinous tumour
b. Macrocystic serous tumour
c. Microcystic serous tumour
d. Pseudo solidpapillary tumour
e. Intraductal papillary tumour
a. Mucinous tumour T cyst + mural nodule. Peripheral eggshell calcification is specific for mucinous cystic neoplasm & is highly predictive of malignancy (RG 05). Mean age 50 years. Size 2-12cm. Surgical removal indicated
.5. Pancreatic mass in 50 year old female, 9cm, mural nodule on MRI, Ca++ in wall on CT, most correct
a. Mucinous tumour T cyst + mural nodule. Peripheral eggshell calcification is specific for mucinous cystic neoplasm & is highly predictive of malignancy (RG 05). Mean age 50 years. Size 2-12cm. Surgical removal indicated.
b. Macrocystic serous tumour F no solid component
c. Microcystic serous tumour F no solid component, septal/central calcification
d. Pseudo solid papillary tumour F cyst + mural nodule; 5-30% have peripheral calcification; often large; younger age group (< 35 yrs)
e. Intraductal papillary tumour F calcification unlikely; can have mural nodule
- Female with rising LFTs, RUQ pain has a hyperechoic liver parenchyma and normal biliary tree, most likely explanation?
a. Cholestasis
b. Hepatocellular necrosis
c. Cirrhosis
d. Fibrosis
b. Hepatocellular necrosis T?? talking about hepatitis – can feature hepatocellular necrosis.
- steroid using guy with jaundice. Normal biliary tree
a. steatohepatitis
b. cholestasis
c. cirrhosis.
d. fatty liver
IF THEY MEAN ANABOLIC STEROIDS… ANSWER IS B (or D?)
Pure (canalicular, bland or noninflammatory) cholestasis is characterized by cholestasis with very little hepatocellular inflammation. Bile plugging is frequently seen, predominantly in zone 3 hepatocytes or canaliculi. Aminotransferases are generally normal or minimally elevated, with greater elevations in alkaline phosphatase and γ-glutamyl transferase. This type of injury is often seen with the use of anabolic steroids or oral contraceptives. Drugs causing this type of injury interfere with hepatocyte secretion of bile constituents and other pigment and dye substances via the bile salt excretory protein (BSEP). Chronic cholestasis may evolve from acute drug-induced cholestasis.Emedicine:Anabolic steroid abuse has been considered a risk factor for nonalcoholic fatty liver disease.
IF THEY MEAN GLUCOCORTICOIDS… ANSWER IS D Drug-induced chronic steatosis is predominantly macrovesicular in contrast to the microvesicular steatosis usually seen in acute drug injury. Serum aminotransferases are typically moderately elevated. Drugs associated with these types of injury include chemotherapeutic agents (eg, 5-fluorouracil, cisplatin, tamoxifen), chloroform, diethylstilbestrol, ethanol, glucocorticoids, gold, griseofulvin, methotrexate, mercury, nifedipine, nitrofurantoin, NSAIDs (eg, ibuprofen, indomethacin, sulindac), tamoxifen, and total parenteral nutrition [44,77,78]. These medications rarely cause steatohepatitis but may exacerbate or precipitate it in patients with risk factors for NASH.
- Guy in MVA. splenic and diaphragmatic rupture. Nodules in the left lung that takes up Tc99 sulphur colloid. most likely
splenosis
Mettler – Nuc Med p203
- 99mTc sulfur colloid is the most commonly used agent in N/M for imaging the liver & spleen
- Uptake by reticuloendothelial system (phagocytes)
o Liver (80-90%, Kupffer cells)
– uptake & distribution reflect distribution of functioning reticuloendothelial cells & distribution of hepatic perfusion
o Spleen (5-10%, phagocytes) o Bone marrow (small amount) - Normal = homogenous distribution throughout liver
- Liver lesions differentiation: o Increased uptake • FNH • Cirrhosis with regenerative nodule • Budd-chiari (caudate lobe) • SVC obstruction (quadrate lobe)
o Decreased uptake • Metastasis (esp. colon) • Cyst • HCC, esp. in cirrhosis • Adenoma • Haematoma • Haemangioma • Abscess • Pseudotumour (cirrhosis) • Cholangiocarcinoma • Liver abscess • Focal fatty infiltration
o Sites of abnormal (non liver/spleen) uptake
• Renal transplant (rejection – current or previous)
• Diffuse lung activity – multiple causes (Table 8-3 p207)
- Hyperechoic lesion on us in liver. takes up labelled rbc. Most likely
cavernous haemangioma
Mettler p211
• 99mTc labelled RBC scan
• Haemangioma highly likely if:
o Increased activity after labelled red cell scan (often need significant delay to show)
o Decreased uptake on sulphur colloid scan
- guy with 3cm pancreatic head mass. segment 4b cystic lesion. segment 6 hyperechoic heterogenous lesion. segment 8 hyper echoic lesion. which one do you biopsy
probably hyper echoic lesion??
35 yo woman. liver MRI. moderate arterial enhancement. Washout portal venous phase. Central high T2. Most likely
a. FNH
b. adenoma.
c. fibrolamellar HCC
ANS = A = FNH (central high T2 = scar)[central scar in fibrolamellar HCC usually hypointense on all MR sequences, rarely T2 hyper]Note large haemangiomas can have a central scar also.
1) Liver Segment III: (note previous exam segment II)
i) Above portal vein and to left of left hepatic vein
ii) Below portal vein and to left of left hepatic vein
iii) Above portal vein and between middle and left hepatic vein
iv) Above portal vein and to right of to right hepatic vein
v) Below portal vein and between middle and left hepatic veins
ii) Below portal vein and to left of left hepatic vein
2) Liver Segment IVa:
i) Above portal vein and to left of left hepatic vein
ii) Below portal vein and to left of left hepatic vein
iii) Above portal vein and between middle and left hepatic veins
iv) Above portal vein and to right of right hepatic vein
v) Below portal vein and between middle and left hepatic veins
iii) Above portal vein and between middle and left hepatic veins
3) Thick-walled, septated collection in liver post diverticular abscess drainage by surgeons. Best option:
i) IV abs only
ii) Needle aspiration
iii) Percutaneous insertion 5fr drain
iv) Percutaneous insertion 10fr drain
v) Surgical drainage
iv) Percutaneous insertion 10fr drain TKandarpa p529- Commonly use 7-14 Fr catheters- Larger catheters used for bigger, more complex collections (e.g. 12-14 Fr – theorectically allow more free drainage)
4) Chronic pancreatitis
i) Calcification is acinar
ii) 15% go on to pancreatic Ca
iii) 60% of pseudocysts in acute pancreatitis resolve within 6 weeks
iv) Peritoneal calcification is a recognised feature
iv) Peritoneal calcification is a recognised feature T?
4) Chronic pancreatitis
i) Calcification is acinar F The ducts become obstructed by proteinaceous plugs that can eventually accumulate calcium carbonate. This obstruction results in ductal ectasia and periductal fibrosis. The calculi occur in ducts of all sizes and vary from microscopic to greater than 1 cm in diameter. (AJR 02). Calcification occurs in 40-60% of patients with alcoholic pancreatitis (StatDx), and 75% of cases in USA are due to alcoholism.
ii) 15% go on to pancreatic Ca F 2-4% (Dahnert)
iii) 60% of pseudocysts in acute pancreatitis resolve within 6 weeks F Pseudocyst occurs in 10-20% of cases of acute pancreatitis, usually ≥ 4 weeks. Spontaneous resolution in 25-40% (StatDx), no time frame given (presumably would be longer). AJR 2011 states 40% resolve spontaneously.
iv) Peritoneal calcification is a recognised feature T?
Liver Segment II
a. Above portal vein and medial to medial hepatic vein
b. Below portal vein and medial to medial hepatic vein
c. Above portal vein and between middle and medial hepatic vein
d. Above portal vein and lateral to lateral hepatic vein
A
Hepatic adenoma. Does it have uptake on sulfar colloid scan???
Not much. FNH takes up more sulfar colloid.
o Increased uptake • FNH • Cirrhosis with regenerative nodule • Budd-chiari (caudate lobe) • SVC obstruction (quadrate lobe)
o Decreased uptake • Metastasis (esp. colon) • Cyst • HCC, esp. in cirrhosis • Adenoma • Haematoma • Haemangioma • Abscess • Pseudotumour (cirrhosis) • Cholangiocarcinoma • Liver abscess • Focal fatty infiltration
o Sites of abnormal (non liver/spleen) uptake
• Renal transplant (rejection – current or previous)
• Diffuse lung activity – multiple causes (Table 8-3 p207)
Young man. abnormal LFT. investigation of choice.
a. ERCP
b. MRCP
c. AXR
d. US
Ultrasound
- NOT a differential Dx for hyperintense lesion of non-con T1 MRI of the liver?
a. Hethaemaglobin
b. Cavernous hemangioma
c. Hepatoma
d. Metastasis
e. Angiomyolipoma
b. Cavernous hemangioma F? iso-hypointense on T1, bright on T2 (light bulb) – however if contains haemorrhage, with contain T1 hyperintensity (although uncommon & not listed in StatDx)
1. NOT a differential Dx for hyperintense lesion of non-con T1 MRI of the liver?
a. Hethaemaglobin T
b. Cavernous hemangioma F? iso-hypointense on T1, bright on T2 (light bulb) – however if contains haemorrhage, with contain T1 hyperintensity (although uncommon & not listed in StatDx)
c. Hepatoma T
d. Metastasis T haemorrhage, melanoma, mucinous (colon, ovary, pancreas), myeloma
e. Angiomyolipoma T macroscopic fat is T1 hyperintense
- Which is NOT a recognised cause of Budd-Chiari syndrome
a. Chronic pancreatitis
b. Bone marrow transplantation
c. Chemotherapy
d. Systemic lupus erythematosus
e. Oral contraceptives
a. Chronic pancreatitis
• Primary: Venous outflow membranous obstructiono Controversial etiology
o Congenital, injury, or infection
• Secondary: Thrombotic, rarely nonthrombotic
o Obstruction of central and sublobular veins
o Obstruction of major hepatic veins
o Obstruction of small centrilobular veins (venoocclusive disease)
o Nonthrombotic: Hepatic & extrahepatic masses
Causes: idiopathic (2/3 (other websites suggest on 1/3 idiopathic).
Thrombosis - hypercoagulable state (5P’s: PCV, pill, pregnancy, increased plts, PNH), or injury to vessel wall (XRT, chemo/IS in BMT patients, Jamaican bush tea) Non-thrombotic - tumour extension into IVC (RCC, HCC), IVC diaphragm (congenital, acquired), right atrial tumour, constrictive pericarditis, RHF. [Dahnert; SLE RG 2004]
- Which of the following proposed conditions is LEAST LIKELY to be associated with primary biliary cirrhosis
a. Hepatic osteodystrophy
b. Choledochocele
c. Lymphadenopathy
d. HCC
e. Gallstones
b. Choledochocele – F
1. Which of the following proposed conditions is LEAST LIKELY to be associated with primary biliary cirrhosis
a. Hepatic osteodystrophy T - a generic definition for the metabolic bone disease that may occur in individuals with chronic liver disease. Osteopaenia occurs in PBC.
b. Choledochocele – F
c. Lymphadenopathy – T more prominent feature in PBC than in other aetiologies of CLD (StatDx); nodes seen within porta & portocaval regions
d. HCC increased T – a complication, but less common than with viral or alcoholic cirrhosis & tend to be well-differentiated (StatDx)
e. Gallstones T 30-40%Primary biliary cirrhosis- idiopathic condition- progressive sclerosis of the biliary tree- non - suppurative
- Which of the following statements regarding gas lucencies in the liver on plain radiograph of abdomen is MOST CORRECT?
a. Gas may be seen in the liver following chemoembolisation of a liver tumor
b. PV gas is a common finding in hemorrhagic pancreatitis
c. Biliary tree gas is a recognised finding after infarction of bowel
d. PV gas is predominantly centrally located
a. Gas may be seen in the liver following chemoembolisation of a liver tumor T
- Which of the following statements regarding gas lucencies in the liver on plain radiograph of abdomen is MOST CORRECT?
a. Gas may be seen in the liver following chemoembolisation of a liver tumor T
b. PV gas is a common finding in hemorrhagic pancreatitis F but can occur as a complication of acute pancreatitis (StatDx – “less common” cause)
c. Biliary tree gas is a recognised finding after infarction of bowel F
d. PV gas is predominantly centrally located F peripheral, mobile
- Liver lesion with a central stellate area that is hypointense on T1 and T2 imaging. What is the most likely cause?
- Hepatic adenoma
- FNH
- HCC
- Fibrolamaller HCC
- Hemangioma
4.Fibrolamaller HCC - T - central scar hypointense on T1 & T2. (=FLC)
- Liver lesion with a central stellate area that is hypointense on T1 and T2 imaging. What is the most likely cause? (JS/SK)
- Hepatic adenoma - F - heterogenous appearance but no central scar
- FNH – F (but ?T as ‘most likely’) – SK: central scar T1 hypo & T2 hyperintense (StatDx, Lin DDx p183)JS: central scar is hyperintense on T2, but 25% can be hypointense. Size of the lesion would also be important as the main DDx is FLHCC.
- HCC - F - variable appearance
- Fibrolamaller HCC - T - central scar hypointense on T1 & T2. (=FLC)
- Hemangioma - F - T2 hyperintense with nodular enhancement from periphery. Large (giant) haemangiomas can have central scar – T1 hypointense & T2 hyperintense
Pearls from StatDx on FLC:
• FLC: Bigger, more heterogeneous mass, frequently with calcified central/eccentric scar and features of malignancy (vessel/biliary obstruction, nodal invasion, and lung metastases)
• Scar on T2WI: Hypointense (FLC), hyperintense (FNH)
• FLC = Large, heterogeneous, hypervascular tumor in young adult
- Clinical scenario of diarrhoea, flushing etc. Portal venous CT suggests mesenteric lesion with desmoplastic reaction and liver mets. What is the next most appropriate investigation?
- MRI
- MIBG scan
- Octreotide scan
- Triple phase CT abdomen
- USS pelvis
- Octreotide scan - T – see flow chart below. As CT ‘suggests’ lesion with mets, the diagnosis is still not confirmed. The next examination would probably actually be serum metanephrines.
- Clinical scenario of diarrhoea, flushing etc. Portal venous CT suggests mesenteric lesion with desmoplastic reaction and liver mets. What is the next most appropriate investigation? (JS, GC, TW)
- MRI - F
- MIBG scan - F - uptake in 44-63%.
- Octreotide scan - T – see flow chart below. As CT ‘suggests’ lesion with mets, the diagnosis is still not confirmed. The next examination would probably actually be serum metanephrines.
- Triple phase CT abdomen - F - liver lesions already thought to be mets 5.USS pelvis - F